ENGIN. LIBRARY A PRELIMINARY REPORT Prepared for Submission to its Principals BY THE AMERICAN COMMITTEE ON ELECTROLYSIS APPOINTED BY National Engineering Societies and other Interested Associations and Corporations (PRINTED NOT PUBLISHED) This preliminary report is intended to include only statements of fact. It does not .attempt to draw conclusions or to make recommendations or to discuss questions of law. NEW YORK CITY October, 1916 TVf Engineering Library Additional copies of this report may be procured from the Secretary of the American Institute of Electrical Engineers, 33 West 39th St., New York. at One dollar per copy. COMMITTEE BION J. ARNOLD, Chairman American Electric Railway Association. ALBERT S. RICHEY Worcester, Mass. R. P. STEVENS, Youngstown, O. CALVERT TOWNLEY, New York City, American Gas Institute. ALBERT F. GANZ, Hoboken, N. J. J. A. GOULD, Boston, Mass. JACOB D. VON MAUR, St. Louis, Mo. American Institute of Electrical Engineers. BION J. ARNOLD, Chicago, 111. F. N. WATERMAN, New York City PAUL WINSOR, Boston, Mass. American Railway Engineering Association. D. J. BRUMLEY, Chicago, 111. E. B. KATTE, New York City, W. S. MURRAY, New Haven, Ct. American Telephone and Telegraph Company. A. P. BOERI, New York City, F. L. RHODES, New York City, H. S. WARREN, New York City, American Water Works Association. A. D. FLINN, -New York City, D. D. JACKSON, New York City. E. E. MINOR, New Haven, Ct. National Bureau of Standards. E. B. ROSA, Sec'y. Washington, D.C. National Electric Light Association. L. L. ELDEN, Boston, Mass. D. W. ROPER, Treas. Chicago, 111. PHILIP TORCHIO, New York City, Natural Gas Association. B. C. OLIPHANT, Buffalo, N. Y. FORREST M. TOWL, New York City, S. S. WYER, Columbus, O. v~. 41489 SUB-COMMITTEES 1: PLAN AND SCOPE: CALVERT TOWNLEY, Chairman. ALBERT F. GANZ, E. B. KATTE, D. W. ROPER, E. B. ROSA, H. S. WARREN, F. N. WATERMAN, S. S. WYER. 2: PRINCIPLES AND DEFINI- TIONS: E. B. ROSA, Chairman, A. P. BOERI, D. J. BRUMLEY, D. D. JACKSON, R. P. STEVENS. PHILIP TORCHIO, Chairman, J. A. GOULD, W. S. MURRAY, FORREST M. TOWL, CALVERT TOWNLEY. 3: METHODS OF MAKING 4: EUROPEAN PRACTICE: ELECTROLYSIS SURVEYS : J. D. VON MAUR, Chairman, L. L. ELDEN, E. E. MINOR, B. C. OLIPHANT, F. L. RHODES, PAUL WINSOR. 6: AMERICAN PRACTICE: 6: F. N. WATERMAN, Chairman, ALBERT F. GANZ, E. B. KATTE, ALBERT S. RICKEY, D. W. ROPER, H. S. WARREN S. S. WYER. PUBLICATION: E. B. KATTE, CHAIRMAN, A. D. FLINN, ALBERT F. GANZ, ALBERT S. RICKEY, E. B. ROSA. PHILIP TORCHIO, H. S. WARREN, F. N. WATERMAN, S. S. WYER. PREFACE. Those familiar with the history of the electric railway in- dustry in the United States in the early 90's and subsequently for a decade, will recall the great rapidity with which the electric railway was developed and the litigation that resulted between the gas and water companies and the electric railway com- panies over the introduction into the field of the electric rail- way using a grounded return circuit. The utility companies whose properties were threatened with damage from elec- trolysis due to these grounded return circuits of the railway com- panies, attempted by all legitimate means to prevent the acceptance of the grounded return circuit, with the result that in one or two cases, for instance, in the city of Cincinnati, a complete metallic overhead return circuit was adopted and is still in operation, but the electric railway operated with a grounded return circuit in connection with the overhead trolley became the standard, and rapidly spread throughout the country, and still remains the standard for electric traction systems. At first when the electric railway systems were small, and light cars were used, the quantity of current flowing through the rails was not large, and the possibility of damage from electrolysis was comparatively small, but as the systems were ex- tended and the weight and number of cars greatly increased, the problem became much more serious, and began to demand special attention. It is only within the past four or five years that the subject has been sufficiently well understood by engineers generally to make it probable that their opinions could be made to agree upon standard methods for the pre- vention or adequate mitigation of electrolysis. At the present time, due to the fact that the grounded return circuit system has been so long established and so extensively adopted, with the result that millions have been invested in copper for supplemental rail return circuits, the engineers now endeavoring to seek a solution of the question find themselves confronted with the problem not only how best to design and in- stall a new system to prevent damage from electrolysis, but also 5 6 PREFACE what can be done with the electric railway systems as they exist in cities today. While recourse to the courts has always been open, the prov- ing in court of the precise amount of damage that has been occasioned by electrolysis, as distinct from other causes, and accurately proportioning such damage between various elec- trical companies, has made the fixing of responsibility extremely difficult. In view of this unsatisfactory condition it was thought best by the National Societies representing those connected with the various utilities involved to take up the subject compre- hensively and endeavor, if possible, by co-operation among them- selves and with other interested associations and corporations to gather and classify information, and if then found feasible to agree upon and recommend methods which without being finan- cially prohibitive will nevertheless practically eliminate damage from electrolysis. The American Institute of Electrical Engineers with this object in view invited the following bodies to officially appoint representatives to serve upon a committee for which the name The American Committee on Electrolysis was finally adopted : American Electric Railway Association. American Gas Institute. American Institute of Electrical Engineers. American Railway Engineering Association. American Telephone & Telegraph Company. American Water Works Association. National Bureau of Standards. National Electric Light Association. Natural Gas Association. The first meeting of the Committee was held in the Directors' Room, American Institute of Electrical Engineers, 33 West 39th Street, New York City, May 27th, 1913, to make pre- liminary arrangements, and the second meeting held at the same place on February 25, 1914, resulted in the selection of a permanent chairman and secretary, and the appointment of the various sub-committees. The result of the work of these sub-committees is embodied in the various sections of the accompanying report. Owing to the complexity of the subject and the need for thorough discussion in the several technical bodies, and for further investigation by the interests involved the Committee has thought best not to attempt to issue a final report at the PREFACE 7 present time, but has endeavored to present the subject in this preliminary report by such statements of fact as its members can, at this time, unanimously agree upon, with the expectation that, after the consideration of these statements of fact by the bodies whom the members of this committee represent, and such further investigation as may be necessary by the Committee, a report will ultimately be prepared, embodying principles, rules and recommendations which will form a basis for solving this com- plicated problem. New York City, September 21st, 1916. PRELIMINARY REPORT. THE AMERICAN COMMITTEE ON ELECTROLYSIS. GENERAL INDEX. PAGE PREFACE: A General Statement of the Scope of the Work. 5 I: PRINCIPLES AND DEFINITIONS: A. ELECTROLYSIS IN GENERAL: 1. Electrolysis 13 2. Electrolyte, Electrode, Anode, Cathode 13 3. Amount of Chemical Action (Faraday's Law) 13 4. Cause of Current Flow 14 5. Electrolysis by Local Action 14 6. Anodic Corrosion ....'. 14 7. Secondary Reactions 14 8. Cathodic Corrosion 15 B. ELECTROLYSIS OF UNDERGROUND STRUCTURES: 9. General 15 10. Self Corrosion 15 11. Acceleration of Local or Self Corrosion 16 12. Coefficient of Corrosion. 16 13. Anodic and Self Corrosion 16 14. Passivity 16 15. Polarization Voltage 16 16. Alternating or Frequently Reversed Direct Current 17 17. Action on Underground Metallic Structures 17 18. Stray Current 18 19. Electrolysis Mitigation 18 20. Electrolysis Surveys 18 21. Overall Potential Measurements 18 22. Potential Gradients 19 23. Positive and Negative Areas 19 24. Drainage Systems 19 25. Uninsulated Track Feeder System 20 26. Insulated Track Feeder System 20 II: METHODS OF MAKING ELECTROLYSIS SURVEYS: A. GENERAL: 27. General Principles of Electrolysis Surveys 21 28. Electric Railways 22 29. Earthed Piping Systems 24 30. Underground Cable Systems 28 31. Bridges, Buildings and Other Earthed Structures 30 32. Steam Railway Rails -. . , 31 33. General Survey Practices 32 34. Application of Remedial Measures Resurveys 36 9 10 GENERAL INDEX B. APPARATUS: PAGE 35. Portable Measuring Instruments 38 36. Recording Instruments 39 37. Normal Electrode 40 38. Earth Ammeter. : 40 39. Testing Electrodes 43 C. RECORDS AND REPORTS: 40. General 43 41. Electric Railways 45 42. Piping Systems 45 43. Cable Systems 45 44. Bridges and Buildings 46 45. General Conditions 46 III: AMERICAN PRACTICE: General A. MEASURES APPLIED TO RAILWAYS: 46. Insulation 47 (a) Complete Insulation 48 (b) Substantial Insulation 48 (c) Partial Insulation 48 47. Reduction of Track Voltage Drop 49 (a) Bonding 49 (b) Cross-bonds . ' 50 (c) Conductivity and Composition of Rails 51 (d) Reinforcement of Rail Conductivity 52 (e) Use of Additional Power Supply Stations and Distribu- tion of Load 53 48. Three Wire Systems 55 49. Reversed. Polarity of Trolley System 56 50. Booster System 57 51. Interconnection of Railway Return Circuits 58 52. Use of Alternating Currents 58 53. Insulated Track Feeder System 59 B. MEASURES APPLIED TO AFFECTED STRUCTURES: 54. Insulating Joints in Iron Pipes and Cable Sheaths 61 55. Insulating Pipes, Cables and Structural Steel from Earth.. .. 65 56. Shielding or the Use of an Auxiliary Anode 68 57. Drainage of Earthed Metallic Structures 69 (a) Lead Sheathed Telephone and Power Cables 69 (b) Pipe Systems 70 (c) Structural Steel 71 C. PATENTED PROTECTIVE SYSTEMS: 58. Foreign and Domestic Patents 71 D. ORDINANCES AND DECISIONS: 59. Ordinances 71 60. Decisions by Courts 72 GENERAL INDEX 11 IV: EUROPEAN PRACTICE: PAGE A. GENERAL: 61. Personal Investigation Necessary 73 62. Countries Visited 73 B. GERMANY: 63. Laws and Ordinances 74 64. Commission Recommendations 75 65. Construction 75 66. Conditions 75 C. ITALY: 67. Laws and Ordinances 76 68. Construction 76 69. Conditions 76 D. FRANCE: 70. Laws and Ordinances 76 71. Construction , 77 72. Conditions 77 E ENGLAND: 73. Laws and Ordinances 77 74. Construction 78 75. Conditions 78 F. SUMMARY AND CONCLUSIONS: 76. Germany, Italy, France, England 79 77. Application to American Conditions 79 G. REGULATIONS ADOPTED AND PROPOSED: 78. Germany Earth Current Commissions' Recommendations.. 81 79. France-^Regulations by Minister of Public Works 99 80. England British Board of Trade Regulations 101 81. Spain Electric Legislation. 107 H. SUMMARY OF EUROPEAN CONDITIONS: 82. Present Electrolysis Conditions 107 83. Protective Measures in Vogue 109 Feeders 109 Voltage and Current Conditions - 110 Miscellaneous Protective Measures Ill 84. Economic Aspects of Electrolysis Problem 115 85. Regulations and Tests 115 I. GENERAL REMARKS: 86. Germany 116 87. France.. . 117 12 GENERAL INDEX J. STATISTICAL OPERATING STRUCTURAL AND TECH- NICAL DATA: PAGE 88. Table 1 Magnitude of Electric Railway Undertakings, German Empire and United Kingdom 117 89. Table 2 Tramways Not Operated by Electricity, German Empire and United Kingdom 118 90. Table 3 Ownership of Electric Railway Undertakings, Ger- man Empire and United Kingdom 118 91. Table 4 Statistics of Tramways in Large Cities, German Empire and United Kingdom 119 92. Table 5 Statistics of Tramways in Small Cities, German Empire and United Kingdom 120 93. Table 6 Rail Bonding Data, United Kingdom 121 94. Table 7 Use of Negative Boosters, United Kingdom 122 95. Table 8 Distribution Systems for Tramway Feeders, United Kingdom 122 K. CURVES AND SKETCHES: Curve Graphical representation of Electric Railways Sta- tistics, United Kingdom, 1878 to 1912. (Fig. 9) 123 Sketch Track Construction, United Kingdom. (Fig. 10) ... 124 " Track Construction, Germany. (Fig. 11) 125 " German Tramway Rails. (Fig. 12) 126 " British Tramway Rails (Fig. 13) 127 Curve Rail Weight Data. (Fig. 14) 128 Sketch Typical Rail Bonds, United Kingdom. (Fig. 15) .. 129 " Cross Bonding Details, United Kingdom (Fig. 16) 130 L. MISCELLANEOUS NOTES: 96. Electrolysis Testing Methods 131 97. Abstract of Laws and Regulations or Recognized Standards in European Countries 131 98. Plan of German Earth Commission Reports 133 99. General Comments on Reports 134 V: BIBLIOGRAPHY: 135 VI: APPENDICES. (Tables.) 100. Table 9. Resistance of Standard Cast Iron Pipe 139 101. Table 10 Resistance of Standard Steel or Wrought Iron Pipe 146 102. Table 11. Resistance of Lead Cable Sheaths 148 103. Typical Report Sheets 149 I. PRINCIPLES AND DEFINITIONS. A. ELECTROLYSIS IN GENERAL. 1. Electrolysis is the process by which chemical changes are caused by an electric current, independent of any heating effect. NOTE. These changes usually occur in a water solution of an acid, alkali or salt. By the passage of an electric current through it, water (containing a trace of acid) is decom- posed into hydrogen and oxygen, copper is deposited from a solution of copper sulphate, silver from solutions of silver salts. Electroplating, electrotyping, and refining of metals by electrodeposition are useful applications of electrolysis in the arts. Electrolysis is involved in the charge and discharge of storage batteries, and in the operation of primary batteries. In order that electrolysis, may occur, the following condi- tions must be present : (a) There must be a flow of electric current through a conducting liquid from one terminal to another; (b) The conducting liquid must be a chemical com- pound or solution which can be altered by the action of the electric current. 2. Electrolyte, Electrode, Anode, Cathode. The electrolyte is the solution (or fused salt) through which the electric cur- rent flows; the conducting terminals are the electrodes; the terminal by which the current enters the solution is the anode\ the terminal by which it leaves is the cathode. NOTE. The chemical changes caused by the current may affect both the electrolyte and the electrodes. In the case of a solution of copper sulphate with copper plates as electrodes, copper is removed from the anode by the current and carried into solution; an equal amount of copper is de- posited upon the cathode. In general, the metal travels with the current toward the cathode. 3. Amount of Chemical Action. -(Faraday's Law). The amount of chemical action taking place at the anode and also at the cathode (as expressed by Faraday's law) is proportional to (1) the strength of current flowing, (2) the duration of the 13 14 PRINCIPLES AND DEFINITIONS current, and (3) the chemical equivalent weights of the sub- stances. NOTE. Otherwise expressed, the quantity of metal or other substance separated is proportional to the total quantity of electricity passing and the electro-chemical equivalent of the substance or substances concerned. The electro- chemical equivalent of a metal is proportional to its atomic weight divided by its valence. Faraday's law is so exactly realized in practice under favorable conditions that it is used as the basis for the definition of the international ampere, one of the fundamental electrical units. 4. Cause of Current Flow. The current flowing through the electrolyte may be due (1) to an external electromotive force or (2) to the difference of potential due to the use of electrodes of different materials or to solutions of different concentrations. NOTE. The first case is illustrated by electrolysis of dilute sulphuric acid using two lead plates and an external battery ; the second by the electrolysis of the same solution using a zinc and a copper .plate, which touch each other inside or outside the solution. The first occurs in charging a storage battery ; the second in the discharging of a primary battery or a storage battery. 5. Electrolysis by Local Action. Instead of two plates of different metals the same result may follow with one plate if it is chemically impure or otherwise heterogeneous, when immersed in dilute acid. NOTE. Such a plate excites local currents and a loss of metal occurs at all the anode areas. This local action causes impure zinc to dissolve rapidly in a solution which has no action on pure zinc. 6. Anodic Corrosion is the term applied to the loss of metal by electrolysis at the anode. NOTE . When iron is anode the iron is carried into solution by the current, the first product being a salt of iron, the nature of which depends upon the character of the elec- trolyte. In dilute sulphuric acid, ferrous sulphate is formed, in hydrochloric acid, ferrous chloride, etc. These first products of the electrolysis are frequently modified by secondary reactions. 7. Secondary Reactions are the chemical changes which occur at or near the electrodes, by which the primary products PRINCIPLES AND DEFINITIONS 15 of electrolysis are converted into other chemical substances, and are sometimes followed by other reactions. NOTE . Ferrous hydroxide formed by the union of iron with hydroxyl ions set free at the anode, is subsequently con- verted into iron oxide due to the reactions with oxygen dissolved in the electrolyte. When lead is cathode in an alkali soil or solution, the alkali metal (such as sodium or potassium) reacts with water at the cathode and forms alkali hydroxide, setting free hydrogen. This hydroxide may (especially after the current ceases) react with the lead chemically and form lead hydroxide, which in turn may combine with carbon dioxide, forming lead carbonate. 8. Cathodic Corrosion is the term applied to the corrosion due to the secondary reactions of the cathodic products of electrolysis, as described in the preceding paragraph. The metal of the cathode is not removed directly by the electric current but may be dissolved by a secondary action of alkali produced by the current. NOTE : The anodic corrosion is more common and more serious; cathodic corrosion, however, sometimes occurs on lead and other metals that are soluble in alkali. Cathodic corrosion never occurs in the case of iron. B. ELECTROLYSIS OF UNDERGROUND STRUCTURES. 9. General. In the electrolysis of gas and water pipes, cable sheaths, and other underground metallic structures, and the rails of electric railways, the moisture of the soil with its dis- solved acids, salts, and alkalis is the electrolyte, and the metal pipes, cable sheaths and rails are the electrodes. NOTE. Where the current flows away from the pipes, the latter serve as anodes and the metal is corroded. Metal or gas or alkali, according to the nature of the soil, will be set free at the cathode. 10. Self Corrosion is the term applied when a "pipe or other mass of impure or heterogeneous metal buried in the soil is corroded due to electrolysis by local action. NOTE. This is called "self corrosion" because the elec- tric current originates on the metal itself, without any external agency to cause the current to flow. Self cor- rosion may also be due to direct chemical action. 16 PRINCIPLES AND DEFINITIONS 11. Acceleration of Local or Self Corrosion. Self corrosion is accelerated by the presence of acids or salts in the soil water which lower its resistance as an electrolyte, and also by cinders, coke or other conducting particles of different electric potential which augment the local electric currents. In the latter case the metal need not be heterogeneous. NOTE. A pipe may be destroyed in a relatively short time by self corrosion or local action if buried in wet cinders or in certain soils. 12. Coefficient of Corrosion. The coefficient of electrolytic cor- rosion, (sometimes called corrosion efficiency) is the quotient of the total loss of metal due to anodic corrosion (after deducting the amount of self corrosion if any) divided by the theoretical loss of metal, as calculated by Faraday's law, on the assumption that the corrosion of the anode is the only reaction involved. NOTE. In practice it is found that the coefficient of corrosion varies widely from unity, being sometimes as low as 0.2 and sometimes even above 1.5, but commonly between 0.5 and 1.1. 13. Anodic and Self Corrosion. Anodic corrosion due to external currents and self corrosion due to local action may occur simultaneously, and the former may accelerate the latter. NOTE. Hence the corrosion due to a given current plus the increased self corrosion induced by that current may give a greater total corrosion than called for by Faraday's law. This explains how the coefficient of corrosion may exceed unity. 14. Passivity is the name given to the phenomenon in which a current flows through an electrolyte without producing the full amount of anodic corrosion which would occur under normal conditions. NOTE. This restricted definition of passivity has regard only to its effect in electrolysis. Many conditions affect the degree of passivity attained, an initial large current density being favorable to it. Plunging iron into fuming, nitric acid renders it temporarily passive. A satisfactory ex- planation of passivity has not been given. 15. Polarization Voltage (sometimes called polarization po- tential) is the temporary change in the difference of potential PRINCIPLES AND DEFINITIONS 17 between an electrode and the electrolyte in contact with it due to the passage of a current to or from the electrode. This change in potential difference, is due to the change in the con- ditions of the surface of the electrode or change in the con- centration of the electrolyte (or both), and under some con- ditions is approximately proportional to the current flowing, but in many cases is not so proportional. 'The magnitude of the polarization voltage also depends on the material of the electrode, the nature of the electrolyte and the direction of the current. 16. Alternating or Frequently Reversed Direct Currents. If alternating currents (or frequently reversed direct cur- rents) flow through the soil between pipes or other under- ground metallic structures, the metal removed during the half cycles when a pipe is anode may be in part replaced when it is cathode. Hence, the total loss of metal on a given pipe is less than one-half of what it would be if the pipe were an anode with direct current of the same average value in the case of frequently reversed direct current and in the case of alternating current at commercial frequency it is less than 1% and in most cases negligible. (See Section 52.) NOTE. In slow reversals of current, the recovery effect is less, but the loss will be less than with direct current continu- ously in the same direction (excepting possibly where the phenomenon of passivity may affect the result). 