y v % ; J|# /\ : ,W; /\ -J^: /% - 1 v* v .A . l «': V^ .*». V^ #fe x/ .-atev v .«m&. \/ && * : ^ *M& ^*** W *M V V 4. s5^ ^> ^oV ^"^ O * - •-•% *&■*£&:.** *vs"'*,\ #*s£te** v •:•<■- *c> jy »i^L'* *> ^J> * c H o > <$r 5v ^ ? .»i^'* *> «5^ 1 " ^ . . 5 « > °o A 6> <* 8?^ .0 o *'.. s 4 a ,4 o^ » ^^ Bureau of Mines Information Circular/1987 Assessment and Determination of Illumination Needs for Operators of Mobile Surface Mining Equipment By Alan G. Mayton UNITED STATES DEPARTMENT OF THE INTERIOR Information Circular 9153 n Assessment and Determination of Illumination Needs for Operators of Mobile Surface Mining Equipment By Alan G. Mayton UNITED STATES DEPARTMENT OF THE INTERIOR Donald Paul Hodel, Secretary BUREAU OF MINES David S. Brown, Acting Director Library of Congress Cataloging in Publication Data: Mayton, Alan G. Assessment and determination of illumination needs for operators of mobile surface mining equipment. (Information circular/Bureau of Mines; 9153) Bibliography: p. 30. Supt. of Docs, no.: I 28.27: 9153. 1. Mine lighting. 2. Strip mining — Equipment and supplies. I. Title. II. Series: Information circular (United States. Bureau of Mines); 9153. TN295.U4- [TN301] 622 s [622'.47] 87-600143 CONTENTS Page Abstract 1 Introduction Acknowledgments Description and procedures 2 Field measurements 3 VTE description and principle of operation . .... 3 CIE-IES method 5 Discussion and results 5 Surface coal mines 6 Draglines 6 Stripping and loading shovels 8 Loaders 11 Haul trucks 11 Blasthole drills 12 Explosives trucks 14 Scrapers 14 Bulldozers 18 Graders 18 Service vehicles 21 Surface metal and nonmetal mines 24 Conclusions and recommendations 26 References 30 Appendix A. — Glossary of terms, abbreviations, and symbols 31 Appendix B. — Calibration and analysis procedures 33 ILLUSTRATIONS 1. Blackwell model 5, serial No. 2, visual task evaluator (VTE) 3 2 . Outer rectangular lens units of VTE 4 3. Minolta 1° luminance meter and RS-1 reflectance standard 4 4. Munsell charts, multicolored chips for judging reflectance 5 5. Typical lighting on dragline operating during nighttime hours 7 6. Stripping shovel with typical lighting system 8 7. Typical illumination on loading shovel 10 8. Typical lighting system on loader 10 9. Haul truck dumping load at waste dump 12 10. Typical illumination on blasthole drill 14 11. Flatbed truck for transporting packaged explosives 16 12. Tank- or drum-type truck for transporting bulk mixture of explosives 16 13. Typical lighting on scraper 17 14. Typical lighting on bulldozer 21 15. Typical illumination system on motor grader 21 16. Truck used for refueling and lubricating equipment 23 17. Luminaires mounted on top rear section of lubrication truck 23 18. Typical portable lighting unit 30 B-l. Contrast control calibration for VTE model 5 33 B-2. Normal population data to determine calibration constant for users of VTE model 5 34 B-3. Correction constant for VTE model 5 35 ii TABLES Page Illumination values resulting from task visibility measurements for — 1 . Coal mine draglines 7 2. Coal mine shovels 9 3 . Coal mine loaders 11 4. Coal mine haul trucks 13 5. Coal mine blasthole drills 15 6. Coal mine explosives trucks 17 7. Coal mine scrapers 18 8. Coal mine bulldozers 19 9. Coal mine motor graders 22 10. Coal mine fuel trucks 24 11. Coal mine lubrication trucks 25 12. Coal mine water truck 25 13. Noncoal mine shovels 27 14. Noncoal mine blasthole drills 28 15. Noncoal mine loaders 29 UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT cd/m 2 candela per square meter in inch deg degree lx lux fc footcandle mph mile per hour fL footlambert s second ft foot yr year h/d hour per day ASSESSMENT AND DETERMINATION OF ILLUMINATION NEEDS FOR OPERATORS OF MOBILE SURFACE MINING EQUIPMENT By Alan G. Mayton 1 ABSTRACT The Bureau of Mines conducted one of the most extensive studies on surface mine illumination to date, to assess the illumination needs of mobile surface mining machinery with respect to the visual tasks re- quired of machinery operators. Field investigations were performed at 22 surface mining operations, coal and metal-nonmetal, within several mining regions of the United States. Visibility and illumination were measured for 159 visual tasks performed by equipment operators on or near 57 surface mining machines, including draglines, shovels, blasthole drills, bulldozers, loaders, haul trucks, graders, scrapers, and several service-type vehicles. The report shows that illumination and/or visibility could be improved for various visual tasks and makes recommendations for these improve- ments. Moreover, the report describes the various equipment studied, gives details of the instruments and measuring techniques used, and pre- sents equations to calculate the luminance and illuminance levels sug- gested for performing mining tasks. Tables are presented that compare values of illumination computed for workers in the 25- and 50-yr age groups. Appendixes to the report includes a glossary of terms, abbrevi- ations, symbols, and calibration and analysis procedures. 