DAVIS-BOURNONVILILE OXY-ACETYLENE WELDING and CUTTING COURSE OF INSTRUCTION LECTURES DAYIS-BOURNOS^VILLE WELDIN© HfSTITOTE Class JILSxjSjgJ] Book. Copyiiglit}]".. CDEflMGHT DEPOSIT. Digitized by the Internet Archive in 2011 with funding from The Library of Congress http://www.archive.org/details/davisbournonvillOOdavi DAVIS-BOURNONVILLE OXY-ACETYLENE WELDIING and CUTTING COURSE OF INSTRUCTION Lectures WELDING AND CUTTING WITH THE OXY-ACETYLENE TORCH DAVIS -BOURNONVILLE INSTITUTE JERSEY CITY, N. J. Form 399 U w o o < P-. >^ H O U < U u REGULATING THE GAS SUPPLY All Gases Compressible — Pressure Reducers or Regulators— ^To Regulate Working Pressure — Principle of Pressure Gauge Operation — Danger of Testing Oxygen Gauges with Oil — Pressure Reducers or Regulators — Principle of Pressure Regulator Action — Direct Acting Pressure Regulator — Line Pressure Regulator of the Indirect-Acting Type — Care of Regulators — Action of Pressure Regulators Reviewed. In the previous lecture we talked about combustion and the structure of flame. Today we will take up the matter of controlling the flow of the oxygen and acetylene gas to the torch. The flow of gas through a pipe depends on the diameter of the pipe and the pressure behind it. If you need little gas a small pipe and low pressure will supply it, but if you need much gas for a large flame a larger aperture and greater pressure will be required. The control of the torch flame then is accomplished by regulating the size of the orifice through which it escapes to the atmosphere and the pressure of the respective gases. This talk will be on regulating the gas pressures. All Gases Compressible You have noticed, of course, that the hose are connected to two pipe-lines or sources of supply. In the field your sources of gas supply will be usually two cylinders like these ; one of the cylinders contains the fuel supply or acetylene gas, and the other the oxygen. The gases in the cylinders are condensed under heavy pressure. All- gases are compressible, which means, for instance, that a gallon of gas may be squeezed into a half-gallon can if sufficient pressure is applied. There is, in fact, hardly any limit to the compressibility of gases in general. Gas is quite different from water in this respect. A gallon of water is a gallon — no more and no less. Practically you cannot squeeze it into much less space, no matter how great the pressure applied. A pressure of 3000 pounds to the square inch will compress water only one per cent. A pressure of 3000 pounds to the square inch will compressure gas into less than one-two hundreth of its free bulk. The oxygen cylinder contains the gas under a pressure of about 1800 to 2000 pounds to the square inch, while the acetylene cylinder contains this gas under a pressure of about 225 pounds to 275 pounds to the square inch. These pressures are the maxi- mum, and they decrease as the gases are used. Pressure Reducers or Regulators You will notice on the oxygen cylinder two gauges, and below one of the gauges a device called the gas pressure regu- lator. This gauge, which registers up to 3000 pounds per square inch, shows the pressure of oxygen in the cylinder when the stop ADJUSTING SCREW WORKING PRESSURE GAUGE Djvis Bournonville Institute FIG. 2. DIAGRAM SHOWING PRINCIPLE OF SIMPLE PRESSURE REGULATOR, AND PRESSURE GAUGE. valve is open. We cannot use a pressure of 1800 pounds to the square inch in the torch ; it is entirely too high, and must be re- duced to a comparatively low working pressure. The working pressure depends on the aperture in the tip, which in turn governs the size of the flame. For welding metals up to }i inch thick the acetylene working pressure is the same as the number of the tip and two times the number of the tip for the oxygen. For instance, if a No. 2 tip is being used we should adjust for a working pressure of two pounds acetylene and four pounds oxygen per square inch. To regulate the gas supply proceed as follows, first making sure that the regulator handles are in the closed position : To Regulate Working Pressure Open the valve on the oxygen cylinder as far as it will go, and admit the gas to the pressure regulator. This Stop valve must be opened very slowly as you are dealing with a very heavy pressure, which will surely damage the apparatus if not handled carefully. The valve must be opened wide in order to prevent leakage around the stem. You will note that as the gas was admitted the hand on the gauge has moved from the zero point. It now indicates about 1800 pounds pressure. Having turned on the oxygen we are ready to adjust the working pressure by means of the pressure regulator. To do this open the oxygen needle valve in the torch and turn the regulator valve handle slow- ly to the right. At first it moves easily and then it begins to offer some resistance. When you feel the resistance increasing, turn the handle slowly. Now the gas is escaping through the hose. The hand of the working gauge begins to move over the gradu- ated dial, and when it reaches 4 stop opening the regulator valve. The flow of gas has been adjusted for a working pressure of four pounds per square inch, which is about right for the No. 2 tip when the gas supply is constant. If, however, the supply is taken from a cylinder it is customary to adjust for slightly higher work- ing pressures in order to compensate for falling pressure as the gas is used up. Now close the oxygen needle valve in the torch, and open the acetylene needle valve. Open the stop valve on the acetylene cylinder also very slowly. The pressure on the gauge rises to about 225 pounds per square inch. Having admitted the acetylene to its pressure regulator we are ready to regulate the working pressure of the fuel supply. Turn the regulator handle to the right slowly as before, until it meets increasing resistance, and then turn very slowly. As the valve opens and admits the acetylene gas the hand of the acetylene gauge begins to move over the graduated dial and when it indicates 2, or slightly more, stop opening the regulator. Close the acetylene needle valve if not ready to immediately ignite the flame. As a rule you should be ready to start using the torch, but we will close the acetylene valve for the moment, and describe the construction of the gauges and the regulators. It is important that you understand' the principles of these parts of the apparatus, as your success as a welder and your personal safety depend on the care you give them. Principle of Pressure Gauge Operation Here is a pressure gauge that has been partly dismantled to show the construction. You notice in the center, a curved flat tube, one end of which is attached to the gauge stem, while the other or closed end is connected by means of a lever and a short curved rack to a small pinion. We will mount this gauge on the cylinder and open the valve. The tube tends to straighten when the pressure is admitted, but the movement is too small to be seen. It is known as a Bourdon tube, and is the pressure part generally used in gauges. A tube like this tends to straighten when subjected to internal pressure, because the flattened cross section tends to become circular. This has the same effect as increasing the inner circumference and shortening the outer. The movement of the end of the tube is so slight that it is necessary to multiply it in order to see the movement of the hand on the dial. This multiplication of move- ment is accomplished by the lever connection and the curved rack and pinion. The pinion is mounted on the spindle that carries the indicator hand. A very small movement of the tube will turn the hand completely around the dial. Beside the pinion is a hair- spring; one end is attached to the body and the other to the spindle. This hairspring offers a slight resistance to the move- ment of the Bourdon tube, and it returns the hand to the zero point when the pressure is released. The movement of the hand over the graduations of the dial is calibrated or compared with a master gauge to make sure that the indications represent correctly the pressure in pounds per square inch. The term "pounds per square inch" means that every square inch in the cyhnd'er shell supports a load, pressure, or weight, and a gauge pressure is a device for weighing the pressure. If the internal area of the shell of an oxygen cylinder, for instance, is 100 square inches, it sustains a load of 180,000 pounds when the pressure is 1800 pounds to the square inch. The outer graduations on the high pressure oxygen cylinder gauge dial read "Pounds per Square Inch in the Cylinder;" the IT Davis Bournonvllle Institute FIG. 3. DAVIS-BOURNONVILLE NO. 2 HIGH-PRESSURE OXYGEN REGULATOR. graduations of the next circle read "Number of Cubic Feet in a 100-Foot Cylinder ;" and the inner circle of graduations "Number of Cubic Feet in a 250-Foot Cylinder." Thus, you can tell at a glance both the pressure and the cubic feet remaining in a 100- foot or 250-foot cylinder. If you have a 200-foot cylinder you simply double the reading for a corresponding pressure in a 100- foot cylinder. The front of the gauge is covered with thick glass. This glass is to protect the hand and the dial from mechanical injury and corrosion. A metal diaphragm is provided between the dial and the works, and the back of the gauge is loosely fastened in. The reason for this construction is that we are dealing with very heavy pressures and a delicate apparatus. The Bourdon tube must necessarily be made of thin metal in order to be flexible. Sometimes the metal in the tube cracks. If this should happen the oxygen gas at a pressure of pejhaps 1800 pounds to the square inch would escape into the gauge case, and explode it. If the back was firmly fastened and no diaphragm was pro- vided, the front or glass part would be blown out, the flying splinters of the glass might seriously cut anyone standing nearby or destroy the sight of the eyes. It is better then to let the back blow out in case of accident, as this being metal will not shatter. When the back is blown out the pressure is relieved and there is no danger then of the glass breaking. The safest position to take when opening a cylinder stop valve is in front of the dial. Danger of Testing Oxygen Gauges with Oil In the early days of the industry it was quite a common experience to have the high-pressure gauge upon the oxygen regu- lator explode. Sometimes the operator was not injured and some- times he was badly hurt. Usually the reason for gauge explosions was the fact that users did not understand that oil and oxygen might cause trouble and the gauges were tested upon an oil gauge testing machine, which was a common piece of apparatus in the ordinary shop. The Bourdon tube of the gauge was filled with oil during the test, and then the gauge was directly screwed into the regulator without removing the oil. Nowadays oil is not used in testing gauges because practically all gauge manufacturers appreciate the risk run in so doing. The best practice is always to test the gauge with water and never with oil. The same remarks do not apply to acetylene or hydrogen gauges and regulators because acetylene and oil or hydrogen and oil do not form an explosive mixture, but it is good practice to avoid the use of oil in connection with all regulators, cylinder valves, etc. Soir.eone wlio does not know the difference may see oil upon an acetylene regulator and believe that it would work equally well in connection with oxygen. The principle of the low pressure working gauge is prac- tically the same as that of the high pressure gauge, but as it is intended for lower pressure, it is not so strongly made. No diaphragm is provided and no provision is made for letting the tack blow out, as these precautions are unnecessary. SAFETY DISK Davis Sournonville li>st{tute FIG. 4. HIGH PRESSURE AND WORKING PRESSURE GAUGES AND PRESSURE REGULATOR FOR OXYGEN CYLINDER. Pressure Reducers or Regulators We will now give attention to the gas pressure regulator. This is a highly sensitive apparatus that has required, perhaps, as much thought to perfect its design as any other part of gas welding equipment. The design of the regulator is important because it should function properly at all times and under widely varying- conditions. If the regulator does not regulate you might as well give up trying to weld because perfect regulation is absolutely necessary for success. Choose your regulator with understand- ing of its function, design and construction. Take the best care of it possible but, remember, that like all sensitive apparatus it may get out of order and require readjustment with even the best of care. You can regulate pressure in a steam radiator by opening the valve a little way when you do not want the full pressure. The steam in a radiator condenses as fast as it enters, and the pressure remains nearly constant. But if you undertook to regu- late the pressure in an air container in the same manner by opening a compressed air valve connected to it a fraction of a turn, you would not be successful. The pressure would "build up" in the container and soon reach the same figure as in the source of supply. It is necessary, then, to provide an apparatus that definitely measures ofif a certain flow of gas and checks the flow as soon as the pressure on the low side has reached a pre- determined figure no matter what it may be. The gas regulator does this automatically when properly made and adjusted. Principle of Pressure Regulator Action The diagram, Fig. 1, is intended merely to show the princi- ple of operation of the primitive or simple form of pressure regulator. It is not the regulator that you use, but its general principles are the same. The diagram shows the connection of the regulator to the high pressure oxygen supply. At A is the cylinder stop valve and at B the cylinder pressure gauge, at C the regulator and at D the working pressure gauge. The high pressure oxygen cylinder is at 0. The pressure in this tank when received from the manufacturer is about 1800 to 2000 pounds, and it must be reduced to a working pressure of say ten pounds to be used in the torch. The regulator case is in two parts, and between them is a thin metal or rubber diaphragm F. Connected to the diaphragm beneath is a stirrup-shaped part or yoke terminating in a flat valve, disc G. This covers the opening in the high pressure 10 oxygen supply nozzle. Above the diaphragm is a coil spring, H, seated between the diaphragm and end of the regulator screw, I. The diaphragm normally holds the valve disc, G, up against the nozzle, and shuts off the oxygen from entering the lower chamber. But when you adjust the gas regulator to get the desired working pressure you screw I to the right, thereby com- pressing the spring H and pushing down the diaphragm. This forces the valve away from its seat and permits the high pressure oxygen to enter the chamber and escape through the hose to the torch. When the oxygen at high pressure enters the lower cham- ber, it exerts pressure on the lower side of the diaphragm and tends to close the valve and shut itself off. The operation of setting the regulator is one of compressing the coil spring until it balances the working pressure desired. Your guide is the working pressure gauge D, mounted on the outlet to the torch. The diagram should serve only to give you an idea of the princi- ple of regulator operation. Do not imagine that it truly represents the actual construction of an up-to-date and reliable gas regulator. There are several types of regulators all operating upon the same general principle but differing in design. These types may be classed as direct-acting and indirect-acting regulators. Direct Acting Pressure Regulator An example of the direct-acting gas regulator is the Davis- Bournonville No. 2 high pressure oxygen regulator shown in Fig. 2. The construction and operation are quite similar to that of the diagrammatic form shown In Fig. 1. Gas under liigh pressure enters through the inlet A to E, where the gas passage turns downward and terminates in a screwed nozzle, L. Straddling E and the nozzle is a bronze loop or stirrup, M, attached at the upper end by a hook to the diaphragm F, and carrying below the valve disc G. The disc is held in a pocket in the bottom of the stirrup, and is supported by the pivot pin N. The diaphragm H when not forced down by the coil spring I tends to pull the stirrup or yoke up and holds the valve disc tightly against the flat end of the nozzle L. When the valve disc is against its seat no gas can pass from A into the chamber K through the nozzle L. To permit the gas to flow the screw I 11 is turned to the right, thus compressing the coil spring H, which in turn forces the diaphragm down and unseats the valve disc. The gas then escapes into chamber K and thence to the outlet P, Fig. 3. This direct-acting regulator provides an auxiliary spring; R beneath the stirrup to hold it aganist the seat when the dia- phragm is relaxed. The gas in chamber K presses upward on the diaphragm and counterbalances the pressure of the coil spring H. The adjust- ment of the regulator then is a matter of compressing the spring by the screw until its pressure is approximately equal to the pressure of the gas in pounds per square inch multiplied by the area of the diaphragm in square inches. Line Pressure Regulator of the Indirect- Acting Type Fig. 3 shows the Davis-Bournonville acetylene pressure regulator of the indirect or lever type for regulating the pressure in supply lines. The lever connection between the diaphragm and the inlet valve is so proportioned that the diaphragm end moves about three times as far as the short end controlling the movement of the valve. Thus a movement of the diaphragm center of say one-hundreth inch is reproduced at the gas valve by a movement of only about one three-hundreth inch. The design thus provides a reducing movement by which the opening of the gas valve may be controlled with very small variations. The regulator shown is for operating under the low pressure of 15 pounds per square inch and reducing it to the torch working pressure. The same general design is also provided for oxygen pipe line pressure control. The inlet A is connected to the pipe line, and the gas passes through a screen or strainer and beneath the valve disc G into the cavity K, where it exerts pressure on the diaphragm F, as in all the other types of pressure regulators. The outlet P to the torch is in direct line with the inlet passage. Pressure regulation is effected by means of the regulator handle I and the compression spring H, which must be adjusted so that the pressure of the spring on top of the diaphragm counterbalances the gas pressure beneath and also the pressure exerted by the auxiliary regulator spring Q seated on the 12 auxiliary diaphragm S. Beneath this diaphragm is a space con- nected by a passage to the gas supply pipe. The coil spring T beneath the diaphragm is provided to balance the pressure of spring Q and relieve the diaphragm S. The function of the 2 PLY FABRIC RUBBER DIAPHRAGM ALL BRASS PARTS TO BE NICKEL PLATED EELOA/ MAIN DIAPHRAGM s Beurnonville Institute FIG. 5. DAVIS-BOURNONVILLE LOW PRESSURE ACETYLENE PRESSURE REGULATOR supplementary diaphragm is two-fold: It increases the sensi- tiveness of regulator action on a pipe line distributing system by acting on the valve control level direct. Fluctuations of pressure are in a sense anticipated and provided for before the change of pressure has affected the pressure in the chamber beneath the main diaphragm. It also provides for automatically 13 shutting off the flow of gas in case the diaphragm is burst by over-pressure. The escape of gas from the chamber K through rupture of the diaphragm permits the gas beneath the supple- mentary diaphragm and the spring pressure to act on the re- ducing lever U in opposition to the pressure of spring H and close the valve G firmly upon its seat. The oxygen regulator of the same type is provided with a bursting disc beneath the supplementary diaphragm to prevent the building up of dan- gerous pressures in the line. Care of Regulators The gas passes through the screen chamber of the regulator and is strained by a fine mesh screen before coming in contact with the seat. The seat rnust be tight or the regulator will give all sorts of trouble. A small particle of scale, grit or dirt lodging under the seat will of course make it leak. It can be readily ap- preciated that the regulator will not give close regulation and may in fact become very troublesome if its use is continued with a leaky seat. The pressure upon the diaphragm in that event does not shut off the nozzle completely and the gas continues to flow into the regulator causing the pressure within the low the flow into the regulator causing the pressure within the low pressure chamber of the regulator to climb or build. This is in- dicated by the small gauge. The pressure creeps higher and higher when the torch is shut off until finally the small gauge is broken or the safety disc in the back of the regulator bursts. This safety disc is a simple disc held in position over an outlet of predetermined size by a nut. The thickness of the disc and the size of the outlet determines the pressure at which it will burst. This pressure is usually some- what greater than the maximum working pressure of the regu- lator. It will be appreciated, however, that there is a good deal of variance in the pressure at which the disc will burst even with discs of the same thickness and outlets of the same diameter ; hence, the function of the bursting disc is largely to prevent ex- cessive pressure remaining long within the regulator casing. The disc will burst long before the casings are blown apart but not always before serious damage is done to the gauge. 14 If a regulator leaks, stop using it and see that it is properly repaired before attempting to operate it again. It is not dififir- cult to repair the regulator; as a rule, it is only necessary to renew the seat and consequently a few extra seats should al- ways be available. It is always good practice to maintain a few extra bursting discs so that in case one bursts a new one can be inserted. It should be borne in mind, however, that if the safety disc bursts, you should always test the seat to de- termine that it is tight before putting a new disc in place. A bursting disc is almost always an indication of trouble elsewhere in the regulator. In setting up the joint in the regulator, a little shellac is usually the best material to use. Do not use paint, white lead or oil. High pressure oxygen and oil or any other inflammable material are likely to cause an explosion under certain con- ditions if confined together. A word should here be said' in this connection about the use of a suitable lubricant upon the adjusting screw of the regulator. The regulating screw of the regulator does not come in contact with oxygen or the gas within the regulator as the gas does not pass the diaphragm. There is then no reason why a suitable lubricant should not be used upon this screw. Care should be taken, however, that this lubricant is not allowed to get into the regulator ; it is best in such instances to use tallow or graphite and not oil. Action of Pressure Regulators Reviewed Now to review the action of a gas pressure regulator. When the cylinder valve is opened, gas is admitted to the chamber communicating with the high pressure gauge but it can go no further so long as the pressure regulator handle I is in the re- leased position. But when you turn the regulator handle to the right or in a clockwise direction it screws in and compresses the coil spring directly beyond it. The pressure of the spring is transmitted to the diaphragm and the resulting movements communicated to the valve stirrup or connecting lever, (de- pending on the type of regulator) opens the gas valve and lets the gas escape into the chamber beneath the diaphragm. The pressure immediately overcomes the pressure of the spring, and 15 more clockwise mbvemenf of the regulator handle is required to compress the spring still further in order to counterbalance the gas pressure. Finally you secure the adjustment required. By the process of adjustment you produce a state of balance between the pressure of the coil spring on top of the diaphragm and the gas beneath it. As soon as the conditions one way or another change, the diaphragm rises or falls and the rate of flow of the gas escaping from the cylinder is changed. Obviously, you cannot adjust a pressure regulator cor- rectly unless the needle valve in the torch is open. If you want the working gauge hand to stand at 8 pounds pressure when the torch is in use the needle valve must be opened while you adjust the regulator handle until the hand shows 8 pounds pressure. If you undertook to adjust the regulator with the needle valve closed the chamber beneath the diaphragm would quickly fill and the working pressure indicated would not be maintained when using the torch. The moment you opened the needle valve it would probably fall below the working pressure desired, and thus make necessary readjustment of the regu- lator valve handle. ■ Copyright 1919 by thk Davis- RouRNONViLLE Company 16 DAVIS-BOURNONVILLE OXY-ACETYLENE WELDING and CUTTING COURSE OF INSTRUCTION Lecture THE OXY-ACETYLENE TORCH DAVIS -BOURNONVILLE INSTITUTE JERSEY CITY, N. J. THE OXY-ACETYLENE TORCH The Simple Blowpipe — The Bunsen Burner — The Bunsen Type Blow Torch — The Injector Type Blowpipe — Acetylene Commercial Development — Oxygen Com- mercial Development — Davis-Bournonville Oxy-Acetylene Welding Torch — The Interchangeable Tip System — The Mixing Head or Carburetor — Gas Pressures for Welding — Care of Torch and Tips. The hand oxy-acetylene torch in general use today for weld- ing is a tool or apparatus for mixing a combustible gas with FIG. 2. THE SIMPLE ALCOHOL FLAME BLOWPIPE, THE SIMPLE BUNSEN BURNER AND THE SIMPLE BUNSEN BLOWTORCH. oxygen in certain definite proportions, burning