17. Action on Underground Metallic Structures. Fara- day's Law applies to electrolysis of metallic structures in soil as elsewhere, the total chemical action being proportional to the average current strength and the time the current flows and to the electrochemical equivalent of the metal or other substances concerned. Although local action and passivity affect the loss of metal and so apparently modify Faraday's law, it is still true that the total chemical action resulting from the current flow is proportional to the total current when local currents are in- cluded. NOTE. Sometimes this chemical action is concerned only with corroding the anode; sometimes it is concerned with breaking up the electrolyte, as when the anode is a noble metal or in the passive state (as iron and lead sometimes are) ; sometimes both these effects occur. The theoretical loss of lead from a lead pipe or cable 18 PRINCIPLES AND DEFINITIONS sheath is 3.7 times as great as that of iron (ferrous) from an iron pipe due to the same current because of the larger electrochemical equivalent of lead. 18. Stray Current. If the railway return utilizes the grounded rails of the tracks, part of the current will flow off the rails or other grounded returns and return through other paths; the current observing the law of divided circuits; i.e. the current flows through all possible paths in parallel, the strength of cur- rent in each path being inversely proportional to its resistance. This statement excludes the effect of polarization on rails and underground structures, which in some cases is appreciable. 19. Electrolysis Mitigation. The two primary features of electrolysis mitigation are (1) the reduction of the flow of cur- rent through the earth and the metallic structures buried in the earth, (2) the reduction of the anode areas of such structures to a minimum, where the current is not substantially eliminated in order to reduce the area of destructive corrosion as far as possible. NOTE: The current in the underground metallic struc- tures will be decreased, other conditions remaining the same, by (1) increasing the conductance of the return cir- cuit, (2) increasing the resistance of the leakage path to earth, (3) increasing the resistance between the earth and the underground metallic structures, (4) increasing the re- sistance of the underground metallic structures. The anode areas of the underground metallic structures will be decreased, other conditions remaining the same, by providing suitably placed metallic conductors for leading the current out of the underground structures so that the flow of the current directly to the earth shall be minimized. This will change a portion of the anode area to cathode. 20. Electrolysis Surveys. A term applied to investigations made to determine the condition of grounded metallic structures and the soil in which they are imbedded and of the overall drops, potential gradients, local potential conditions, current densities, etc. in the railway tracks, or other grounded metallic structures, and positive and negative feeders connected to them to deter- mine what conditions tending to produce damage exist. 21. Overall Potential Measurements. Overall potential measurements show the difference in electric potentials between PRINCIPLES AND DEFINITIONS 19 points in the tracks at the feed limits of the station and the point in the tracks which is lowest in potential, and are obtained by means of pressure wires and indicating or recording volt- meters. NOTE: The pressure wires may be telephone or other wires utilized temporarily, or wires permanently installed for the purpose. 22. Potential Gradients. The potential gradient is the rate of change of electric potential along the rails of a track or other grounded structure in the earth, and is usually expressed in volts per thousand feet or volts per kilometer. 23. Positive and Negative Areas. Positive areas are those areas where the current is in general leaving the pipes or other underground metallic structures for the earth. Such areas are often called danger areas. Negative areas are those areas where the current is in gen- eral flowing to the pipes or other underground metallic structures. NOTE : As the current often flows from one underground metallic structure to another, it is evident that within a positive area there are local negative areas and vice versa. Hence the terms are applied somewhat loosely, and according to which condition predominates. Besides the positive and negative areas there are areas of more or less indefinite extent in which the current flow be- tween metallic underground structures and earth normally re- verses between positive and negative values. These areas are called neutral areas or neutral zones. 24. Drainage Systems. A drainage system is one in which wires or cables are run from a negative return circuit of an electric railway and attached to the underground pipes, cable sheaths or other underground metallic structures which tend to become positive to earth, so as to conduct current from such structures to the power station, thereby tending to reduce the flow of current from such structures to earth. NOTE. Three kinds of drainage systems may be dis- tinguished. (1) where direct ties with wires or cables are made between underground metallic structures and tracks, (2) where uninsulated negative feeders are run from the negative bus to underground metallic structures, (3) where separate insulated negative feeders are run from the negative bus to underground metallic structures, or a main feeder with taps to such structures. 20 PRINCIPLES AND DEFINITIONS 25. Uninsulated Track Feeder System. An uninsulated track feeder system is one in which the return feeders are electrically in parallel with the tracks. Under such circum- stances the cables may be operating very inefficiently as current conductors and as a means of reducing track voltage drop, particularly where voltage drops in the earth portion of the return are maintained at the low values usually required for good electrolysis conditions. (See Section 47 (d)). 26. Insulated Track Feeder System. An insulated track feeder system, sometimes called an insulated return feeder system, is one in which insulated wires or cables are run from the insulated negative bus in a railway power station and attached at such places to the rails of the track as to take cur- rent from the track and conduct it to the station, in such a manner as to reduce the potential gradients in the tracks and the differences of potential between underground metallic structures and rails, and so reducing the flow of current in un- derground metallic structures. (See section 53). NOTE. The insulated negative feeders may run separately from the negative bus to various points in the track network, or a smaller number of cables may be used with suitable resistance taps made to tracks at various places. With this system the drop of potential in the track feeders is independent of the drop of potential in the tracks. ELECTROLYSIS SURVEYS 21 METHODS OF MAKING ELECTROLYSIS SURVEYS. A: GENERAL. 27. General Principles of Electrolysis Surveys. The princi- pal measurements made in electrolysis surveys of under- ground structures are measurements of the potential differ- ences between the structure tested and all other neighboring metal structures in earth, neighboiing rails, and neighboring earth, and measurements of current flow on selected sections of the structural system under test. The potential difference be- tween the structure tested and earth affords more complete information than can be secured from the results of any other practicable class of observations. The difficulties are, however, to make these measurements so as to obtain the true potential difference between the earth and the earthed structure, and frequently also to obtain contact with earth in the immediate neighborhood of the structure tested. If an electrode is used for the earth potential measurement, not consisting of the same metal as the structure tested an error may still be introduced due to difference in the polariza- tion potential of the two electrodes. A non-polarizable electrode has been devised by Dr. Haber, as described later in this report, but it has been used only to a very limited extent in this country. On account of the difficulties of making earth potential measure- ments, measurements of the potential differences between the structure that is being surveyed and neighboring metal structures are much more generally made. Measurements of stray current flowing in selected sections of any structural system are practicable if a suitable length of the structure can be made accessible. By comparison of such measurements conclusions can be reached as to the areas in which stray currents are being taken from or delivered to the earth and as to the amounts of current which are concerned in these exchanges. Measurements of this character usually cannot be made on sections so close together as to give for 22 ELECTROLYSIS SURVEYS many points definite values for the current flowing to or from earth on account of the high cost of the necessary excavations and permanent replacements. We have therefore included a description of the " earth ammeter " which has been used abroad, and to a limited extent also in this country, for ob- taining direct measurements of current flow in the earth. A survey of the earthed structures which are liable to electrolytic corrosion by stray currents consists in making such observations relating to their electrical condition as may determine the route followed by the stray cunent and its degree of concentration, thereby permitting deductions to be made relative to the extent and the intensity of the electrolytic injury to which the structures may be subjected. While measurements of potential are most frequently made (to such an extent that the term ;< Potential Survey " is often applied to this work), it should be borne in mind that the real object of the survey is to determine where current may flow from structure to earth or from earth to structure and the magnitude of the current flowing for each of the smallest sections into which the structure can practically be subdivided. In discussing methods of survey, the measurements of poten- tial and current peculiar to each class of earthed structures will first be described, together with any special observations or precautions to be taken. A discussion of the measurements of a general nature common to all classes of structures will then follow. Measuring instruments and other apparatus employed in connection with this work will be described in detail in the section devoted to apparatus. 28. Electric Railways. Before making measurements re- lating to an electric railway system the available informa- tion as to its extent, its construction features and particularly the arrangement of its earthed return circuit and the connections thereto should be collected. The best available maps should be procured and all information pertinent to the electrolysis investigation recorded, either by annotation on a suitably arranged map, or in some other convenient form. All electrical connections made for any purpose with the rails or other parts of the return circuit should be noted with special care, and the location of any structures to which connection is thus made ascertained and recorded. The principal measurements to be made upon the grounded return system of an electric railway are as follows : ELECTROLYSIS SURVEYS 23 1. Potential differences between the point of lowest potential on the tracks, and selected points on the tracks throughout the feeding district of the station under observa- tion. 2. Potential gradient measurements along the railway tracks to determine the difference of potential between points on the track separated from each other by dis- tances of from 1,000 to 3,000 feet. 3. Differences of potential between all points where negative feeders or other connections between bus-bars and rail return make contact with track; also differences of potential between these points and the station bus-bar. 4. Currents carried by each separate connection between bus-bar and rail. For most of the potential measurements listed above, it is necessary to have available insulated wires con- nected with all points on the railway return system, whose potential relations are to be determined, all of these insulated wires being brought to some common point so that measurements may be made between them. Where pilot wires have been installed by the electric railway, many, if not all of the points at which it is desired to make tests will be accessible without the necessity of any special preparations. Where pilot wires are not available or where it is desired to reach points not included in the pilot wire system, the most economical plan will be to procure the use of any avail- able circuits found in the local telephone distribution system. Short lengths of insulated wire will need to be run to connect such circuits with the tracks and the testing circuits thus established can readily be brought together at some common point for measurements between them. Where neither of the above alternatives is available, wires can be installed in some temporary manner over available pole line routes to connect with the points whose potentials are to be observed. Such wires should be insulated from earth except at the point where they connect with the tracks. When the testing circuits are established, the required poten- tial measurements should be obtained by connecting to a volt- meter the wires leading to the two points where difference of potential is to be determined. The voltmeter should be kept in circuit and under observation for a time sufficient to insure that the normal fluctuations of the railway load have been accounted for. When long time observations of the potential difference between two points are desired, a recording voltmeter 24 ELECTROLYSIS SURVEYS should be employed. If circuits to a sufficient number of points have been installed, the measurements of potential gradient in the tracks may be taken by connecting the proper wires at the central point to the voltmeter. If the requisite number of pressure wires for gradient tests is not available, these measurements may be obtained by carrying a suitable length of insulated wire along the track and connecting it through a voltmeter to the track at the two points between which the gradient is to be measured. Measurements of current flowing in negative feeders or in other connections to the track return can be taken by inserting an ammeter in the circuit to be measured, when this is possible, or by taking the voltage drop along some accessible section of the connecting lead, which is sufficiently uniform in dimensions to permit of a ready calculation of its resistance. It is important that all such measurements of current should be taken either simultaneously with measurements of potential difference be- tween the bus-bar and the track end of the connection, or under such conditions as to permit of their accurate correlation with the potential observations. A station load curve should also be obtained on account of the information which it gives as to the characteristics of the power supply. Measurements of rail bond resistance are not necessarily a part of the work to be done in an electrolysis survey. It is, however, occasionally necessary in connection with a survey to test the resistance of particular rail bonds in order to obtain data necessary for the explanation of results obtained in making some of the regular measurements. When such tests are made, the fall of potential across the joint in the rail should be observed simultaneously in comparison with the difference of potential for some short measured length of the adjacent rail. If one of the special rail bond testing devices is not available for this work, two voltmeters can be employed and read simultaneously, or one voltmeter can be connected with a quick acting switch and employed so as to secure practically simultaneous observations. This latter method may give unreliable results unless a large number of readings are averaged. 29. Earthed Piping Systems. Before tests are made to determine the electrolytic condition of any piping system, all available information as to its extent and the character- istics of its construction should be collected and studied. The best available maps of the system should be procured and any ELECTROLYSIS SURVEYS 25 special information of importance in connection with an elec- trolysis survey not noted on the maps, such as the metals of which the pipes are composed, the location of insulating joints, the relative locations of other piping, and cable systems, the location of electric railway tracks and return circuits, etc., should either be recorded upon them or arranged in some convenient form for reference. The observations which should systematically be taken in examining a piping system are as follows: 1. Difference of potential between piping system and electric railway rails, other piping systems, cable systems, metal bridges, steam railway rails, etc., at points where these cross the piping system or come in close proximity to it. (Potential survey). 2. Measurements of potential difference between ad- jacent hydrants, or adjacent drip or service connections. (This will serve to give the direction of the current flow- ing in the pipe line and some rough indications of its amount) . 3. Measurements of current flowing upon exposed sec- tions of pipe. (Current survey). 4. Difference of potential between points on the piping system and the adjacent earth if contacts with earth can be obtained. To make a potential survey, potential differences between the underground pipes and rails are usually measured at a number of points along every street where there are pipes and electric railway tracks. Where there are other underground pipes and lead-sheathed cable systems, it is desirable to make simultaneous measurements of potential difference between the piping system being surveyed and the neighboring pipe and cable sheaths. It is desirable to make all of the measure- ments of potential difference at any one point simultaneously between all structures tested. Contact with the underground pipes for these potential measurements may be made by means of service pipes, hydrants, or drip connections. The connec- tions used for the potential measurements may be tested for electrical continuity by means of an ammeter connected be- tween the contacts with a dry cell in series if necessary. Measurements of potential difference between adjacent test points on the piping system should also occasionally be taken. As the resistance of pipe joints is usually not uniform, only an approximate idea of the current flowing can be obtained 26 ELECTROLYSIS SURVEYS in this manner. The principal object of this test is to obtain an indication of the direction of the flow of current. It is therefore desirable to make a rather large number of these tests at quite frequent intervals, since the results may be interpreted only in a general way; individual tests may be expected to vary widely, and in some cases they may even conflict. This test may be made for shorter intervals and in greater detail, where some sudden change of potential difference to earth or neighboring structures has been observed. Owing to the uncertainties as to resistance of joints it is best not to at- tempt to translate these voltage readings into terms of current. They may, however, be used in comparisons to assist in fixing the points for more accurate measurements of current as described in the next paragraph. When the potential observations have been completed and transferred to a map or in some other way assembled for study, consideration should be given to them with a view to deter- mining what parts of the piping system appear likely to'be re- ceiving substantial amounts of current from earth or passing substantial amounts of current to earth. The neutral sections of piping between positive and negative potential zones should also be located. With this information at hand sections of the piping system should be selected both in the positive and negative zones and in the neutral area at which excavations can be made and determinations of the current flowing in the pipes obtained. In selecting points for excavations, preference should in general be given to the main piping routes, but attention should also be given to any branch lines which appear likely to be receiving or delivering relatively large amounts of current. Any cases where sections of the system located with- in the " negative area" give positive readings to earth, should also be given preference in this study. The method of measuring current consists in determining the fall of potential along a measured length of pipe of known di- mensions. For the purpose of this measurement it will generally be found advisable to attach insulated wires permanently to the pipe and to carry them to some suitable point underneath the sidewalk from which they may be led up to the surface to terminate in service or other suitable boxes so as to be available for measurements of current in the future after the excavation has been filled. (See Fig. 1.) Tables giving the resistances of unit lengths of pipe of different diameters and materials are attached ELECTROLYSIS SURVEYS 27 o < li " 1 O (n z a cr D O u a a 28 ELECTROLYSIS SURVEYS to this report. (See Appendix Tables 9- 10). The current flowing in the pipe may be obtained by computation from the observed drop of potential and the unit resistance for the class and weight of pipe. In addition to the observations made upon the piping system, careful attention should be given to the condition of the service pipes to buildings, particularly in locations where the services cross other piping systems, cable systems, etc. The potential between these service pipes and earth and between the service pipes and the other earthed structure crossed should be determined. It will not be within the scope of the usual survey to determine the condition of all service pipes in the area covered, but it is desirable that some of the services be tested in order to ascertain whether there is any serious tendency towards the local electrolytic corrosion of service pipes. When buildings are entered for the purpose of testing service connections, tests of potential should always be made to any other service pipes or cables which enter the same build- ing, in order to detect cases where one structural system is making contact with the other. Current measurements may also conveniently be made on service pipes in buildings, since the pipes are exposed. Such tests should be made frequently, as they often reveal an interchange of stray current between piping systems which may be in contact in the building. 30. Underground Cable Systems. Before tests are made to determine the electrolytic condition of any cable system, all available information as to its extent and the charac- teristics of its construction should be studied. Available maps of the system should be procured and any special in- formation of importance in connection with an electrolysis survey not noted on the maps, such as the metals used for the armor or sheathing of cables, the location of drainage connec- tions, insulating joints and other protective devices, the relative locations of other cable systems and of piping systems, the location of the electric railway tracks and return circuits, etc., should either be recorded by annotation upon them or arranged in some convenient form for reference. The observations which should systematically be taken in examining the cable system are as follows: 1. Difference of potential between the cable system and electric railway rails, other cable systems, piping systems, ELECTROLYSIS SURVEYS 29 metal bridges, steam railway rails, etc., at points where these cross the cable system or come in close proximity to it. 2. Difference of potential between points on the cable system and the adjacent earth. 3. Difference of potential between cables in the same subway system where they are not cross bonded. 