1 Mining engineer, Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. INTRODUCTION Surface mines, which can cover many square miles of land, use very large, electric- or diesel-powered, mobile con- struction-type equipment. Most surface mines run their machinery 24 h/d to meet production quotas and to recover costs of capital investments. When persons work on or about equipment of this size and power, safety is obviously a major con- cern. When work activities take place during nighttime hours, safety practices take on an important dimension — the provision for proper and effective illumination. Since the passage of the Coal Mine Health and Safety Act of 1969, the Bureau of Mines has played a major role in illu- mination research and in the development of illumination criteria and technology to provide adequate lighting for workers in U.S. mining operations. This has been accomplished most notably in underground coal mining, and to a degree, in surface mining. In 1977, the Mining Enforcement and Safety Administration (MESA) under the Department of the Interior (now the Mine Safety and Health Administration (MSHA) under the Department of Labor) proposed mandatory safety standards of illumina- tion for surface coal mines and surface work areas of underground coal mines (1). These standards, however, were never approved. In 1981, the Inter- national Commission on Illumination (CIE) began to focus attention on illumination standards for surface mining by estab- lishing a program to develop recommenda- tions for opencast (surface mine) light- ing. Concurrent with its involvement with the CIE and in view of the lack of approved lighting standards, the Bureau initiated a program to study illumination on mobile surface mining equipment from the viewpoint of the equipment operators. The objective of the program was to as- sess the illumination needs of various surface mining equipment on the basis of the visibility required by workers in performing the necessary visual tasks as- sociated with their jobs. Overall, the intent of the study was to provide useful data and information for MSHA and the CIE to use in establishing lighting standards and recommending lighting practices for surface mines. ACKNOWLEDGMENTS The author thanks C. L. Crouch, presi- dent of CLC Associates, Floral Park, NY, and Port Charlotte, FL, for his assist- ance with the collection and analysis of the data. The author also thanks H. R. Blackwell, president of Visioneering Lab- oratories, Sarasota, FL, and Frankfurt, MI, for his cooperation and assistance with the visual task evaluator (VTE) instrumentation. DESCRIPTION AND PROCEDURES The study was conducted using a VTE (a visibility meter, described in detail la- ter) according to the methods and prac- tices recommended by the CIE and the Il- luminating Engineering Society of North America (IES). The main program effort involved the collection of visibility and illumination data through on-site visits to various surface mines and quarries in several mining regions of the United States. Field investigations were con- ducted at 22 different surface mining operations in Michigan, Indiana, Alabama, Florida, Ohio, Massachusetts, New Hamp- shire, and New York. Useful data were obtained from 12 of them: 5 metal and nonmetal (M-NM) mines and quarries and 7 coal mines. The M-NM operations included two iron ore mines and three limestone 2 Underlined numbers in parentheses re- fer to items in the list of references preceding the appendixes. quarries. 3 The visual tasks of equipment operators were identified on or about 57 surface mining machines, including quarry equipment. The equipment included drag- lines, shovels, blasthole drills, bull- dozers, loaders, haul trucks, graders, scrapers, lubrication trucks, fuel trucks, and a water truck. Visibility was measured for 159 tasks using the Blackwell model 5 VTE. 4 The existing il- lumination was determined using the re- flectance standard RS-1 (a barium sulfate plaque with a nominal reflectance of 98%) and the Minolta 1° luminance meter. FIELD MEASUREMENTS After a visual task of a particular equipment operator was identified, the VTE (fig. 1) was set up in the location from which the operator would normally view the critical detail of the task. The approximate angular position of the VTE and the approximate distance from the outer lens of the VTE to the object or surface of interest were estimated or measured and recorded. The proper outer