the resulting mixture and directing the intensely hot flame upon the parts to be welded. The Simple Blowpipe The gas welding torch is a comparatively recent develop- ment of the simple blowpipe that you have often seen used, no doubt, by jewelers and watch-makers. Blow-pipes have been used from time immemorial by the workers of gold, silver and brass to melt their solders and brazes. The ordinary blow- pipe is a simple tube curved at the tip through which the workman blows against the flame to increase its intensity. It is generally used with an alcohol lamp both to increase the heat of the flame and to direct the flame point where it is re- quired to heat. A skillful workman can direct the flame with great precision, and make it melt any of the hard solders. The blow-pipe probably antedates the blacksmith's forge. It corresponds to the bellows and is a much simpler means of producing a blast of air. The first blow-pipe, no doubt, was a hollow reed that some primeval man used with astonishing effect on a fire and the bits of virgin metal that he had collected. The Bunsen Burner Following long after the Iblow-pipe came the Bunsen burner or gas torch. This, like some other very valuable de- vices, had its origin in the laboratory. The Bunsen burner differs from the blow-pipe in that the air required to increase the intensity of combustion is so applied that it mixes with the gas before it reaches the zone of combustion. The air Is introduced through a tube at the base of the burner where it mixes with the combustible gas, and the mixture burns at the mouth of the tube with an intense blue flame. The temperature of the flame in the simple Bunsen burner depends on the gases used and their pressure. The proper mixture of air and gas is obtained by adjusting the ring at the base which acts like a stove damper. When the ring is set so that the openings in the ring and tube coincide the maximum amount of air is admitted. Bunsen burners of the simple air induction type are generally made so that an excess of air is admitted when the ring is adjusted for the full opening. The Bunsen Type Blow-Torch The Bunsen burner we have here is a laboratory apparatus of the simple so-called air induction form to demonstrate the principles of combustion. It differs from the commercial Bunsen burner considerably. Brazing burners or torches are generally made so that they may be conveniently handled and usually the air is supplied through a separate hose under some pres- sure. The Bunsen burner referred to consists of two brass tubes united by a cross tube set at a convenient angle, and terminating in a nozzle. At the rear are two stop valves by which the workman can adjust the flow of air and gas and secure the size of flame desired. It is a very simple apparatus, ACETYLENE MEDIUM PRESSURE Davis Bournonville Institute FIG. 3. .SECTIONS OF POSITIVE PRESSURE AND INJECTOR TYPE TORCH HEADS. and is much used for heating, soldering, sweating, brazing, lead burning and other purposes where it is necessary to apply heat locally. When used for lead burning, the Bunsen burner is supplied with pure hydrogen gas and compressed air. In the hands of a skilled lead burner it becomes a most eiifective tool for uniting the lead sheets of acid tanks. This work, by the way, is a form of so-called autogenous welding that has been long in use but which is well known to but comparatively few. It is rather curious to find that all the elements apparently of the modern gas torch were in use years ago; why then has it remained for the extraordinary development of the oxy- acetylene torch to take place in the past fifteen years? The answer is acetylene and oxygen. Acetylene Commercial Development The discovery of a commercial method of making calcium carbide and producing acetylene by Thomas L. Willson in 1892 gave the world a new combustible of extraordinary char- acteristics and value. The commercial possibilities of acety- lene made by slacking calcium carbide were early recognized in the lighting field but its value as a gas for producing intense combustion was not recognized so soon and it was nine years FIG. 4. SMALL STYLE C WELDING TORCH WITH REMOVABLE INTERCHANGEABLE TIPS. later before the first practical oxy-acetylene welding torch was developed by Edmund Fouche of Paris in 1901. The oxy-acetylene torch is another example of valuable com- mercial apparatus that has been m.ade possible by different re- searches and discoveries seemingly far apart but which later were combined with astonishing success. It had long been known that pure hydrogen and pure oxygen burned in the Bunsen burner in the proportions of two parts of hydrogen to one of oxygen produced an intensly hot flame. The tempera- ture produced by the oxy-hydrogen flame is 4000 degrees F. It was for many years the source of the greatest flame intensity within the reach of the chemist and physicist. The first oxy-acetylene torches made by Fouche were very crude affairs compared with the modern welding torch equipped with its interchangeable tips and efficient gas regulat- ing system. Simple and crude as it was it represented tre- mendous steps in the advancement of science. Beginning with the blow-pipe as a means of increasing the intensity of flame the next step was the simple Bunsen burner, burning hydrogen and air. The next step of refinement was the burning of hydrogen and pure oxygen. This, step was a very important one as a supply of pure oxygen will greatly increase the in- tensity of any flame. But the next step in the development of the oxy-acetylene torch could not be taken as acetylene gas was not available. But, when Willson discovered acetylene, FIG. 5. SHOWING HOW GASES MAY PASS THROUGH MIXING TUBE WITHOUT MIXING IF NOT BROKEN UP. then Fouche could develop his torch. The development of the liquid air process of deriving oxygen from the atmosphere a few years later completed a cycle of discovery which made possible a great commercial development. It has transformed the old art of welding and made it one of the most advanced methods of fabrication. ■ ■ The Davis-Bournonville Oxy-Acetylene Welding Torch We have in the foregoing tried to give you an idea of the importance of the oxy-acetylene torch development and what it has meant from scientific standpoint. The first oxy-acetylene torches used in this country were introduced by Mr. Eugene Bournonville, formerly of the Davis-Bournonville Company, and Mr. Augustine Davis, president of the company, was one of the chief pioneers in its commercial development. Here is a Davis-Bournonville oxy-acetylene welding torch. It is a simple device, consisting of a handle, two needle valves, two tubes for the oxygen and acetylene, head and tip. The tubes are silver soldered in the head and fixed in the handle so as to give them stability and strength. The head is made with a conical seat and is threaded at the mouth for a nut which holds a tip with a conical head in position. The upper tube is connected to the oxygen supply as you will see by tracing the black hose to the oxygen cylinder. The lower tube is joined to the acetylene cylinder by the red hose. The Interchangeable Tip System One of the very important and valuable features of the Davis-Bournonville torch is the system of interchangeable tips. There are many styles and sizes of interchangeable tips pro- vided for this torch, all of which designed for a given size of torch may be used in the same torch head at will. Hence, you have the means of producing many sizes of flames from the smallest to the largest required in commercial welding for which a given style of torch is adapted. The choice of tip is very important as the size of flame should be proportional to the thickness of material to be welded and as the size of flame is governed by the size of tip, you must consult the table giving the sizes of tips for various thicknesses of metal until you become so familiar with torch practice that you will instinctively use the right size tip. The Mixing Head or Carburetor FIG. 6. LARGE STYLE C WELDING TORCH AND TIPS. The intimate mixing of the acetylene and oxygen gases is accomplished in the conical end of the tip where it fits into the torch head. This part is identical in function with the car- buretor of a gas engine of a motor car. The carburetor pro- vides for mixing a certain definite amount of air with the vaporized gasoline thus forming a combustible and explosive mixture. The carburetor in the torch tip is the mixing cham- ber where the oxygen flowing longitudinally through the tip meets the cross currents of acetylene gas flowing in through the holes in the sides. The cross currents form a vortex or whirlpool, mix and flow through the longitudinal passage to the end of the tip where they burn. The diameter of the holes in the tip and the pressures of the respective gases determine the quality of the mixture. The diameters of the holes are graded, and the tips are numbered to correspond. A low number tip means small diameter gas pas- sages and a small flame suitable for welding thin metal, where- as a high number tip means comparatively large gas passages and a large flame suitable for welding thicker metal. The following table compiled by the Davis-Bournonville Company- represents the result of years of experience in welding practice. Acetylene and Oxygen Pressures Davis-Bournonville Style C Welding Torches with Style 99 and 100 Tips Thickness Acetylene Oxygen Acetylene* Oxygen* Tip of Metal Pressure Pressure Consumption Consumption No. Inches Lbs. Lbs. Per Hour Per Hour 00 /Veryl iLight/ 1 1 0.6 CU. ft. 0.8 CU. ft. 1 2 1.0 1.3 1 32 16 1 2 3.2 3.7 2 J 3_ 16 32 2 4 4.8 5.5 3 A-H 3 6 8.1 9.3 4 li-% 4 8 12.5 14.3 5 K-A 5- 10 17.8 21.3 6 ^-% 6 12 25.0 28.5 7 i-,-y2 6 14 33.2 37.9 8 Vi-y^ 6 16 42.0 47.9 9 %-% 6 18 58.0 65.9 10 /4-up 6 20 82.5 94.0 11 r Extra \ 8 22 89.0 101.2 12 1 Heavy/ 8 24 114.5 130.5 Operators frequently adjust the pressure regulators from one to two pounds above the figures given in the table to allow for gauge variations and drop of pressure when the gases are supplied in cylinders. * Gas consumption per hour is the maximum with torch burning continuously. This table gives the tip number, the thickness of metal for which it is suited, the acetylene pressure and the oxygen pressure and the hourly consumption of each gas when torch is used continuously. The No. 00 tip should be used in the Small Style C torch for welding metals of the thinnest gauges only. It uses very little gas and the regulators should be set for one pound per square inch acetylene pressure and one pound oxygen pressure. The next tip is No. 0. This also is used only on very thin materials and little gas pressure is required. The acetylene pressure should be one pound, the oxygen pres- sure two pounds. The No. 1 tip is suitable only for light gauge metals from 1/32 to 1/16 inch thick. The gas pressure should be the same as for the No. 0, or one poimd acetylene and two pounds oxygen. 10 The tips, as you already know, are readily interchangeable. To change tips is simply a matter of loosening the tip nut, re- moving the tip and replacing it with another and screwing the nut firmly to place. The operation takes but a few moments, and there is no excuse for not changing the tip and using the one best suited to the work. Even if you have only an inch of welding to do it is better to change the tip than to fuss along with a flame too large or too small. It is a bad habit to fall into, and should be avoided. You will note in the table that the No. 6 tip which is pro- vided for use with the large Style C torch should be used for metals from 5/16 to ^ inch thick, and that the acetylene pres- sure should be six pounds and the oxygen pressure twelve pounds. The acetylene pressure is the same as the number of the tip and the oxygen pressure is two times the number of the tip, or twelve pounds. This rule holds for all tips from No. to 6 inclusive but it does not hold true with the higher num- bers of tips. The No. 12 tip requires an acetylene pressure of 8 pounds and oxygen pressure of 24 pounds. However, the rule of setting the acetylene pressure to the number of the tip, and making the oxygen pressure two times the number of the tip holds true throughout a large range of commercial welding. When using gases from acetylene and oxygen cylinders it is customary to break the rule to the extent of making the working pressures slightly more than the theoretical or table pressures when starting to weld. This is done to compensate for the loss of pressure as the gases are used from the cylinder. Regulators are likely to let the working pressure drop as the cylinder pressure falls ; hence it is customary when using gases from cylinders to set the regulators to one or two pounds above the table pressures. But when the gases are supplied through the pipe lines, as they are in the welding institute workroom, they are under nearly constant pressure, and you should set the regulators closely to the pressures specified in the tal)le. Care of Torch and Tips When changing the tips be careful to wipe the tip clean so that no dust or foreign substance will remain on the conical 11 ground seat and prevent it fitting closely in the head. If this precaution is not observed you are likely to have trouble from the gases leaking by the tip and causing flashbacks and other troubles. Always keep the tips standing vertical in a suitable box or holder, and keep them covered. This will insure the conical ground seats being protected from bruising and col- lecting dust. The needle valves seldom give trouble. If one should de- velop a leak it is doubtless due to dirt or scale getting on the seat and preventing the conical point seating properly. It can be readily removed and the foreign substance cleaned out. In general, however, avoid taking apart unnecessarily. Follow the very good rule of not tinkering with any apparatus when it does not require it. The oxy-acetylene torch is a simple and durable apparatus but it is not fool-proof. Always hang it up when through with it. Don't let it lie around on the bench as something may fall on it and spring it out of shape. Never use the head as a hammer. If you knock the work around with it you are likely to injure it and cause trouble. The head casting is bronze and though the bronze is of high tensile strength and great dur- ability it is easily dented by a blow. If dented the conical seat will be distorted and the tips will not fit ; consequently the gases will leak by the tip and cause trouble. The late model torches have drop-forged heads and these also should be handled carefully. When using the torch take good care of the end of the tip. If you let it drop occasionally into the puddle you are likely to cause a flashback or melt the end of the tip, distort its shape and perhaps clog the hole. A good workman is known by the way he cares for his tools, and the oxy-acetylene welding operator is no exception to the rule. Never attempt to remove the tubes in the head. They are sweated in with silver solder and can only be taken apart by an expert who is provided with the proper tools and apparatus. If your torch requires a new head, it should be sent to the factory where it will be inspected and the defective parts will be replaced. 12 Questions 1. What is the form of the simple blowpipe used by- jewelers? 2. What is a simple Bunsen burner? 3. Where is the oxygen taken from to supply the flame of a simple Bunsen burner? 4. What is the source of oxygen in a shop Bunsen torch using illuminating gas and compressed air? 5. Who discovered the oxy-acetylene blowpipe? 6. What is the blowpipe called in America? 7. What is the mixing chamber like in principle? 8. Where is the mixing chamber in the Davis-Bournon- ville torch? 9. Is the interchangeable tip system advantageous? Why? 10. What are the needle valves? The handle? The tubes? The head? 11. How is the tip held in the head? 12. What pressures of gases are required for welding ^-inch steel? 13. What size of tip should be used for welding ^-inch metal? 14. How is the head secured to the tubes? 15. What is the danger of letting a flashback burn in the tip? 16. How close should the tip be held to the metal when welding? 13 Not es 14 Notes 15 Copyright 1919 by the Davis-Bournonvii,t.e Company DAVIS-BOURNONVILLE OXY-ACETYLENE WELDING and CUTTING COURSE OF INSTRUCTION Lecture EXPLOSIVE GAS MIXTURES- FLASHBACKS AND BACKFIRES DAVIS -BOURNONVILLE INSTITUTE JERSEY CITY, N. J. Copyright 1919 by the Davis-Bournonvili,e Company EXPLOSIVE GAS MIXTURES-FLASH- BACKS AND BACKFIRES Combustion of Common Fuel Progressive — Combustion of Air and Combustible Gas Mixture Sudden and Explosive — Coal Mine Explosions Due to Mixture of Mine Gas and Air — Flame Propagation — Principle of Davy Mine Safety Lamp — Application in Oxy-Acetylene Torch — Flashbacks and Backfires — Importance of Correct Procedure in Starting to Weld — How to Set up the Apparatus and Blow^ Out Foreign Substances — What to Do in Case of Stoppage. When a candle is lighted the wick takes fire and the wax beneath melts and forms a pool of liquid which saturates the wick and feeds the flame. As the candle burns it becomes shorter and shorter. The burning or combustion of the wax or wick is progressive and practically constant. So it is with ordinary fire. If we start a fire of sticks and shavings the fuel is progressively consumed. The rate of combustion may not be constant, however, as that will depend on how the fire is built and whether it is in a firebox or open grate, but the fuel does not burn all at once. It burns until the wood is gone, and then it goes out. When you light a gas- jet, the rate of combustion is constant. The gas burns as it escapes from the jet; the flame remains practically the same size, and the consumption of gas is a certain number of cubic feet per hour. Combustion of Air and Combustible Gas Mixture Sudden and Explosive But if we let some gas escape unburned into a bottle and then apply a match to the opening we get instantaneous combustion and an explosion. The gas mixes with the air when it enters the bottle and forms a mixture that burns instantly. When the match was applied to the mouth of the bottle the flame spread instantly in all directions, and the gas and air combined in a fraction of an instant. The re- sult was a tremendous expansion of the air and gas due to the heat produced, and a loud noise or report. Explosive mixtures of gas and air are always danger- ous and should be avoided. Never look for a gas leak in the cellar with a lighted candle ; you are likely to be a subject for the coroner if you do. The gas escaping into the cellar mingles with the air and forms an explosive mixture which may be of sufficient volume and power to blow the house from its foundation and kill the occupants. Coal Mine Explosions Due to Mixtures of Mine Gas and Air Coal mine explosions occur in coal mines in which ac- cumulations of combustible gases are released by removal of the coal. The explosion is caused by the accidental ignition of the mixture of this coal gas and the air which has reached the explosive state. It is a curious fact that a mixture of combustible mine gas and air is not explosive when the pro- portion of gas to air is much greater than a certain figure SOLID FUEL WOOD OR COAL,TO GAS SLOW COMBUSTION |1 jll ,ll />.■' All SOLID FUEL TALLOW OR PARAFFINS, TO GAS SLOW COMBUSTION AIR AND GAS MIXED INSTANTANEOUS EXPLOSION Davis Bournonville Institute FIG. 1. OPEN FIRE, CANDLE FLAME, GAS JET AND INSTANTANEOUS COMBUSTION COMPARED. generally about 10 to 12 per cent; neither will a mixture of mine gas and air explode if less than a certain figure, say about 8 to 9 per cent. While the over-rich mixture is non- explosive up to a certain figure it again becomes explosive when very rich. Thus, we have the condition first of the non-dangerous mixture of gas and air up to about 8 or 9 per cent dilution depending on the quality of the gas ; from 8 to 12 per cent is a highly dangerous mixture ; and from 12 per cent to about 80 per cent or 85 per cent may not be violently explosive but slightly greater dilution may again create an explosive condition. Acetylene gas, however, forms an explosive mixture with air when the mixture reaches 3 per cent acetylene. All gas mixtures in closed places are potentially dangerous and should be treated very cautiously. The odor of acetylene is noticeable when a very small per- centage is present, and the warning should never be disre- garded in closed places. Flame Propagation — Principle of Davy Safety Lamp Extensive experiments conducted by the Bureau of Mines to determine the explosibility of gas mixtures have not only determined the percentage of gas mixture that is dangerous but they have also determined the rate of flame propagation in an explosive mixture. Many hard coal mines would be un- workable were it not for the Davy safety lamp. The safety principle of this lamp was discovered by Humphrey Davy many years ago and it has proved to be one of the most valuable safety devices. The safety feature of the Davy lamp is very interesting as it has an important bearing on the action of the oxy-acetylene torch. Humphrey Davy discov- ered that an open flame in the miner's lantern could be made safe by surrounding it with a fine mesh metal gauze — in other words, woven wire cloth. The gas and air entering the lan- tern through the gauze burns quietly and without explosive effect. Remove the wire gauze envelope and immediately the surrounding gas laden air takes fire and explodes. The reason for this apparently strange action is easy to understand when explained. Flame is incandescent gas ; it is gas in the state of combustion. If the flame is cooled it dis- appears and no longer ignites an adjacent combustible mix- ture. The metal gauze cools the flame spreading from the light and prevents its propagation. We have here two candles. One is lighted and the other is not. When we touch the flame of the lighted candle to ACETYLENE FIG. 2. SHOWING THREE CONDITIONS OF FLASHBACK, TWO OF WHICH HAVE DEVELOPED BACKFIRE. the wick of the unlighted one it immediately takes fire and burns. Now we will blow one candle out and bring the flame of the other close to the wick but not touching it. It immediately takes fire. Why? The gas escaping from the hot wick is combustible and the adjacent flame starts combustion. Now we will blow the candle out again and bring the lighted one close to the wick as before but with this fine wire gauze between. The unlighted wick no longer catches fire when the flame is brought close to it. In fact, it will not take fire when the gauze is placed directly against the wick, and the lighted candle is brought close up to the gauze. Why is this? The reason is that the gauze being metal and compara- tively cool reduces the temperature of the flame below the igniting point. The metal radiates the heat rapidly and we could hold the flame close to the wick with the gauze be- tween for a long time before the metal would get hot enough to fire the unlighted wick. This, then, is the principle of the Davy safety lamp. The explosive air and gas passes through the gauze to the flame and burns but the flame cannot propagate through the gauze because the moment it reaches the gauze it cools below the igniting point. The gauze, in fact, is a refrigerator or icy barrier that stops the flame and thus preserves the miner from the dangers of a mine explosion. BURNT METAL PASSAGE OBSTRUCTED FLASH BACK FLAME PROPAGATION GREATER THAN VELOCITY OF ESCAPING GAS Davis Bournonville Institute FIGS. 3 AND 4. — SHOWING NORMAL FLAME AND FLASHBACK FROM EXTERIOR. Application in Oxy-Acetylene Torch You have the Davy principle in effect in the tip con- struction of the oxy-acetylene torch. The holes through which the combustible gases enter the mixing chamber are of small diameter and comparable in dimension to the mesh of the wire gauze in the safety lantern. If the flame tends to fol- low the mixture of oxygen and acetylene back into the tip and into the head the tendency is checked ordinarily by the rapid flow of the gases and the cooling effect of the tip. Under normal working conditions the head and tip are com- paratively cool and the flame entering the tip is extinguished. Moreover, the velocity of the escaping gases is high, and in excess of the flame propagation rate. Should, however, the tip become very hot and the flow of gases be momentarily checked, then it is possible for the flame to enter the tip and pass back into the mixing chamber and burn there. This is called a flashback. If a flashback penetrates beyond the mixing chamber into the torch handle, hose, or even to the regulator chamber, it is called a backfire. Flashbacks and Backfires The terms flashback and backfire are loosely interchanged but there is a well defined difference which should be clearly understood by all using the oxy-acetylene apparatus. The first is a more or less petty annoyance due to local con- ditions, while the other is serious and demands an investiga- tion to determine the cause. To make the distinction clear we will again state the action of each and the causes that produce them. A flashback is the snapping out of the flame and pene- tration of the flatne into the torch tip or mixing chamber. It is generally caused by an obstruction in the tip such as a globule of metal adhering to the end or by holding the tip too close to the puddle and thus obstructing the flow of gas so that the flame is able to propagate back to the mixing chamber. A flashback is checked by shutting off the oxygen needle valve. The fire in the torch is immediately extinguished and the pure acetylene gas issuing from the tip may be relighted and then the oxygen needle valve opened and adjusted as before. Overheating of the tip due to use on a preheated casting or long continued welding in a closed place may cause popping back. Cooling of the tip may then be necessary but ordinarily the Davis-Bournonville torch never requires dipping into a pail of water