4. Current flowing upon the cables. In making surveys the potential of the -cable with respect to the adjacent earth should always be determined at each test- ing point. In original surveys the greatest practicable number of testing points should be utilized. In some systems it will be desirable to test at every manhole, but in extensive networks of power cables it will ordinarily be sufficient to test at less frequent intervals in many districts, if tests are made at shorter intervals in the most important places. The potential difference between the cable and rails in the same street should also be determined, but in cases where the street railway rails parallel the cable route for a considerable distance, such tests may be made less frequently. If pipes or other earthed metallic struc- tures run close to the cable system at the point of testing, it is desirable that the potential difference between the cable system and the other structure be determined, provided an electrical connection can be made, e.g., through a hydrant, etc. Tests to determine the direction and amount of stray current flowing on the cable sheaths should be made at appropriate intervals. In fairly simple cable systems, with few laterals, it may be sufficient to make these tests at comparatively infre- quent intervals, such as every fifth manhole. In complicated networks, however, such as power distribution systems with many branches and service connections, it will generally be desirable to test more frequently. The current flowing on the cable sheath is to be calculated from the observed fall of potential over a measured length of sheath, and the known resistance of this length of sheath. A table for determining current on lead cable sheaths from voltage drop in measured length of sheath is appended. (See Table 11.) In the course of the survey, measurements should also be made of the current flowing in any drainage connections or in any accidental connections which connect the cable system with the electric railway return if any such exist. In case insulating joints have been inserted to protect any parts of the cable system from electrolytic corrosion, measurements of the po- 30 ELECTROLYSIS SURVEYS tential difference between cable sheath and earth should be made at each side of the insulating joint, and also of the dif- ference in potential across the joint. In a' preliminary study it should be ascertained whether it is the local practice to insulate from the main cable system those branches which enter buildings. When such branches are not insulated from the main system, tests of difference of potential should be made, between the branch cable and any pipes or other cables which may enter the same building. From such tests it may be ascertained whether there are accidental contacts between the cable system and other earthed structures within buildings, and if any such are found in a portion of the total number of installations, a conclusion can then be reached as to the desirability of checking the conditions in all buidlings entered. In localities where it is the practice to insulate from the main system cable branches entering buildings, the possibility of defective insulation should be checked by measuring the potential difference between- cable inside of the building and cable outside at some point beyond the supposed location of any insulating joint. Tests for differ- ences of potential between the branch cable and other metal structures within a building can be omitted in case the insulating joint is found to be in good condition. The condition of the bonds installed to equalize the potential of the cables entering such manhole should be observed and noted. If bonds are lacking, or if it is suspected that the con- dition of any bond is faulty, observations of the difference of potential between the cables should be taken and recorded. 31. Bridges, Buildings and Other Earthed Structures. Through the study of maps, etc., collected as preparatory data for surveys of piping and cable systems, informa- tion will presumably have been secured concerning the locations, and some, at least, of the structural characteristics, of the highway and railway bridges located within the area to be studied. The locations of steam railway tracks will similarly have been obtained. In making electrolysis surveys of bridges, measurements of potential to earth should be made at each end of the metal structure. In case the bridges are crossed by electric railway tracks, piping systems or cable systems, measurements should also be made from the metalwork of the bridge to these struc- ELECTROLYSIS SURVEYS 31 tures to determine whether there is any difference in potential between them. Where the metalwork of the bridge structure, piers, or other intermediate supports makes contact with earth or with water, measurements of potential difference to earth or to water also should be made. The observer should follow up closely any indication of poor electrical contact between different sections of the metalwork of the bridge, or between the metalwork and any other of the earthed structures crossing the bridge which are supposed to be in good electrical contact with the metalwork. In the course of the survey, metal frame buildings may be found in locations where it would be possible for them to collect appreci- able amounts of current, either directly through the earth or indirectly through the contact of rails, pipes, or cables with the framework. If it appears that such contacts exist, measure- ments by the fall of potential method should be made to ascer- tain whether appreciable currents are flowing into the building through these contacts, if this is found to be the case tests should be made at a number of points from the building structure to ground for the purpose of determining where the current leaves the framework and whether there is any indication that ap- preciable damage is being done. In the case of buildings extending over a considerable area it is desirable that measure- ments of potentials be made from the framework to earth* at a number of points, even in case no contacts are found between the metal framework of the building and. other metal structures which may be carrying stray currents. 32. Steam Railway Rails. Steam railway rails, either through direct contact with electric railway rails or, in the absence of an insulating ballast, through contact with earth, are liable at times to collect and discharge appreciable amounts of stray current, and this may occur in such a manner as to be detri- mental to the track rails, spikes and adjacent earthed structures. Because of this, as has already been indicated, measurements of potential to steam railway rails should be made whenever the structures that are being surveyed are in close proximity to steam railway tracks, and it is also desirable to determine directly by survey the condition of metal steam railway bridges as well as the condition of metal highway bridges. When steam railways are equipped for electric block signaling the signal battery will affect the potential of the rails. The potential due to the signal- 32 ELECTROLYSIS SURVEYS ing connection is, however, practically uniform in value and can be determined through observations made at times when no stray current can be flowing. With this potential fixed, a con- clusion as to the presence and amount of any potential can readily be reached. 33. General Survey Practices. All measurements, excepting 24-hour records, should be made during the period of normal load on the portions of the railway system which are suspected of being the sources of stray currents. In general, it is desirable to express the results of short time measurements in terms of ''average day load" on the railway system. In localities distant from the source of railway power supply, the foregoing consid- erations make it necessary to take into account the presence or absence of moving cars at points beyond the testing station, especially on the tracks nearest to the structure which is being tested. In such localities the duration of a test should be ex- tended to include at least one complete cycle of car movement, unless previous experience at other testing points in the immediate neighborhood have clearly indicated that parts of the cycle may safely be neglected. As the railway lines converge toward a common center, or as the source of railway power supply is approached, the probability of normal load condition increases but even under these conditions it is necessary for the tester to insure that the railway load conditions are substantially normal, when measurements are being made. At a number of points observations of potential differences and of current flowing along the structure should also be made with 24-hour recording instruments and the characteristics, of these currents and potentials compared with the characteristics of railway load curves. This will serve to indicate whether the current and the potential are identified with the railway source. The 24-hour averages for currents and potentials obtained at these points of measurement will also be of use in indicating what allowances should be made in the readings taken systematically at all points of the system in order to make them represent the average day conditions. During observations of potential or current the movements of the needle in the measuring instrument should be closely watched so that the maximum and minimum readings may both be obtained as well as any change in the polarity of the potential or in the direction of the current. The observer should also bear ELECTROLYSIS SURVEYS 33 in mind that collected results of the individual tests will be plotted on a map or otherwise compared so as to get a general idea of the conditions prevailing. When, therefore, there is reason to believe that the recorded maxima and minima are abnormal, notes should be made giving the reasons for such a belief and indicating the value which is thought to be more nearly comparable with the values obtained at other points. In regular field survey work portable measuring instruments, will be found most suitable for the great majority of the measure- ments to be taken. Occasionally, however, conditions will arise under which it is desired to observe the potential or the current at some particular point for several hours and even for one or more 24-hour cycles. In the case of such long period observations recording voltmeters, milli voltmeters and am- meters will be found of great assistance and should be employed if available. Instruments of this kind are described in the apparatus section. (Sec. 35-39.) When bodies of water or areas of swampy earth cross or are located in close proximity to earthed structures, stray current may flow from the structure to earth locally. This is par- ticularly true if the water is brackish or salty. In case such relatively high conductive sections of the earth afford a path of lower resistance for the return of current than the structure itself, the probability of a large flow of current to earth is considerable. The flow of current from the earthed struc- ture is not necessarily stopped when such highly conductive strata have been hidden by building over them or by filling in with surface soil. It is, in consequence, neces- sary to observe closely the physical geography of the areas covered by the survey and unless the observer is per- sonally familiar with the history of the locality and the changes which have occurred, it is desirable for him to ascertain the facts from those familiar with them. If the structure under observation is accessible for tests at intervals of a few hundred feet and care is taken to make tests of potential to earth at all of these points, the presence of any condition which tends to cause the localized flow of current from the structure to earth will usually be detected. While the labor of making the survey is increased through the necessity of such frequent observations, it is preferable to include all accessible points in the original survey and to eliminate testing points in subse- 34 ELECTROLYSIS SURVEYS quent surveys when sufficient experience has been gained to indicate that greater distance between points of observation is safe. When the electric railways in the area under investigation receive current from two or more sources of supply and there are indications that electrolytic damage is occurring at any point upon the earthed structures investigated, it may become necessary to ascertain the origin of the current causing the injury. The preliminary study of the electric railway system or systems will have included the detailed methods for distri- buting power, whether the trolley systems are interconnected or divided into insulated sections and whether or not all of the rails are interconnected at junctions, etc., as well as the methods of bonding and cross-bonding. If the trolley is supplied from several sources in parallel, the effect of any one of these upon the distribution of stray currents may most easily be studied in connection with the starting or shutting down of that particular source. When substations are operated only during part of -the day, tests may be arranged to take advantage of this. When the substations are continually in operation, resort may be had to the method of simultaneously observing the load indicated by the station instruments, and the quantities to be measured on the structure being surveyed. Recording instruments are often useful for this purpose. When the sources of power are not supplying the trolley in parallel but are confined to certain definite districts, a close study of the railway schedule should be made as it will fre- quently be possible to select some set of conditions where the current at points of observation must be coming almost wholly from one of the sources on account of the relative positions of cars, etc. Where two electric railways operate independently without connection between their trolleys but with inter- sections or junctions between their tracks, the situation is similar to that just described where the railway trolley is divided into insulated sections and the same methods of investigation can be followed. Where there is no connection between either trolleys or tracks of two independently operated electric rail- ways this same method should also be followed, i.e., of ob- serving stray current conditions when one road is using con- siderable current in the immediate neighborhood and the other road is using little or none and comparing the observations with those obtained when both roads are using normal amounts ELECTROLYSIS SURVEYS 35 of current in the neighborhood. It is to be noted that when two railways are without any electrical interconnections be- tween either trolleys or tracks, the track return of either may carry stray current from the other railway and if the track return is of high conductivity it may assist materially in pro- ducing adverse electrolytic conditions on other earthed struc- tures particularly in cases where it provides a short route between two points between which considerable potential dif- ference exists. The earth ammeter, previously referred to, may occasionally be found useful in checking up conditions indicated in the systematic survey observations. The construction of the de- vice is described in the apparatus sections. If care is taken to have the plates placed perpendicular to the direction of cur- rent flow, the current density at the point of measurement may be indicated by the current flowing through the instru- ment. If necessary, the lines of current flow may be deter- mined by voltage readings between test electrodes before burying the instrument. The greatest care should be taken in placing the instrument to avoid unnecessary disturbance of the soil, in order that the flow lines may follow, as nearly as possible, their normal direc- tions. Whenever excavations or other exposures of pipe surfaces make it possible, measurements of the resistance of pipe joints should be made. Where the joints are of moderate resistance, that is, not so high as to prevent current flow upon the pipes, this measurement may be made by simultaneous observations of the fall of potential across the joint, and along a measured length of the pipe ; the pipe joint resistance may then be expressed as equivalent length of pipe, or, by reference to tables, in ohms. These measurements are of importance in indicating the char- acteristics of the pipe line as an electrical conductor, in estimating the probability of corrosion at joints due to shunting, etc. Wherever the surfaces of the earthed structures under in- vestigation are exposed during the course of the tests, their conditions should be noted. The pitting of the metal surfaces or the presence upon them of rust or other oxidation products, or an obvious reduction in the thickness of the metal or any other evidence that corrosion has taken place, is not of itself direct evidence that electrolytic corrosion has oc- curred. Corrosion from any cause whatever would be expected 36 ELECTROLYSIS SURVEYS to reduce the thickness of the metal, and the rate at which such corrosion occurred and its possibilities in the way of irregularity of attack on different portions of the surface, would determine the occurrence of pitting. Many of the products of corrosion which will be encountered can also be produced through purely chemical reactions, as well as by electrolysis. When the meas- urements made in the survey demonstrate that current is flow- ing from structure to the earth at the point where corrosion is observed, conclusions can be drawn as to the causative relation between the presence of stray current and the evidences of cor- rosion. Whatever the conditions found in the survey readings, the condition of obviously corroded metal surfaces should always be carefully noted, as it is, of course, always possible that at some past time stray current has been flowing from the surfaces to earth, or that some local condition has been favorable to the " self -corrosion " of the structure. Points where substantial corrosion of the structures under investigation is found, are always to be regarded as good locations for taking the samples of soil referred to in the following paragraph. It is often desirable to gather data relative to the electrical and chemical characteristics of the soils in the area studied. As different types of soil are encountered in the course of the survey either in the making of excavations or through the observation of changes in surface conditions, samples should then be taken and their electrical conductivities determined. It is often desirable also to make chemical analysis of a number of samples of ground waters and of the water-soluble portion of soil samples secured for conductivity tests. 34. Application of Remedial Measures Re-surveys. The survey methods described in the previous paragraphs include practically all of the work which would be done in an extensive original survey, that is, in a district where no work had been done previously. While this problem in all of its aspects has been investigated in only a few American communities, it will be found that more or less complete surveys have been made in almost any area traversed by electric railways. The test methods described are not all of equal value for all problems; their application depends upon the particular prob- lem under consideration. Further, many of the tests require considerable experience and technical skill in application, to avoid erroneous and misleading results. For these reasons, ELECTROLYSIS SURVEYS 37 extensive surveys should only be undertaken by experienced investigators. Following the completion of the original survey, a decision will be reached as to whether measures for mitigating electro- lytic corrosion are necessary, and if so, what methods are to be applied. Conclusions as to the effectiveness of any protective measures should be based upon repetitions of the test made in the orginal survey. The amount of repetition necessary will depend upon the character of the protective measures adopted. Thus, general improvements in railway return circuits will ordinarily require a complete re-survey of the affected area. The insta v lation of an insulating joint between the main line structure and a branch should, on the other hand, require little more than tests over short sections either side of the joint, to determine that the current flowing has been reduced and that no objectionable corrosive conditions have been introduced at the joint itself. If railway return circuits are being changed, some observa- tions of overall potentials and potential gradients will naturally be made during the course of reconstruction, to check the design upon which the work has been based. Observations should be made before installing drainage systems for cables, if necessary using available conductors temporarily to connect the cable sheath and the railway bus-bar or some other suitable point on the railway return, and the effect of drawing current from the cable system observed. The installation of such protective measures as insulating joints or insulating coverings should be carefully supervised as much depends upon the thoroughness with which the work is done. In re-surveys after the installation of protective measures, the character of the underground structure will make it necessary to pay special attention to some particular class of observations. With piping systems and power distributing cable systems special attention should be given to the amount of stray cur- rent flowing on the structures, since a principal object of the remedial measures will have been a reduction in this current. When insulating joints have been installed tests of potential to earth from each side of the joint are required to make sure that the local flow of current to earth has not risen to an amount which will endanger the structure. Tests of stray current in the system on either side of the joint are also required to determine that the effect desired from its installation has been obtained. 38 ELECTROLYSIS SURVEYS When drainage connections are attached to cable systems, tests of potential to earth must be made throughout the area affected. The connection should make the cable negative to earth at all points, but only by slight amounts at or near the point of its attachment, as otherwise the cable will carry more stray current than is needed for its protection, and it becomes a source of danger to other un drained structures. Where insulating joints or other protective measures are applied to structures buried in the earth, care should be taken to attach testing leads to be used in future surveys. Such connections will be of the same general type as the current measuring leads for pipes (See Fig. 1.). Electrolysis surveys should be repeated at suitable intervals. In case the original survey did not disclose conditions requiring the application of remedial measures, it is still necessary to make sure that adverse conditions have not since arisen. Where protective measures have been applied, surveys are needed to make sure that the remedies remain effective and adequate The interval between surveys will depend upon the importance of the structure and upon the time required to produce appre- ciable damage in case a substantial change in stray current conditions occurred. The results of all such surveys should always be compared with those of previous surveys to ascertain whether changes in stray current conditions are taking place. When any substantial changes or additions are made in the electric railway plant, surveys of the earthed structures liable to be affected by the new conditions should promptly be made. B: APPARATUS. In this section descriptions are given of the apparatus and tools which are essentially special for electrolysis work. The tools ordinarily used for handling wires and making good contacts in electrical work will also be needed but no special description or listing of them seems to be necessary in this place. 35. Portable Measuring Instruments. The portable measur- ing instruments required in electrolysis survey work include voltmeters, milli voltmeters and ammeters. Separate instru- ments of each kind can, of course, be carried but it will usually be found more convenient to employ the special portable instru- ments which have been designed particularly for this work. ELECTROLYSIS SURVEYS 39 Two such instruments which the Weston Electrical Instrument Company manufacture for this class of work are as follows : Model 1, combination millivoltmeter and voltmeter, has its zero in the center of the scale and reads in both direc- tions. Ranges of 5, 50 and 500 millivolts and of 5 and 50 volts are convenient. It is made with a specially high resis- tance of from 500 to 600 ohms per volt so that the 5 milli- volt range has a resistance of about 3 ohms. These high resistances increase the accuracy of measurements and par- ticularly minimize errors due to resistances of leads or contacts. Ordinary switchboard shunts provided with binding posts and adjusted for 50 millivolts may be used to make this instrument serve as an ammeter. Convenient ranges for these shunts in electrolysis work are, 5, 50 and 500 amperes. Model 56, combination volt-ammeter, has its zero in the center of the scale and reads in both directions. Ranges of 10, 50 and 500 miUivolts, 5 and 50 volts and 100 amperes are convenient. The center scale feature referred to in the description of these instruments is an important one in electrolysis work, as it is not always possible to determine in advance the direction of current or potential, and readings may also vary from positive to nega- tive values during the making of observations at many testing points. When simultaneous readings have to be taken at two or more testing points it is important to use similar instruments at all points. If dissimilar instruments are used their periods of vibration may differ and with the fluctuating voltages and currents encountered in much of this work accurate simultaneous measurements cannot be made unless the instruments used have the same periods of vibration. 36. Recording Instruments. Recording measuring instru- ments are usually arranged to give 24-hour records without change of chart. By using a sensitive millivoltmeter in the recording instrument and providing it with a number of voltage ranges as well as with suitable shunts, a single instrument can be made available for taking all of the voltage and current readings required in electrolysis work. The original type of Bristol recording instruments make their records upon a smoked chart which has to be treated subsequently with a fixative supplied with the instrument in case it is desired to preserve the record. The Bristol instruments are regularly made with a clock supplied with a changing lever so that the disc can be made to 40 ELECTROLYSIS SURVEYS rotate either in one hour or twenty-four hours. Both the Bristol Company and the Esterline Company have recording instruments which give an ink record on a paper strip. In either type of instrument center scale zeros should be called for so that varia- tions between positive and negative values will be recorded on the chart. 37. Normal Electrode. The Haber normal electrode also called non-polarizable electrode consists of a rod of zinc which is enveloped in a wet paste of zinc sulphate contained in a glass tube which has had cemented to it at the bottom a porous clay cell. The other end of the tube is closed with a stopper from which the zinc rod is supported an insulated wire is led from the end of the zinc rod through this stopper to the upper end of a wooden rod which also enters the stopper and serves for the purpose of handling the electrode. A capillary tube is also run through the stopper in order to have the interior of the tube at normal atmospheric pressure. The zinc sulphate paste is made by adding saturated zinc sulphate solution to fine zinc sulphate crystals until the mixture has attained a semi-fluid condition. A sketch showing details of construction for this device is shown on the opposite page. (See Fig. 2.) 38. Earth Ammeter. The Haber earth' ammeter consists of two thin copper sheets laid one upon the other with a thin sheet of mica or other non-absorbent insulating material between them. These two plates are gripped in a hard rubber rim which forms part of a square wooden frame. A paste made by mixing pow- dered copper sulphate crystals with a 20% aqueous solution of sulphuric acid is spread over the exterior surfaces of each of the two sheets of copper, the paste being enclosed on each exterior surface by a covering of parchment paper or some similar tough permeable membrane. Insulated wire leads of suitable length are run from each plate through the frame to connect with the measuring instrument. The opening in the frame may conven- iently be square. Four inches is a convenient dimension for the sides of this square opening as this will yield an area of one-ninth of a square foot which is approximately equivalent to a square decimeter. The detailed construction of the instrument is shown in an attached sketch. (See Fig. 3.) When using the instrument, the spaces between the parchment paper and the outer edges of the wooden frame are first filled with ELECTROLYSIS SURVEYS 41 SECTION OF NON-POLARIZABLE ELECTRODE Insulated Copper wire Zinc Rod (r Glass Tube Wooden Rod, 3 'Long Capillary Tube Rubber Stopper ^_Hooksfor Binding Wire to hold 5 topper Zinc Sulphate Paste Clay Porous Cup Resin Cement cm. CROSS SECTION Figure 2 42 ELECT ROL YSIS S UR VE YS SECTION OF EARTH AMMETER Ammeter Leads wooden Frame - Copperplate GopperSulphate Paste Earth - Wooden Frame - Hard Rubber Frame Copperplate (Sheet oFMica [separating Plates Parchment Paper Hard Rubber Frame CROSS SECTION Figure 3 ELECTROLYSIS SURVEYS 43 closely packed soil taken from the spot where it is intended to make the measurement and the frame is then placed in a position perpendicular to the flow of current which it is desired to measure and completely buried in earth removed in the course of making the excavation to reach the structure whose condition is to be determined. A suitable low resistance milliammeter can then be connected to the two terminal wires and observations of the current flowing made. 39. Testing Electrodes. The details of metal tipped testing electrodes for use in readings of potential to earth are given in an attached sketch. (See Fig. 4.) Two of these testing rods may be conveniently carried at all times; one of the two should have as its testing tip a piece of the same metal as that contained in the structure whose potential to earth is to be tested, the other should be provided with a steel tip so that contact may be maintained from a distance with any pipe or cable which is below the surface of the ground. The metal on the tips of these rods should always be kept clean and bright and care should also be taken to remove rust and other products of corrosion from the points on the surface of the structure to be tested against which the steel tip presses so that a clean, bright surface will be available for the contact. C: RECORDS AND REPORTS. 40. General. Much detailed information is necessarily gathered in the course of an electrolysis survey. It is desirable to prepare in advance of the work for the convenient recording of these data upon suitably arranged testing sheets, which either have upon one line or upon one sheet, as may be necessary, all of the data collected at any stated testing point during a single period of observation. Several typical data sheets prepared for recording observations made upon piping and cable systems are attached hereto as suggestive of possible arrangements for report sheets. The data thus collected can usually be best aranged for study if they are transferred to a map showing the system or systems included in the tests, and indicated thereon either in numerical form or through some graphical representation. It is desirable to indicate positive and negative relations by making records on the maps in different colors. Apart from the data obtained through observations in the ELECTROLYSIS SURVEYS V----J ELECTROLYSIS SURVEYS 45 work of the electrolysis survey it will be seen that the records obtained relating to the systems under observation should include the following: 41. Electric Railways. 1. Maps showing locations of sources of power supply, tracks, and negative feeders and other connections between bus-bar and track. Also locations of positive feeding connec- tions to trolley and of all section insulators in trolley. 2. Information as to size of rails, methods of bonding and standards of bond maintenance. 3. Information as to any direct ground connections ap- plied to the railway return system, and any special track features which may affect the flow of stray currents. 42. Piping Systems. 1. Maps showing all main piping lines and branches (except building connections) and sources of water, gas, etc., from which the piping systems are supplied. 2. Information as to sizes of pipes and metals of which they are composed, and details of the standard methods of joining main and branch line pipe sections. 3. Information as to method of joining building connec- tions to main supply pipes including metals used for the building connection pipes and the depth to which such connections are buried. 4. Location and description, of any protective devices such as insulating joints or drainage connections which may have been made a part of the piping system. 5. Information as to methods of attachment and con- struction employed in carrying pipes over highway or rail- way bridges or under water courses, swamps, etc. 43. Cable Systems. 1. Maps showing locations of all subway and conduit routes and giving number and sizes of cables in place therein or the total cross-section of lead sheaths expressed in equiva- lent copper, also locations of power stations, sub-stations or other centers from which cables radiate. 2. Locations, route and sizes of all drainage connections attached to cable systems, also locations of all insulating joints in cable systems, of any jumpers which may be run to establish a metallic circuit across an insulated gap in the cable system and of any conductors run to reinforce the carrying capacity of the cable system for stray currents. 3. Information as to methods of attachment and con- struction employed in carrying cables over highway or railway bridges or under water courses, swamps, etc. 46 ELECTROLYSIS SURVEYS 44. Bridges and Buildings. 1. Locations of structures with respect to electric railways. 2. Information as to methods of construction employed in carrying electric railway, pipes and cables across bridges and particularly as to whether any of these other structural systems make electrical contact with the metal structure of the bridge. 45. General Conditions. 1. Maps showing locations of water courses, swamps and other features tending to produce locally earth of high unit conductivity. 2. Records of electrical resistance of soil samples repre- sentative of the area. 3. Records of experience obtained in the use of different metals for pipes, etc., in the soils o'f the area. It is desirable that in the preparation of records and of reports, consideration be given to the necessity of their perpetuation. All records which will be of permanent value in connection with the continued study of electrolysis conditions within the area which will be necessary in order to make sure that injurious changes in conditions do not occur, should be prepared in a permanent form capable of withstanding considerable handling. AMERICAN PRACTICE 47 III. AMERICAN PRACTICE. There is no standard practice in the treatment of elec- trolysis problems in America. In many localities the exist- ence of such a problem is scarcely recognized; in others the problem has been given much study, and mitigating systems widely varying in character have been installed. Much of the information made available to the committee is contained in confidential reports to which it is not possible to make reference, because electrolysis is the subject of con- troversy between conflicting interests. Unfortunately, also it is impossible in some cases even to refer to places where par- ticular expedients have been employed, or to state either the extent or the results of such use. It has, therefore, been neces- sary in most instances to make statements of what is the prac- tice, without citing the authority or naming the places where such practice may be found. In compiling this report, there- fore, the committee has been influenced most largely by those instances of practice within its knowledge where the greatest amount of study has been given to the subject, and where the results obtained seem best to justify its use. The committee has embodied in this report only matters of fact for which it has authority. A. MEASURES APPLIED TO RAILWAYS. - 46. Insulation. Under this sub-heading have been con- sidered three general measures, namely: a. Complete Insula- tion, which does not involve the use of the running rails as a portion of the electric circuit, b. Substantial Insulation, which does involve the use of the running rails as a portion of the circuit, but, due to the type of construction employed, to a very large extent prevents stray currents, and c. Partial In- sulation, which comprises using such means as are available to insulate the running rails of ordinary street railways in so far as practicable. 48 AMERICAN PRACTICE (a) Complete Insulation. Instead of using the running tracks as part of the return circuit, a separate insulated return con- ductor is employed for this purpose. In this case the entire electric circuit of the railway system is insulated from ground, and, there being no voltage drop in contact with earth, stray currents are entirely prevented. Complete insulation of the railway circuit is accomplished in the double underground conduit trolley system, by employing insulated positive and negative conductors in underground conduits. This system is in use on the surface lines on Manhattan Island and in por- tions of Washington, D. C. This is also accomplished in the double overhead trolley system by employing separate positive and negative overhead trolley wires insulated from ground; many years ago examples of this system were installed in Washington, D. C., and Cincinnati, Ohio. The practice while effective in this respect and in use for a long term of years has not spread to other cities possibly because of the unsightly ap- pearance of the overhead structures due to the multiplicity of wires and because of the increase in operating difficulty and ex- pense which it entailed. (b) Substantial Insulation. Interurban and electrified steam roads generally require the rails to be supported on wooden ties set in well drained broken stone or gravel ballast. The insulation afforded by such construction practically removes danger from electrolysis. Leakage is in some instances found to be as low as .00016 ampere per rail per tie under dry weather conditions, increasing to .0055 ampere when wet with 10 volts between the rail and ground. On steel structures where the ties are only partially in contact with ground and the ties cannot become waterlogged, this leakage is even less. The substantial insulation of a ballasted roadbed has, in some installations, been rendered ineffective by bare negative cables in damp earth or by metallic connections between the tracks and steel supporting construction. Conditions are found to be very favorable for rail insulation where the tracks are in subways or under cover protected from the weather, permitting the ballast and ties to become permanently dry. (c) Partial Insulation. The escape of current from tracks largely buried is decreased by high contact resistances between the tracks and the surrounding medium. The total resistance AMERICAN PRACTICE 49 to flow of escaping current is found to vary with the earth resistance and the contact resistance between earth and rail. Since the earth resistance is usually low, the contact resistance is generally found to be the controlling factor in the leakage path; hence, partial insulation is found effective in reducing leakage with the low voltages commonly encountered. On a grounded trolley system in city streets it has been found bene- ficial to have the rails as nearly enclosed with insulating material as possible. 47. Reduction of Track Voltage Drop. (a) Bonding. The best types of solid rail joints in actual use give the same electrical conductivity at the joint as in any other part of the rail length. The standard of good practice in some electrified steam roads is that, the resistance through the rail joint shall be equivalent to that of a 20-inch length of the rail adjacent, and should the resistance exceed 42 inches, that the bond should be remade. With respect to the practice of bonding in street railway systems, it may be said that there is no standard equivalent length of rail to cover all conditions, but each railway company establishes its own standard, de- pending on local conditions. The equivalent resistance of the rail joint in terms of length of rail will depend on the length and size of the bond, the terminal contact resistance and the conductivity of the rail. In large cities bonding to an equivalent resistance of from three to six feet of rail is common practice. In suburban districts higher bond resistances are often used. The equivalent resistance of rail joint which is adopted by different railroads necessarily varies widely with the condition of load and class of bond employed. The class of bond chosen is in many cases determined by mechanical conditions, such as the founda- tion upon which the track is laid. Bonds are generally classified according to the method of fastening them to the rail. Soldered bonds are soldered to the head, base or web of the rail. Pin expanded bonds have holes drilled in their terminals, through which a steel pin is driven to expand the terminal into a hole drilled in the rail. After expansion a steel cylindrical plug is driven in the expanded hole to prevent contraction. Brazed or welded bonds are attached to the rail by heat generated electrically or by an oxy-acetylene flame applied to the terminal of the bond. Compressed terminal bonds and compressed multiple terminal bonds have their term- 50 AMERICAN PRACTICE inals formed into a solid cylindrical stud, or studs, and are compressed in the rail holes with screw or hydraulic com- pressors or by hammer blows, which expand the studs in threaded or beaded holes of the rail. A special type of this bond has large contact surfaces about the terminal, so that the bonds can be soldered and compressed to the rail. The carrying capacity of bonds has sometimes been found insufficient to keep their temperature within safe limits under conditions of maximum load where bonds involving soldered joints are used. The resistance of a rail joint is found to be affected largely by the contact resistance between the bond terminals and the rail. Good contact and large surface of contact at the bond terminals are found necessary to low joint resistance. Replacement of 'bonds is generally made necessary by depreciation at the contacts, the breaking of strands by vibration or by mechanical injury. There are now in general use several different types of rail joints which- render additional bonding unnecessary. Among these types of rail joints are the following: Cast Welded: The rails are connected together by pouring molten iron into a mold that surrounds the joint, and when the metal cools the joint is rigid and of low electrical resistance. Thermit welding is another example of this method, the iron being liberated at a white heat from a mixture of iron oxide and aluminum which is ignited in a crucible. Electrically Welded: Iron splice plates are electrically welded to the rail. Nichols Zinc Joints: This joint is made by pouring molten zinc between the fish plates and the rail ends. The zinc is poured in after the fish plates are bolted on, and the expansion of the zinc in solidifying is relied upon to make a contact between the fish plates and rail ends which is reported to be permanent. Romapac Continuous Rail: The rail consists of two pieces which are so laid that the rail head joint and the rail base joint are staggered, then the rail head is rolled or crimped on to the rail base thus forming a continuous electrical path. (b) Cross-bonds are electrical conductors for equalizing the current flow in the rails. When the roadbed is dry they are usually installed bare in the ground. Insulated cable is, how- ever, sometimes used, and the insulation is protected by a heavy braid or circular loom tubing. The important objects of cross-bonding are to equalize the AMERICAN PRACTICE 51 current flow between rails and to insure continuity of the return circuit in case of a broken rail or bond in any one rail. It is usual practice on suburban railways to place cross-bonds at intervals of 1,000 to 2,000 feet and at shorter spacing, some- times as low as 300 feet on street railways. Cross-bonding between parallel tracks is in some cases installed with the same frequency as between the rails of the single track; in other cases at less frequent intervals. In determining the location of cross-bonds in connection with alternating current single track signal circuits, a departure from ideal spacing becomes necessary, owing to the fact that cross- bonds are permissible only at the reactance bonds. The signal reactance bonds are located between the signal block sections, and these sections are more or less fixed for train operating conditions. The general method used under these conditions is to cross-bond at all signal reactance bonds and install addi- tional cross-bonds with reactance bonds at intermediate loca- tions to obtain the most satisfactory resistance conditions in the sections fixed by the signal system. The common practice of electrified steam railroads is to use cross-bonds with a conductance equal to one track rail, or about 1,000,000 circular mils. Street and interurban railways employ copper having a cross-section of from 200,000 to 500,000 circular mils. Some companies provide jumpers at switches, frogs and at other special track work, to insure that the electrical continuity of the bonded rail will be maintained. This is usually accom- plished by jumpers extending around the special work, except where broken rail signal protection is required, and in such cases the frogs are bonded in the return current system. In recent practice these jumpers are made of insulated copper cables, except in dry locations, as, for instance, in permanently dry rock ballast, or on elevated structures with wooden ties and no ballast, the cables being kept clear of the steel structure. The electrical leakage from a bare negative jumper in damp earth has been known to offset the effect of many miles of most careful track insulation. Under such conditions the bond is gradually destroyed by electrolysis. (c) Conductivity and Composition of Rails. The conductivity of the track rails used by several interurban and electrified steam railroads has been found to be equivalent to about 1/12 52 AMERICAN PRACTICE that of copper, and this figure generally holds approximately true for girder types of rails, except when alloy steel is used, in which case higher resistances are found. The track rails are specified for their mechanical qualities, and, where these interfere with the electrical requirements, it is customary to give the mechanical qualities preference. The composition of rails for heavy service used by one of the large electrified steam railroads, in percentages, is as follows: Carbon 0.62 to 0.75 Manganese 0. 