to keep it cool. A backfire is a much more serious matter than a flashback as it may burn or burst a hose and scare the operator. In a manufacturing welding room where operators are close to- gether a bursting hose might cause a panic and result in the injury of some of the welders, especially if girls. A back- fire results in the penetration of the flame through the torch into the handle, hose or pressure regulator and is caused by an accumulation of mixed gases due generally to faulty manip- ulation of the cylinder stop valves, improper regulator ad- justment, incorrect procedure of turning on and lighting gases or dipping the tip into the puddle. It is of the utmost im- portance that welding operators be required to follow a fixed procedure in turning on and lighting the torch both for their own safety and the safety of others. Even though a backfire may cause no more damage than the bursting of a hose, that is serious enough. A burst hose means the destruction of property and time lost in replacing it. It is a reflection on the operator's ability and may cause the uninformed observer to conclude that there is something radically wrong with the whole apparatus. We have given considerable attention to the principle of the Davy safety lamp. Do not get the idea that the metal gauze strainers in the gas regulators are effectual barriers to flame propagation, however, because unfortunately they are not. The heat of the oxy-acetylene backfire is so intense that the cooling effect of the gauze is overcome, the gauze melted and the flame passed on beyond. This will give you an idea of the intensity of the heat at your command. The gauze strainers may tend to check the flame but they can- not be depended on with certainty. The function for which they are designed is to stop scale and dirt from: entering the torch and clogging the tip. The illustration. Fig. 2, shows in diagram four conditions of combustion that may develop in the oxy-acetlylene torch apparatus. The normal condition is shown at A for a weld- ing torch in which acetylene is supplied under five pounds pressure and oxygen under ten pounds pressure. The pro- portions of the mixing head or carburetor and the outlet are such as to give a stable flame. But at B the balance has been lost due to overheating of the torch head, obstruc- tion in the tip or an excessively oxidizing flame. The flame has popped back or propagated to the mixing chamber where it continues to burn. This is a flashback. A more serious condition is shown at C which may develop as a consequence of holding the tip immersed in the puddle causing a flash- back and prolonging the abnormal state. The outlet is stopped and the oxygen pressure being in excess of the acety- lene pressure tends to equalize which results in the oxygen flowing back into the acetylene tube and burning there. This is the propagation of the flashback into the hose and is known as a backfire. A condition similar to C is shown at D but the oxygen pressure being less than the acetylene pressure the flashback is propagated into the oxygen hose. This is a serious hazard as it invariably ends in burning the oxygen hose and spat- tering burning molten rubber over the surroundings. It is an inherent hazard of the equal pressure or balanced pressure torch. The three conditions shown are the result of a flash- back and its propagation. A backfire is regarded as a propaga- tion of a flashback into mixed gases, and may take place in the torch handle, hose, regulator or even as far back as the acetylene generator if proper safeguards are not provided in the acetylene gas line. Importance of Correct Procedure In the lecture "Regulating Gas Supply" detailed instruc- tions were given for opening the valves and gas regulators. You were told to open the cylinder valve on the oxygen cylinder first, and to open it very slowly but to open it full. The reason for opening it slowly is that a sudden rush of oxygen gas at a pressure of 1,800 or 2,000 pounds per square inch may injure the diaphragm in the gas regulator and make 10 it unworkable. The reason given for opening the valve as far as it will go is to prevent leakage around the stem. The cylinder valve is made with two seats, one of which acts in the ordinary manner to check the flow of gas while the other backs up against another seat beneath the stufhng-box end and prevents the leakage around the stem when the valve is open. You were directed to open the oxygen valve first and to regulate the oxygen regulator while the oxygen needle valve is open. The reason for having the needle valve open is that you will be unable to adjust the working pressure accurately if the gas is not escaping the same as when being used. The reason for opening the oxygen valve first and regulating the flow is to prevent forming a mixture with the combustible in the torch tubes or hose. Oxygen is not com- bustible ; it supports combustion only. You cannot light the oxygen gas when it is escaping from the tip alone, but you can light the acetylene when it is escaping from the tip alone — because the flame takes the necessary oxygen from the air. Now consider what might happen if the acetylene gas valve was opened first and the acetylene regulator was ad- justed first. The torch would be filled with acetylene gas, and when the oxygen was admitted the operator might not let it flow long enough to clear out all the acetylene and oxygen mixture. The result may be a disagreeable backfire when the gas is lighted. Even if no damage results the effect on the nerves is something to be avoided. Causes of Trouble Reviewed To reiterate, there is little danger of flashbacks and back- fires if the operator knows his business and attends to it. He needs only to follow the rules in opening the valves, regulating the gas supply and manipulating the torch to avoid them. Under normal conditions the flame cannot enter the torch or hose. The velocity with which the gases escape is greater than the speed of the flame traveling in an explosive mixture. The gas coming out pushes the flame ahead of it and keeps it at the tip where it belongs. Experiments have 11 shown just how quickly a flame spreads in an explosive gas mixture. This rate or speed called the "speed of flame propagation" is from 300 to 600 feet per second, depending on conditions, the gases, etc. We can burn an explosive mixture of acetylene and oxygen at the tip if the speed of the gases escaping is greater than the rate of flame propa- gation. If the speed of the gases escaping is greater than the rate of flame propagation, the flame cannot enter the tip and follow back into the hose ; the gases are coming out faster than the flame can travel against them. Keep this fact in mind and avoid doing anything that removes this safeguard. When the valves are properly adjusted a flashback or backfire can occur only when something checks the flow of gas or the head and tip become overheated. If you hold the tip too close to the metal you may check the flow of gas so that the flame can enter the tip. This will cause the flame to pop out sometimes, but very rarely will it follow back into the hose. How to Set Up Apparatus and Blow Out Foreign Substances If care is not taken to blow out the hose before connect- ing up, loose dirt may enter the torch and clog the tip so that the gas cannot flow freely. The operator should follow a certain set procedure when setting up welding or cutting apparatus as follows : 1. Before attaching the oxygen regulator to the cylin- der "crack the valve" to blow out any dirt that may have lodged in the opening. 2. Clean off any dirt that may have lodged on the nipple connection of the regulator, and shake it with the opening down so that any loose dirt within will rattle out. 3. Connect the regulator to the gas cylinder and crack the cylinder stop valve slightly and blow gas through the regulator for a moment. 4. Connect the hose to the regulator and again blow through. 5. Connect the hose to the torch, open the needle valve and again blow through. 12 6. Repeat the procedure with the acetylene regulator and hose connection. If in the course of welding or cutting the torch begins to give trouble and the cause is suspected to be some foreign substance, proceed as follows to remove it : Disconnect the hose from the torch and blow each hose out separately. Remove the torch tip and open the needle valves, and insert the nipple of the oxygen hose into the head and blow through. This should remove any ordinary obstruction. Above all, avoid getting excited when things don't work properly. Remember always that fixed laws govern the work- ings of the oxy-acetylene apparatus the same as of every- thing else. If it refuses to work satisfactorily there is a cause, and it is up to you to find it and remedy the trouble. Questions 1. What sort of combustion takes place in a coal fire? 2. Why does a mixture of air and gas explode? 3. What is an explosion? 4. What is the rate of flame propagation in a coal mine explosion? 5. Why does the Davy safety mesh prevent firing ex- plosive mixtures in mines? 6. Is the Davy screen effective in oxy-acetylene ap- paratus? Why? 7. Does the cooling principle apply at all in the torch? 8. What is a flashback? 9. In what respect does a flashback differ from a back- fire? 10. What should be done immediately when the flame pops back? 11. How many conditions of flashback and backfire are recognized? 12. Is a certain set procedure important in starting to weld? 13. What should be done first in setting up the equip- ment? 14. How do you blow out the torch if it becomes stopped ? 15. What advice should be observed when things go wrong? 13 Notes 14 DAVIS-BOURNONVILLE OXY-ACETYLENE WELDING and CUTTING COURSE OF INSTRUCTION Lecture HEAT AND TEMPERATURE DAVIS -BOURNONVILLE INSTITUTE JERSEY CITY, N. J. y//.-v/.\y. ■? TEMPERATURE-2800'^ F LARGE VOLUME OF HEAT Vu.^^% MIXING CHAMEER_J ^ Davis Bournonville Institute HEAT AND TEMPERATURE OF OXY-ACETYLENE TORCH AND BOILER FURNACE COMPARED HEAT AND TEMPERATURE Heat and Temperature Not the Same — Radiation, Convection and Conduc- tion — British Thermal Unit Measure of Heat — ^Temperature Measured with Thermometers or Pyrometers — Expansive Effect of Heat — Specific Heat — Oxy- Acetylene Torch Means of Producmg High Temperatures. You probably think of heat and temperature as one and the same thing, but they are not the same ; it is highly important that you clearly understand the difference and are able to make the distinction. You will understand the oxy-acetylene torch action much more clearly when you realize the difference between a large fire and a very hot fire. A Large Fire may be no Hotter than a Small One — Radiation — Convection and Conduction A large fire is not necessarily a very hot fire. A large fire fire gives off a great amount of heat, but the temperature may never rise much above 2000 degrees Fahrenheit. When an open fire, burning any combustible like wood, rises to a certain tem- perature it can become no hotter, no matter how long it burns or how much fuel is added. There is a limit to the intensity of combustion, but the limit to the amount of heat produced is the amount of fuel consumed. If heat must be provided for a small room, a small coal stove or a gas-heater will be sufficient, but if a whole house is to be heated a large furnace must be used. The temperature of the furnace fire will be little higher, if any, than the temperature of the small coal fire, but the furnace will give off a much greater volume of heat, and it wih warm more rooms than the small coal stove, because more coal can be burned in the furnace than in the small stove. Heat is dissipated by radiation, convection and conduction. Heat rays are invisible. A fireplace warms a room by radiated heat chiefly, the rays from the fire give the body the sensation of warmth and comfort on the side facing the fire, even when the air in the room is comparatively cold. A steam radiator heats the air and radiates invisible heat rays also. The fireplace fire is inefificient because most of the heat goes up the chimney with the smoke and gases of combustion. The steam radiator heats chiefly by convection ; the air circulating over it finally fills the room and all parts become warm. Heat travels by conduction in a metal piece. If one part is made very hot the heat flows to the colder parts and warms them. When you hold the red hot end of a steel bar near your face you feel radiated heat. If you hold your hand over the bar you will feel hot air rising from it; that is heat of convection, and if you hold the bar long enough it will become unpleasantly hot at the lower end. That is due to conducted heat. Remember that heat tends always to equalize the temperature by traveling from hot zones to cooler ones. Heat Can Be Measured The practical man is likely to look upon science as being some- thing impractical and beyond his comprehension. But that is a very erroneous view. While some scientists are impractical in workaday matters they have, as a class, found out the methods of weighing and measuring imponderable substances and unseen forces, and thus making them available for practical purposes. Now when you can measure something or weigh it you ca i deal with it understandingly. It no longer is mysterious. Electricity was a very mysterious and incomprehensible force until the scientists learned how to produce it, to measure its capacity, to weigh its force and to control and direct it. Then the practical man could apply it to useful purposes. Heat can be measured and the amount of heat in a pound of coal may be accurately determined. Heat is measured by thermal units, or in calories in the French system used by scien- tists. A British thermal unit is the amount of heat required to raise the temperature of 1 pound of water 1 degree Fahrenheit. If one pound of water is raised in temperature 100 degrees it has absorbed 100 British thermal units. (Abbreviated to B. T. U.) A pound of clean coal when so burned as to secure perfect com- bustion generates about 13,000 B. T. U., a pound of kerosene about 20,000 B. T. U., and a pound of acetylene about 23,000 B. T. U. Authorities differ on these figures, especially on acety- lene. Thermometers Used To Measure Temperatures The intensity of the source of heat is the temperature. Tem- peratures are measured with thermometers or pyrometers. A glass thermometer may be used when the temperature is comparatively low, say up to 400 or 500 degrees Fahrenheit. High temperatures, such as are encountered in a furnace, are measured with pyrometers. The common form of a pyrometer comprises two dissimiliar metal wires which are twisted together at one end, and separated by some insulating material like porce- lain that withstands a high heat. The twisted ends of the wires are thrust into the furnace. The other ends are connected to a millivolt meter which records the feeble electric current produced by the metal couple when highly heated. The graduations on the the dial of the millivolt meter indicate the temperature in degrees. Another form of pyrometer works on the optical principle. The light emitted by the furnace is compared with the filament of an incandescent electric lamp, and by this comparison the observer is able to tell the temperature of the furnace. The temperature of this room is measured by a glass ther- mometer. It registers about 68 degrees Fahrenheit. This is a Fahrenheit thermometer because it has the Fahrenheit scale. The two standards of measuring points of the Fahrenheit scale are the melting point of a mixture of finely chopped ice and salt, and the boiling point of pure water at sea level. The melting point of ice and salt is called zero. The space on the tube between the zero point and the boiling point is divided into 212 graduations called degrees. Pure water freezes at 32 degrees on the Fahren- heit scale. Therefore there are 180 degrees between the freezing and boiling points. Thermometer Scales The Fahrenheit scale is commonly used in shops and factories and is the common scale of every-day use to indicate the tem- perature outdoors and indoors. There is another thermometer scale commonly used in scientific work called the Centigrade scale. In the Centigrade scale the zero point is the freezing point of pure water at sea level and the boiling point is the other ex- treme of the scale. The space between the freezing and boiling point is divided into 100 parts, each of which is called a degree. There is still another thermometer scale — the Reaumur — but little used and seldom referred to in text books. The zero point is the temperature of freezing pure water and the space between this and the boiling point is divided into 80 parts or degrees. In the Fahrenheit scale there are 180 degrees between the freezing point and the boiling point of pure water at sea level, while in the Centigrade scale there are only 100 parts. Hence, it is apparent that the Fahrenheit and Centigrade degrees are not the same ; 1 degree Centigrade is equal to 1.8 degree Fahrenheit. The Centigrade scale is generally used, as we have said, for scien- tific work and the Fahrenheit scale is used for common purposes. When temperatures are mentioned hereafter in these lectures they will be in the Fahrenheit scale. The abbreviation for Fahrenheit is F. and for Centigrade C. From the foregoing it should be clear that temperature may be compared to pressure while heat may be compared to volume or quantity. We may use the water pipe analogy. If a water pipe carries water under pressure, the pressure can be determined by the use of a pressure gauge. The temperature of the water wOuld be determined by a temperature gauge or thermometer. The amount of water flowing through the pipe could be measured by a meter. We have no simple meters for heat but you can imagine that the amount of heat could be measured by something like a meter. We are, in fact, able to determine the amount of heat in a given volume of water, very readily from the tem- perature, the weight of the water and its specific heat. Specific Heat Specific heat is the quantity of heat required to raise the tem- perature of a body 1 degree in comparison with water; water is the standard. The specific heat or heat capacity of metals is less than that of water. The specific heat capacity of some metals is much greater than others. This has an important effect on welding with the oxy-acetylene torch. A metal that has high specific heat, or heat capacity is more difficult to weld than one that has low specific heat. This is a characteristic quite different from the melting point. The melting point may be comparatively low while the specific heat is high as is the case of aluminum. What has been said should make it clear that heat and tem- perature are not the same, but they are closely related. There can be no heat without temperature, and no temperature without heat. The higher the temperature the more rapidly will the heat flow to bodies of lower temperature. The higher the temperature of your torch flame the more quickly will it melt the steel or cast iron. The temperature of the hottest part of the oxy-acetylene flame is about 6300 degrees F. It is so high that almost all solid substances melt and run like water when exposed to it. The tem- perature is the highest known with the exception of the electric arc. The temperature of the electric arc is supposed to be about 7800 degrees F. Expansion and Contraction Changes of temperature affect the length, breadth and thick- ness of a metal piece. If the temperature is raised the part ex- pands and if the heat is abstracted and the part cools it shrinks. The changes are proportional to the changes of temperature within a wide range of limits. If you know that a steel bar two feet long is to be heated up 1000 degrees F. you can calculate very closely the amount of expansion, and make allowance for it. The change in length due to change of temperature is called the coefficient of expansion or contraction, and it has been de- termined for all the metals. The coefficient is a factor generally expressed as a fraction of inch and for 1 degree. A cast aluminum bar expands over 5/33 inch to the foot when heated from 60 degrees F. to the melting point, or 1218 degrees. Amount of Heat Produced by Torch is Small Notwithstanding the fact that the hottest part of the oxy- acetylene torch flame has a temperature of over 6000 degrees F. the ajiwunt of heat given off by a torch flame is comparatively small. We can get much more heat from the blacksmith's forge because we burn much morel' fuel, and produce more thermal units in a given time, but we cannot get the high temperature. The temperature of the hottest forge fire is only about 2800 to 3000 degrees F. When large masses of iron require heating to moderate tem- peratures, the economical method is to use a coal fire or an oil flame. The cost of the heat will be much less than when pro- duced with oxygen and acetylene. But when the metal must be melted and welded the high temperature flame is required. Now you begin to realize that you have in the oxy-acetylene torch a tool or instrument of extraordinary quality. Its flame is one of great intensity but remember that the zone of great in- tensity of temperature is confined to the white hot cone. The flame adjacent is comparatively cold. The cone tip is keen like a razor blade while the remainder is "dull as a hoe." When manipulating the torch then it is plain that the tip of the cone — the keen razor blade — should be applied to the parts you want to melt. Don't "hoe around" with the other part of the flame if you want to make progress. Questions 1. Are heat and temperature the same? 2. What do you understand by radiation, convection and conduction? 3. What are the measures of heat? 4. What is a British Thermal Unit? 5. What are the means used to measure temperatures? 6. What is the common thermometer scale? 7. What is the boiling point of water on the Fahrenheit scale ? 8. What is the effect of heat on a bar of steel? 9. What temperature is produced by the oxy-acetylene torch flame? 10. Is the amount of heat given off by the torch flame large compared with that produced by the blacksmith's forge? DAVIS-BOURNONVILLE OXY-ACETYLENE WELDIING and CUTTING COURSE OF INSTRUCTION Lecture OXYGEN AND ITS MANUFACTURE DAVIS -BOURNOINVILLE INSTITUTE JERSET CITY. N. J. Copyright 1919 by thb Davis-Bournoxvii,i,e Company OXYGEN AND ITS MANUFACTURE Oxygen a Common Element — Methods of Producing Oxygen — Liquid Air Process — Oxygen Cylinders, Tanks or Bottles — Weight of Oxygen and Oxygen Cylinders — Electrolytic Process of Producing Oxygen and Hydrogen — Pure Water Required for the Electrolyte. From the lectures on "Combustion" and "Flame and its Structure" we learned something about oxygen and the im- portant part it plays in the subject of combustion in general. The oxygen in the atmosphere is the supporter of life and fire. Because of its dilution the oxygen in the atmosphere cannot be made to develop the high temperature possible from the use of pure oxygen. Hence, methods of separating or producing oxygen in the commercially pure state have been very im- portant to the art of oxy-acetylene welding. In this lecture we propose to briefly describe how oxygen is manufactured and compressed into steel bottles for distribution and use. While it is not absolutely essential to your success as torch welders that you know all about the sources of supplies used in your work it is nevertheless highly desirable that any intelligent workman know something about the commercial side of his occupation. Most men have the ambition to be independent and run a business of their own. We hope that in the not distant future some of you at least will be running welding shops. You will then have to deal with the commer- cial side of the business, and the question of gases and other supplies will loom up large and important. i Oxygen a Common Element Oxygen is one of the most common elements in this world of ours. The air we breathe is made up of oxygen and nitrogen mixed in the proportion of about 23 parts of oxygen and 71 parts nitrogen. The oceans which cover three-fourths of the earth's surface are one-third oxygen by measure and the same applies to the fresh water of lakes, rivers and streams. The earth's crust is largely made up of oxides of one form or another but common as oxygen is it is never found in the pure undiluted state. It is either chemically combined or mixed with nitrogen in the atmosphere. It is not strange, however, that oxygen is never found in the free, pure state ; it has such a strong affinity or attraction for carbon, hydro- gen, metals and many of the earths that long ago in the early geological ages it formed combinations or close partnerships that can be dissolved only with difficulty. The important exception to the chemically combined state is the free oxygen in the air but it is much diluted, and although the atmosphere contains 23 parts oxygen in mixture with nitrogen and other gases it is not by any means an easy matter to separate them. It is only within comparatively recent years that processes have been developed by which the separation can be effected on a commercial basis. Commercial methods of producing pure oxygen have had a most important influence on the development of oxy-acety- lene welding and cutting. In fact, the processes could never have reached the important stage of development they now have attained had it not been for the enterprise of the concerns that developed oxygen production methods and plants for com- mercial distribution. The discovery of a commercial method of producing calcium carbide and cheap acetylene was only one step in the development. Cheap oxygen commercially distributed was also required in order to put the industry on a sound basis. Methods of Producing Oxygen There are. three general methods by which oxygen may be manufactured. They are, in order of importance, as fol- lows : the liquid air process, the electrolysis of water process and