70 to 1 . 00 Silicon 0.10 to 0.20 Phosphorus . . not to exceed . 04 The American Electric Railway Engineering Association has adopted the following standard composition for heavy service rails : Class A Rails Class B Rails Carbon 0.60 to 0.75 0.70 to 0.85 Manganese 0.60 to 0.90 0.60 to 0.90 Silicon . Not more than . 20 Not more than . 20 Phosphorus Not more than 0.04 Not more than 0.04 d. Reinforcement of Rail Conductivity. Early track con- struction practice in this country often included bare wire laid between the rails and connected to each bond. Some- times ' one such wire was used for each rail ; sometimes one for each track, and sometimes one served for a double track. The wires varied from No. 4 to No. 1, and were either of copper or galvanized iron. Their conductivity was small and they were subject to electrolytic injury and frequent break- age. This construction has practically gone out of use. It is, however, common to find the rails supplemented in the vi- cinity of supply stations by large conductors connected in par- allel to the rails. This is not infrequently done by the use of bare copper wire or cable buried between rails, and hence in full contact with the earth. Old rails, bolted and bonded to- gether and buried beneath or beside the track, have also been used in some cases. Buried bare conductors, however, increase the contact area between the return circuit and the earth, and the tendency to augment stray currents thus caused off sets, to a greater or lesser extent, the benefits attained by the reduction of drop. The AMERICAN PRACTICE 53 benefits to be derived, therefore, from an electrolysis stand- point, may, if use is made of bare conductors buried in the earth, be open to question. The direct benefits that accrue from the practice of reinforcing the conductivity of the rail, listed in what may be considered their order of importance, are : (1) Reduction of energy losses; (2) The maintenance of a higher average voltage at the cars, especially at times of peak load, thus resulting in improved car service and car lighting; and (3) The reduction in potential drop in the rails, thus reducing stray currents and, in turn, therefore, lessening the damage to the extent that these stray currents are reduced, qualified, how- ever, in accordance with the statement previously made if buried bare conductors are used. Where conductors paralleling the rails are installed as an electrolysis mitigation measure, they are usually insulated from earth by carrying them overhead or in underground conduit. The practice varies as to the method of connecting such conductors to the rail; they are sometimes connected at the ends only but more generally at intermediate points also. Where this arrangement is used the track rails are connected to the negative bus at the nearest convenient point. Conductors are here regarded as in parallel with the rails when one end is connected to the track and the other to a station bus-bar which is connected directly to the rail by a conductor of negligible resistance. The use of such conductors should not be confused with the "Insulated Track Feeder System," which has for its prime object the mitigation of electrolysis. This is treated under a subsequent heading. (e.) Use of Additional Power Supply Stations and Distri- bution of Load. The growth of electric railway systems in large cities has often led to the installation of additional power stations or substations for the more economical and satis- factory operation of the railroad. This has also reduced the track voltage drop and subdivided the areas over which leakage from rail to earth occurs and thus has had the effect of reducing the stray currents. The effect of providing additional centers of power supply can best be illustrated by the curves on Figure 5, which, while deduced from theory, illustrate in a simple case effects such as have been observed in practice. The curve SAO of Figure 5 represents the track voltage 54 AMERICAN PRACTICE REDUCTION OF TRACK VOLTAGE DROP BY ADDITIONAL POWER SUPPLY STATIONS DISTANCE Figure 5 AMERICAN PRACTICE 55 drop on a portion of an electric railway system having a uni- formly distributed load. This curve is a parabola with a vertical axis and with the apex at that is, at the end of the line. The curve SB F illustrates the condition of a substation lo- cated at P (33 per cent of the distance from Q to S) carrying 20 per cent of the total load. In this curve the portion BF is identical with AO. As the load is uniformly distributed, 33 per cent of the load is on the portion of the line shown by PQ, and of this 33 per cent, 20 per cent is carried by the sub- station P. The remainder, or 13 per cent, is carried by the station S. The point B on the curve SBF, therefore, corresponds to the point N on the curve SAO, the distance QR being 13 per cent of QS. In the same manner the curves SCG, SDH and SEK are drawn showing the conditions when the station P carries 40 per cent, 60 per cent and 80 per cent, respectively, of the total load. The summit of the curve SMD, in which .the station P carries 60 per cent of the load, is located so that PL equals 60 per cent minus 33 per cent, or 27 per cent of the total length SQ to the left of P. The distance- QL is, therefore, 60 per cent of the total length QS. In general, the conditions are more complicated than those here assumed, and will ordinarily prevent an accurate deter- mination of the relative location of the negative busses of the two stations. It is possible, however, to make tests which will verify each of the points which have been used in preparing the curves, although it may not be possible to verify all of them at any one test or in one location. 48. Three-wire Systems. As far back as 1894, and possibly earlier, consideration was given to a three-wire system of opera- tion for electric street railways, wherein the tracks acted as the neutral circuit. The reason for considering such a system was to reduce stray currents through the earth. Installations of this sort were tried out in Pittsburgh, Pa., Lowell, Mass., Portland, Ore., and Seattle, Wash., in the earlier days; some- what later an experimental installation was made in Cambridge, Mass. In the Transactions of the American Institute of Elec- trical Engineers for 1907, Vol. XXVI, No. 1, pages 268 to 280, Messrs. Paul Winsor and J. W. Corning report the results of an investigation to determine the feasibility of using the three 56 AMERICAN PRACTICE wire system for the purpose of reducing stray currents through the earth. This investigation showed that the three- wire system of operation materially reduced the track voltage drop, and therefore reduced the amount of stray current in the earth and in underground metallic structures. The figures and curves shown by Mr. Corning indicate that there is a reduction in current flowing on pipe lines tested by him of the order of nearly 90 per cent. Until very recently it was thought that three-wire systems contained certain serious inherent disadvantages. It was felt that the complications in machinery, difficulties in successfully insulating trolleys of different polarities, difficulties in equalizing the load between different sections, and, fuither, the necessity for the installation of larger generating units to compensate for the difficulties in balancing than were required with the single- trolley grounded system, were so great as to preclude the con- sideration of the three-wire system for electrolysis mitigating purposes. Recently, however, interest in this system has been renewed, and at least some of the difficulties successfully over- come, with the result that at the present time there are in operation or being installed two sectionalized three-wire sys- tems one in operation in the Hollywood district of Los Angeles, Cal., and the other in process of installation in West Springfield, Mass. It is known that the three-wire system has been in operation for some twelve years in Niirnberg, Germany, and for a considerable length of time in Brisbane, Australia. The three-wire system may take two different forms, which, though the same in principle, differ decidedly as to the arrange- ment of the feeders. In one form, known as the Parallel Three- wire System, one trolley of a double track road is negative and the other positive, the tracks being neutral. In the other form, known as the Sectionalized Three-wire System, the feeding district is di- vided into sections and alternate sections are supplied by feeders running directly from the positive bus, while the remaining sections are supplied by feeders from the negative bus. For a more detailed description of these two forms of three-wire systems reference is made to the Bureau of Standards' Tech- nologic Paper No. 52. 49. Reversed Polarity of Trolley System. With the ordinary construction of electric railways using the running tracks as a part of the electric circuit, the overhead trolley wire or third AMERICAN PRACTICE 57 rail is made the positive conductor, and the running tracks the negative or return conductor, only one exception to this rule being known to the Committee. With the usual arrangement stray currents escape from the running rails into ground and flow to underground structures at points distant from the power station, and such escape of stray currents from the rails gener- ally takes place from a large area of outlying lines. The cur- rent then returns to the tracks from ground and from under- ground structures in the neighborhood of the power station. For this reason the most acute danger from electrolysis is usually produced on underground structures in the neigh- borhood of the power station. To reverse this arrangement of polarity and make the rails the positive conductor, causes current to leave the structures over widely scattered areas, so that the current density leaving the underground structures will be so small as to prevent acute danger from electrolysis. This arrange- ment is being used in New Haven, Conn, at the present time. It is found, in this instance, that all potentials and currents which formerly existed when the rails were the nega- tive conductor have now reversed in direction, but have the same magnitude. It is also found that current leaves under- ground structures over a widely scattered outlying area. This arrangement has not been in operation a sufficiently long time to determine whether or not the danger from electrolysis at any one outlying point will become acute. The reversal of polarity renders extremely difficult the effective drainage of un- derground structures, because there is no definite point of mini- mum potential to which to drain. 50. Booster System. Negative boosters have, in the past, been employed in connection with drainage systems, and are in use in connection with the insulated track feeder system abroad, but not in this country, so far as known. The use of nega- 'tive boosters is simply a means of caring for voltage drop other than by the use of copper. Boosters have proved economical under certain conditions , and uneconomical under others . In general it is simply a question of the fixed charges on copper as against the fixed charges and operating cost of machines. In one in- stance where a booster was employed in connection with a drainage system it was discontinued, not because the addition of a booster to a drainage system was unsatisfactory, 58 AMERICAN PRACTICE but because the drainage system itself did not adequately care for the trouble. Various special arrangements involving the use of boosters in electrolysis mitigation have been proposed, but in so far as is known they have never been placed in suc- cessful operation. 51. Interconnection of Railway Return Circuits. Where- ever two or more electric railway tracks come close together, whether they belong to the same railway system or to different railway systems, large differences of potential between them, with resultant high potential gradients through ground, are often found to occur unless the tracks are electrically connected. Interconnection of tracks has been found to be of partic- ular advantage where two or more lines of electric railway, operating in one locality and belonging to the same or to different systems, are supplied from two or more power stations located in different parts of the city. By interconnecting the tracks of such lines in the neighborhood of the power stations, and also at several intermediate points, an interchange of current has been brought about, whereby the .drop formerly existing in one track has been balanced by the drop in the opposite direction in the other track, the rail drop in each track greatly reduced, and all high potential gradients between the tracks eliminated. This reduction in rail drop resulted also in a corresponding reduction of losses. 52. Use of Alternating Currents. When the first alternating current railways were proposed, the question of possible elec- trolytic effects received special investigation. Considerable work was done upon a laboratory scale, in which it was estab- lished that alternating currents could produce corrosion on electrodes of the metals commonly used underground, such as lead and iron, but that the effects were very much less in magnitude than those produced by equivalent quantities of direct current, usually less than one per cent and in most cases negligible. It has not as yet been possible to determine whether these effects, demonstrated in an experimental manner, are being reproduced in the case of actual installations. In the case of practically all actual exposures which have occurred up to the present time it has been impossible to dissociate effects which might be due to an alternating current exposure from AMERICAN PRACTICE 59 the effects which are due to a simultaneous exposure to stray currents from direct current railways. Whether alternating current corrosion is proceeding at the relatively slow rate in- dicated by the experimental investigations and will at some time produce damage to subsurface structures, cannot now be determined. Special measures for the reduction of leakage of current to earth are being tried out in one alternating current railway, but neither the construction nor the results have yet been made public. (See Bureau of Standards Technologic Paper No. 72.) 53. Insulated Track Feeder System. The insulated track feeder system or the insulated return feeder system is employed in a number of American cities at the present time, and plans are being made looking to its installation in a number of other cities. The arrangement of feeders described under this title is not generally understood, and as it is commonly confused with the reinforcement of track conductivity, the following explanation is therefore made. Stray current which is the cause of electrolytic corrosion is traceable directly to voltage drop in the rails. With a given resistance between rails and earth any means which will most effectively reduce this voltage drop is, therefore, the means which will most effectively reduce electrolytic corrosion. The reinforcement of the conductivity of the rails by paralleling them with other conductors operates definitely in this direction, provided the paralleling conductors are not themselves in contact with the earth. When, however, it is desired to reduce the volt- age drop to such a point as will insure reasonable immunity from electrolytic troubles, the employment of copper in parallel with the rails generally proves prohibitively expensive. For example, an average grade of rail has a resistance 12 J times that of copper of the same cross-section. Its conductivity is therefore ap- proximately the equivalent of 10,000 c. m. of copper per pound per yard. Such a rail weighing 100 pounds per yard would be approximately equivalent to a 1, 000,000 c. m. cable. To reduce the track voltage drop to one-half its former value, where such a rail is employed, would require a 1,000,000 c. m. cable laid parallel to each rail of the track for its entire length. This large investment in copper would reduce the losses of track trans- mission by but one-half, and would reduce the stray current by 60 AMERICAN PRACTICE one-half. If bare copper in contact with the earth were used the stray current would be reduced by somewhat less than one- half. Thus, the practice to install return copper to reduce track drop with a grounded bus-bar is either prohibitively ex- pensive or ineffective. It was because of these recognized diffi- culties that the Insulated Track Feeder System was introduced. The insulated track feeder system employed in the Amer- ican cities above referred to has the following distinguishing characteristics : (a) The negative bus is insulated that is, not connected to earth nor directly to the rails at or near the power or sub-station, except that, in some instances, it is connected to the rails through resistances sufficient in magnitude to insure that this point is at approximately the same potential as other track feeder points. (b) The current is returned to the negative bus by insulated feeders leading from selected points on the track network. (c) These feeders are connected to the track at their extremi- ties only, or, if connected at intermediate points, are connected through resistances of such magnitude as to keep all connected points at approximately the same potential with respect to the bus. The Insulated Track Feeder System is thus an arrangement having for its prime object the reduction of stray current through the earth. The insulated feeders are installed either overhead or in underground ducts, and extend from the negative bus to such points on the track network as have been determined, by either observation or computation, to be those from which the removal of current will prevent excessive track voltage drop. The negative bus is connected to the rails at the power house only through a resistance sufficient in magnitude to insure that this point is at approximately the same potential as other feeder connection points. When all feeder connection points are at the same potential the maximum effectiveness of the system as a means of reducing stray currents is found. The attainment of this condition requires track bonding of a reasonably high order of uniformity. In most cases feeder connection points are not brought to the same potential, but a certain drop is allowed in the direction of the power station. The insulated track feeder system is the equivalent of having the negative bus-bar of the power supply station divided into branches corresponding in number to the number of track feeder AMERICAN PRACTICE 61 points, and distributed geographically over a considerable por- tion of the track network. This reduces both maximum and average current in the rails and also reverses the direction of the current in the rails on one side of each feeder point. These changes in the rail current directly reduce track voltage drop. The area from which current leaks to earth and to underground structures, and also the area from which current returns from underground structures and earth to the rails are subdivided. The combined effect of these factors is a substantial improve- ment in electrolysis conditions of underground structures. (See G. I. Rhodes, Trans. A. I. E. E., 1907.) The efficacy of this system in reducing stray current is practically independent of the weight of copper in the individual feeders that is to say, the voltage drop in the feeders may be either large or small, without material effect upon the stray currents. As was pointed out under a prior sub-heading, negative boosters may be used with this system. The principles underlying the insulated track feeder system are the same, whether or not negative boosters are used. B. MEASURES APPLIED TO AFFECTED STRUCTURES. 54. Insulating Joints in Large and Small Iron Pipes and in Lead- sheathed Cables. In a number of installations flow of stray current on metallic pipe lines has been prevented by the use of a sufficient number of insulating joints. It is found that where a pipe line is laid with every joint an insulating joint, the line has such a high electrical resistance that no measurable current flows on the line, although considerable potential gradient exists in earth parallel to the pipe line. In some installations it has been found sufficient to use comparatively few insulating joints to break up the electrical continuity of a pipe line and protect the line from electrolysis, but in these cases it was necessary to make adequate tests to assure that sufficient current did not shunt through earth around the joint to damage the pipe on the positive side of the joint. In these installations it has been found necessary to install such insulating joints, not only in the positive areas, but also in the negative areas in all places where con- siderable potential gradient in earth parallel to the pipe existed. It is found, in fact, that the frequency with which insulating joints must be installed in a pipe line in order to assure reasonable protection from electrolysis, depends upon the potential gradient 62 AMERICAN PRACTICE 'through the earth and upon the electrical resistivity of the earth in the neighborhood of the pipe line. Tests on joints buried in earth have shown that the resistance of a short insulating joint is practically the same as that of a long joint, but that a long insulating joint gives a more even distribution of leakage current than a short joint, and that, therefore, a long insulating joint is to be preferred where there is considerable potential difference across the joint or where the resistivity of the surrounding soil is very low. It has also been found that the effect of a long joint can be secured from a short insulating joint by surrounding the joint and the pipe for some distance on each side of the joint with a heavy layer of insulating material. In a number of installations of such insulating joints in important pipe lines, each joint and the pipe for a distance of from 5 to 25 feet on each side of the joint have been surrounded by a wooden box leaving a space of from 1 to 2 inches between the outside of the pipe and the inside of the box, and the space then rilled with pitch, parolite, or similar material. In this way an insulating joint having an effective length of from 10 to 50 feet was secured. (See also Bureau of Standards Technologic Paper No. 52). In a large number of cases small service pipes have been damaged by electrolysis from stray current leaving the service pipes for earth, which current was found to flow to the service pipes either from the main or from house piping. In the latter case the current was found to reach the house piping by way of a service pipe from another piping system. In some cases of this kind such current flow to service pipes has been greatly re- duced or prevented and the service pipe thereby protected ffbm electrolysis, by placing an insulating joint in the service pipe at the main or in the building, as the case may be. In some cases it was however found necessary to install an insulating joint in the service at the main and a second joint in the building, the necessary locations of the joints being determined from the results of electrical measurements. This method of protecting pipes has been applied to isolated cases which were specially studied, but has not been generally applied to a large complicated city system of mains and services. For wrought-iron or steel pipes of small and moderate size, various commercial, insulating joints have been largely used. For large sizes of pipe a flanged type of insulating joint has been commonly used. This insulating joint has been AMERICAN PRACTICE 63 made up by placing a disc of insulating