various chemical processes. Chemical separation methods were first employed for the commercial production of oxygen used in the oxy-acetylene process. It is comparatively easy to drive off oxygen from chlorate-of-potash, for example, it being necessary only to heat the chlorate in a closed retort and collect the oxygen, as it escapes. Manganese dioxide is mixed with the chlorate-of-potash but apparently takes no part in the chemical reaction. Its effect is to reduce con- siderably the temperature at which the chlorate gives up its oxygen. Thus, the use of manganese dioxide saves fuel and reduces the cost of furnace upkeep. There are other chemical processes of making oxygen, among which may be mentioned the chloride-of-lime process, the sodium peroxide process, the barium monoxide or Brin's process. None of the chemical processes are now considered commercial in this country except perhaps, for certain remote localities where it may be easier to get chemicals than bottled oxygen. The cost of the chemicals and the necessary labor are so high that the oxygen produced by chemical processes is, in general, much higher than that made by the liquid air or electrolytic processes. Liquid Air Process A volume could be written on the liquefaction of gases, the discovery of liquid air and the subsequent development of the fractional distillation process by Prof. Linde in 1897. The liquid air process is based on the fact that air can be liquefied by the process of compression, expansion and conse- quent refrigeration. High hopes were entertained of the commercial value of liquid air but they have not been realized except in the production of gases. When the air is liquefied and allowed to evaporate, the nitrogen evaporates first at a temperature of about 20 degrees F. higher than the boiling point of oxygen. Hence, if care is taken it is possible to boil out the nitrogen and leave the liquid oxygen. The oxygen thus produced is commercially pure, containing but little nitrogen and other gases and some impurities that are in the atmosphere. The commercially pure oxygen is pumped into seamless steel bottles or cylinders for distribution and use. These steel bottles are drawn with hydraulic presses from steel billets, and though the shell is thin and light the cylinder, neverthe- less, is very strong. Each cylinder is subjected to a hydraulic test pressure of about 3600 pounds per square inch to discover leaks and defects. The cylinder stop valves arc provided with safety discs designed to blow under excessive pressure or temperature. The oxygen is pumped into the cylinders to a maximum pressure of 1800 to 2000 pounds per square inch. Formerly the maximum was 1800 pounds but during the war period the manufacturers raised the pressures to 2000 pounds in order to conserve cylinders, steel and transportation facilities. A cylinder filled with oxygen to a pressure of 2000 pounds contains one-ninth more oxygen than if compressed to a pressure of only 1800 pounds. In other words, a 200- cubic foot cylinder holds 220 cubic feet when the oxygen is compressed to 2000 pounds. Oxygen Cylinders, Tanks, Flasks or Bottles Davis Bournonvllle Institute Fig. 1. PORTABLE OXY- ACETYLENE WELDING OUTFIT SHOWING TYPICAL OXYGEN AND ACETYLENE CYLINDERS 6 The commercial pressure containers for the gases used for welding and cutting are called cylinders, tanks, flasks or bottles. But the term cylinder seems to be preferable to tank or bottle. The term bottle is more appropriate to the seamless cylinders used for laboratory work and for physicians. The work tank ordinarily means a stationary container used under little or no pressure except that due to the weight of the fluid con- tained, and often it is open at the top. The term flask is seldom used to designate a gas cylinder. Weight of Oxygen and Oxygen Cylinders The weight of 100 cubic feet of dry oxygen is about 8.9 pounds and one cubic foot weighs 1.42 ounce. A 200-cubic foot oxygen cylinder weighs about 142 pounds when filled and 124 pounds empty, the average weight of the full and empty cylinder added together and divided by 2 being 133 pounds. Oa"is Bournonville Institute Fig. 2. oxygen pressure regulator with low pressure and high pressure gauges, the high pressure gauge being graduated to INDICATE CUBIC CONTENTS AS WELL AS PRESSURE The contained oxygen in a charged cylinder weighs close to 18 pounds. It is not necessary, however, to resort to the weight method to ascertain the amount of oxygen remaining in a cylinder, inasmuch as the amount remaining is very nearly porportionate to the drop in pressure, if the temperature remains constant. If the cylinder pressure is 1800 pounds per square inch at the start, the drop in pressure per cubic foot withdrawn will be 1800 divided by the cubic foot capacity in feet or 200, if it is a 200-cubic foot cylinder. Hence, the drop is 9 pounds per cubic foot withdrawn. If 120 cubic feet have been withdrawn the drop should be approximately 1080 pounds and the gauge should indicate but 720 pounds pressure. Air reduction methods of producing oxygen have de- veloped commercially to a great importance and are, as stated, the chief means of producing commercial oxygen. But these processes have the disadvantage of requiring a costly plant that must be operated by experts and it is not feasible nor allowable for a manufacturer to produce his own oxygen from the atmosphere. The bottled oxygen must be shipped from central distribution plants, and the empty cylinders have to be returned at considerable expense and trouble. These disadvantages give to the electrolytic processes commercial advantages under some conditions, and we will describe the process and apparatus in some detail. Electrolytic Process of Producing Oxygen and Hydrogen The electrolytic process of producing oxygen and hydro- gen from water is a fascinating study in the principles of chemistry and electricity. It is one of common chemical experiments performed in the laboratory to demonstrate the composition of water and it never fails to excite interest and wonder. It is hard for the practical man to believe that the water we drink, all the water in seas, lakes, rivers and streams and that snow and ice are composed of two invisible gases, but it is true. All water is made up of oxygen and hydrogen chemically combined in the proportion of one part oxygen to two parts hydrogen. The familiar chemical formula for water is HoO which means that the water molecule is composed' of two atoms of hydrogen and one atom of oxygen. Davis Bournonville Institute Fig. 3. davis-bournonviille electrolytic generator for producing oxygen and hydrogen from water When water is separated into two component gases by passing a current of electricity through it the hydrogen collects on the negative electrode and the oxygen on the positive electrode. It is then merely a matter of cell construction to keep the gases separated and to provide means for drawing of¥ the two gases into separate containers where they are immediately ready for distribution and use. But, of course, there is much more to the apparatus for separating oxygen and hydrogen from water than in the simple experimental apparatus used in the laboratory for demonstration purposes. Although apparently simple, the fact is that the development CROSS SECTION OF THREE WAY VALVE -UPPER ASPIRATOR BOTTLE -AMMOMIACAL SOLUTION -RUBBER TUBING SPECIAL FLASK, COPPER MESH (1 LB. REQUIRED) Davis Bournonville Institute Fig. 4. apparatus for determining chemical purity of oxygen 10 of commercial electrolytic cells has resulted only from a costly process of experimentation. The illustration shows the Davis-Bournonville 1000- ampere electrolytic generator. This generator, which operates with a current of two volts and 1000 amperes generates or separates, theoretically, 7.92 cubic feet of oxygen and 15.84 cubic feet of hydrogen an hour. In some installations the hydrogen is not used and it is allowed to escape to the atmosphere. The oxygen is drawn off into a gasometer from which it is pumped with a water-cooled air compressor into cylinders or into a distributing pipe for use in the factory. If the hydrogen is also to be saved, it is also collected in a separate gasometer and pumped into cylinders or piped to the factory for use. Inasmuch as hydrogen is somewhat more effective as a ■preheating gas in the cutting torch for cutting thick steel than acetylene it is obvious that the manufacturer, making con- siderable use of cutting torches, could advantageously provide the comparatively simple apparatus for manufacturing both gases required for cutting. Pure Water Required for the Electrolyte It will not do to use water drawn from the city mains for the electrolyte of the generator. Pure water must be provided. By this we mean distilled water which, by the process of distillation has been freed from earthly impurities, nitrates and other compounds that have an injurious effect on the electrolytic cell. But although we provide pure water we do not use it in the pure state for the reason that pure water is not a good conductor of electricity. In order to make the cell operate satisfactorily we must introduce into the water a chemical that increases its electric conductivity but which at the same time has no injurious effect on cell parts. Caustic soda has been found to work satisfactorily and it is used for this purpose. It has no injurious effect on the plates or con- tainers and it remains in the water unchanged indefinitely. In short, a cell once charged with water and the proper proportion of caustic soda requires only the addition of dis- 11 tilled water from time to time, as the caustic soda is not used up. The cells must be insulated and the pipes connecting them to the manifold are provided with short sections of hard r^ ^ r ASPIRATOR BOTTLE - COMBUSTION PIPETTE^ PLATINUM SPIRAL- -ASFSBATOSt BOTTLE TO ELECTRIC SUPPLY ABSORPTION PIPETTE NG CLAMP ■^100 C.C. D.B. BURETTE __5/i6 RUBBER TUBING Davis Bournonvllle Insl'tute Fig. 5. apparatus for determining chemical purity of hydrogen 12 rubber or rubber tubing interposed for insulating purposes. The matter of insulation and short circuits is highly important, and care must be taken that nothing is laid on the cells that might short circuit the bus bars. It is also important that the electrical connections are always kept tight and free from corrosion. The same remarks apply to the 500-ampere cell which is of the same design and construction as the 1000- ampere cell. The production of oxygen and hydrogen is just one-half of that produced hourly by the 1000-ampere cell. Electrolytic cells are set up in batteries connected in series and in parallel depending on the number required to produce the quantity of gases needed. Suppose that a con- stant supply of 40 to 45 cubic feet of oxygen is needed hourly. Then six 1000-ampere cells will be required to produce the oxygen, if operated steadily. They should be connected in series, and as the voltage required for each cell is two volts, a voltage of 12 volts will be required to operate the six cells in series. The apparatus required for operating an electrolytic gas generator is fully automatic in practice. The chief duties of an attendant are to supply the distilled water daily and to make an occasional sample test of the purity of the gas in order to be sure that everything is proceeding satisfactorily. The motor-generator operates on any commercial current, direct or alternating and generates the required low volt- age direct current. The electrical apparatus stops and starts the gas compressor as the pressure falls and rises. If the oxygen is distributed through the building by a pipe line the compressor automatically maintains the pressure to which the controller is set. If the gases are to be bottled they are stored in a gasometer and pumped into cylinders at set intervals. The distilled water should be supplied daily and in amount depending on the production of gases. Approximately, one gallon per 100 cubic foot of oxygen at atmospheric pressure is required. The oxygen generated by the electrolytic process has an average purity of 99^ per cent while the hydrogen^ — two times the volume of oxygen — is practically 100 per cent 13 or absolutely pure. The purity of the gas is a very important factor in the efficiency of the cutting torch,; hence, electrolytic oxygen and hydrogen are most efifective gases for the cutting torch. Questions 1. About what proportion of the atmosphere is oxygen? 2. Is oxygen otherwise found in the free state? 3. What are the three principal methods of producing commercially pure oxygen? 4. Are chemical processes of producing oxygen now commercially profitable? Why? 5. Briefly, what is the liquid air process? 6. How is oxygen furnished to the trade? 7. What is the pressure in pounds to the square inch in an oxygen cylinder when received from the manu- facturer ? 8. What gases are produced by the electrolytic process? 9. From what is oxygen produced in the electrolytic process 10. What is the oxygen capacity per hour of a 1,000 ampere Davis-Bournonville electrolytic gen- erator? 11. Is it safe to distribute oxygen throughout a factory in iron pipe? 12. What precaution should be taken in regard to the use of oil and grease in oxygen apparatus? Why? 13. What is hydrogen used for chiefly? 14. What is likely to happen if oxygen cylinders are stored in a warm place near furnaces, boilers, etc.? 15. How should the cylinder stop valve be opened to prevent leakage around the valve stem? 16. Is it safe to let an oxygen cylinder stand beneath a line shaft or countershaft? Why? 17. What should be done with the valve protecting cap when the cylinder is returned to the manufacturer? 18. Is it safe to use an acetylene regulator on an oxygen pipe line? 14 Notes 15 DAVIS-BOURNONVILLE OXY-ACETYLENE WELDING aisd CUTTING COURSE OF INSTRUCTION Lecture ACETYLENE AND ACETYLENE CYLINDERS DAVIS -BOURNONVILLE INSTITUTE JERSEY CITY, N. J. g 1— 1 ^ >! u > u M J 2; > Pm O H < T— 1 Q 2; tJ4 ACETYLENE AND ACETYLENE CYLINDERS Acetylene from Calcium Carbide — Acetylene an Endothermic Compound — Acetylene Absorbed in Acetone — Construction of Acetylene Cylinders — Cylinder Stop Valve — Danger of' Leaky Pipes and Connections — ^To Find the Amount of Acetylene Remaining in a Cylinder — Importance of Maintaining Acetone Content — Recharging Acetylene Cylinders — Care of Cylinder Stop Valves. In 1892 Thomas L. Willson conducted an experiment at Spray, N. C, with an electric furnace for the purpose of pro- ducing metallic calcium. He subjected a mixture of coal, tar and lime to an electric current of 2000 amperes and 36 volts in a Heroult furnace. The temperature produced in the elec- tric furnace is very high, and some chemical changes take place at high temperatures that are impossible at a lower temperature. Willson hoped that the re-action of the mixture subjected to the high temperature might produce metallic calcium. But he produced a substance of much greater value — although he was at first bitterly disappointed. Acetylene from Calcium Carbide When the furnace was opened it was found to contain a dark-colored mass which on cooling was solid and brittle. This clearly was not metallic calcium, and in disgust the Willson engineers broke it up and threw it into a nearby stream. Bubbles of gas were soon noticed rising from the fragments at the bottom of the stream, and someone applied a match to one of the bubbles as it escaped from the water. It burned with a bright but smoky flame — quite different from hydrogen flame or any other combustible gas that the world was then familiar with. An analysis of the furnace product proved it to be calcium carbide. Calcium carbide was not unknown to chemists, but it had never before been produced in quantities nor was its great commercial possibility realized. The electric furnace made available a new product with which in a comparatively simple apparatus, a gas of astonishing possibilities could be cheaply produced. Calcium carbide, like calcium oxide (quick lime), slakes in water. When calcium carbide is thrown into water it absorbs water and produces slaked lime and acety- lene. The slaked lime settles to the bottom while the gas escapes from the water and passes off into the atmosphere or a suitable receptacle like a gasometer, where it is stored for use. Acetylene an Endothermic Connpound Acetylene is carbon and hydrogen chemically united and is very rich in British heat units. In other words, it will produce a very hot flame when burned with the proper oxygen supply. It is the fuel used in the oxy-acetylene torch, and as has been stated in a previous lecture, the discovery of acetylene was a step in progress that made gas welding the Davis Bournonville Institute FIG. ACETYLENE PRESSURE REGULATOR AND HIGH AND LOW PRESSURE GAUGES important industry that it is today. It may be manufactured in an acetylene generator for use in the factory or it may be purchased, compressed into steel bottles the same as oxygen. But unfortunately, acteylene cannot be as safely compressed in the same way as oxygen, hydrogen and other gases. It is what is called an endothermic or heat-absorbing substance, having the peculiarity of absorbing heat when it is generated. The atoms in the molecule are in an unstable condition and are likely to dissociate under heavy pressure, thus releasing molecular heat and causing an explosion. Acetylene Absorbed in Acetone This peculiarity of acetylene makes it dangerous to com- press free acetylene to a pressure much more than 30 pounds to the square inch into an ordinary container. It is liable to explode, with disastrous results. However, we are able to accomplish, indirectly what cannot be done directly with safety. Acetylene dissolves freely in acetone. This product of wood distillation will absorb over twenty-four times its volume of acetylene at atmospheric pressure and ordinary temperature, and its absorptive capacity increases directly as the pressure rises. At two atmospheres pressure a given volume of acetone absorbs over forty-eight volumes of acety- lene, and so on. Hence, we can dissolve our acetylene in acetone, and by compression force a large quantity into a small space. But the acetone slightly increases in bulk as it absorbs acetylene, and as it gives the acetylene off it shrinks. This means that if we have an ordinary steel cylinder filled with acetone, containing dissolved acetylene at a pressure of say 225 pounds to the square inch, a safe condition would exist only while the full pressure of acetylene is maintained. As soon as any acetylene is drawn off the acetone shrinks and leaves a space at the top of the cylinder in which free acetylene will collect under heavy pressure. This immediately becomes dangerous and likely to explode from shock or even rapid discharge of the cylinder contents. Construction of Acetylene Cylinders The difficulty is overcome by filling the cylinder with a porous mixture consisting of charcoal, infusorial earth, as- bestos and a small quantity of cement. This mixture though compacted until solid, is highly porous and capable of absorb- ing a large amount of acetone. The porosity is from 75 to 80 per cent of the total bulk. It is thus a sort of sponge for the liquid acetone. The cylinder is packed completely full, and slowly dried and baked. The air is then exhausted to about 9 pounds absolute and the cylinder is charged with acetone, which fills the pores. Then the acetylene may be pumped in safely to a pressure of 225 pounds per square inch or more, and discharged with equal safety. The porous filler co.mpletely fills the cylinder and there are no large spaces in which free acetylene can collect. So long as it is prevented from collecting in considerable volume in the free state no danger need be feared. The filler thus becomes a mineral sponge filled with a liquid sponge which absorbs the gas. The illustrations show sectional views of a dissolved acetylene cylinder, and the principle of the filling apparatus. Great care must be taken to fill every part so that no settle- ment will take place while in use. The cylinder is jounced on a platform that is kept in rapid vibration while the filler is being put in. It is necessary to fill the cylinder completely up to and including the neck, which is no easy operation. Not a cubic inch should be left between the filler and the valve nipple. After the filler has hardened a hole is drilled into it and filled with an asbestos wick. This provides for drawing ofif the acetylene through a considerable size outlet from the filler. The acetone gives up the acetylene readily when the pressure is reduced, and there is little tendency for it to go over with the escaping gas unless the rate of discharge is too high. If the acetylene is used too rapidly the acetone will also be drawn out with injurious effect on the welded joint. The escape of acetone can be quickly detected by the odor. No trouble will be experienced with escaping acetone in ordinary welding when using regular commercial cylinders provided the cylinders are kept in a vertical position. If necessary to lay the cylinders down they should be supported at an angle with the nozzle as high as possible. Cylinder Stop Valve The view at the lower left, Fig. 1, shows the construction of a stop valve used on one make of acetylene cylinders. It is quite different from that of an ordinary stop valve used for controlling pressvires, and you should study it so that in case it is necessary to take one apart you can assemble it properly. The stem is round and flattened on one side. This makes the use of a special key necessary, and thus prevents tampering by unauthorized persons. The valve stem cannot be turned except with the key. The collar around it prevents the use of a pipe wrench. The lower end of the stem sets in a shoe which rests on a stack of thin steel discs separated by a thin sheet steel ring. Beneath the discs is a perforated disc, containing live holes, four in a circle and one in the center. The holes in the circle are directly over a circular groove which is tapped by a hole leading to the outlet. When the stem is screwed down the discs are forced firmly together and the lower one seals the opening in the center of the perforated disc. Screwing the stem out releases the pressure on the discs and permit the gas to escape to the center hole beneath the discs down through the holes into the circular valve and out to the torch. A fine mesh wire screen or felt plug is provided beneath the cylinder stop valve to prevent scale, earth and other foreign matter being drawn out with the gas. Small particles of scale might lodge in the valve and prevent it being tightly closed when the gas is shut off. The cylinder valve is double seated, the same as the oxygen cylinder valve, to prevent the gas leaking around the stem. The valve stem should therefore be opened full or as far as the stem can be turned, when in use. The upper seat then prevents the gas getting to the stem and leaking. Danger of Leaky Pipes and Connections Acetylene cylinders are provided with a safety plug which is screwed into the shell beside the stop valve. Its purpose is to relieve the contents in case of over-pressure. If a cylinder is exposed to high temperature for a considerable period the pressure may run up to a dangerous point and the safety valve is required to relieve the pressure. Acetylene cylinders should never be stored near boilers or furnaces nor should they be left outdoors in the summer exposed to the hot rays of the sun. If the safety valve blows outdoors nothing worse is likely to happen than the loss of acetylene, but the blowing of the plug in a closed room near a furnace may cause a disastrous fire. This brings up the matter of leaky pipes and connection, which could never be tolerated, as a leak in any acetylene apparatus may be a grave danger. An accumulation of acety- lene in a closed room becomes highly explosive if the gas dilution is slightly in excess of 3 per cent. A spark produced by a nail in a shoe heel even may serve to ignite and cause an explosion of sufficient force to wreck a building and kill the occupants. No pains should be spared to prevent leaks, nor should there be any delay in stopping leaks that develop in service. Fortunately, acetylene has a peculiar and quickly recognized odor somewhat like garlic, which even in minute quantities is perceptible to any one with normal perception of odors. Explosions resulting fro'm leaky acetylene pipes are rare because very few would continue to endure the odor long before the mixture has reached the dangerous or ex- plosive stage. A great danger is incurred when entering a closed room with open lights if the air is contaminated with acetylene. Under no circumstances should a fire or any other open light be carried into any closed space where the odor of acetylene is very strong. It is hardly necessary to caution an intelligent person against the danger of exploring a leaky pipe with a torch or lighted match to find a leak. Use the senses of hearing and smelling to find the leak, or if it is minute apply soapsuds to the joints with a brush and watch to see bubbles form. To Find the Amount of Acetylene Remaining in a Cylinder Because the gas in an acetylene cylinder is dissolved in acetone the pressure gauge is not an indication of the amount of gas remaining. The pressure indicated in an oxygen or hydrogen cylinders tells you how much gas remains, but not so in an acetylene cylinder. The way to tell how much acety- lene remains is to clean off the cylinder and weigh it on accu- rate scales. Compare the weight with the weight stamped on the name plate. The difference is the weight of the acetylene contained, provided the acetone content is up to the standard. Acetylene under atmospheric pressure and normal temperature is rated commercially at 14^ cubic feet per pound. Suppose that the cylinder is found to weigh 211 pounds and the stamped weight is 207 pounds, then the dit- ference or four pounds should be the weight of the dissolved acetylene. Multiplying 14^ by 4 gives 58 cubic feet, the amount of gas still remaining. Importance of Maintaining Acetone Content If acetylene is discharged rapidly from an acetylene cylinder, the acetone is drawn out also because of the rapid bubbling of gas and consequent vaporization of the liquid. The rule is to never draw from an acetylene cylinder at a rate of more than one-seventh of the capacity in cubic feet per hour. Suppose that the rated capacity of an acetylene cylinder is 225 cubic feet. Then the maximum hourly rate of gas consumption should not exceed 32 cubic feet. The No. 7 tip, if used continuously, is rated at 33 cubic feet acetylene consumption, or slightly more than one-seventh of the rated capacity of the 225-cubic foot cylinder. However, the cylinder should not be overtaxed to supply a No. 7 tip in ordinary welding usually as the use of gas is almost always inter- mittent. Recharging Acetylene Cylinders Inasmuch as there is always uncertainty as to the acetone content when a cylinder is returned to the recharging station it should be weighed and the acetone content checked up. If below weight sufficient acetone should be injected to bring the weight up to the standard. Then the cylinder may be recharged safely to the standard pressure, but not otherwise. If the acetone content is not standardized there is no way of knowing how much acetylene can be safely charged into the cylinder. If a cylinder is returned to the charging station containing 40 or 50 pounds pressure, it will be necessary to discharge the gas into a gasometer before testing the weight. If the charging station is connected with a manufacturing plant, however, and the man in charge keeps an accurate record of all the cylinders in his care he may ignore the rule to recharge and weigh all cylinders at every recharging, pro- vided he knows the conditions of use and makes it an in- variable rule to test periodically, say at every fifth or sixth charging. If this procedure is followed each cylinder should be tested with the pressure gauge and the pressure chalked on each cylinder. Then when connected to the manifold for recharging the following order should be observed in opening the charging valves. Suppose that four cylinders are to be charged and that the tests show pressures remaining of 15, 25, 38 and 45 pounds. These numbers are chalked on the respective cylinders. When the compressor is started the cylinder marked 15 is charged first and the stop valve of the cylinder containing 25 pounds pressure is opened only when the compressor gauge shows 25 pounds pressure. This order should be observed throughout. The reason for it is to pre- vent the cylinders containing comparatively high pressures charging back into the cylinders containing gas at low pressures at so rapid a rate that the acetone is drawn over. Care of Cylinder Stop Valves The cylinder stop valves on acetylene and oxygen cylinders are protected in transit by rail with a metal cap or shield that screws over the end of the cylinder nozzle, covers the valve and prevents it being broken ol¥. The welder should always replace the valve protectors when transporting acety- lene cylinders and oxygen cylinders to field jobs or even if he is moving them from one part of the plant to another. It is, of course, necessary to remove the regulators before the cap can be screwed in place. But this is always advisable when cylinders are being shifted on a truck. A regulator is easily 10 broken and no chances should be taken to save the few minutes required to unscrew the connections and replace it when set- ting up again. Questions 1. When was acetylene commercially discovered? 2. In view of the fact that acetylene had long been known, why was this a commercial discovery? 3. How is acetylene generated? 4. By what process is calcium carbide manufactured ? 5. Is it safe to compress acetylene to a pressure of more than 30 pounds? Why? 6. What is the recommended safe pressure? 7. What is acetylene composed of? 8. How is acetylene safely compressed to 225 pounds per square inch? 9. What is the chief characteristic of the filler used in acetylene cylinders? 10. What is the liquid used to dissolve the acetylene? 11. What happens if you use acetylene too rapidly? 12. Is acetone injurious when welding? 13. Can you determine how much acetylene remains in a cylinder by weighing it? 14. How many cubic feet in one pound of acetylene at atmospheric pressure? Copyright 1919 by thh; Davis-Bournonvilx^e Company DAVIS-BOURNONVILLE OXY-ACETYLENE WELDING and CUTTING COURSE OF INSTRUCTION Lecture ACETYLENE GENERATORS DAVIS -BOURNONVILLE INSTITUTE JERSEY CITY, N. J. Copyright 1919 by the Davis-Bournonville Company ACETYLENE GENERATORS Commercial Acetylene Generators — Generator Types — Principal Requirements of Generators — Davis-Bournonville 200-Pound and 300-Pound Generators — Acety- lene Generator House — Directions for Charging — Rules for Recharging — Safety Rules. •The generation of acetylene from calcium carbide is very simple, in fact, so simple that it was discovered by accident ; and the experiment can be made by anyone having a lump of calcium carbide and a glass of w^ater. Drop the carbide into water and immediately bubbles of gas begin to rise which, if ignited, burn with a red, smoky flame as they come to the surface. That, you may know, is what happened when Will- son undertook to produce metallic calcium in 1892, but obtained calcium carbide instead. The rejected mass result- ing from the failure produced an unknown gas when thrown into a nearby stream. Someone with an investigating spirit, undaunted in the face of apparent failure, discovered that a new means of producing a combustible gas had been created. Commercial Acetylene Generators While it is true that the apparatus needed for the labora- tory experiment to make acetylene is very simple, the commercial generation of acetylene is far from being a simple matter. In the first place, acetylene is a good servant but a bad master. Under normal conditions it performs beauti- fully, but if mishandled the results may be disastrous. The apparatus required for the commercial generation of acetylene should be efficient, safe and automatic in operation and convenient to take care of. Such generators are available, but they were developed only after much experimenting and costly mistakes. There are, available today acetylene genera- tors that require so little attention that they are practically automatic and so safe that there is little difficulty in getting permission to use them for factories in towns and cities. Generator Types There are two systems or types of generators, differ- entiated chiefly by the manner in which the water and car- bide are brought together. One called the water-to-carbide type, is that in which the water is applied to the carbide by sprinkling or injection. The other and principal type of acetylene generator is the carbide-to-water type, in which a comparatively large body of water is provided and means for dropping the carbide into the water automatically and in amounts determined by the consumption. The carbide-to- water type of generator has certain advantages that recom- mend it to users in general as well as safety engineers and insurance companies. A large volume of water is provided in this type to absorb the heat produced when the carbide slakes and gives off gas. The water "drowns" the carbide and prevents the temperature rising to a dangerous point. It is obvious that as long as the carbide is under water the temperature cannot rise above the boiling point or 212 degrees F. Cool generation is an imperative requisite for safe and efficient generation. Acetylene is an endothermic compound and is liable to so- called spontaneous explosion under certain conditions such as high compression, overheating, the presence of impurities, sudden shock, etc. The subject of safety, therefore, looms large in the consideration of an acetylene generator, and it is desirable to outline the principal requirements of a generator that meets the insurance requirements as well as the require- ments of the commercial users. Principal Requirements of Generator 1. It should provide for automatic generation of gas, and at no time should the temperature rise above the boiling point of water. 2. A safe generator should produce at no time an ex- plosive mixture of acetylene and air. 3. It should be so constructed as to be positive in opera- tion and should be well built of lasting materials. 4. The mechanism should be simple and not likely to get out of order. Generators are required to work automatically and are likely to be attended by un- skilled labor. They should, therefore, be absolutely \ Davis Bournonville Inslltule Fig. 1. DAvis-BOURNONviLLE NO. 200 (and no. 300) ACETYLENE GENERATOR reliable and easily understood by men of limited mechanical knowledge. 5. The insurance underwriters require that acetylene generators must operate with a comparatively low pressure. The pressure should never exceed 20 pounds per square inch, and in general should be somewhat less than 15 pounds. 6. The generator should be so constructed that it is easily cleaned and recharged. The construction should be such that little gas escapes when cleaning and recharging, and no explosive mixture is pro- duced when it is again started into operation. 7. Safety devices should be provided to prevent over- pressure. Davis-Bournonville 200-Pound and 300-Pound Generators The illustration shows the construction of the Davis- Bournonville acetylene generator of the 200-pound and 300- pound sizes. It is of the carbide-to-water type, a large reser- voir for water being provided in the base and a weight motor for feeding the calcium carbide automatically to the water, as required. The carbide falls from the hopper upon a rotating feeding disc from which it is slowly scraped off to fall into the water beneath. The operation of the feed mechanism is controlled by the pressure of acetylene in the generator. When acetylene is being generated faster than it is used the pressure rises, and when it has reached a certain limit — generally 10 to 12 pounds maximum for welding and cutting — the opera- tion of the motor is stopped and the rotation of the feeding disc ceases. The carbide sinks to the bottom and slakes, giving off acetylene which bubbles to the top and finally escapes through the backfire valve and filter to the outlet service pipe. The capacity rating of the Davis-Bournonville generators is ex- pressed by a number. The No. 200 generator holds 200 pounds of calcium carbide in the hopper and generates 200 cubic feet of acetylene hourly. The water reservoir contains 200 gallons, thus providing one gallon per pound of carbide. On the basis of 43/2 cubic feet of acetylene generated from one pound of carbide, the No. 200 generator will produce 900 cubic feet of gas at atmospheric pressure from one charging. The motor is driven by the weight X acting through the cable upon the drum of the motor A. An interference clutch or stop checks the motor when the pressure runs too high, being operated by a feed controlling diaphragm. The calcium carbide is stored in the hopper from which it drops to the feeding disc N. To prevent clogging and stoppage a floating displacer ring O is provided. This is suspended so that it is free to swing to one side or the other in case a lump of car- bide too large to pass through the feed mechanism falls upon the feeding disc. The spent carbide or residuum collects in the bottom of the reservoir in a compact, sticky mass which requires break- ing up and agitating in order to discharge it to the lime pit when recharging the generator. An agitator operated by a crank outside the shell is provided for the purpose. The mass of water and lime stirred up with the agitator runs ofif to the pit when the connection valve is opened. One of the rules never to be broken is to discharge the slaked carbide from the generator at each recharging. If the residuum is allowed to remain it reduces the water capacity and may cause over- heating and polymerization. The development of polymers is injurious to the acetylene and it reduces the amount gen- erated from the carbide. Polymerization is indicated by the presence of yellow tarry deposits on the residuum. In case of over-pressure developing the gas blows off and escapes through the vent pipe V to the atmosphere. The v^ent pipe is connected to the water seal or trap on the side of the generator. This trap fills a double function. It pro- vides for the overflow of water from the generator when re- charging. The reservoir cannot be filled above the level of the out-flow pipe. The second function is to give warning of stoppage in the vent pipe should one occur. The gas escaping through the blow-off valve then forces the water seal and escapes. The odor of acetylene prevading the premises gives notice that something is wrong. 7 Generator Parts A. Motor drum for weight cable. B. Carbide filling plugs. C. Backfire or flashback chamber. D. Emergency locking collars. E. Lever on feed controlling diaphragm valve, F. Lever of emergency diaphragm valve, v^^hich operates emergency locking collars D. G. Feed controlling diaphragm valve. H. Emergency diaphragm valve. J. Main shaft driving carbide feed disc. K. Generator shell. L. Generator top plate. M. Carbide hopper. N. Carbide feed disc. O. Carbide displacer ring. P. Backfire or flashback chamber valve and float. Q. Outlet pipe to backfire or flashback chamber. R. Overflow plug of backfire or flashback chamber. S. Filter. T. Water filling pipe for backfire or flashback chamber. U. Pressure gauge bushing. V. Blow-off pipe. W. Outlet pipe to gas service line from generator. X. Operating weight. Y. Vertical controlling rod. Z. Motor locking thumb pin. Aa. Vent valve. Bb. Handle of vertical controlling rod. Dd. Water filling funnel. Ee. Valve in water filling pipe. Ff. Water filling pipe of generator. Gg. Overflow pipe of drainage chamber. Hh. Lever of blow-off valve. li. Residuum discharge valve. Jj. Handle of agitator. Kk. Valve in outlet pipe to backfire or flashback chamber. LI. Generator blow-off valve. Mm. Backfire chamber blow-off valve. Nn. Charging platform. Oo. Residuum gutter. Qq. Residuum discharge pipe. BLOW OFF VALVE L I FEED CONTROLLING DIARHRSGM VALVE G EMERGENCY DIAPHRAGM VALVE B Fig. 2. top of davis-bournonville no. 200 (and no. 300) showing motor and control valves Xx. Blow-off pipe from flashback. Yy. Motor interference pin. Acetylene Generator House Acetylene generators may be placed within an isolated building, preferably of fireproof construction. It should be located away from boilers, furnaces, railway tracks or any source of fire or sparks. The fact should be recognized th?' an acetylene generator is used to produce an inflammable gas which, mixed with air, becomes highly explosive and danger- ous. A generator may be placed within a building used for other purposes provided it is isolated by partitions and the room is vented to draw off any accumulation of gas. Pre- ferably the generator room should be so located that artificial heat will not be required in the winter to prevent the water from freezing. But if this is not feasible a steam coil or radi- ator may be provided for use in extremely cold weather. While it is true that a generator in use is not likely to freeze because of the heat produced in generation, no chances should be taken of a generator freezing when not in use as the result may be serious. Inasmuch as the conditions are generally such that the residuum cannot be discharged into the sewer it will be nec- essary to provide a pit adjacent to the generator house into which it can be deposited. In some localities the slaked lime has commercial value and can be sold at a price sufficient to pay a profit on the cost of handling and selling. Open lights should never be used in an acetylene gener- ator house. Incandescent lights should be provided, but all switches should be placed outside. The light bulbs should be protected by gas-tight glass. Incandescent bulbs attached to flexible cables provided with wire protectors may be used for examining the generator when absolutely necessary. The use of such lights, however, should be limited to emergencies, as, there is always danger of short circuits, broken bulbs or other accidents that might cause ignition of inflammable gas. Copper pipe or tubing should never be used for an acety- lene pipe line, as the acetylene may, under favorable condi- 10 tions form copper acetylide, which is an explosive compound. Brass (which contains copper) is not so affected except when in contact with the sludge formed in an acetylene generator. No brass parts should be used in a generator that make coii- tact with the water. Brass parts in the generator above the water exposed only to the gas itself are not likely to be affected. Directions for Charging I. Close the vent valve Aa by turning the handle Bb to the left as far as it will go. This releases the motor interference pin Yy. 2. Release the motor by means of the motor locking thumb pin Z and raise the lever on the feed con- trolling diaphragm valve, thus allowing the weight to descend a short distance in order to determine whether the motor is operating properly. Then rewind to the full height and lock with the motor locking pin. 3. Open the vent valve Aa by turning the handle Bb to the right as far as it will go. 4. Close the residuum valve li. 5. Open the water filling valve Ee. 6. Close the valve Kk in the outlet pipe to the flash- back or backfire chamber. 7. Remove the out-fiow plug R from the flashback chamber C and the plug from the water filling pipe T. Fill with water at the lower opening until it overflows at R and then replace both plugs tightly. 8. Fill the generator with water through the funnel Dd until it overflows at Gg, then close the valve Ee. 9. Remove the carbide filling plugs B and fill the hopper with 1^-inch by ^-inch carbide (nut size). Replace the carbide filling plugs tightly. 10. Close the vent valve Aa by turning the handle Bb to the left as far as it will go. II. Unlock the motor thumb pin Z. 12. Raise the feed control diaphragm lever, allowing the motor to run until the valve shows about 5 pounds 11 pressure. Then raise the lever Hh of the blow-off valve LI and discharge the gas until the pressure has dropped to 2 pounds. This is done to remove all air from the generator and avoid producing an explosive mixture of air and acetylene. Again raise ; the feed control diaphragm lever and permit the generator to operate until the gauge shows 8 pounds pressure, after which the motor will operate auto- matically as the gas is consumed. 13. When ready to use acetylene, open the valve Kk slowly and thus admit the acetylene to the service pipe through the backfire chamber and filter. Rules for Recharging The rules for recharging the generator dififer somewhat from those for charging and starting, as follows : 1. Close the valve Kk in the outlet pipe to the backfire or flashback chamber. 2. Close the vent valve handle Bb to the right as far as it will go. 3. Revolve the agitator handle Jj several times. 4. Open the residuum discharge valve li and draw off all the water and sludge, after which the valve should be closed. 5. Open the water inlet valve Ee thereafter, fill the generator with water. Revolve the agitator again and draw off all water and sludge as before. 6. Having closed the valve li, fill the generator with water at the funnel Dd until it overflows at Gg. (It is desirable when filling to let the water run in as rapidly as possible in order to keep the filling pipe full and thus prevent air entering the chamber at the same time.) 7. Close the valve Ee in the water filling pipe. 8. Rewind the motor and lock it with the motor lock- ing thumb pin Z. 9. Remove the carbide filling plugs B and fill the hopper with l^^-inch by ^-inch carbide (nut size). 12 Replace the filling plugs. 10. Close the vent valve Aa by turning the handle Bb to the left as far as it will go. 11. Unlock the motor thumb pin Z. 12. Raise the feed controlling diaphragm lever, allowing the motor to run until the gauge shows about 5 pounds pressure. Then raise the lever Hh of the blow-off valve LI and discharge the gas through the vent pipe until the pressure has dropped to 2 pounds. This is done to remove all air from the generator. Again raise the feed control diaphragm lever until the gauge shows 8 pounds pressure, after which the motor will operate automatically as the gas is con- sumed. 13. When ready to use the acetylene, slowly open the valve Kk. Safety Rules 1. Remember that an acetylene generator produces in- flammable gas and that all precautions should be taken to prevent the escape of gas through careless handling of apparatus, leaks, etc. 2. Do not carry or permit lighted pipes or cigars or open fires of any kind within a generator house or room. 3. Always remove all the, residuum that is clogged in the bottom of the generator and fill with fresh water before recharging. Neglect of this rule may cause the generator to be seriously overheated. In such an event do not open the generator until it has cooled down, as the admission of air to the heated gas may cause trouble. If through neglect a generator be- comes overheated stop its operation and play a water hose upon it until it has cooled down. 4. Make sure that all the joints and pipes are tight before operating the generator. Joints may be tested for leaks by applying soap suds with a brush. Never use a light for the purpose. 13 5. Never force carbide into the filling openings or fun- nel with a metal rod. 6. Always discharge the air mixture from the generator each time it is recharged, as is directed in Rule 12. 7. After recharging the generator discharge all the air mixture from the pipe system before lighting torches. A back pressure valve should be provided in the pipe system, however, to prevent the escape of acetylene when recharging and thus making this precaution unnecessary. 8. The operating weights fall a certain distance in dis- charging the carbide charge in the hopper. If the operator notes the position of the driving weight when a full charge has been fed to the generator he will know thereafter when the charge is nearly exhausted by merely noting the , position of the weight. 9. When making repairs to the generator always remove the carbide hopper and fill the shell completely full of water before applying a welding torch or solder- ing iron. Repairs of this nature should not be made in a generator house if there are any other generators in the same house. 10. The generator is designed to operate at a pressure from 10 to 12 pounds and the blow-ofif valve to operate at a pressure of 15 pounds. If for any rea- son the blow-off valve should fail the emergency diaphragm valve will raise a lever and thereby en- gage an emergency locking collar, thus stopping the motor. The motor cannot be operated again until the gas pressure has been reduced and the cause for the excess pressure found and removed. It should be understood, however, that the emergency dia- phragm valve is designed only for operation in an emergency and that it is not likely to go into action in the ordinary operation of the generator. 11. The flashback or backfire chamber C must be kept filled with water at all times up to the level of the overflow plug R. 14 12. Care should be taken when charging a generator that no foreign substance is mixed with the carbide. A piece of brass or copper getting into the generator may cause trouble. The generator thus provides for automatic gas production, it Hmits the pressure produced and is provided with safety devices which prevent careless and dangerous practice in charging. Of course, no apparatus can be made foolproof. Common sense is required of the one who takes care of a gas generator as much as of one who attends a heating furnace. [f the rules are followed no trouble should be feared. Questions 1. How is acetylene produced? 2. What are the principal types of generators? 3. Which is the best type? Why? 4. How are generators rated? 5. Why is a large water capacity desirable in an acety- lene generator? 6. What is the rule for water capacity in an acetylene generator? 7. What precaution should be taken in regard to open lights when working around a generator? 8. Is it safe to use an incandescent lamp? If so, how should it be guarded? 9. What is the function of the clockwork motor? 10. What should be done with the residuum before re- charging? 11. What is the danger of leaving the residuum in the generator? 12. What should be done when a leak develops? 