material between the surfaces of the flanges, by placing insulating tubes over the bolts, and by placing insulating washers under the bolt heads and nuts. Red fibre has been most commonly used for the in- sulating material, except that for water pipes in some cases soft sheet rubber has been used for the packing between the flanges. Where such flanged insulating joints have been used in cast-iron mains the flanges have generally been cast as part of the pipe. For water mains various forms of insulating joints employing white pine wood for the insulating material have also been used to a considerable extent. For cast-iron water mains with bell and spigot joints, these joints have in some installations been rendered insulating by placing a short wooden ring between the inside of the bell and the end of the spigot to prevent metallic contact between the pipe lengths, and then calking the joint with wooden staves of clear white pine shaped to fit the curvature of the pipe. In these cases the spigot end of the pipe was either cast without a bead or the bead was removed. The leaks that developed in the joint were stopped with white pine wedges. These simple joints have been found satisfactory for pressure up to about 75 pounds per square inch (5.27 kg. per sq. cm.) Where with higher pressures leakage developed through the pores of the wood, this was overcome by dipping the inner ends of the staves in red lead. The staves have also been reinforced in some cases by an iron band clamped around the spigot end of the pipe. It is found that cement joints in cast iron pipes as ordinarily made have a very high resistance between adjoining lengths of pipe and that such joints may properly be classed as insulating joints. When pipe lines are laid with every joint, or even every other joint made of cement, the resistance of the pipe line becomes so great that the current flowing on the pipes will be greatly re- duced. In practice, however, for mechanical reasons it has been found that cement or other insulating joints cannot be used under all conditions or for all sizes of pipe. In such cases, the entire drop of potential of the pipe line is distributed more or less uniformly over all of the cement joints and the drop in potential around any one joint is too small to cause any injury through leakage of current around individual joints unless the soil is of great conductivity. This, however, will not prevent electrolytic corrosion in local- ities where current can reach the pipe by way of laterals, or when 64 AMERICAN PRACTICE it is closely adjacent to other conducting structures which nul- lify the effect of the joints, or when there is leakage from another transverse pipe. Insulating joints in lead sheaths of underground cables are in use to some extent, but they are not found to afford an effective primary means of preventing electrolysis. In some installations such insulating joints have been used in positive areas for the purpose of breaking up the electrical continuity of the lead cable sheathing and stopping rapid localized destruction from electro- lysis, but such joints have not generally been found to afford permanent and complete protection. In certain special cases in practice insulating joints have been used in the lead sheaths of certain cables for the purpose of preventing current from reach- ing the remainder of a cable system. Common examples of this are found where laterals or services from a cable system pick up considerable current from an iron conduit or from pipes with which the cable or iron conduit may be in accidental metal- lic contact, which current is then delivered to the cable system. Such current flow to the cable system has frequently been effec- tively stopped by introducing an insulating joint in the lead sheath of the lateral or service where it leaves the iron conduit and before it is connected to the main cable system. Particular points on main cable runs have also been found where considerable current was picked up. Such cases have frequently arisen where a cable crosses a bridge in an iron conduit, and where the conduit is in metallic contact through the structure of the bridge with trolley tracks on the bridge, whereby large currents were found to flow from the tracks through the bridge structure and iron conduit to the cable system. In such cases insulating joints have been installed on each side of such sections or crossings so as to interrupt the metallic continuity of the main cable sheath and prevent current from the bridge reaching the cable system. Where, after this was done, considerable potential differences were found to exist across the outer ends of the cable sheaths, these were equalized by connecting the cable sheaths at the two ends together by an insulated wire. A simple and cheap form of insulating joint for lead cable sheaths which has been very generally used consists in cutting out a narrow strip of lead and covering the break with a suit- able insulating and waterproof material so as to effectively prevent entrance of moisture. AMERICAN PRACTICE 65 This method of protecting underground structures has not been widely used as a primary means of electrolysis protection, partly because of the great expense involved. Further, insulat- ing joints unless used with caution may introduce serious trouble at many points. This method has proved useful especially in certain new installations, but to protect existing installations by this means would involve prohibitive cost. It is usually re- garded as a suitable auxiliary measure to be used in certain cases which cannot economically be taken care of by other means. 55. Insulating Pipes, Cables and Structural Steel from Earth. Many attempts have been made in practice to protect under- ground pipes from electrolysis by insulating the pipes from earth by paints, dips or insulating coverings. It has been found, however, that no dip or paint will permanently protect a pipe from electrolysis in wet soil. The first difficulty that is met is to apply the paint so as to form an absolutely perfect coating, and then to prevent mechanical damage to the coating. Where a coated pipe is in a positive area it has been found that aggravated trouble from rapid destruction of the pipe has resulted at spots in the pipe where there are imperfections in the coating. It has further been found that even where paints or dips are apparently intact, electrolytic action has taken place causing severe pitting under apparently good coatings. It has been found that in most cases the coatings applied have either been completely destroyed by the effects of the wet soil and electric currents, or defects in the coating have de- veloped, causing concentrated corrosion at such defective spots.' It has, in fact, been found- that pipes located in positive areas covered with imperfect insulating coatings are more rapidly destroyed by electrolysis than bare pipes under the same con- ditions. It has been found that coating pipes in negative areas with insulating coverings accomplishes some good by reducing the amount of stray current which reaches the pipe. Investigations indicate that the destruction of paints in wet soil where subjected to an electric current is probably due to a trace of moisture finding its w.ay through the coating, giv- ing rise to the flow of a feeble current and resulting in a very slight amount of electrolysis. The gases and other products of electrolysis then form blisters and finally rupture the coating. Attempts have been made in practice to apply a molten material like pitch or asphaltum to a cold pipe in the field by 66 AMERICAN PRACTICE means of brushes, but it has been found impossible to com- pletely cover the pipe in this way. A type of insulating cover- ing which has been successfully applied in a number of installa- tions, and which appears to afford certain protection, consists of a layer of at least from 1 to 2 inches of a material like pitch or parolite of such a grade that it is not brittle and so will not. crack, but yet is hard enough to remain in place. It has been found best to apply such a layer by surrounding the pipe with a wooden box, supporting the pipe upon creosoted blocks of wood or upon blocks of glass, and then filling the space between the box and the pipe with the molten material. The cost of carrying out such an installation is, however, large. The method has been applied in special cases, such as service pipes in very bad localities, and in the case of some very important individual pipe lines of comparatively small size. Attempts have been made to protect a pipe from electrolysis by imbedding it in cement or concrete, but these attempts have not been successful, even where the cement or concrete was several inches in thickness. The reason for this is that concrete in damp earth acts as an electrolytic conductor, like damp soil, and therefore cannot afford protection from elec- trolysis. The following experience and practice is that of a gas com- pany in a large city which uses cast-iron pipes in general in their distributing system with wrought -iron services. They make it a uniform practice to protect all of their service pipes with an insulating coating. As a preliminary the pipes are first cleaned with a wire brush, in order to remove all scale. They are then dipped into a hot coal tar compound, then wrapped for the entire length with a strip of canvas, and then again dipped in the compound. In spite of this protection, however, they have some trouble with their services. The difficulty is due to their inability to get a continuous coating over the entire surface of the pipe. Small pin holes are left in the coating due to minute bubbles of air, or some similar cause, so that if the pipes are positive the flow of current from the pipe through moist earth is confined to these minute pin holes through the insulating compound. The result is that the action of the current forms a small blister of iron rust at the point where the pin hole is located, and after the blister becomes so large as to loosen a piece of the compound, the action takes place at a very rapid rate and soon destroys the pipe. In some locations some of the AMERICAN PRACTI-CE 67 service pipes have to be renewed within a period of six months on account of the leaks caused by the electrolytic corrosion. Attempts have been made to insulate lead-sheathed cables from earth, but these attempts have not generally been at- tended with beneficial results. The experience of the telephone companies, who are the largest users of lea-d-sheathed cables, has been that it is futile to attempt to insulate lead-sheathed cables from earth. It is, however, the practice of the telephone companies to make every effort to prevent metallic contact between their lead-sheathed cables and other grounded struc- tures throughout the run of the cable, except where it has been determined by a careful survey that a drainage connection to some particular structure is required for the protection of the cable. The use of insulating ducts has been proposed at various times, but investigations of the telephone companies do not show that their use affords satisfactory insulation of the cable sheaths from earth, with the result that the telephone com- panies do not place any reliance in any insulating property that any of the duct material may inherently possess. The principal duct material at present used by the telephone com- panies for main cable subway runs is vitrified clay and creo- soted wood. For laterals and short cable runs iron pipe is frequently used. Laying telephone cables in troughs and surrounding them solidly with asphalt was a method employed in the early days of telephone construction, but this method was abandoned because of its inflexibility and because of the great difficulty of repairing defects or replacing cables. It was further found that this method did not positively insulate the cables every- where from earth on account of cracks and other discontinuities in the asphalt which were found in practice to develop. Steel tape armored cables protected with a thoroughly saturated jute covering have been used buried directly in earth. Such covering has been found to be effective for a number of years in protecting the armor against electrolytic corrosion, except at points where the jute has been abraded or cut so as to expose the metal. Where steel structures extending underground are located so as to be subjected to electrolytic action, the portions below ground have been enclosed with insulating materials. For this purpose any material that excludes water, as for instance 68 AMERICAN PRACTICE paints having an asphalt base, have been successfully used, while many of the ordinary paints have not been found effective. It has also been found that surrounding steel with concrete where this is imbedded in damp earth does not afford absolute protection against electrolysis, although the electrolytic action is most severe at first and becomes less with time, because the formation of chalk in the concrete fills the pores of the concrete and increases its resistance and the iron oxide forming on the surface of the metal also increases the resistance. Special preparations of Portland cement properly applied so as to be watertight have also been found to afford good protection. 56. Shielding, or the Use of an Auxiliary Anode. In some special cases underground structures have been protected from electrolysis by connecting to the structure an auxiliary metallic conductor located so as to cause the current to flow to earth from the auxiliary conductor. This mode of protection is known as shielding. When applying this method it has been found necessary to take care that the auxiliary shielding con- ductor does not merely increase the electrode areas from which the current leaves, because in this case the current will continue to leave from the structure which is to be protected. This has been found to be the practical result where a shielding conductor of the same or less contact area was placed in earth near the structure to be protected and where the stray current then left from both structures. The shielding conductor must be so placed that current will be prevented from leaving the structure to be protected or so as to cause its magnitude to be greatly reduced. The method has in some installations been applied to a structure which forms the dead end of an underground metallic system and where the structure is highly positive to earth. In cases of this kind it has been found that the current leaves at relatively high density from and near the dead end of the structure, with the result of rapid destruction of the portion near its dead end. In such cases an auxiliary shielding conductor of adequate contact surface extending be- yond the dead end and electrically connected to the structure to be protected has been installed in such a manner that the bulk of the current was caused to leave the auxiliary shielding conductor, thus affording a certain degree of protection to the dead end of the structure. The shielding method has also been effectively applied for AMERICAN PRACTICE 69 the protection of relatively small iron or steel pipes, such as service pipes. In these cases the service pipe has been sur- rounded by a larger metal pipe electrically connected to the smaller pipe. One application of this method which is in use is that of a service pipe crossing under tracks or crossing other structures to which it is positive and where the pipe comes relatively close to the rails or other structures at the point of crossing. In these cases a larger shielding pipe, usually of heavy cast iron, has been placed around the service pipe and electrically connected to the service pipe and extended suf- ficiently on each side of the crossing so that the major part of the current was caused to leave the shielding pipe, thereby corroding the shielding pipe while protecting the service pipe. 57. Drainage of Earthed Metallic Structures. (a) Lead-sheathed Telephone and Power Cables. The method of protection against electrolysis used generally by telephone companies for their cable sheaths consists of installing insulated conductors, called drainage wires, between the negative re- turn system of the railway and points on the cable system where the positive potential to earth is highest. The purpose of these drainage wires is to conduct the stray railway current from the cable sheaths to the railway negative return circuit, thereby preventing this current from flowing from the cable sheaths to earth and causing corrosion from electrolysis. In order to afford complete protection it has been found that such drainage wires must have sufficient conductivity and must be so located that the lead sheath of the cable network is every- where lower in potential than the adjacent earth. As the potential of the cable sheath is lowered by the con- nection of the drainage wire from the railway negative return circuit the current flowing on the cable sheath is thereby in- creased. In order that this current does not become excessive, care is taken to prevent contacts between cable sheaths and other underground structures, through which currents could flow to the cable sheaths. The drainage method is also employed to a considerable extent for the protection of underground power cables, and the principles involved in its application are the same as for tele- phone cables. When power cables are worked at relatively high temperatures they should not also carry a heavy drainage current which might cause over heating. Where such conditions 70 AMERICAN PRACTICE prevail drainage is not employed, but insulating joints are used to break up the continuity of the lead sheaths. (b) Pipe Systems: The early success of the drainage method in affording protection against electrolysis of lead-sheathed cables led to the proposal to apply the same method of protection to underground piping systems. The result has been that in some cases drainage has been applied to gas and water piping systems to a greater or lesser extent. Some of these installations are reported to be a success, while others are reported to have been attended with objectionable results. It has been found that there are certain differences between the application of drainage to pipes and the application of drain- age to cable sheaths. The principal difference that has been found is that the cable sheaths are electrically continuous and uniform conductors, while the pipes are generally non-uniform and sometimes discontinuous conductors, by reason of the joints. It is found that where current flows along a pipe and encounters a high resistance joint, part of the current will leave the pipe on the positive side of the joint to flow to some other underground conductor or to shunt around the joint and thereby cause electro- lytic corrosion of the pipe on the positive side of the joint. Another difference between lead -sheathed cables and piping systems is that the cables are relatively small and are con- tained in ducts, so that unless they are submerged they are not in direct contact with earth, except at infrequent points, whereas gas and water pipes form extensive systems and are buried directly in earth. It is found as a result of this that a drainage connection from an underground piping system generally causes very much larger currents to flow on the piping system than a drainage connection from an underground cable system. In the application of the drainage system it has been found that unless all sub-surface metallic structures affected by stray currents have been bonded together in such a way that at every point where the different structures come into proximity to one anotherall are maintained at the same potential, damage to the un- connected structures has in certain instances resulted from a flow of current through earth from the structure of higher to that of lower potential, thus causing electrolysis of the former. As struc- tures owned by different interests cannot be bonded together ex- cept by an agreement between the owners, this has frequently of AMERICAN PRACTICE 71 itself made it impossible to apply a comprehensive drainage sys- tem to all structures, because of the impossibility of obtaining an agreement of all owners to allow connections to their struc- tures, except on condition that another interest assume liability for any injury which may result from such connections. Current flowing on piping systems which convey inflammable substances such as gas or oil constitutes a danger, as cases have been reported where stray currents on pipes have caused arcs which have ignited the gas or oil when an intentional or accidental break in the pipe has occurred. In other instances serious damage from explosions and fire has been caused by an arc due to the intermittent contact between pipes. (c.) Structural Steel. In a .number of installations special precautions have been taken to prevent stray current from reach- ing structural steel. Where in these cases such currents were found to reach the structure by means of pipes or other metallic connections, insulating joints have been placed in such connec- tions, or these pipes or conductors have been carried on insulated supports. In some cases where flow of stray currents to a steel structure could not be entirely prevented, drainage connections from the structure to the railway negative return circuit have been installed to remove the stray current from the structure, and where there were expansion joints in the structure these have been bonded across by metallic conductors. C. PATENTED PROTECTIVE SYSTEMS. 58. Foreign and Domestic Patents. There have been many patents taken out in this country and abroad within the last twenty years, covering systems of electrolysis mitigation. Reference may be had to Technologic Paper No. 52 issued by the Bureau of Standards, Washington, D. C. D. ORDINANCES AND DECISIONS. 59. Ordinances. A number of cities have ordinances directed to the construction and operation of electric railways. The Committee, however, does not possess . sufficiently definite information as to the extent to which they have been put into effect or the results secured to warrant it in stating any facts regarding them at present. 72 AMERICAN PRACTICE 60. Decisions of Courts. While there have been several cases of electrolysis litigation in this country each of these has either been concerned only with certain phases of the subject or has been limited by local conditions, so that there are no -leading decisions by courts in this country which define specifically the duties and rights of the several parties concerned'. EUROPEAN PRACTICE 73 IV. EUROPEAN PRACTICE. A. GENERAL. 