13. How would you proceed to find a leak? 14. What happens if the vent valve becomes obstructed? IS DAVIS-BOURNONVILLE OXY-ACETYLENE WELDING and CUTTING COURSE OF INSTRUCTION Lecture OXY-ACETYLENE WELDING DAVIS -BOURNONVILLE INSTITUTE JERSEY CITY, N. J. Copyright 1919 by the Davis-Bournonvii,x,e Company OXY-ACETYLENE WELDING What Welding is — Importance of Correct Torch Movement — Importance of Holding Welding Torch and Welding Rod in Proper Relation and Position — Desir- able Characteristics of Welders — Classes of Welding — Grading Steels with the Emery Wheel — Learn to Estimate Costs — Safety Considerations. We have lectured about combustion, structure of flame, heat and temperature, controlling gas supply, the oxy-acety- lene welding torch, and several other matters closely pertain- ing to oxy-acetylene torch practice, and you have done some Avelding and are beginning to comprehend the possibilities as well as the difficulties of the art. We will, therefore, talk today about welding in the light of your experience. The work you have done in the past few days has helped, no doubt, to make clear some of the things that we have harped on but which you did not, perhaps, fully comprehend. The fact is that a full knowledge of oxy-acetylene torch practice requires a knowledge of so many things that it is somewhat difficult to start at any really logical place and tell you about it. About the best we can do is start you at welding and then tell you about the principles as you learn. When you are able to apply more or less successfully the principles of welding you are more interested in everything that makes for progress. What Welding Is In the first lecture on combustion, welding was defined as a process of uniting metals by fusing or partly melting the parts to be joined which then flow together and be- come one. That is the foundation of oxy-acetylene welding. You must fuse the edges of the plates you wish to join, and let the fused metal run together. You do not force the metal together ; it runs together of its own accord when properly fused. The success of the welder depends on how well he fuses the metal and how systematically and intelligently he goes at his work. It will not do to fuse the metal with a carbonizing or oxidizing flame; it must be done in a neutral flame in order to prevent injuring the metal and making a poor joint. You must learn to make welds with as little de- terioration of the physical structure as possible. Remember that welds can be made having 90 to 95 per cent the strength of the unwelded steel. The expert welder must be able to weld cast iron, steel, bronze and aluminum ; he should be able to braze all the metals including copper, brass, malleable iron and other metals that may be brazed more effectively than welded, sometimes. He must be able to make the castings ready for welding, Davis Boumonville Institute Fig. 1. SCARFED JOINT WELD MADE BY THE BLACKSMITH bevel the joints, adjust them for alignment and preheat them so as to avoid destructive stress on the welded joint after the job is done. Importance of Correct Torch Movement The welder must go through a course of training that de- velops manual skill. He has to learn to hold the torch un- consciously with the tip of the' white hot cone from an eighth to three-sixteenths inch above the puddle and at the same time give the torch a motion across the joint that will distribute the heat to the best advantage. On prepared joints the welder is instructed to give the torch a sort of semicircular zig-zag movement. The reason for the semicircular instead of the plain zig-zag movement is that the flame dwells longer on the margins of the joint where heat must be supplied to com- pensate for that lost by conduction and where it is generally difficult to obtain sufficient temperature to insure perfect fusion and penetration. If the torch tip is given the simple straight zig-zag movement the flame will dwell only momen- FlG. 2. TORCH HANDLE HELD PARALLEL TO JOINT. INCORRECT tarily on the margins. Consequently, the metal will remain comparatively cool, and lapping and cold-shuts will likely be produced. If, however, the tip is given a semicircular movement the flame is concentrated for a considerably longer time on the margins of the joint and sufficient heat is thereby imparted to produce fusion and union. Importance of Holding Welding Rod and Welding Torch in Correct Relation and Position The accompanying illustrations, Figs. 2, 3, 4 and 5, show some of the errors to be avoided in welding as regards the direction of welding, position of torch and the melting of the adding material. Fig. 6 shows the correct position of the torch in relation to the joint and the angle made by the tip with the surface of the metal. It also shows the correct direction of welding a prepared joint and the proper way to hold the welding rod. Prepared joints should be welded from left to right with the torch handle held at right angles to the joint and the head inclined to the right to an angle of about 50 degrees. The welding rod should be held in the left hand, and the white hot cone of the flame should never be used to melt the rod. It must take its heat from the puddle Davis Bournonville Institute Fig. 3. welding from right to left in a prepared joint. incorrect as that is the only way the welder can make sure that he is imparting the necessary heat to obtain penetration. Fig. 2 shows correct practice as regards the direction of welding and the manner of manipulating the welding rod but the torch handle is held approximately parallel to the joint. This is an awkward constrained position for the welder to assume, and should never be permitted except when the sur- roundings make it necessary. Fig. 3 shows welding from right to left in a prepared joint. It illustrates the disad- vantage at which the flame operates on the declivity of the weld. The flame is not directed squarely against the side of the weld and lapping is likely to result. Moreover, there is danger of overheating the bottom of the vee and blowing a hole through. The torch should always be held in relation to the direction of welding so that the flame is directed more or less squarely against the declivity formed by the joint material. A left-handed welder may logically weld from right to left in a prepared joint as he will hold the torch in the left hand and the welding rod in the right. Fig. 4 shows welding proceeding correctly from left to right in a prepared joint but the torch head is inclined to the left so that the flame is not directed squarely against the Fig. 4. torch head inclined to left, incorrect weld declivity and hence, the same fault is developed as in welding from right to left in Fig. 3. The welder must hold the torch at the proper angle to develop the best results from the flame. To do otherwise is to waste gas and to invite poor results. You have been repeatedly warned not to fuse the add- ing material directly with the torch flame. Fig. 5 shows this error as it would appear to one standing in front of the weld being made by a left-handed operator. It is ob- vious from this illustration that the flame is not being di- rected where it should be to produce a puddle of molten metal that will blend perfectly with the parent metal. The welder is more intent on fusing the welding rod and seeing the drops fall. The invariable results of such practice are cold-shuts, laps and weak welds. Desirable Characteristics of Welders The welder should be an all-around type of man who combines good common sense, judgment and manual skill and who is not afraid to work. It is not sufficient that he should be able to weld the casting so that when finished the parts will be in line and the shape will be nearly the same as before. If the welded casting is so distorted after welding Fig. 5. melting adding material with direct flame. BAD practice that it cannot be used or is an eye-sore, the job is a failure no matter how strongly the joint may be made. He must be able to choose the proper adding material, and use it economically; he should also recognize at a glance when flux should be used and what kind will yield the best re- sult. If the welder is able to do good sound work, he should be able to tell bad work no matter how skillfully it may be camouflaged. But avoid knocking. Be generous and give others the credit due them. The knocker hurts himself and the booster helps every one, himself included. 8 We have not, heretofore, said much about preparing joints for welding nor have we discussed preheating. Both these subjects will be taken up later in detail. We will mention them here in order that you can get an idea of the manifold requirements of a successful welder. He must not only be able to weld but he must be able to prepare for welding, line up on floors or surface plates, build up temporary pre- . heating furnaces, apply the heat where it will be most ef- fective, protect parts that might be injured by overheating, learn to do his own rigging; in short he should be a master of his trade, able to handle a wide variety of repair work in a workmanlike manner. Classes of Welding Oxy-acetylene repair welding is divided into two general classes, shop work and field work. Repair work that can be carried to the workshop is, of course, taken where the ap- pliances are at hand for lining up and preheating. Work that can be taken to the workshop, lined up on the bench or floor and welded, generally presents less difficulties than that which Fig. 6. correct practice in welding prepared joint. PUDDLE melting THE WELDING ROD must be done outside or, as we say, in the field. Often it is necessary to make a weld on a heavy casting where it lies and where rigging must be erected to lift it and turn it over. Many field jobs are very difficult, and the job may be in a remote region where nothing is available except that which the welder takes with him. He must, therefore, learn to systematize his business and to prepare for the unexpected when he goes to do an outside job. The welder should begin his career if possible in the shop where the tools and apparatus necessary for successful all- around welding are provided. When he has learned to know the conditions under which welding can be successfully ac- complished in a shop, he will be able to create these con- ditions to a larger degree when sent out to do field work. The field work will require much more preparation than shop work and will often call for a higher range of skill and good judgment. Very often, if not usually, the field work is done under pressure. A mill or factory may be partly at a stand- still because some apparatus has failed. The welder should learn to work quickly but without excitement no matter how great the emergency or how many are advising him that speed is imperative. Machine steel, tool steel, steel castings, high-speed steel, cast iron and malleable iron have certain well defined char- acteristics which the oxy-acetylene welder should be able to recognize at a glance. It is important that he recognize these metals in order that he will not undertake to do im- possible or unprofitable welding. Machine steel is steel low in carbon, and it can be welded with ease. Gray cast iron is easily welded but malleable iron is a difficult metal to weld because of the peculiar heat treatment it goes through in order to give it the malleable characteristics. Brazing is better than welding. Tool steel and high-speed steel can be welded but not by the usual methods. Grading Steel with the Emery Wheel A simple test for grades of steel is grinding them on an emery wheel. The steel high in carbon makes many white 10 hot sparks while a low carbon steel throws comparatively few. Mushet and high-speed steels when ground, produce dull red sparks. It is difficult to describe the characteristics of all metals as shown by the grinding test, and the best way for the welder to learn them is to take samples of known steels, wrought iron, cast iron, malleable iron, etc., and test them one after another. A little time spent in this way will be well repaid. While it is possible to weld almost any metal with the oxy-acetylene torch, it is not commercially feasible to do certain classes of welding by this process. The welder should learn to distinguish between the classes of work that are commercially weldable and those which should be undertaken only to meet an emergency and which, under ordinary con- ditions, could be done more cheaply by other methods. It is better for him to reject a proffered job of welding than to undertake it when he knows that the result will be unsatis- factory to the customer because of the high cost. It is not good business to do work that will cause dissatisfaction either because of the quality of the work or its ultimate cost. Bar- gains are good bargains only when both parties are pleased and satisfied. Cutting iron and steel with a torch is easily learned. The welder, however, should not despise the cutting game. He may find it very profitable to do cutting either in an emer- gency where the prompt removal of steel debris is neces- sary or in preparing for welding. Therefore, the welder should be able to use the cutting torch with skill and pre- cision. The cutting torch can be used in preparing work for welding oftimes at costs far below any other. Suppose, for example, you are required to make a frame of angle iron. The torch will cut the angles to a 45-degree bevel quickly and at low cost. No other tools but the torch will be required ex- cept a bevel protractor to lay off the angle. Learn to Estimate Costs Knowledge of costs of the materials used, comprising oxygen and acetylene gases, adding material or welding rods, 11 fluxes, etc., is highly desirable. The oxy-acetylene welding NO. 738-LARGE STYLE O" TORCH MACHINE WELDING NO. S13-A LARGE STYLE "o" TORCH MACHINE WELDING -WATER COOLED Fig. 7. types of welding torches available for all kinds OF welding 12 business is one that offers large opportunities to the wide- awake progressive workman. He can start in business for himself with a comparatively small capital. If one goes into business for himself he should know the names of concerns from which he can obtain the best supplies and should com- pare the cost of acetylene in cylinders and of the gas made on his own premises with an acetylene generator. Safety Considerations Safety considerations and care of health are as important in the oxy-acetylene welding and cutting business as in any other line. The welder often is required to go into danger- ous places to do emergency work. He should first of all pro- vide suitable spectacles and goggles for protecting the eyes and should wear clothes suitable to his trade. Care of ap- paratus is imperative both for economy's sake and safety's sake. An acetylene cylinder filled with dissolved acetylene is commercially safe provided it receives ordinary care. But if it is mishandled and allowed to fall over or be struck by falling objects, the shell may be ruptured or the regulator broken off. It may be argued that this would mean only the escape of gas and no particular harm other than the loss of the gas and perhaps a shock to the nerves. But that is only part of the truth. Escaping acetylene in a closed room is exceedingly dangerous. Open lights will fire the gas and cause a disastrous fire. The flames may spread so quickly that men in the room will be unable to escape with their lives. In the foregoing we have undertaken to give you some idea of thz oxy-acetylene welding business and the require- ments of the skillful welder. He has to be a pretty capable sort of a man who, first of all, is a good workman but who should have some commercial sense that would enable him to run a business of his own or to manage a department. He must be careful of his men and that means that he must be careful of his apparatus and in the methods he follows. He should also be careful of his reputation for keeping prom- ises and being trustworthy. 13 Questions 1. How does one learn to use the torch? 2. What is autogenous welding? 3. What makes a successful weld? 4. What percentage of weld strength may be reason- ably expected in mild steel? 5. What is the proper torch movement for thin steel? 6. What movement should be used on all prepared joints? 7. What is the difference in efrect on the two torch movements on the parts to be welded? 8. How should the torch be held in relation to the joint? 9. What kind of a man would you pick to be a welder? 10. What is the best guarantee of a sound welded joint? 11. Can you tell different grades of steel by grinding them on an emery wheel? 12. What kind of sparks are thrown by high carbon tool steel? 13. How can you identify a malleable casting? 14. What would you do if required to mend a broken malleable casting? 15. Suppose that oxygen costs 2 cents a cubic foot and acetylene 1 cent a cubic foot? What would be the cost for gases when using the torch continuously with the No. 5 tip for one hour? 14 Acetylene and Oxygen Pressures Davis-Bournonville Style C Welding Torches with Style 99 and 100 Tips Thickness Acetylene Oxygen Acetylene* Oxygen* Tip of Metal Pressure Pressure Consumption Consumption No. Inches Lbs. Lbs. Per Hour Per Hour 00 ^Veryl \Light/ 1 1 0.6 CU. ft. 0.8 CU. ft. 1 2 1.0 1.3 1 1 1 1 2 3.2 3.7 2 A" A 2 4 4.8 5.5 3 A-H 3 6 8.1 9.3 4 Ks-M 4 8 12.5 14.3 5 J4-A 5 10 17.8 21.3 6 A-^s 6 12 25.0 28.5 7 1^-^ 6 14 33.2 37.9 8 H-^ 6 16 42.0 47.9 9 ^-M 6 ■ 18 58.0 65.9 10 M-up 6 20 82.5 94.0 11 / Extra \ 8 22 89.0 101.2 12 \ Heavy/ 8 24 114.5 130.5 Operators frequently adjust the pressure regulators from one to two pounds above the figures given in the table to allow for gauge variations and drop of pressure when the gases are supplied in cylinders. * Gas consumption per hour is the maximum with torch burning continuously. 15 DAVIS-BOURNONVILLE OXY-ACETYLENE WELDING and CUTTING COURSE OF INSTRUCTION Lecture EXPANSION AND CONTRACTION PREHEATING DAVIS -BOURNONVILLE INSTITUTE JERSEY CITY. N. J. Copyright 1919 by thb Davis- BouRNONViLX-E Company EXPANSION AND CONTRACTION- PREHEATING Changes of Temperature Change Length, Breadth and Thickness — Expansion Must be Provided for in Welding — Cost of Heat Produced by Torch too High for Preheating Use — Preheating Necessary for Large Castings — Setting Up a Cast- ing for Preheating and Welding — Preheating a Broken Pulley. Preheating a Bronze Valve Seat Casting — General Theory of Preheating. Heat is a mode of motion. According to scientific theory the molecules of all matter are in a state of vibration or move- ment to and fro. The extent of vibration depends on the temperature, increasing as the temperature rises, and decreas- ing as it falls. According to this accepted theory there is no movement or heat vibration at absolute zero. The absolute zero or point of no temperature is 273 degrees below the freezing- point of water on the Centigrade scale and 459 de- grees below the zero point on the Fahrenheit scale. Matter exists in three forms — solid, liquid and gaseous. At very low temperatures all gases and liquids become solid. On the other hand, all solids melt at some temperature; and at very high temperatures they become gases. We find water in the three forms in nature. It freezes at 32 degrees and becomes ice, and boils away in steam or gas at 212 degrees F. Changes of Temperature Change Length, Breadth and Thickness Changes in temperature mean changes of length, breadth and thickness. A bar of iron or steel expands as it is heated and contracts as it cools. The expansion of a bar of steel by heat is attended with great force. It is practically impos- sible to prevent a bar expanding with heat, and contraction cannot be prevented as it cools. In fact, so great is the contraction force that if a long rod is heated and fixed firmly in a cast iron frame so that it cannot contract as it cools, it will rupture or pull itself apart, and then each part will contract. The same holds true of a casting. If a casting is made in the foundry without due regard to the contrac- tion stresses, it may come out of the mold broken. Some parts will have contracted more than others, and not being able to contract freely, naturally they have pulled apart. Every molder and pattern-maker knows how necessary it is to provide for contraction stresses in making castings. The success of the heavy iron founder largely depends on adapt- ing his work to the peculiarities of cast iron in this respect. Expansion is Proportional to the Rise in Temperature The expansion in length, breadth and thickness is pro- portional to the rise in temperature, and contraction is also proportional to the fall in temperature in the same ratio. The expansion rates of metals differ, being greater for copper and aluminum, for example, than for cast iron. The expansion of copper is about one-tenth of an inch per 1000 degrees F. per foot. This means that a copper bar one foot long expands one-tenth of an inch when raised 1000 degrees in temperature. A gray iron casting when preheated to 1500 degrees expands a little over one-tenth of an inch per foot, the expansion rate being 0.068 inch per foot 1000 degrees rise in temperature. Aluminum expansion is over twice that of cast iron ; the ex- pansion per foot per 1000 degrees is 0.148 inch. Great care must be taken when preheating aluminum cast- ings that the safe temperature is not exceeded. It is not safe to preheat aluminum over 600 to 800 degrees, and when heated the aluminum casting must be handled with great care as it becomes weak and brittle. Expansion Must be Provided for in Welding When we undertake to weld two pieces of metal together, we must provide for expansion, or we shall not be success- ful. The flame of the torch raises the temperature enorm- ously at the place where the weld is being made, and the heat spreads throughout the pieces. The welding is pro- gressive and as the metal is welded at a given point, the torch moves on and the metal begins to cool off and contract. The force of contraction may be so great that the joint will pull apart in places after it is welded. When preparing to weld two bars of steel together, we must lay them so that expansion and contraction will be provided for. The rule is to provide 2^ per cent of the length of the weld for expansion and contraction. If the joint is 10 inches long we should lay the pieces so that the far end of the weld will be % inch further apart than the end at which welding is begun. If this rule is followed you will have little, or no trouble on a simple job. The action is this : The two pieces are laid with a space between them, which tapers so that it is %. inch greater at the far end. We tack them together and begin to weld. As welding proceeds, the molten metal cools and contracts. The contraction causes the parts welded to act like a hinge, drawing the unwelded ends closer and closer together as the welding proceeds. Finally, when the torch has reached the far end you will find that the ends have been pulled together to just about the right space for finishing the weld. If in- sufficient space is left contraction cannot take place in the cooling parts and destructive stresses may be set up. It is often an extremely difficult matter to provide for expansion and contraction when welding castings. In fact, the skill of the welder is displayed by the way in which he prepares the job and provides for expansion and contraction stresses. Effect of Torch Flame Comparable to Wedge The efifect of the torch flame on a casting may be com- pared to that of a wedge or tapered drift if driven into the crack or between the parts to be welded together. Suppose that a casting has a crack running from one edge toward the center. The place to start welding is the inner end of the crack. If the crack is short no preheating may be necessary because the stresses produced will be comparatively slight. But if the crack is long the local expansive effect of the torch flame may be disastrous unless it is reduced by preheating. You can see what the probable effect would be on a thin casting, say two feet square and having a crack in one side running toward the center a distance of six inches, if you drove a thin wedge into the crack. The effect would in- variably be to extend the crack and make the conditions worse. Suppose that the same casting has a blowhole near the center which you wish to weld up. If you start to weld in the hole you heat the metal to a high temperature around the hole and' produce expansion stresses of great force. The condition is practically the same as though you drove a tapered drift into the blowhole with a heavy sledge. The drift forces the metal apart to such an extent that the elastic limit of the iron is exceeded and a rupture results. So it may be when welding cast iron without preheating. "All that goes up must come down," and all that is ex- panded by heat above normal, must sometime contract to normal dimensions when the temperature returns to normal. Often the inexperienced welder has the unhappy experience of making a good weld in a casting and then seeing the metal crack elsewhere as it cools. He mends in one place and breaks it another. This is clearly due to contraction stresses resulting from not preheating or preheating at the wrong place. Preheating may be done so badly that it makes conditions worse instead of better. In the talk on heat and temperature we endeavored to make clear the difference between the heat of a body and the temperature of a body. Heat is expressed in quantity and temperature in degrees of intensity. The oxy-acetylene torch produces a flame of great intensity but of not much volume. It is true that we can change the amount of gas consumed, the size of flame and the amount of heat by changing the tips. But even with a large tip, the total amount of heat produced is not great compared with that which can be produced in a comparatively small furnace. Cost of Heat Produced by Torch too High for Preheating Use The cost of the heat produced by the oxy-acetylene torch is much higher than the cost of heat generated in a forge or with an oil blowtorch. You should get this very clearly in mind, as it has an important bearing on oxy-acetylene welding in general. The oxy-acetylene torch produces a flame of high temperature, but it yields comparatively little heat. The heat produced is more costly than the heat of a coal fire, charcoal furnace or an oil blast. In what has just been said about expansion and con- traction you learned something about the forces produced by heating and cooling and the necessity of providing for their free play. You cannot prevent a piece of metal expanding when it is heated, nor can you keep it from contracting as it cools. If you attempt to prevent expansion or contraction you are likely to cause a fracture in the welded joint or some other place. FIG. 1. HAUCK KEROSENE BLOWTORCH FOR PREHEATING CASTINGS AND FORGING FOR WELDING Preheating Necessary for Castings When welding a large casting or any casting of other than simple form, or even castings of simple form under most conditions preheating will be necessary. By preheating we mean heating the part to be welded with some other source of heat than the oxy-acetylene torch. The black- smith's forge fire may be used when the parts are compara- tively small but in general it is better to use some source of heat that can be readily applied to the parts when lined up on the welding table or to provide a special preheating fire or furnace on which the parts can be lined up and welded without moving after having been heated to the required temperature to relieve the expansion and contraction stresses. The choice of source of heat depends on local conditions and character of the work. An oil blowtorch or several oil FIG. 2. PREHEATING A BROKEN PULLEY SECTION WITH A FIRE- BRICK OVEN AND KEROSENE BLOWTORCHES blowtorches may generally be used with satisfaction if the castings are not too large. These torches are made in a variety of styles and capacities. They are simple, compact and produce a large soft flame of great heating power. One or more of these torches will soon heat castings to the degree where the broken parts may be welded without fear of setting up destructive expansion and contraction stresses. In localities where hardwood charcoal c^n be ob- 8 tained it is used in preference to oil blowtorches by some welders, however, as they believe better results can be ob- tained especially with large castings into which the heat has to be soaked for a long time before the internal stresses can be equalized. Another advantage of a hardwood charcoal pre- heating fire is that heat can be applied to the casting while welding is going on without creating highly uncomfortable conditions for the welder. The blowtorch flame, is likely to make things very uncomfortable for the welder if kept going after the welding starts. A preheating stove is a useful if not indespensable ac- cessory of the welding shop. It is satisfactory for preheat- ing comparatively light castings which may be laid on the top and heated by conduction and convection. The stove is operated with oil or gas and the flames do not come di- rectly in contact with the casting to be preheated. The pre- heating stove is not intended to be used as a welding table but merely for preheating parts which can be quickly welded after being removed to the welding table. Setting Up a Casting for Preheating and Welding When preparing a casting for preheating and welding it should be laid on the welding table, the preheating forge or a brick floor and blocked up with firebricks so that the flames from the blowtorch or charcoal may pass beneath. It is essential that the floor or table be fireproof, of course. In order that the blowtorch may be used economically it is desirable that the casting be so protected that the heat is not radiated rapidly. Asbestos paper is a convenient and efifective material for the purpose. It is furnished by the manufacturers in large sheets and is light, clean and easily applied. All parts of the casting should be covered except that part where the welding is to be done, and when the joint is welded it should be cov- ered also and the whole casting allowed to cool down uni- formly. If asbestos paper is not available, dry ashes or dry sand may be used to cover the casting and conserve the heat but such substances are not satisfactory for the purpose. It is difficult to apply dry ashes so as to cover all parts of a casting without using an excessive quantity. They are in the way when welding and are likely to fall into the joint and give trouble. When the job is finished there is a mess to clean up. By all means use asbestos paper if you can get it. The cost will be repaid many times in satisfaction, clean- liness and general efficiency. Preheating a Broken Pulley In the foregoing we have dealt with general preheating but often it occurs that preheating all over is unnecessary and even undesirable. If you have to weld a broken pulley you have a problem that requires some study. If a spoke is broken it could not be welded without providing for expansion and it is a difficult, expensive, and troublesome job to preheat a large pulley all over and, in this case, undesirable. What we should do in a case like this is to preheat the pulley rim and spokes each side of the broken spoke. The rim is ex- panded by preheating and the broken spoke pulled apart at the break. Now the oxy-acetylene flame can be applied and the break welded without fear of disastrous consequences. When the weld is finished it should be covered with asbestos paper and the heated parts of the rim may be ex- posed to the air. The problem is to make the rim and spoke cool down at such respective rates that there will be no severe contraction stress produced. A job like this requires some experience as a job welder but the theory is one that you can readily understand and apply as you are gaining experi- ence. If the pulley is broken in the rim, the hub should be pre- heated and a jack should be applied between the spokes so as to spring the broken rim apart. When the rim is sprung apart space is made available for welding and the conse- quent expansion. Here again experience is required in order to judge just how much the hub should be preheated and the rim sprung apart so that when welded and cooled it will be round and true. 10 Preheating a Bronze Valve Seat A bronze casting for an air pump valve chamber which forms a seat for several flap valves must be preheated for welding with due regard to the thin metal spiders that sup- port the guide for the valve stem in the center. If a casting of this type is preheated with a charcoal fire without proper protection for the thin metal sections the gases and flames will naturally pass through the openings and the thin metal parts will heat quickly to a high temperature long before the body of the casting has become hot. This is improper pre- heating. If a crack between adjacent valve seats is welded after preheating in this manner the probability is that the casting will pull apart in another place as it cools. The con- traction stresses set up are so severe that it would be a miracle if fresh cracks do not develop. A casting of this type must be handled intelligently. More skill is required for pre- heatitig than the actual welding. The flame of the preheat- ing fire must be prevented from passing through the openings and overheating the thin metal sections. This may be ac- complished by laying a thin metal plate over the fire and placing the casting on the plate. The flames then must pass around the plate and heat the casting indirectly. It will take longer to preheat in this manner but the results will un- doubtedly be much more satisfactorily in the long run. When a casting of this kind has a crack between two adjacent valve seats the aim in preheating should be to ex- pand the rim so as to separate the margins of the crack slightly. Then when welded the metal in the joint which has been raised to the fusing temperature will be able to con- tract without exerting a tremendous stress in the adjacent part. The rim will follow the contraction stress because it has it- self been expanded beyond the normal size. General Theory of Preheating The general theory of preheating may be expressed in a few words. Parts to be welded are preheated in order to overcome expansion and contraction stresses. It is cheaper H to heat a large metal casting with a charcoal, coal or oil fire than with the oxy-acetylene flame. Preheating must be done with reference to the individual job and no set rule can be laid down for preheating castings of irregular shapes. They should, in all cases, however, be preheated for the pur- pose of providing room for the local expansion produced by the oxy-acetylene flame and the amount of preheating should be calculated so that the parts will come back to approxi- mately their original position when cool. When large castings are preheated the radiating heat will be considerable no mat- ter how well they are protected. The welder should be suit- ably dressed for the job, and shields should be provided to fend off the radiated heat whenever possible. Effect of Preheating on Torch On very large and heavy work the use of special water- cooled torches will be necessary as the torch of the ordinary type may become so hot as to be unmanageable because of flashbacks. However, the skilful use of asbestos paper on a preheated casting will largely overcome the trouble many times. Another resort is a pail of water into which the torch is dipped from time to time to cool ofif the head. Questions 1. In how many forms does matter exist? 2. What is the effect of changes in temperature on dimensions of a casting? 3. Why is it necessary to provide for changes of dimen-, sion due to changes in temperature? 4. Why not use the torch for preheating castings? 5. What is the advantage of the oil blowtorch for pre- heating? 6. Why is hard wood charcoal preferred by some welders ? 7. What should be done to conserve the heat when preheating? 8. What precaution should be taken with a welded casting when cooling down? 12 9. How would you proceed to preheat a pulley with a broken rim? 10. What would you do if a spoke only was broken? 11. Having welded a broken pulley rim, how would you protect it while cooling down? 12. How should the parts of a pulley be protected when the spoke only has been welded? 13. What effect may preheating have on the torch? 14. What should be done to stop the trouble? 13 Notes 14 Notes 15 DAVIS-BOURNONVILLE OXY«ACETYLENE WELDING and CUTTING COURSE OF INSTRUCTION Lecture PREPARING THE JOINT FOR WELDING DAVIS -BOURNONVILLE INSTITUTE JERSEY CITY, N. J. Copyright 1919 by the Davis-Bournonvilx-e Company PREPARING THE JOINT FOR WELDING Reason Why Beveling is Necessary — Angle of Bevel — ^Thick Casting Should be Beveled on Both Sides when Possible — No Beveling Required on Thin Alumi- num Castings — Methods of Cutting Bevels — Care Must be Taken to Remove All the Slag and Oxide from the Joint Before Starting to Weld — ^Parts Should be Cleaned — Alignment and Allowance for Contraction. One of the first principles of sound welding, as has been repeatedly stated in these lectures, is securing complete fusion and perfect union of the welding material and the edges of the plates to be welded. When the material is thin — say -^ to }i of an inch — you can weld successfully when the edges are square or as left by the cutting shear. The heat of the oxy-acetylene flame will penetrate deep enough to produce complete' fusion and satisfactory union. But when thicker plates are to be welded it is necessary to bevel the edges in order to obtain the best results. By beveling we; mean cutting away the corners so that when the two plates are brought close together they form a trough or vee. Reason Why Beveling is Necessary The reason for beveling the plates to be welded is easy to understand. It is necessary because the heat of the flame suitable for welding will not penetrate and produce perfect fusion beyond a depth of say ^ to -^^ inch. The depth of penetration, of course, depends on the size and shape of the flame ; the neutral flames that can be obtained with the smaller sizes of tips will not give much greater penetration than the depth stated. Hence, when the parts to be welded are thicker than % of an inch, we should cut away the metal at the sides in order that the flame may be free to operate on the center of the joint and fuse it perfectly clear through. We then fill in the vee by using adding material until it is level full. Angle of Bevel It has been found by experience that the sides of steel and cast iron plates should be beveled at an angle of about 45 degrees. When two plates which are beveled at an angle of 45 degrees are butted together the included angle is double or 90 degrees. A lesser angle may be used on brass and bronze, and is generally advisable but the welder should not experiment with any but the recommended bevels until he has become skilled in the use of the torch and able to recog- nize instictively when he is getting perfect fusion and union. Then he can try welding plates with lesser angles of bevels until he finds just what the limits are. It is, of course, advantageous to use a lesser angle wherever possible as the amount of adding material and gas required are reduced. Thick Castings Should Be Beveled on Both Sides When Possible If the part is very thick and it can be approached' and welded on both sides, it is better to bevel and weld on both sides. The cross section area of the two vees when made of the standard angle is only one-half the cross section area of the single vee of the standard angle made all from one side. This you can readily prove for yourself by laying out a vee say for a two-inch plate, and then laying out two vees opposite in the same thickness of plate. The double vee reduces the amount of adding material and the quantity of gases required to weld. Moreover, you will obtain a better weld and less labor will be required for beveling the joint also. In many cases, however, it will be impossible to work on both sides of the piece. In that case, of course, the beveling must be done on one side only. Should the piece be very thick it is then advisable to reduce the included angle considerably ; if the angle is reduced to say 60 degres for a thick weld, the skilled workman should be able to produce good work because he can so manipulate the torch that the actual welding will take place in an angle of approximately 90 degrees while the untouched sides of the trough will be at a lesser angle. In other words, if the sides of the vee are inclined at 60 degrees the skilled workman will start to work at the bottom and fill in so that the sides of the zone of welding are at a 90-degree angle and he will maintain this relation throughout until the job is finished. It fig; 6 COMPARISON OF PREPARATION FIG. 7 FOR VERY HEAVY SECTIONS Copyright 1919, by Davii-Boumonville Co, Davis Bournonville Institute SHOWING METHODS OF PREPARING THIN AND THICK METAL FOR WELDING would not pay, of course, to resort to this expedient on thin sections but on thick sections it will save much time, labor, adding material and gas. . No Beveling Required on Thin Aluminum Castings Cast iron and steel, as already stated, should be beveled at an angle of 45 degrees on each edge, making the included angle about 90 degrees. Aluminum need not be beveled so much as the lesser angle will work satisfactorily in most cases. In fact, when welding aluminum ^ inch thick or less no beveling at all is necessary where the welding iron or spud is employed to break up the oxide. Experience is re- quired, however, to work successfully in this manner as the operator must produce the weld without actually seeing it. He manipulates the molten metal with the welding tool work- ing out the oxide with a puddling hook so that the pure metal can flow together and produce intimate union. Methods of Cutting Bevels Various methods may be employed for cutting the bevel depending on the tool available. The quickest and easiest method generally to follow in the work shop is to grind the edges with an emery wheel using an ordinary floor grinder for the pur- pose when the parts are not too heavy. In the case of heavier castings which cannot be taken to the wheel, it is good prac- tice to use a portable grinder driven by a flexible shaft or an electric motor. In some welding shops swinging frame grinders are provided for beveling joints but they take up considerable room and are not as convenient to use as the flexible shaft arrangement. In the absence of means for grinding a bevel the work- man must cut away the metal with a hammer and chisel or with a file. Filing is a very slow and expensive process and the welder should learn to use the hammer and chisel ef- fectively. Chipping with a hammer and chisel requires con- siderable training but like most other operations, requiring manual skill, it is largely a matter of practice provided one starts out with the right kind of tools and follows approved methods. The choosing of hammer is important. Use a ball pene machinist's hammer weighing about 1^ pounds. The handle should be smooth and flexible. The length of the ham- mer over all should be about 16 inches. This is the hammer that will be used for most ordinary use but heavier and lighter hammers should be used for heavy and light work. A supply of sharp chisels should be provided. It is useless to try to chip a bevel on cast iron or steel without a sharp chisel. You cannot do it effectively any more than a carpenter can plane a board smooth with a dull plane. Hold the chisel easily in the left hand and grasp the ham- mer handle at the end and swing the hammer freely over the shoulder. Do not look at the end of the chisel but look at the point where you are cutting the chip. Of course, you will hit your hands some nasty raps when learning but you will make more rapid progress if you start right and stick to right principles. The workman who tries to chip holding the chisel in a death grip and hammer handle in the middle while he looks at the end of the chisel, is making hard work of an easy job. He works in anything but a workmanlike manner. The hammer and chisel when properly used are very effective tools, and we hardly over estimate the importance of learning to use them effectively. When chipping steel the chisel point will move more smoothly if it is dipped oc- casionally in oil. A small bunch of cotton waste saturated with oil may be laid alongside the work to lubricate the chisel edge. The hacksaw may be advantageously used for beveling castings, especially when light and easily broken. Successive cuts should be made with the saw along the margins, at an angle of 45 degrees. These cuts should be not more than ^ inch apart in ^ inch metal. When the saw cuts are finished the metal is cut away with the hammer and chisel. The saw cuts make chipping much quicker and easier, and reduce the chances of breakage. If a drilling machine is available, a series of circular vees can be drilled along the crack with a flat drill ground on the point to an angle of 90 degrees. The vees should be drilled until the point of the drill nearly penetrates the cast- ing. The hammer and chisel can then be used to cut away the partitions between the drilled vees very quickly. The vees should be drilled as close together or should even over-lap in order to leave as little metal as possible to be cut away with the chisel. If preparing steel parts for welding and much beveling is necessary it can be done much more quickly with a cutting* torch, however. The torch will remove ten cubic inches while one is being cut away by an emery grinder or a hammer and chisel. The welder should take advantage of all possibilities of his trade to save time and labor. Care must be taken to remove all the slag and oxide from the joint before start- ing to weld. When beveling the joint it is advisable in many cases to leave narrow parts unbeveled to assist in lining up when ready for welding. These narrow unbeveled parts are "wit- ness points" by which the original relation of the pieces can be ascertained and maintained. The location of these un- beveled parts will depend on the nature of the piece and its size. It should, in general, be as narrow as possible in order not to make broad defective spaces in the weld. It may be advisable in some cases to chisel them away after the casting has been tacked together and partially welded. Parts Should Be Clean When preparing parts for welding that are covered with oil or grease, it is generally advisable to clean them thor- oughly, using gasoline or kerosene to cut the grime loose. This may seem like unnecessary labor but it is not so. The workman cannot do the job justice if he is smeared with dirty oil and is in a generally uncomfortable condition. A little time spent in making the work clean and placing it in a position where he can work comfortably will be well spent. Cleaning the work will not only permit better welding to be done but it will save accumulating an unnecessary amount of grime and making the welder present a disreputable appear- ance. A skilled workman should be able to work without getting grease and dirt all over him unless it be on some emergency job where he is surrounded by unclean parts. Alignment and Allowance for Contraction Preparing the joint for welding includes alignment. When working in the workshop the alignment will be simplified by the use of a welding table. But when welding in the field the workman may have to resort to various expedients in order to obtain a satisfactory job. The use of straight- edges, levels, plumb bobs and the eye may be necessary. Look the broken casting over and see how the parts should be when welded. Block them up so that when tested with a straightedge they are in line or if the straightedge can- not be used, measure from a level floor. Unless means are available for aligning the broken parts carefully, it may be very unsafe to go ahead and weld as the result is likely to be unsatisfactory. It may be necessary in some cases to place the broken parts in their original position and mark them in such a manner that they can be aligned on the weld- ing floor to agree with the position when assembled. Remember that allowance must be made for the effect of contraction when welding without preheating. A steel test bar should be adjusted out of line slightly so that it will be approximately straight when welded. The contraction on the side of the vee will be somewhat more than for the opposite side unless preheated. Questions 1. How deep will the fusing heat of the smaller torch flames penetrate into metals when welding? 2. Why is beveling necessary? 3. What is the greatest thickness of steel than can be welded without beveling? 4. What is a prepared joint? 5. What is the recommended angle of bevel? 6. What should be the included angle when two beveled edges of steel plates are butted together? 7. Why should thick castings be beveled on both sides? 8. What is the reason why gas and adding material are saved by beveling on both sides? 9. Is it necessary to bevel an aluminum casting %. inch thick? 10. How would you proceed to cut the bevels on a light casting? 11. Of what use is the hacksaw in beveling? 12. When can the cutting torch be used for beveling? 13. What precaution should be taken in regard to slag and oxide on a joint beveled with the torch? 14. What is the first thing to be done when preparing to weld a greasy casting? 15. What is the straightedge used for when setting up for welding? 10 Notes 11 DAVIS-BOURNONVILLE OXY-ACETYLENE WELDING and CUTTING COURSE OF INSTRUCTION Lecture WELDING RODS AND FLUXES DAVIS -BOURNONVILLE INSTITUTE JERSEY CITY, N. J. Form 387 Copyright 1919 by the Davis-Bournonvii,i. -I 03 ^^ /^ POINT AT WHICH SELF CONFIDENCE IS REGAINED ill > / DROP IN MANIP TO LOSS OF S JLATIVE SKILL DUE ELF CONFIDENCE »- / CAUSED BY CHANGED CONDITIONS | -1 3 0. z < / COURSE OF INSTRUCTION > ^ POINT AT WHICH SUBCONSCIOUS MANIPULATION STARTS 1st WEEK 2nd WEEK 3rcl WEEK INDEFINITELY | Davis Bournonville Institute FIG. 10. CHART ILLUSTRATING PROGRESS OF WELDERS WHEN LEARN- ING. ACCIDENTS LIKELY TO HAPPEN IN THIRD WEEK. Don't use a regulator with a leaky valve. Don't use matches to light the torch; use a flint ignitor. Don't use a porous or leaky hose. Don't let oil drip on the hose. Don't let the hose become overheated from close contact with a preheated casting. Don't let flashbacks burn in the head ; close the oxygen valve at once. Don't turn on the acetylene cylinder valve first in starting to weld. Don't open the oxygen needle valve first when lighting the torch. Don't fail to wear goggles to protect the eyes. 11 Don't wear ragged clothes likely to catch fire when welding or cutting. Don't fail to wear an apron or overalls. Don't wear broken shoes in a welding shop. Don't neglect the torch ; hang it up when through welding. Don't use the torch head as a, hammer. Don't let the tip drop into the puddle. Don't let the tip of the white hot cone touch the molten metal. Don't fail to give the torch a semicircular zig-zag motion on prepared joints. Don't use ordinary iron or steel wire for adding material. Don't use common cast iron welding sticks. Don't try to make your own fluxes. ; Don't waste flux. Don't let tips lie around on the welding table ; keep them cov- ered in a box. Don't try to remove the head of a torch from the tubes. Don't fail to clamp the hose firmly to the nipples. Don't lay an acetylene cylinder down flat on its sides. Don't use acetylene too fast from a cylinder. Don't neglect the odor of acetone when welding; you are using the acetylene too fast. Don't leave gases under considerable pressure in cylinders; use as much as you can before returning an "empty". Don't neglect to put the cylinder cap over the cylinder when returning it to the manufacturer. Don't move cylinders about the plant with the regulators in place ; always take them ofif. Don't pull on the regulator with the hose. Don't let an acetylene or oxygen cylinder stand near a fur- nace or boiler. Don't let an acetylene or oxygen cylinder stand out in the hot sun when fully charged without protection. Don't handle gas cylinders roughly either when filled or empty. Don't let an oxygen cylinder stand beneath a dripping line- shaft. Don't let an oxygen cylinder get oily or greasy. 