61. Personal Investigation Necessary. In the study of the practice followed in European countries in handling the problem of electrolysis, it appeared impossible to secure reliable and satisfactory information by mere correspondence and consulta- tion of published reports and regulations ; and further, since the important independent investigations made by American in- vestigators several years ago were private and made from the standpoint of some special industry rather than from a com- prehensive all-around point of view the necessity of an in- dependent investigation was made evident. The Chairman of this Sub-Committee, after consultation with its members and the General Chairman decided to visit several important European countries during the summer of 1914. He was accompanied by Mr. A. Maxwell, Testing Officer of The New York Edison Company, who was thoroughly conversant with electrolysis measurements and surveys. The effort to have the Bureau of Standards appoint a representative to join the visiting representatives failed on ' account of ex- tensive engagements of the Bureau, but a consultation was held in Washington, and the field of inquiry and special points to be looked after were carefully discussed, and a list of classified questions prepared, so that as far as possible uniformity of system of investigation could be followed in all instances. Similar consultations were held with members of the main Committee. Information on important foreign cities and authorities, was 'received from Mr. H. S. Warren, also foreign papers, suggestions and references from Prof. Albert F. Ganz. 62. Countries Visited. The visiting Committee spent June and July in its investigation, covering Germany, Italy, France and England. In each country an effort was made to take measurements and collect data and surveys, also to interview the most prominent people in each branch of the different 74 EUROPEAN PRACTICE interests affected by the problem of electrolysis; in each case extended and often repeated conferences were held with the engineers most familiar with the details, either in their capacity of specialized consulting engineers or officials of corporations or public authorities directly concerned in the surveys, disputes, administrative measures, etc. relating to electrolysis. The essential and characteristic results of the investigation are briefly outlined in the following paragraphs, classified by countries visited. The references and appendixes to this sum- mary should be consulted for details of design, operation and statistical information. B. GERMANY. 63. Laws and Ordinances. There are no specific statu- tory laws. The common law of most States prescribes that all the conditions under which a corporation is to operate must be prescribed in the original grant or for any extension of lines, and the law prescribes that due publicity be given to any request for a franchise or extension of lines, so as to enable all parties which may be affected to place on record any limitation, or possible damage they wish to be pro- tected against, before the concession is granted to the applicant. Hence, a pipe owning company organized subsequently to the existence of an electric railway, could not claim damages for electrolysis from this electric railway unless the original franchise to the -railway contained a clause regarding electrol- ysis damages from stray currents. On the other hand, when the municipality undertakes the construction and operation of a tramway system, the pipe owning companies then in existence are deprived of the privilege of demanding that protection against possible future damages by electrolysis which would be accorded to them in the case of a new private railway company. The municipality does not assume legally the obligation to protect the existing interests against possible damages by electrolysis. The municipalities, however, both for their new railway constructions, as well as for new extensions of existing companies' railways, always prescribe that they be constructed and operated in accord- ance with existing technical standards. The recommendations of the German Earth Current Com- mission are recognized as the existing technical standards re- EUROPEAN PRACTICE 75 garding matters relating to electrolysis, and in this manner they have assumed almost the importance of law. 64. Commission Recommendations. The German Earth Cur- rent Commission's recommendations adopted in 1910 by the German Electrotechnical Society prescribe the following: In large cities, the maximum rail drop is to be limited, in the urban net-work and for a distance of 2 km. beyond, to 2.5 volts and to 1 volt per km. beyond this central district. Exceptions are made for roads operating only a few hours a day. (It may be noted here that the maximum drop is interpreted to be the average maximum drop for the period of the normal day traffic, usually 18 hours in every 24 hours.) Bonds must not increase the resistance of tracks over 20% must be tested yearly and when a connection shows a resistance higher than 10 meters of rail it must be repaired. Connections to pipes are prohibited. Bare feeder returns are not allowed. Pilot wires are prescribed. Since these regulations were promulgated from 20 to 30 installations in Germany (some municipally owned and some privately) have taken steps to bring up their standard of con- struction to meet these regulations. 65. Construction. In large cities, like Berlin, the railways are 'supplied by a great number of combination light and rail- way substations feeding limited districts, entailing relatively small positive line drops of potential. In some cases like Berlin, each feeding point is fed by positive and negative cables of equal cross-section. Insulated returns with balancing resistances are predom- inantly used in Germany, though there are a few installations with negative boosters, like Danzig, where, however, insulated returns with balancing resistances as well as boosters are used. There are very few large installations using bare returns. The "drainage system" was used in Aachen but it is now a subject of litigation. 66 Conditions. In general the electrolysis conditions through- out Germany are now very satisfactory. In the past the majority of troubles have been on gas and water pipes, or at least these have received more attention in the reports. The railway experts expressed the opinion that the regulations were too 76 EUROPEAN PRACTICE stringent; the gas and water pipe experts expressed the opinion that the regulations were too lenient. The studies are made in the most excellent, technical manner and the conclusions arrived at appear to be practicable* and reasonably acceptable to all parties concerned. Measurements were made by the Sub-Committee of one large installation and it was found that the maximum drops in rails were well within the limits prescribed by the German regulations. More extended measurements were omitted, depending for other information on the surveys made by the German Earth Current Commission. C. ITALY. 67. Laws and Ordinances. The Government has not en- acted any law affecting the operation of electric railways in relation to electrolysis problems, nor has any municipality issued regulations on the subject. 68. Construction. Bare returns are generally used, in large installations. 69. Conditions. From a survey made in a city six years ago, it was found that the maximum differences of rail potential were as great as 17.5 volts between station and distant points about three miles away. In this installation they had not received complaints of serious damages by electrolysis, except a few gas service pipes, though the railroad itself had experi- enced some difficulties on water pipes at one of its yards. Some of the larger systems in important cities are alive to the situation and are following with interest the developments in other countries. In general, troubles from electrolysis have been considered in- significant in the Italian practice. D. FRANCE. 70. Laws and Ordinances. A Ministerial Decree of March 21, 1911, prescribes that the maximum voltage drop in rail returns of electric tramways shall not exceed one volt per kilo- meter, except in locations where there do not exist metallic masses in the neighborhood of the tracks, where the limit EUROPEAN PRACTICE 77 may be exceeded. No definition is given of the time element in the measurement of the maximum drop, 'except by stating that it must be the average during the normal passage of the cars. The same decree prescribes that the bonds must be kept in the best possible condition, that the resistance of each must not be greater than 10 metres of normal rail and that periodic tests must be made and recorded on a register which must be subject to inspection on the call of the control service. The return feeders must be insulated. 71. Construction. While the Government regulations pres- cribe the use of insulated returns, we were informed that in general the practice is to connect the rails to the negative bus and to rarely use insulated returns. Noticeable exceptions are the Paris conduit system tramways using complete insulated returns, and the Paris Nord-Sud Subway Company operating a three wire system with the rails as neutral. 72. Conditions. The investigation was somewhat limited in France. In general serious electrolysis troubles were found only in a few situations, either created by installations of heavy traffic electric lines, or by peculiar conditions not readily ex- plainable. The maximum drop of potential between pipe and rail measured by this Committee was about 6 volts at a loca- tion where trouble has been persistent and serious. Damage has been caused in the past to gas pipes in Paris during the period of transformation of the old two-wire, three- wire and five- wire systems of electric light distribution, but all of these troubles were only of temporary character and were promptly remedied as soon as discovered. Many suits (about twenty) for electrolysis damages are being tried in Paris. On account of the situation created by these suits the Paris municipality and the government have recently appointed a Commission to investigate the subject and make recommendations regarding the electrolysis situation in the City of Paris. E. ENGLAND. 73. Laws and Ordinances. The Board of Trade regulations prescribe that the maximum rail drop shall not exceed seven volts. In practice the Board takes as the voltage drop the mean 78 EUROPEAN PRACTICE between the average and the momentary maximum values for the period of a schedule run at time of maximum traffic, exclu- sive of exceptional occasions like athletic games, etc. The per- iods assumed vary from 15 to 30 minutes. The regula- tions also contain other requirements, prescribing measure- ments of track leakage, etc.; in actual practice, however, little attention is paid to any other requirements as long as the seven volt over-all rail drop is not exceeded. 74. Construction. Whenever the resistance of the rails would give a drop in excess of seven volts, insulated return feeders with resistances, or negative boosters are used; the latter more extensively than in any other country. 75. Conditions. The sub-committee found that in all the several cities visited the Board of Trade regulations were met well within the limits. In fact, on the average the maximum drops measured in all large cities visited in the months of Ju*ie and July were about two volts. The Board of Trade regulations are not considered onerous by any of the railway engineers we consulted. All authorities representing the pipe owning companies, the railways, the State telegraph and telephone and the Board of Trade were unanimous in stating that the electrolysis situation on the properties under their respective control was entirely satis- factory. The only question raised, and this only by a limited number of pipe owning entities, is whether the electric railways should not be held legally responsible for any damages, even when they comply with the Board of Trade regulations. Two or three attempts have been made to have a law passed by the Parliament to this effect, and two or three pipe exhibits have been repeatedly presented to prove electrolysis damages, but the Parliament refused to act. The seven volt limitation is considered somewhat of a hap- hazard empirical measure formulated many years ago, but having given good results it is* considered good enough, though it is conceded that some more rational measure could probably now be devised to replace it. However, no demand was dis- covered for a change on the part of anyone concerned. EUROPEAN PRACTICE 79 F. SUMMARY AND CONCLUSIONS. 76. Germany through voluntary co-operation has probably remedied the former dangerous electrolysis conditions in all of its important systems. The instrumentality of agreements on definite technical standards was sought in preference to legislation for different states. Italy will probably give more consideration to the subject of electrolysis whenever the general conditions will permit. France has not been as successful in bringing prompt results through legislation, as has Germany through technical co- operation. England, which has had the benefit of Government regula- tion for many years, has now no electrolysis troubles nor dis- putes. In Germany and England, the subject of electrolysis has received extensive study and consideration. The attached typical abstracts of reports of the German Earth Current Commission and the appendix of the detail report of the Sub- Committee are evidence of the methods followed and the satis- factory results obtained abroad by adopting the following measures : 1st. Maintenance of good bonding. 2nd. Elimination of intentional contacts, and liberal separ- ation, whenever possible, of pipes and rails. 3rd. Avoidance of bare copper returns and use of insulated returns in all installations where the conductivity of the rail alone would give a too great maximum rail drop. 4th. Use of insulated returns with balancing resistances, or to a lesser extent "boosters," for the purpose of maintaining equality of rail potential at the feeding points of all feeders. 5th. Small feeder drops and frequent substations to" give close line regulation. 77. Application to American Conditions. This study has not been made with the object of arriving at definite recommenda- tions, but to point out that disputes on account of electrolysis troubles have been prevalent in the past in all countries before sys- tematic cooperative studies or regulations had been applied, not- withstanding the fact that the mode of life and distribution of population and industries are more favorable than in American cities. The average weight of cars in foreign cities is essen- 80 EUROPEAN PRACTICE ^ sD V' K^Bb $ ^Tfcr xH^- 1 iV fe K? v> ffj 15ft sRii ^ #>J 1 ; >>> ?? iq ^ Wi * 5rf*i-! n M >^ \ \^ t ; r < ; - :,'".:.'', rt.' -.>*.- 1 -..;-' v/^ ;.' : ."t-.'f ^ ^ ** '\-'?': ' ' ' ''t'- ,^M BH ****** **/ ****** *-{*. * > ^ Ml s SIR V ^ '^v ^S* f V* v ^r-7 .,. W 7 V* n - v"*.- 1 " ' . '*"- * ** ** '"^ * k * u< ?K * ' 5X'^ lj L>-*> n : ^ : r ^ 3'-^ < ^ * -;V h * '' \ \ iV? 8 i -^f. b 3 r - \.. M ^ i. iS**.*' E 1 ' V'^ \ ^SS ^ j .'V- y * ' > y ^ i^v : . ^ >>) yi- 9 r' : "1 [^ m EUROPEAN PRACTICE 125 TRACK CONSTRUCTION AND RAILS - GERMANY Jt-Jt_- : ^w^^ Typical Construction for paved street STRASSBUR6 Haarman 3 piece Rail, and foot plate Figure 1 1 126 EUROPEAN PRACTICE GERMAN TRAMWAY RAILS U^Fbr curved track RlLLENSCHIENE Phonix Profit land la 42.8 and 45.7. Kg/ m (777777//V/777777K VlGNOLSCHIENE Special profile for Tramway (a) Rillenschiene with foot fish-plate OVERLAPPING RAIL JOINTS (b) Haarman 2-piece Rail & tys ji jl fT// \ ^7% D O (c) and (d) Haarman 2-piece Rail Figure 12 EUROPEAN PRACTICE 127 BRITISH TRAMWAY RAILS i 7 Standard prior to 1908 \ Present Standard "Brit. Stand." N? 4 Bessemer Steel 100-105 Ibs per yd. Fish plates 2' long 63.5 Ibs.per pair. Outer fish plate 2' lonq 30.5 Ibs. 7" Straight track, 110 Ibs. per yard r "British Standard" Section R 5. Curved track 116 Ibs. per yard. British Standard Section N?5c. Figure 13 128 EUROPEAN PRACTICE RAIL WEIGHT DATA 3000? Rillenscniene Vignolschiene Wechselsteg 5902 Km 1020 Km. 714 Km. 60 1000 750 . j 500 250 I INITE D Kl MGDO ^ Clas s if led T by lr otals ackg ackGa uges 2'f 5|". 2'lli M and i 3; | tr 3' 6" auge% 29:6 mi - =1056'. 6 es i 4' n rtted. > of he ?s-2' Corp.= Omile 6.5 mi miles -a N n 293 = 404 = 1039 114 8 8 - *-t '7| H a 4'tf *N ot pk sterriv 15 mil (ham ~d = IO v~^ 19 -108 4 2 _ Lar fk^ rminc radfo asgov ublin r than Stan li'juaot . I67miles- s - 4' gauge les-4'7j"g -5.'3"gaug dard bauge B B 3'6"gc uge. UF G D auge. e. 1 3'e "&4'^ -1 1 1 1 40 60 80 100 120 Figure 14 EUROPEAN PRACTICE 129 TYPICAL RAIL BONDS - UNITED KINGDOM MANCHESTER (Standard) /N? 0000 Copper Rod O* =3 -Flexible ;Copper Bond. 8- J GLASG o w (Standard) Figure 15 130 EUROPEAN PRACTICE CROSS- BONDING DETAFLS, ETC -UNITED KINGDOM GLASGOW Standard Cross-Bonding Single Cross Bondr*. Double Rail Bond 40 yards (2 rail lengths). Method of connecting one return cable to track LONDON L.C.C. Return Feeder Connections V f 4-N ? 0000 B&S Bonds per terminal, about Rail 34"long A 1 ^ Bond Terminal - 5^ clamped and _> [\ Rail soldered. ^[ H f%f f Bare Cable-^ Rail ~i ~ 7 N Rail A M Kl ^ Lead Sleeve Method of connecting two return cables to track at same point. LC.CaWe Figure 16 EUROPEAN PRACTICE 131 96. Electrolysis Testing Methods. The surveys made by the engineers of the Earth Current Commission of Germany are systematically planned. They start with a general investiga- tion of geological conditions, the character of the soil, ground water, and so forth, continuing with a general survey of the present condition of the railway property, including distribu- tion of load, track and rail resistance, location and loading of supply and return circuit cables, and any other electrical data relating to the investigation. The surveys then take up the specific measurements relating to stray current, such as poten- tial differences between pipes and rails, current in pipes, and so forth. The surveys conclude generally with recommenda- tions for betterments where such are needed, and often include estimates of the cost of such improvements. In England very little testing is done to investigate electrolysis questions and no technique has been developed for such work. The only extensive work in recent years is that of the Cunliffe brothers, and their work was directed mainly toward the in- vestigation of certain theoretical questions rather than toward the systematic investigation of any railway system. The work of the Cunliffes appears in two papers presented by them before the British Institution of Electrical Engineers. 97. Abstract of Laws and Regulations or Recognized Standards in European Countries. (See next page.) 132 EUROPEAN PRACTICE rt a, CO w of Ma 900. La lie o laws or unicipal egulations a IsS Germany ii l 5 o "^ *-> 'o n o P (U-C > O H -4-3 .j .2 o w 2 cu c C^ . II Up, EUROPEAN PRACTICE 133 L. MISCELLANEOUS NOTES. 98. Plan of German Earth Current Commission Reports. In abstracting these reports we have selected at random characteristic studies which would illustrate the method pur- sued in the investigations. We have not made any attempt at all to select studies for direct comparison with any specific American condition. In interpreting these results, the above qualifications should, therefore, be kept in mind. The reports are quite uniform in character and contain in general the following data : I. Maps showing the location and extent of the tram- way, water pipe and gas pipe systems, location of the generating station or stations, points of connection of the supply and return feeders. II. Soil kind (clay, sand, loam, etc.) moisture content, chemical composition, resistance per cubic meter. III. Pavements (in some cases only). IV. Piping systems both water and gas pipes. Total length, diameter, material, age, depth below surface, kind of joints, resistance of pipe only and of pipe including joints. V. Tramway system. (a) General details of ownership and operation, car schedule, maximum and average loads. (b) Track and rails total miles of single and double tracks, gauge, rail profile and cross section, standard length, resistance of rail alone and including bonds. (c) Rail bonds and cross bonds, type, cross section, per cent increase in rail resistance caused by bonds. (d) Feeders, both supply and return feeders length each, cross section, total weight of copper, current maxi- mum and average, return feeders bare or insulated and with or without regulating resistance. VI. Tests. (a) Voltage between pipes and rails, maximum, mini- mum and average, with polarity, determined at numerous points on the system. (b) Voltage drop per kilometer on pipes and on rails, and calculated current flowing on pipes. (c) Determination by means of telephone wires of the relative potential of various points on the piping and on the rail systems. VII. Excavations in likely places to determine the ex- istence and extent of the electrolytic damage. VIII. Plates accompany the reports, giving graphically many of the above data, frequently on transparent paper so that when placed over the city map the details of streets, railroads, etc. can be observed. 134 EUROPEAN PRACTICE Reasoning from the data contained in the body of the report, recommendations are made for improving conditions, some- times accompanied by an estimate of cost. In some cases a supplementary report is made which shows the conditions after the changes recommended had been made, in whole or in part' 99. General Comments on Reports. The electrolysis troubles in all cases were confined to a few localities, and in no case was the yearly cost of repairs of such amount that, on the surf ace, would justify large expenditure of money for improvements. The Com- mission, however, while recognizing the importance of the financial aspect of the problem, still recommended the adoption of the relatively expensive remedies for the reason they state "that the repairs will certainly become more frequent with lapse of time, and besides the increased expense so caused, there is the liability of service interruption, disturbance of traffic, pavement replacement and even danger of explosion to be considered." BIBLIOGRAPHY 135 V. BIBLIOGRAPHY This committee has made a complete search of the Ameri- can literature on the subject of electrolysis, but in compiling the following bibliography no attempt has been made to list this literature in its entirety. This bibliography may be considered a selected list of such contributions to the subject known to the committee, as, in its opinion, are of permanent value. Bureau of Standards Publications: The following Techno- logic Papers upon electrolysis have been published by the Bureau of Standards at Washington, D. C. No. 15. Surface Insulation of Pipes as a Means of Preventing Electrolysis. No. 18. Electrolysis in Concrete. No. 25. Electrolytic Corrosion of Iron in Soils. No. 26. Earth Resistance and its Relation to Electrolysis of Underground Structures. No. 27. Special Studies in Electrolysis Mitigation. No. 28. Methods of Making Electrolysis Surveys. No. 32. Special Studies in Electrolysis Mitigation, No. 2, Electrolysis from Electric Railway Currents and its Prevention Experimental Test on a System of Insulated Negative Feeders in St. Louis. No. 52. Electrolysis and Its Mitigation. No. 54. Special Studies in Electrolysis Mitigation, No. 3. A Report on Conditions in Springfield, Ohio, with Insulated Feeder System Installed. No. 55. Special Studies in Electrolysis Mitigation in Elyria, Ohio, with Recommendations for Mitigation. No. 62. Modern Practice in the Construction and Maintenance of Rail Joints and Bonds in Electric Railways. No. 63. Leakage of Current from Electric Railways. No. 72. Influence of Frequency of Alternating or Infrequently Reversed Current on Electrolytic Corrosion. No. 75. Data on Track Leakage. 136 BIBLIOGRAPHY Deiser, George F. "The Law Relating to Conflicting Uses of Electricity and Electrolysis," T. & J. W. Johnson Co., Philadelphia, Pa., 1911. Farnham, Isiah H. "Destructive Effect of Electric Currents on Subterranean Metal Pipes," Trans. A. I. E. E., 1894. This paper probably covers the first investigation under- taken of real scientific value. The discussion of the paper is also important and interesting. "Means for Preventing Electrolysis of Buried Metal Pipes," Gassier s Magazine, August, 1895. This article is of particular interest, in that it shows that at a very early date the value of the insulated negative feeder system as a means of mitigating electrolysis was recognized. Ganz, Albert F. "Electrolytic Corrosion of Iron by Direct Current in Street Soils," Trans. A. I. E. E., Vol. XXXI, p. 1167, 1912. This paper gives the results of a laboratory investigation of considerable scientific value and interest. "Electrolysis from Stray Electric Currents," Proc. New England Association of Gas Engineers, 1913. This paper treats the subject in a popular, but nevertheless scientifically correct manner, and leads to the conclusion that the insulated negative feeder system is the logical one to employ for the purpose of mitigating electrolysis. "Effects of Electrolysis on Engineering Structures," Trans. Inter. Eng. Congress, San Francisco, Cal., 1915. This paper gives a review of electrolysis conditions and of mitigating methods in America with a brief statement of the electrolysis situation in Europe. Haber, F., and Goldschmidt, F. "Der Anodische Angriff des Eisens Durch Vagabundierende Strome im Erdreich und die Passivitat des Eisens." (The Corrosion of Iron by Stray Currents in the Ground and the Passivity of Iron.) Zeitschrift fur Electrochemie, January 26, 1906. Breslau. A paper of considerable scientific value, particularly with respect -to the electrochemistry of the subject. In so far as is known no English translation exists. Harper, Robert B. "Comparative Values of Various Coat- ings and Coverings for the Prevention of Soil and Electrolytic BIBLIOGRAPHY 137 Corrosion of Iron Pipe," Proc. Illinois Gas Association, Vol. 5, 1909. A paper based upon a rather elaborate series of tests carried out in a thoroughly scientific manner on many coatings and coverings, leading to the conclusion that no coatings or cover- ings are of permanent value in positive areas. Of all coatings investigated, dips of coal tar pitch applied hot, were found to be best. Paints were found to be practically useless. Hayden, J. L. R. "Alternating-Current Electrolysis," Trans, A. I. E. E., 1907. Vol. 26, Part I. A report of a laboratory investigation tending to show that alternating current electrolysis is small as compared with direct current electrolysis. The tests also bring out the inhibiting effect of the superposition of a small direct current. Jackson, Dugald C. "Corrosion of Iron Pipes by Action of Electric Railway Currents." Journal of Association of En- gineering Societies, September, 1894. An account of some early laboratory investigations carried out at the University of Wisconsin, in which it was definitely proven that corrosion due to electrolysis could take place at very low voltages considerably lower voltages than are re- quired to decompose water. Michalke, Carl. "Stray Currents from Electric Rail ways." Translated and edited by Otis Allen Kenyon, McGraw Publish- ing Company, New York City, 1906. A relatively non-mathematical, though scientific and valu- able treatment of the subject. Rhodes, George I. "Some Theoretical Notes on the Re- duction of Earth Currents from Electric Railway Systems, by Means of Negative Feeders." Trans. A. I. E. E., Vol. XXVI, p. 247, 1907. A mathematical paper showing quantitatively the difference in effectiveness of copper paralleling the rails and insulated negative feeders in reducing stray currents. Schaffer, Guy F. "Corrosion of Iron Embedded in Con- crete." Engineering Record, July 30, 1910. This is a report of a series of tests made at the Massachusetts 138 BIBLIOGRAPHY Institute of Technology, carried out with the view of obtain- ing some data on the effect of currents of low potential on steel embedded in concrete. The study included the effect on steel in both the stressed and unstressed condition, also the effect of setting cement on paint films. It was shown (a), that con- crete does not act as an insulator; (b), that iron under stress does not go into solution as rapidly as unstressed iron; and (c), that the paints used to-day for structural work embedded in concrete do not fulfill the conditions of proper protection from electrolytic action, and it is doubtful whether they are of use for protection in any sense after a lapse of some months. Sever, George F. "Electrolysis of Underground Conductors." Trans. International Electrical Congress, St. Louis, Vol. 3, p. 666, 1904. This is a summary in tabular form, consisting of street rail- way practice, municipal reports, ordinances and letters in force in the United States at the time the report was prepared, 1904. The discussion which followed the presentation of this report is of interest. Stone, Charles A. and Howard C. Forbes. "Electrolysis of Water Pipes." New England Water Works Association, Vol. 9, 1894-95. This is the report of the results of an investigation of elec- trolysis conditions in Boston. It is one of the best early papers on the subject. The discussion of this paper is interesting. Topical Discussion on Electrolysis. Proc. New England Water Works Association, Vol. XX, 1905. This is the report of a discussion entered into by various New England Water Works superintendents. Several phases of the discussion are instructive. APPENDICES 139 VI. APPENDICES. 100. Resistance of Standard Cast Iron Pipe. Note: The values given in this table are for one assumed specific re- sistance for cast iron, wrought iron and steel, respectively. For exceed- ingly accurate work, measures should be taken to determine the actual specific resistance of the metal under test. Experience has shown that this may vary widely from that assumed in the tables; in other words, the table values can only be used for approximate results unless definite information is at hand as to the specific resistance of the metal under test. From pages 379 and 386, 1913, Proceedings American Electric Railway Engineering Association. TABLE FOR DETERMINATION OF CURRENT FLOW ON PIPING FROM MILLI-VOLT DROP ALONG CONTINUOUS LENGTH OF PIPE BETWEEN JOINTS. L = Distance between contacts in feet E = Instrument reading in milli- volts, K = Constant from table. KE L = Current flow in amperes. TABLE 9 STANDARD CAST IRON PIPE. (Based on a resistance of 0.00144 ohm per Ib. ft.) CLASSIFICATION ACTUAL DIMENSIONS K = current *Asso- Weight for one milli- Nomi- cia- Class per ft. volt drop nal. tion Let- Head Press. Outs. Ins. exclu- per ft. of Dia.in. Stand- terf Feet Ibs. per dia. dia. sive of continuous ard sq. in. in. in. hub-lb. pipe. Amperes. 4 N A 4.80 4.12 14.9 10.3 4 N C 4.80 4.08 15.7 10.9 4 N E 4.80 4.02 16.9 11.7 G 4.80 4.00 17.2 12.0 W A 100 43 4.80 3.96 18.0 12.5 N G 5.00 4.16 18.9 13.1 N I 5.00 4.10 20.0 13.9 W B 200 86 5.00 4.10 20.0 13.9 4 N K 5.00 4.04 21.3 14.8 *W = American Water Works Association Standard. N = New England Water Works Association Standard. G = American Gas Institute Standard. t = As used by the American Water Works Association and the New England Water Works Association. 140 APPENDICES TABLE FOR DETERMINATION OF CURRENT FLOW ON STANDARD CAST IRON PIPE FROM MILLI-VOLT DROP ALONG CONTINUOUS LENGTH OF PIPE BETWEEN JOINTS. (Continued.) CLASSIFICATION ACTUAL DIMENSIONS K = current *Asso- Weight for one milli- Nomi- cia- per ft. volt drop nal. tion Class Head Press. Outs. Ins. exclu- per ft. of Dia.in. Stand- Letter Feet Ibs. per dia. dia. sive of continuous ard t sq. in. in. in. hub-lb. pipe. Amperes. 4 W C 300 130 5.00 4.04 21.3 14.8 4 w D 400 173 5.00 3.96 22.8 15.8 6 N A 6.90 6.14 24,3 16.9 6 N C . . . 6.90 6.06 26.7 18.5 6 G ... 6.90 6.04 27.2 18.9 6 W A 100 43 6.90 6.02 27.8 19.3 6 N E 6.90 5.98 29.1 20.2 6 W B 200 86 7.10 6.14 31.1 21.6 6 N G 7.10 6.10 32.4 22.5 6 W C 300 130 7.10 6.08 32.9 22.8 6 N I 7.10 6.02 34.8 24.2 6 W D 400 173 7.10 6.00 35.3 24.5 6 W E 500 217 7.22 6.06 37.7 26 2 6 w F 600 260 7.22 6.00 39.6 27.4 6 w G 700 304 7.38 6.08 42.8 29.7 6 w H 800 347 7.38 6 00 45.2 31.4 8 N A 9.05 8.21 35 5 24.7 8 G 9.05 8.15 37.9 26.3 8 W A 100 43 9.05 8.13 38.7 26.9 8 N C 9.05 8.09 40.3 28.0 8 W B 200 86 9.05 8.03 42.7 29.6 8 N E ... 9.05 7.99 44.3 30.7 8 W C 300 130 9.30 8.18 47.9 33.3 8 N G 9.30 8.14 49.6 34.5 8 W D 400 173 9.30 8.10 51.2 35.5 8 N I 9.30 8.04 53.6 37 2 8 W E 500 217 9.42 8.10 56.7 39.4 8 W F 600 260 9.42 8.00 60.6 42.1 8 w G 700 304 9.60 8.10 65.0 45.1 8 w H 800 347 9.60 8.00 69.0 48.0 10 N A 11.10 10.16 49.0 34 10 G 11.10 10.12 51.0 35.4 10 N B 11.10 10.10 51.9 36.1 APPENDICES 141 TABLE FOR DETERMINATION OF CURRENT FLOW ON STANDARD CAST IRON PIPE FROM MILLI-VOLT DROP ALONG CONTINUOUS LENGTH OF PIPE BETWEEN JOINTS. (Continued.) CLASSIFICATION ACTUAL DIMENSIONS K-current "Asso- Weight for one milli- Nomi- cia- per ft. volt diop nal. tion Class Head Press. Outs. Ins. exclu- pei ft. of Dia.in. Stand- Letter Feet Ibs. per dia. aia. sive of continuous ard t sq. in. in. in. hub-lb. pipe. Amperes. 10 10 W N A C 100 43 11.10 11.10 10.10 10.04 51.9 54.9 36.1 38.1 10 N D 11.10 9.98 57.9 40.2 10 W B 200 86 11.10 9.96 58.9 40.9 10 N E 11.40 10.20 63.6 44.1 10 W C 300 130 11.40 10.16 65.5 45.5 10 N F 11.40 10.14 66.5 46.2 10 N G 11.40 10.06 70.5 49.0 10 W D 400 173 11.40 10.04 71.5 49.7 10 N H 11.40 10.00 73 5 51.1 10 W E 500 217 11.60 10.12 78.7 54.6 10 W F 600 260 11.60 10.00 84.6 58.8 10 W G 700 304 11.84 10.12 92.4 64.1 10 W H 800 347 11.84 10.00 98.5 68.4 12 N A 13.20 12.22 61.1 42.5 12 N B 13.20 12.14 65.9 45.7 12 G ... 13.20 12.12 67.0 46.5 12 W A 100 43 13.20 12.12 67.0 46.5 12 N C 13.20 12.06 70.6 49.0 12 N D 13.20 11.98 75.3 52.3 12 W B 200 86 13.20 11.96 76.4 53.0 12 N E 13.50 12.20 81.9 56.8 12 W C 300 130 13.50 12.14 85.5 59.4 12 N F 13.50 12.12 86.6 60.2 12 N G . . . 13.50 12.04 91.5 63.6 12 W D 400 173 13.50 12.00 93.8 65.1 12 N H 13.50 11.96 96.2 66.8 12 W E 500 217 13.78 12.14 104.0 72.3 12 W F 600 260 13.78 12.00 112.0 77.9 12 W G 700 304 14.08 12.14 125.0 86.7 12 W H 800 347 14.08 12.00 133.0 92.4 14 N A 15.30 14.24 76.8 53.4 14 N B 15.30 14 16 82.3 57.1 14 W A 100 43 15.30 14.16 82.3 57.1 142 APPENDICES TABLE FOR DETERMINATION OP CURRENT FLOW ON STANDARD CAST IRON PIPE FROM MILLI-VOLT DROP ALONG CONTINUOUS LENGTH OF PIPE BETWEEN JOINTS. (Continued.) CLASSIFICATION ACTUAL DIMENSIONS K current *Asso- Weight for one milli- Nomi- cia- per ft. volt drop nal. tion Class Head Press. Outs. Ins. exclu- per ft. of Dia.in. Stand- Letter Feet Ibs. per dia. dia. sive of continuous ard t sq. in. in. in. hub-lb. pipe. Amperes. 14 N C 15.30 14.08 87.9 61.0 14 N D 15.30 13.98 94.8 65.8 14 W B 200 86 15.30 13.98 94.8 65.8 14 N E 15.65 14.25 103.0 71.4 14 W C 300 130 15.65 14.17 108.0 75.0 14 N F ... 15.65 14.15 109.0 76.2 14 N G 15.65 14.07 115.0 80.0 14 W D 400 173 15.65 14.01 119.0 82.8 14 N H 15.65 13.99 121.0 83.9 14 W E 500 217 15.98 14.18 133.0 92.4 14 W F 600 260 15.98 14.00 145.0 ' 101.0 14 W G 700 304 16.32 14.18 160.0 111.0 14 W H 800 347 16.32 14.00 172.0 120.0 16 N A 17.40 16.30 90.9 63.1 16 N B . 17.40 16.20 98.9 68.6 16 W A 100 43 17.40 16.20 98.9 68.6 16 G 17.40 16.16 102.0 70.7 16 N C ; 17.40 16.10 107.0 74.1 16 N D 17.40 16.00 115.0 79.6 16 W B 200 86 17.40 16.00 115.0 79.6 16 N E 17.80 16 30 125.0 87.1 16 N F 17.80 16.20 133.0 92.6 16 W C 300 130 17.80 16.20 133.0 " 92.6 16 N G 17.80 16.10 141.0 98.2 16 W D 400 173 17.80 16.02 147.0 102.3 16 N H 17.80 16.00 149.0 103.5 16 W E 500 217 18.16 16.20 165.0 114.5 16 W F 600 260 18.16 16.00 181.0 125.5 16 W G 700 304 18.54 16.18 201.0 139.5 16 W H 800 347 18.54 16.00 215.0 149.0 18 N A 19.25 18.11 104.0 72.5 18 N B 19.25 17.99 115.0 79.8 18 W A 100 43 19.50 18.22 118.0 82.2 18 N C 19.50 18.12 127.0 88.5 18 N D 19.50 18.00 138.0 95.8 18 W B 200 86 19.50 18.00 138.0 95 8 APPENDICES 143 TABLE FOR DETERMINATION OF CURRENT FLOW ON STANDARD CAST IRON PIPE FROM MILLI-VOLT DROP ALONG CONTINUOUS LENGTH OF PIPE BETWEEN JOINTS. (Continued.} CLASSIFICATION ACTUAL DIMENSIONS K. current 'or one milli- *Asso- Weight volt drop Nomi- cia- Ins. per ft. per ft. of nal. tion Class Head Press. Outs. dia. exclu- continuous Dia. in. Stand- Letter Feet Ibs. per dia. in. sive of pipe. ard t sq. in. in. hub-lb. Amperes. 18 N E 19.70 18.10 148.0 103.0 18 N F 19.70 17.98 159.0 110.4 18 W C 300 130 19.92 18.18 162.0 113.0 18 W D 400 173 19.92 18.00 178.0 123.8 18 W E 500 217 20.34 18.20 . 202.0 140.5 18 W F 600 260 20 34 18.00 220.0 152.6 18 W G 700 304 20.78 18.22 245.0 170.0 18 W H 800 347 20.78 18.00 264.0 183.3 20 N A 21.30 20.10 122.0 84.6 20 N B 21.30 19.98 134.0 93.0 20 W A 100 43 21.60 20.26 137.0 95.4 20 G 21.60 20.24 140.0 97.0 20 N C 21.60 20.16 147.0 102.5 20 N D 21.60 20.02 161.0 112.0 20 W B 200 86 21.60 20.00 163.0 113.0 20 N E 21.90 20.20 175.0 122.0 20 N F 21.90 20.06 189.0 131.0 20 W C 300 130 22.06 20.22 191.0 132.0 20 W D 400 173 22.06 20.00 212.0 148.0 20 W E 500 217 22.54 20.24 241.0 167.0 20 W F 600 260 22.54 20.00 265.0 184.0 20 W G 700 304 23.02 20.24 295.0 205.0 20 W H 800 347 23.02 20.00 319.0 221.0 24 N A 25.40 24.12 156.0 108.0 24 N B 25.40 23.96 174.0 121.0 24 G 25.80 24.28 187.0 130.0 24 W A 100 43 25.80 24.28 187.0 130.0 24 N C 25.80 24.20 196.0 136.0 24 N D 25.80 24.04 215.0 149.0 24 W B 200 86 25.80 24.02 217.0 151.0 24 N E 26.10 24 . 20 234.0 163.0 24 N F 26.10 24.04 253.0 176.0 24 W C 300 130 26.32 24.24 258.0 179.0 24 W D 400 173 26.32 24.00 286.0 198.0 24 W E 500 217 26.90 24.28 328.0 228.0 24 W F 600 260 26.90 24.00 362.0 251.0 144 APPENDICES TABLE FOR DETERMINATION OF CURRENT FLOW ON STANDARD CAST IRON PIPE FROM MILLI-VOLT DROP ALONG CONTINUOUS LENGTH OF PIPE BETWEEN JOINTS. (Continued.) CLASSIFICATION ACTUAL DIMENSIONS K. current for one milli- *Asso- Weight volt drop Nomi- cia- per ft. per ft. of nal. tion Class Head Press. Outs. Ins. exclu- continuous Dia.in. Stand- Letter Feet Ibs. per dia. dia. sive of pipe. ard t sq. in. in. in. hub-lb. Amperes. 30 N A 31.60 30.18 215.0 149.0 30 N B 31.60 29.98 245.0 170.0 30 G 31.74 30.04 257.0 179.0 30 W A 100 43 31.74 29.98 266.0 185.0 30 N c 32.00 30.18 277.0 192.0 30 N D 32.00 29.98 306.0 213.0 30 W B 200 86 32.00 29.94 312.0 217.0 30 N E 32.40 30.20 337.0 234.0 30 N F 32.40 30.00 367.0 255.0 30 W C 300 130 32.40 30.00 367.0 255.0 30 W D 400 173 32.74 30.00 422.0 292.0 30 W E 500 217 33.10 30.00 479.0 333.0 30 W F 600 260 33 . 46 30.00 537.0 373.0 36 N A 37.80 36.22 287.0 199.0 36 N B 37 . 80 36.00 326.0 226.0 36 G 37.96 36.06 345.0 239.0 36 W A 100 43 37.96 35.98 358.0 248.0 36 N C 38.30 36.26 373.0 259.0 36 N D ... 38.30 36.04 412.0 286.0 36 W B 200 86 38.30 36.00 418.0 290.0 36 N E 38.70 36.20 459.0 319.0 36 W C 300 130 38.70 35 98 497.0 346.0 36 N F 38.70 35.96 502.0 349.0 36 W D 400 173 39.16 36.00 581.0 404.0 36 W E 500 217 39.60 36.00 666.0 463.0 36 W F 600 260 40 04 36.00 753.0 523.0 42 N A 44.00 42.26 368.0 256.0 42 N B 44.00 42.00 422.0 293.0 42 G 44.20 42.06 452.0 314.0 42 W A 100 43 44.20 42.00 465.0 323.0 42 N C 44.50 42.24 480.0 333.0 42 N D 44.50 41.96 538.0 374.0 42 W B 200 86 44.50 41.94 542.0 376.0 42 N E . . . 45.10 42.30 600.0 416.0 42 N F 45.10 42.04 654.0 454.0 APPENDICES 145 TABLE FOR DETERMINATION OF CURRENT FLOW ON STANDARD CAST IRON PIPE FROM MILLI-VOLT DROP ALONG CONTINUOUS LENGTH OF PIPE BETWEEN JOINTS. (Continued.) CLASSIFICATION ACTUAL DIMENSIONS K. current :or one milli- Asso- Weight volt drop Nomi- cia- Class Head Press. Outs. Ins. per ft. per ft. of nal tion Letter Feet Ibs. per dia. dia. exclu- continuous dia.in. Stand- t sq. in. in. in. sive of pipe. ard hub-lb. Amperes. 42 W C 300 130 45.10 42.02 657.0 456.0 42 W D 400 173 45.58 42.02 763.0 530.0 48 N A 50.20 48.30 459 319.0 48 N B . . . 50.20 48 . 00 529.0 367.0 48 N C ... 50.80 48.30 608.0 422.0 48 G 50.50 47.98 608.0 422.0 48 W A 100 43 50.50 47.98 608.0 422 48 N D 50.80 48.00 678.0 471.0 48 W B 200 86 50.80 47.96 686.0 477.0 48 N E 51.40 48.30 757.0 526.0 48 N F 51.40 48.00 828 575.0 48 W C 300 130 51.40 47.98 832.0 578.0 48 W D 400 173 51.98 48.06 961.0 667.0 54 N A 56.40 54.34 559.0 388.0 54 N B 56.40 54.00 650.0 452.0 54 W A 100 43 56.66 53.96 731.0 508.0 54 N C 57.10 54.36 750.0 521.0 54 N D 57.10 54.02 840.0 583.0 54 W B 200 86 57.10 54.00 845.0 586.0 54 N E 57.80 54.26 946.0 657.0 54 N F 57.80 54.00 1041.0 723.0 54 W C 300 130 57.80 54.00 1041.0 723.0 54 W D 400 173 58.40 53.94 1230. 854.0 60 N A 62.60 60.40 664.0 460 60 N B 62.60 60.00 782.0 543.0 60 W A 100 43 62.80 60.02 836. '0 581 60 N C 63.40 60.40 910.0 632.0 60 W B 200 86 63.40 60.06 1010.0 701.0 60 N D ... ' 63.40 60.00 1028.0 714.0 60 N E 64.20 60.40 1160.0 806.0 60 W C 300 130 64.20 60.20 1220.0 848.0 60 N F 64.20 60.00 1280.0 889.0 60 W D 400 173 64.82 60.06 1455.0 1010.0 72 W A 100 43 75.34 72.08 1178.0 819.0 72 W B 200 86 76.00 72.10 1415.0 983.0 72 W C 300 130 76.88 72.10 1745.0 1212.0 84 W A 100 43 87.54 84.10 1445.0 1005.0 84 W B 200 86 88 54 84.10 1878.0 1304.0 146 APPENDICES 101. Resistance of Standard Steel or Wrought Iron Pipe. TABLE 10 STANDARD STEEL (Or Wrought Iron) PIPE. (Based on Resistance of steel 0.00021 ohms per Ib. ft. Based on sistance of wrought iron 0.000181 ohm per Ib. ft.) Actual Dimensions K = current for one millivolt Weight drop per ft. of continuous Nomi- per ft. pipe-amperes. nal Classifi- Outside Inside plain ends- dia. in. cation diameter diameter steel-lb. inches inches Steel Wrought iron 1/8 S 0.405 0.269 0.244 1.16 1 32 1/8 X 0.405 0.215 0.314 1.50 1.70 1/4 s 0.540 0.364 0.424 . 2.02 2.30 1/4 X 0.540 0.302 0.535 2.55 2. go 3/8 s 0.675 0.493 0.567 2.70 3.07 3/8 X 0.675 0.423 0.738 3.51 4.00 1/2 s 0.840 0.622 0.850 4.05 4.60 1/2 X 0.840 0.546 1.09 5,18 5.88 1/2 XX 0.840 0.252 1.71 8.16 _ 9.28 3/4 s 1.050 0.824 1.13 5.38 6.11 3/4 X 1.050 0.742 1.47 7.03 7.98 3/4 XX 1.050 0.434 2.44 11.6 13.2 1 s 1.315 1.049 1.68 7.99 9.09 X 1.315 0.957 2.17 10.3 11.8 XX 1.315 0.599 3.66 17.4 J9.8 1/4 s 1.660 1.380 2.27 10.8 12.3 1/4 X .660 1.278 3.00 14.3 16.2 1/4 XX .660 0.896 5.21 24.8 28.2 1/2 s .900 1.610 2.72 12.9 14.7 1/2 X .900 1.500 3.63 17.3 19.6 1/2 XX ..900 1.100 6.41 30.5 34.7 2 s . 2.375 2.067 3.65 17.4 19.8 2 X 2.375 1.939 5.02 23.9 27.2 2 XX 2.375 1.503 9.03 43.0 48.8 21/2 s 2.875 2.469 5.79 27.6 31.4 2 1/2 X 2.875 2.323 7 66 36.5 41.5 21/2 XX 2.875 1.771 13.69 65.2 74.2 3 s 3.500 3.068 7.57 36.0 41.0 3 X 3.500 2.900 10.2 48.8 55.6 3 XX 3.500 2.300 18.6 88.5 101.0 3 1/2 s 4.000 3.548 9.11 43.4 49.3 3 1/2 X 4.000 3.364 12.5 59.6 67.8 3 1/2 XX 4.000 2.728 22.8 109.0 124.0 4 s 4.500 4.026 10.8 51.4 58.4 4 X 4.500 3.826 15.0 71.3 81.1 4 XX 4.500 3.152 27.5 131.0 149.0 APPENDICES STANDARD STEEL (OR WROUGHT IRON) PIPE. Continued. 147 Actual Dimensions K = current for one millivolt Weight drop per ft. of continuous Nomi- per ft. pipe-amperes. nal Classifi- Outside Inside plain ends- A * . j . j . steel-lb. u.13,, in. CciT-ion. inches inches Steel Wrought iron 4 1/2 S 5.000 4.506 12.5 59.8 67.9 4 1/2 X 5.000 4.290 17.6 83.9 95 3 4 1/2 XX 5.000 3.580 32.5 155.0 176.0 5 S 5.563 5.047 14.6 69.7 79.2 5 X 5.563 4.813 20.8 98.9 112.0 5 XX 5.563 4.063 38.5 183.0 209.0 6 S 6.625 6.065 19.0 90.3 103.0 6 X 6.625 5.761 28.6 136.0 155.0 6 XX 6.625 4.897 53.2 253 . 288 7 S 7.625 7 023 23.5 112.0 127.0 7 X 7.625 6.625 38.0 181.0 206.0 7 XX 7 . 625 5.875 63.1 300.0 342.0 8 S 8.625 8.071 24.7 118.0 134 8 S 8.625 7.981 28.5 136.0 155*0 8 X 8.625 7.625 43 4 206.0 235.0 8 XX 8.625 6 . 875 72.4 345 392.0 9 S 9.625 8.941 33.9 161.0 184.0 9 X 9.625 8.625 48.7 232.0 264.0 10 S 10.750 10.192 31.2 149.0 169.0 10 S 10.750 10.136 34.2 163.0 185.0 10 S 10.750 10.020 40.5 192.0 219.0 10 X 10.750 9.750 54.7 261.0 297.0 11 S 11.750 11.000 45.6 217.0 247.0 11 X 11.750 10.750 60.1 286.0 326.0 12 S 12.750 12.090 43 8 208 . 237.0 12 S 12.750 12.000 49.6 236.0 269.0 12 X 12.750 1 1 . 750 65 4 311.0 351.0 13 S 14 . 000 13.250 54.6 260.0 296 . 13- X 14 000 13.000 72 1 343 391.0 14 S 15.000 14.250 58 6 279.0 317.0 14 X 15.000 14 . 000 77 4 369.0 420.0 15 S 16.000 15 250 62.6 298.0 339.0 15 X 16.000 15.000 82. 8 394.0 449.0 S = Standard pipe. X = Extra stiong pipe. XX = Double extni strong pipe. 148 APPENDICES 102. Resistance of Lead Cable Sheaths. TABLE 11. TABLE FOR DETERMINING CURRENT ON LEAD CABLE SHEATHS FROM VOLTAGE DROP IN MEASURED LENGTH OF SHEATH. Resistivity, 1 ft. length, 1 sq. in. sectional area = 0.00010 ohm Outside Thick- Current Outside Thick- Current diam. of ness Resistance for 1 diam. of ness Resistance for 1 lead of lead of lead millivolt lead of lead of lead millivolt sheath sheath sheath per ft. sheath sheath sheath per ft. (in.) (64th in.) ^ohm per ft.) (amp.) (in.) (64th in.) (ohm per ft.) (amp.) 0.50 4 0.001163 0.860 2.00 6 0.0001781 5.61 0.50 5 . 000965 1.036 2.00 7 0.0001538 6.50 0.50 6 . 000836 1.196 2.00 8 0.0001359 7.36 0.625 4 . 000906 1.104 2 125 6 0.0001672 5.98 0.625 5 . 000745 1.343 2.125 7 0.0001443 6.93 . 625 6 0.000640 . 1.563 2.125 8 0.0001273 7.86 0.75 4 0.000741 1.350 2.25 6 0.0001575 6.35 0.75 5 . 000606 1.650 2.25 7 0.0001359 7.36 0.75 6 0.000518 1.931 2.25 8 0.0001198 8.35 0.875 4 0.000627 1.594 2.375 6 0.0001488 6.72 0.875 5 0.000511 1.957 2 . 375 7 0.0001284 7.79 0.875 6 0.000435 2.300 2.375 8 0.0001132 8.83 1.00 5 0.0004419 2 . 263 2.50 7 0.0001217 8.22 1.00 6, 0.0003750 2.668 2.50 8 0.0001073 9.32 1.00 7 . 0003268 3.061 2.50 9 . 0000959 , 10,43 . 1.00 8 0.0002913 3.437 2.625 7 0.0001156 8.65 1.125 5 0.0003892 2.569 2.625 8 0.0001019 9.81 1.125 6 0.0003294 3.037 2.625 9 0.0000911 10.98 1.125 7 0.0002866 3.491 1.125 8 . 0002547 3.926 2.75 7 0.0001102 9.08 2.75 8 0.0000971 10.30 1.25 5 . 0003476 2.876 2.75 9 . 0000868 11.53 1.25 6 . 0002939 3.404 1.25 7 . 0002552 3.918 2.875 7 0.0001050 9.51 1.25 8 0.0002265 4.415 2.875 8 0.0000927 10.79 2.875 9 . 0000828 12.08 1.375 5 0.0003142 3.183 1.375 6 . 0002650 3 . 773 3.00 8 . 0000887 11.28 1.375 7 . 0002299 4.35 3.00 9 . 0000792 12.62 1 375 8 0.000203S 4.91 3 . 00 10 0.0000716 13.96 1.50 6 0.0002416 4.14 3.125 8 . 0000849 11.77 1.50 7 . 0002092 4.78 3.125 9 0.0000758 13.18 1.50 8 0.0001853 5.40 3.125 10 . 0000686 14.58 1 625 6 0.0002218 4.51 3.25 8 0.0000815 12.27 1.625 7 0.0001920 5.21 3.25 9 0.0000728 13.74 1.625 8 0.0001698 5.89 3.25 10 0.0000659 15.19 1 75 6 0.0002051 4.88 3.375 8 . 0000783 12.77 1.75 7 0.0001772 5.64 3.375 9 . 0000700 14.29 1.75 8 0.0001567 6.38 3.375 10 . 0000633 15.83 1.875 6 0.0001906 5.25 3.50 8 0.0000755 13.24 1.875 7 0.0001648 6.07 3.50 9 . 0000674 14.84 1.875 8 0.0001456 6.87 3.50 10 . 0000609 16,42 APPENDICES 103. Typical Report Sheets. 149 ooaiuoddns saiavo i03i03iOad saiavo nviaaivw iona . iaiOHNVi* Nl H31VM iU3H1390i oaaNoa saiavo *IHi f i'iW SISA10H10313 aiflvo NO iNaaano dO Nouoadia POTENTIAL, CABLE TO 1 i- TRACK \ + 3 1 + K U 3 1 + DUCT 1 f 1 + DATE TESTED BY LOCATION ..._ AVE. OR ST. .'. < t 3 WIJ. 8 150 APPENDICES CUR 3EN r MEASUREMENTS 6^ g Qf H '.'.'.'. '. : : '. ::::::: 8 1 a! i> < g <^ * *? c J2 0> 2 P Q *. : : : : :::::::::!"::: c d i L_LJ_J \ \ \ : . \ \ ^j "cu to cd V-i CO "o o > < : : : : ::::::::::::: O 3 d t/j i i c cu Q C 0) ca *? > C CJ a ftl-,^ I 8 ? -W d a 1^^ = Td c o O ei 3 C 0-2^ J d 5i ;;;;; ! ! 1 1 * ! * ! ! cd in '.'.'. r '.'.'.'.'.'.'.'.''. > d w g '. '. ::::::: ::::::::>: S^ j ^^ Q* / ,^ ...^.... i3.!J Slfoj : : : : *o 1 3 '. '. ^ !!!"!!! ''.'.'.'.'. 3 S c 1 * s ^ '.'.'.'.'.'.'.'.','.'.'.'.'.''' , 81*11 Q^ HS '.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'. -' " ; l ! '. '. '. :::::::::::::: '.'.'"'.'.'. ; ! : : : : : :::::::::::::: : ' S Q S S * S Q <3 ^H 152 APPENDICES pnog APPENDICES 153 REMARKS i III g a is u < o 1 2 ^ c S * s U *3 A < yj - is 1 1 ] Q w 3 -5 "* S ^ *J - ^ 5 Z Q PQ , S 5 J5 4 LOCATION i H 154 APPENDICES U H 1 y 72" a 1 (4 o u BJ e- C o H ' j H Z g 1 PH J. 0) , 6 CJ ; ; H > 1 a 7) u ^r* W z o PH H s . 7) Q d 73 a I ] I ^ CO H O Z' a a R . . 7) H g !^ 'a X cJ ! 1 O B *o 2 fl) ^* ! I '. to H | j s PH H oj . t/3 Qj U ^ Q '< 3 z S o " 5 cx 2 7) s o 7) 2* OJ CD 7) > s .j c" Qj 3 i. O 1 a i 1 O to ' ex ^j 2 72 at 3 1 *E "5 C O CJ || H Z CO 7) 72 J3 S" 3 I o fe C 2 o .2 w 44 e o K. 'a c o i 5UREME II II CO .55 I DATA SHEET FOR ELECTRO City : Location : Size and kind of pipe: D^-TT ~~4-. Location of nearest trolley u u u u Approximate age and cond Duration of each test Potential, pipe to rails, vol Current through temporary Distance between contacts 'o ' o a OH O Q Current on pipe, amperes Direction of current flow: SIMULTANEOUS DROP MEA: CU 'a, "o | +j a> >- *+H ^J .s i a P o o S-H l-l Q Q -LJ g [o 1 0) 73 a a YC 33597 A& d UNIVERSITY OF CALIFORNIA LIBRARY