12 Don't let acids drip on gas cylinders. Don't test a pressure valve with oil; use water or glycerine. Don't melt the welding rod with the torch flame. Don't neglect to break down the sides of the vee when welding. Don't forget that the puddle must melt the adding material. Don't use a -^jr inch welding wire on a ^ inch weld. Don't use square or twisted wire adding material. Don't let adding material get rusty. Don't fail to bevel the edges when preparing to weld. Don't overheat brass or bronze when welding or brazing. Don't try to weld a broken malleable iron casting ; braze it instead. Don't forget that a brazed joint is very strong and often preferred to a welded joint. Don't forget to support aluminum under the weld. Don't try to weld aluminum without using a puddling stick. Don't forget that aluminum can be welded smoothly with flux. Don't overheat an aluminum casting. Don't use the torch flame for preheating ; it is too expensive. Don't forget that high carbon steel melts at lower tempera- ture than low carbon steel, and is easily burned. Don't forget that cast iron melts at a lower temperature than steel and that it requires scaling powder. Don't go into an acetylene generator house with a lighted pipe, cigar or cigarette. Don't neglect to remove all the residuum when recharging an acetylene generator. Don't neglect a leaky pipe joint in an acetylene line. Don't force carbide into the opening of a generator with a metal rod ; a spark might be struck that would ignite the gas. Don't forget to blow off the acetylene and air mixture in a generator when first starting. Don't undertake to weld or solder an acetylene generator shell without filling it with water to force out all gas. Don't do any welding or soldering on an acetylene generator if there are other generators in the same room. Remove the 13 generator before making the repair. Don't let an acetylene generator run on a pressure of more than 15 pounds per square inch. Don't forget to keep the backfire or flashback chamber filled with water to the level of the overflow plug. Don't let any foreign substances go into the hopper of an acetylene generator with the carbide. Questions 1. Why should you be careful in handling an oxy-acetylene welding outfit ? 3. What is the pressure in an oxygen cylinder when re- ceived from the manufacturer? 3. How does the pressure in an oxygen cylinder compare with the pressure in a steam boiler? 4. What might be the effect on an oxygen or acetylene cylinder if set close to a furnace or if left out in the sun on hot days? 5. How is acetylene stored in an acetylene cylinder? 6. What happens if the acetylene is drawn off too rapidly? 7. How can you tell when gas is being drawn too rapidly from an acetylene cylinder? 8. How should one proceed to find a gas leak in an acety- lene pipe? 9. Why should a welder wear colored glasses? 10. When may spectacles with colored glasses be worn ? When should goggles be worn? 11. How would you determine whether a pair of goggles were suitable for your eyes? 12. What causes pitting of colored glasses? 13. Did you ever see colored spectacle glasses pitted on the inside? How could that be possible? W^hat does it show ? 14. What precaution should be taken with all goggles when used by a number of welders? 15. What provision is made to prevent the expensive colored glass in goggles becoming pitted? 14 16. What kind of shoes is safest in a welding shop, foun- dry or other place where molten metal is liable to fall on the feet? 17. What should be done when the flame flashes back in the torch? 18. What precaution should be taken with hose? 15 i DAVIS-BOURNONVILLE OXY-ACETYLENE WELDING and CUTTING COURSE OF INSTRUCTION GLOSSARY Terms used in Oxy-Acetylene Welding and Cutting DAVIS-BOURNONVILLE INSTITUTE JERSEY CITY, N. J. COPYRldHT 1919 BY THB; Davis-BournonviIvLE Company GLOSSARY Definitions of terms and words used in oxy-acetylene welding and cutting, together with chemical names and formulas. Acetone. (CgHgO) An inflammable liquid of distinctive odor and biting taste made by the destructive distillation of wood. It has remarkable solvent power for acetylene gas, the absorptive capacity being 24 to 25 volumes acetylene per volume of liquid per atmosphere. Used as the solvent liquid in acetylene cylinders. Acetylene. (CoHo) A combustible gas of high thermal value made by slaking calcium carbide with water, and used for welding, cutting, lighting and cooking. Acid Sodium Carbonate (NaHCOg) Bicarbonate of soda or common baking soda (saleratus). Adapter. A screw fitting for coupling pressure regulators to cylinders and provided with right or left hand threads, or both, of various diameters to fit. Adding Material. The filler rod used in welding. Also called welding rod or welding wire. Adhesion. Condition in a weld resulting from imperfect union and little penetration, comparable to a glued or cemented joint. Agitator. The revolving paddle of an acetylene generator for stirring up the residuum before discharging it to the sewer. Alignment. The state of being in line or in the original relation. A broken curved casting is in alignment when the parts are placed in the original relation. Alloy. A homogenous mixture of two or more metals. Ammonia. (NH^OH) Spirits of hartshorn, the aqueous solution of gaseous ammonia, NHg. Ammonium Chloride. (NHj^Cl) Sal-ammoniac. Angle Bar. A rolled steel bar the cross section of which is usually an angle of 90 degrees. Anode. The negative electrode of an electrolytic gener- ator on which the hydrogen gas collects. Aqua Regia. A mixture of nitric and hydrochloric acids in the proportion of 1 part nitric acid to 3 parts hydrochloric. Used for dissolving gold and for etching metals. Asbestos. A mineral substance composed mainly of magnesium silicate, which is spun, woven or felted and having high heat-resisting and insulating qualities. Used for pro- tecting work when preheating and after welding. Asbestos Blanket. The woven absestos fabric of an elec- trolytic generator to separate the gases. Atmosphere. The pressure of the air at sea level, 14.7 pounds per square inch. A pressure of 10 atmospheres is 147 pounds per square inch. Autogenous. Self-produced, and as applied to welding, meaning the welding of metals by fusing without the use of additional metal and without hammering. The term is loosely applied to all gas welding with or without the use of adding material. Babbitt. An anti-friction nietal used for lining bearings. The original babbitt formula is said to be about 50 parts tin, 2 parts copper and 4 parts antimony. Backfire. Penetration of a flashback through the torch into the handle, hose or pressure regulator. A backfire is caused by firing an accumulation of mixed gases, due generally to faulty manipulation of the cylinder stop valves, improper regulator adjustment, incorrect procedure in turning on and lighting the gas, or dipping the tip into the molten metal. See Flashback. Bearings. The support or wearing surface in a box or a revolving shaft. See Journal. Bell. A receiver for storing gases, consisting of an in- verted metal cup floating in water and water sealed at the mouth. Bevel. An angle of other than 90 degrees formed on the margin of a plate or casting when prepared for welding. Blowhole. A hole or cavity in metal formed by gas. Blow-off Valve. Hand operated safety valve of an acety- lene generator to clear the chamber of air and acetylene mix- ture after charging. Blowpipe. Originally a straight or curved pipe used by- workers of precious metals for ^blowing' an alcohol flame against the parts to be melted or soldered. A gas burner in which the combustible gas and air or oxygen are mixed and burned to produce a high temperature fliame. The term "torch" is given the preference in America when applied to the oxy-acetylene apparatus for welding and cutting. Bourdon Tube. The flattened curved tube of a pressure gauge which tends to straighten under internal pressure. Bottle. A pressure container for transporting acetylene, oxygen, hydrogen or other gas. See Tank or Cylinder. Brazing. A process of uniting metals by heating with a brass or bronze alloy of low fusing temperature. Also called hard soldering. Burning. Applied to lead, meaning the process of joining lead sheets for acid tanks by autogenous welding. Burning on. The process of replacing part of a broken casting in the foundry by pouring molten iron through a sand mold containing the casting until it is preheated and fused along the margins of the broken parts when the pouring is stopped and the metal permitted to cool and unite. Butt Joint. A seam made by butting two edges together. By-pass. Passage in the cutting torch connecting the oxygen supply with the preheating oxygen tube. Calcium Carbide. (CaCo) Material used for the produc- tion of acetylene gas by slaking with water. Calcium Chloride. (CaOClo) Chloride of lime. Bleach- ing powder. Calcium Hydroxide. (Ca(OH)2) Slaked lime. Calcium Oxide. (CaO) Quick lime. Camograph. A hand-operated torch cutting machine for cutting slotted holes in rails. Cap. The metal protector screwed over a cylinder stop valve to prevent injury in transit. Carbide Filling Plug. The screw plug in the top of an acetylene generator which is removed when filling the hopper. Carbon Dioxide. (CO2) A product of perfect combus- tion of carbon, a heavy colorless incombustible gas. Carbonite. Carbon compressed into rods and sheets used as a fire resisting dam in building bosses, lugs, gear teeth and other parts. Also called carbon blocks. Carbonizing. Having the quality of imparting carbon and meaning, when applied to the torch flame, an excess of combustible gas which deposits carbon in the molten metal. See Carburizing. Carbon Monoxide. (CO) Product of imperfect combus- tion. Carburizing. Same 'as carbonizing, but preferable 'for carbon imparting. Casehardening. The process of carburizing the surface layers of mild steel and raising the carbon content to the point where the steel will harden when heated to a cherry red and dipped in water. Cathode. The positive electrode of an electrolytic gener- ator on which the oxygen gas collects. Cell. An electrolytic generator unit. Channel. Structural shape having flanges turned on each side forming a trough. Chipping. Removing metal with a hammer and chisel. Coefficient. The factor used to determine the expansion of metals by heat. Generally expressed per one degree change of temperature F. The coefficient of expansion of steel is 0.00000636. Cohesion. Condition resulting from perfect fusion and penetratioji which locks the molecules of parent metal and adding material together. Column. A vertical support made of structural steel or cast iron. Combustible. Anything that burns in the air or an atmos- phere of oxygen. Same as Inflammable. Compressor. A water cooled gas pump for compressing oxygen, hydrogen, or acetylene into cylinders. Connector. A fitting for joining lengths of hose. Content. The quantity of a material contained in a metal,, such as the carbon, nickel or titanium content of steel. Contraction. The shrinkage of metal in cooling. Copper Sulphate. (CUSO4) Bluestone or blue vitriol. Countersink. To bevel the edge of a hole to fit the tapered head of a bolt or rivet. Coupling. A threaded sleeve for joining pipes. Conical Seat. The joint in the torch head fitting the inter- changeable tip. Creeping. The building up of pressure in a pressure regu- lator when not in use. Caused by gas leaking through the regulating valve. Cross Bar, The handle of the regulating screw of a gas pressure reducer or regulator. Cutting. The term applied to the burning of wrought iron, steel, and cast iron with a jet of oxygen. Cutting Torch. A torch or blowpipe with one or more heating jets and an oxygen jet, used for cutting iron and steel. Cylinder. A pressure container for holding gas under pressure. Also called Tank and Bottle. Cylinder Filler. The porous contents of an acetylene cylinder made of asbestos, charcoal, infusorial earth and cement, compacted to completely fill and leave no open space for the collection of free acetylene gas under pressure. Cylinder Valve. The outlet stop valve of a gas cylinder. Dial. The graduated face of a pressure gauge. Diaphragm. The flexible partition in a regulator beneath the regulator spring. Also the partition in a high pressure gauge to protect the glass from being blown out when the Bourdon tube bursts. Dissociation. Separation attended by the release of heat such as develops intensely in the combustion of acetylene with oxygen in the torch and produces the white hot cone having a temperature of about 6300 degrees F. Dissociation of acety- lene may result from over-pressure and shock. Drift. A tapered hand punch for enlarging and lining up rivet holes in plates. Ductile. That which can be drawn or stretched. Ductility. The property of iron, steel, copper, brass and other metals which permits them to be drawn into wire. Duograph. A motor driven torch welding machine for welding cylinders, containers, steel barrels, etc. Elastic Limit. The maximum load sustained by a test bar just before it begins to stretch. Electrode. Either of the poles of an electrolytic cell. Oxygen is liberated on the positive electrode and hydrogen on the negative electrode. Electrolyte. The water and caustic soda solution in an oxygen and hydrogen electrolytic generator. Elongation. The stretch of a bar when pulled apart in a testing" machine. Genearally ex;pressed in [percentage of a definite length of the specimen. Endothermic. Pertaining to the absorption of heat. Acetylene gas is an endothermic substance, heat being ab- sorbed in the reaction of calcium carbide and water by which it is produced. Few chemical compounds are endothermic. Etching. Corroding a polished metal surface with acid or other chemical to show the physical structure. Exothermic. Pertaining to compounds whose formation is attended with development of heat, and whose dissociation absorbs heat. Most chemical compounds are exothermic. Expansion. The increase in length, breadth and thick- ness of metals due to heat. Feeding Disc. Revolving plate on which the carbide drops from the hopper of an acetylene generator when feeding. Filler Rod. The adding material or welding rod used to fill a welded joint. Also called Adding Material and Welding Rod. Fillet. The material used to fill a corner and to round the angle. Filter. An apparatus for removing dust and floating im- purities from acetylene gas. Flame. The combustion of gas. Flashback. Snapping out of the flame and penetration of the flame into the torch mixing chamber but no further. A flashback is generally caused by an obstruction in the tip or by overheating of the tip and head. See Backfire. Flux. Any material used to dissolve oxides, to release trapped gases and slag and to clean metals for welding and soldering. Fracture. A break. Applied to broken metal surfaces. Fuse. To melt. Fusing. Melting (with heat). Gas. The form of matter usually invisible which may be indefinitely compressed and expanded, having no coherence or form, such as acetylene, oxygen, hydrogen, nitrogen, chlorine,, etc. Gasometer. A bell or receiver for storing gases. See Bell. Gauge. An instrument usually having a circular gradu- ated dial and movable hand for measuring pressures of gases in pressure containers. Generator. An apparatus for producing gas and usually applied to the means for producing acetylene or oxygen. Girder. A beam of I section built of plates and angles. Goggles. Colored glasses for protecting the eyes from destructive heat and light rays. Grain. The arrangement of the large crystals visible in a metal fracture. Handle. The part of the torch held in the hand. Handwheel. Any disc or wheel handle of a valve or other apparatus. Holograph. A hand operated torch cutting machine for cutting holes in the webs of rails and structural steel. Hopper. The receiver for calcium carbide in an acetylene generator. Horizontal. Level or parallel with the horizon. Applied to welding in a level position. Hose. Flexible rubber pipe reinforced with fabric. Used to connect the torch with the sources of gas supply. Hydrochloric Acid. (HCl) Muriatic acid. Hydrogen. (H) A colorless, odorless, combustible gas, the lightest known. Used for welding and cutting. I-Beam. A structural shape having a cross section like the letter I. Inflammable. That which can be burned. Same as Com- bustible. Interchangeable. That which can be interchanged, like the tips of Davis-Bournonville cutting and welding torches. Jet. The stream of gas issuing from a torch tip. Journal. The wearing surface of a revolving shaft in a bearing. See Bearing. Kerf. The fissure made in iron or steel by the cutting torch. Key. The handle used to open and close a cylinder stop valve. Laminated. Composed of sheets in layers. Lead Carbonate. (PbCOg) White lead. Lead Oxide. (PbO) Litharge. Line. A metal pipe or rubber hose for gas. Liquefaction. Reducing a gas to the liquid state by com- pression and refrigeration. Magnetograph. A hand operated torch cutting machine for cutting holes in ship plates, provided with magnets to hold the machine in place. Main. The principal distributing pipe of a gas line system. Malleable. That which can be shaped by hammering, bending or drawing. Manifold. A metal header or multiple connection for con- necting several gas cylinders to a pipe line. Mercury. (Hg) Quicksilver. Mild. Applied to steel to indicate low carbon content and characteristics similar to wrought iron. Mixing Chamber. That part of the torch in which the combustible gas and oxygen are brought together. Monel, A natural alloy of copper and nickel. Motor. Weight or spring-driven clockwork mechanism for revolving the feeding disc of an acetylene generator. Muriatic Acid. (HCl) Hydrochloric acid. Needle Valve. A small valve with a conical seat capable of fine adjustment and used in cutting and welding torches for regulating the gas mixture. Neutral. Applied to flame meaning neither carbonizing nor oxidizing. 10 Nipple. A short piece of screwed pipe. Nitric Acid. (HNO3) Aqua fortis. Nozzle. The discharge part of an apparatus. Sometimes applied to the tip of a torch. Overhead. Applied to joints in a ceiling or overhead. Oxide. Combination of oxygen with metal generally in the form of rust, corrosion, coating, film or scale. Oxidization. Combining with oxygen and forming an oxide. Oxidizing. Applied to the torch flame meaning a flame containing an excess of oxygen gas which burns the molten metal. Oxygen. The supporter of combustion comprising about one-fifth the atmosphere. Furnished commercially pure, com- pressed in cylinders to a pressure of 1800 to 2000 pounds pres- sure per square inch for torch welding and cutting. Oxygraph. A machine cutting torch mounted on a panta- graph reducing gear with a motor driven tracing wheel, so designed that a drawing can be traced and reproduced in the part cut out with the torch. Parent. The metal welded. Used to distinguish the parts welded from the adding material or welding rod. Peening. Stretching cold metal by striking with the peen of a hammer. Penetration. Welding clear through' the joint. Indicated by the molten metal appearing in drops or globules on the far side. Pet-cock. A small discharge valve with a plug or key re- quiring a 90-degree turn to open or close. Photomicrograph. Photograph of microscope enlarge- ment of a metal specimen. Plumb-bob. A weight with conical tip suspended with string to show the vertical line. Pole. One of the two terminals of an electrolytic genera- tor, know as positive and negative. Polymer. Product of high temperature generation in an acetylene generator. Polymerization. The effect of high temperature in acety- 11 lene generators which is shown by the presence of yellow tarry deposits. Pool. The small body of molten metal formed by the torch flame. Also called Puddle. Potassium Carbonate, (KgCOg) Potash. Potassium Chlorate. (KCIO3) Chlorate of potash. Preheating. Heating metal plates or castings previous to welding in order to minimize expansion and contraction stresses and to save gas. Pressure. The force exerted by a confined gas or liquid. Measured in pounds per square inch. Pressure Reducer. An apparatus for reducing and regu- lating the pressure of gases used for welding and cutting. Pressure Regulator. An apparatus for maintaining a nearly constant pressure of the gases used for welding and cutting. All pressure regulators are reducing valves, and operate by lowering the pressure of gas supplied from cylinders, generators or pipe line systems to the working pres- sure required. Puddle. The fused body of metal directly beneath the torch flame. Also called the Pool. Puddle Stick. A steel rod flattened at the end and formed in various shapes for breaking up oxides and removing slag. Used especially in welding cast aluminum without flux. Puddling. The breaking up of oxide and elimination of slag and oxide from the puddle, especially when welding cast aluminum without flux. Purifier. An apparatus for removing sulphurreted hydro- gen and other gases from acetylene. Pyrograph. A torch cutting machine for beveling and trimming flanged boiler heads and boiler plates. Radiagraph. A motor driven torch cutting machine for cutting straight lines or circles in steel and iron plate. Reaction. The change resulting from a chemical combi- nation or a mechanical action. Reducing. Applied to flame, meaning carbonizing or carburizing, the opposite of oxidizing. Regulator Screw. The part of a pressure regulator by 12 which the tension of the diaphragm spring is adjusted. Residuum. The shidge or accumulation of water and slaked lime in the bottom of an acetylene generator. Ribbon Flame. The torch flame produced with a tip having a narrow slot orifice. Ripple. A general characteristic of steel welds made with the hand torch, similar in appearance to the surface of water under an air current. Safety Disc. A sheet brass disc in combination with a fusible alloy designed to blow out under excessive pressure or heat or both. Safety Valve. A fitting connected to a gas pipe system containing a metal diaphragm designed to blow out when gas pressure exceeds a certain figure. Scale. The coating of oxide on (molten) iron and steel. Scaling Powder. Flux used for dissolving oxides formed in cast iron welding. Screen. A fine mesh wire cloth part to prevent foreign matter entering the regulator or torch. See Strainer. Scrubbing. An apparatus for removing ammonia, dust and other free impurities from acetylene gas. More elaborate than a washer. See Washer. Seam. A joint welded or unwclded. Applied generally to thin metal. Seat. The surface against which 'a valve disc is held when closed. Shell. The circular part of a cylinder. Side Seam. Applied to welding, meaning a horizontal seam in the side of an upright part. Slag. Oxidized metal and other impurities formed in welding 'and liable to be trapped in the molten state. Also applied to the oxidized metal and scale blown out when cut- ting iron and steel. Sludge. The accumulation of slaked carbide in the bottom of an acetylene generator. Sludge Valve. The discharge valve for removing resi- duum from an acetylene generator. Sodium Carbonate. (NaXOa) Carbonate of soda or 13 soda ash. Sodium Chloride. (NaCl) Common salt. Sodium Hydroxide. (NaOH) Caustic soda. Used in the electrolyte of oxygen and hydrogen generators. Sodium Silicate. (Na2Si409) Water glass. Sodium Sulphate. (NaoSO^) Glauber's salts. Sodium Tetraborate. (NaoB^O^) Borax. Crystalline borax contains ten parts water, its formula being Na2B4O-.+10H2O. Calcining or burning borax drives off the water of crystalliza- tion. Solder. A fusible alloy used for uniting metals. The soft solders melt at a comparatively low temperature and are alloys of lead and tin. The hard solders melt at higher temperatures and are usually alloys of zinc and copper. Soldering. The process of uniting metals by fusing an alloy of low melting temperature and heating the parts to be joined to the amalgamating temperature. Spectacles. Colored glasses with steel or aluminum frames and generally without side shields for protecting the eyes. Spelter. Hard solder, usually a one-to-one alloy of copper and zinc. Spoon. A wire flattened at the end for smoothing the surface of an aluminum joint welded without flux. Stirrup. The yoke connecting the diaphragm of a pres- sure regulator and the valve disc. Straightedge. Generally a steel bar with one edge planed straight and beveled. Used for lining up. Strainer. A part made of fine mesh wire cloth through which the gas passes and which stops the passage of dirt and foreign matter. Stuffing Box. The provision made for preventing gas leaking around the needle valve stems and high pressure valve stem of the cutting torch, etc. Sulphuric Acid. (H0SO4) Vitriol or oil of vitriol. Sweating. Soldering broad metal surfaces by coating the surface with solder, clamping the parts together and applying heat. 14 Tacking. Uniting metal parts with spots or buttons of fused metal. Tank. A pressure container for transporting acetylene, oxygen, hydrogen or other gas. See Cylinder or Bottle. Tinning. The process of coating metals with tin. Also applied to the preparation of tool steel for welding with machinery steel by coating the tool steel with adding material before welding. Tip. The copper or brass nozzle of the welding or cut- ting torch. Torch. A gas burner or blowpipe for welding or cutting. Torch Bushing. The nut for holding the tip in the torch head. Torch Head. The part of a ^welding or cutting torch carrying the tip. Torch Tube. The pipe connecting the torch head and handle. Ultimate Strength. The maximum load sustained* by a test bar before rupture. Union. A pipe coupling in parts held together with a nut. Used where pipes may require disconnection. Valve. The means for shutting off the flow of gas or liquid. Vee. The angle or groove between two beveled edges when prepared for welding. Vee Block. A block cut out in the shape of a vee or angle, and used for supporting shafts in line when welding. Vent Valve. Water sealed trap for discharging the excess water in an acetylene generator. Also a safety device to indicate the presence of an obstruction in the vent pipe. Vertical. Applied to welding, meaning a seam in an up- right or vertical position. Washer. An apparatus for removing ammonia and dust from acetylene gas. See Scrubber. Water Seal. A safety device to prevent backfires being propagated through a pipe line to the generator. Welding Rod. The metal used to supply the filler re- quired in a welded joint. Also called Adding Material and 15 Filler Rod. Welding Sticks. Adding material or welding rod of cast iron, cast aluminum and other cast metals. Welding Table. Metal table for supporting work for welding. Welding Wire. Wire adding material of the smaller gauges. Z-Bar. Structural shape having cross section similar to the letter Z. Zinc Chloride. (ZnCl,) Chloride of zinc or tinner's acid. 16 LIBRARY OF CONGRESS 003 338 411 7