lens unit (fig. 2) was selected based on the measured (or estimated) distance and attached to the front of the VTE. Then, no fewer than five readings were obtained while looking through the VTE and turning the contrast control dial. After the VTE readings were taken, the luminances of the target (critical detail of the task) and its background were measured with the Minolta meter. The illuminance or illu- mination of the task was determined by measuring the luminance of the RS-1 plaque (placed on or directly above the 3 Ten other M-NM operations were vis- sited. However, the visibility and illu- mination data from two granite quarries and two limestone quarries are not in- cluded because the VTE was later found to be out of calibration. Also, it was not possible to obtain visibility measures at five phosphate mines and one other lime- stone quarry. 4 Reference to specific products does not imply endorsement by the Bureau of Mines. FIGURE 1. — Blackwell model 5, serial No. 2, visual task evaluator (VTE). target) with the Minolta meter (fig. 3). In addition, Munsell charts were used where needed to determine the reflectance of surfaces of interest (fig. 4). Slide photographs were also taken of the equip- ment and the detail of each task. VTE DESCRIPTION AND PRINCIPLE OF OPERATION The Blackwell model 5 VTE is the latest in a series of visibility meters devel- oped by H. Richard Blackwell (2) of Vi- sioneering Laboratories. The main advan- tage of the new meter is that it uses light from the task environment rather than an internal, diffuse, incandescent g^ IW m FIGURE 2.— Outer rectangular lens units of VTE. FIGURE 3. — Minolta 1° luminance meter and RS-1 reflectance standard. source. This makes for use in the surfa (3). The VTE operates to vary the visual seen through the ins the luminance of a same time introduci luminance, or "opti the VTE very flexible ce mining environment by allowing the user contrast of objects trument by fading out scene while at the ng a uniform veiling cal fog." The point at which critical detail of the task can be seen just barely through the interven- ing optical fog is called threshold. The proportion of the original contrast pass- ing through the instrument's optics is called the contrast transmittance (CT) of the instrument, which ranges from almost 100% to almost zero as the backeround lu- minance remains nearlv constant (M« FIGURE 4.— Munsell charts, multicolored chips for judging reflectance. A measure of how easy or how well a given target can be seen is expressed in the amount of reduction in task contrast that is needed to bring the detail to threshold. If, for example, a given tar- get object reaches visibility threshold at a value of CT equal to 0.10, the tar- get is inherently 10 times above its threshold value. The target is said to have a relative visibility level (VL) of 10. Thus, a measure of relative visi- bility for objects is determined mathe- matically by taking the reciprocal of the contrast transmittance; namely, VL = 1/CT. Consequently, scenes that are highly visible will require more contrast reduction (optical fog) to reach visibil- ity threshold, while those that are mod- erately visible will require less (4-5_ ) . CIE-IES METHOD The use of the VTE to obtain visibility measurements is based on the CIE-IES method, which compares an actual, real- world visual task with a standard visi- bility reference task. The visibility reference task consists of an observer viewing (through the VTE) a luminous disk whose diameter subtends A' of arc at the observer's eyes when it is presented in a series of 0.2-s exposures on a. task back- ground with uniform luminance. In turn, the visibility reference task is the ba- sis for the visibility reference func- tion, which represents visibility thresh- old values obtained by a 20- to 30-yr-old reference observer (6^). A detailed ex- planation of this method is contained in CIE Report 19/2 (7^. Further, measuring task visibility with the VTE requires that the VTE user go through a specific calibration procedure. This procedure, with the procedure for analyzing the field data, is included in appendix B at the end of this report. DISCUSSION AND RESULTS This section includes a brief descrip- tion of the different equipment studied, with corresponding tables of illumination data based on measurements of task visi- bility for equipment operators. The data presented should not be construed as absolute, but should be used as a general guide to help In better understanding the illumination needs of machinery and vehi- cle operators at surface mines. Also, note the following regarding data in the tables: Values appearing under the column head- ings "Computed luminance" and "Computed illuminance" were calculated for the me- dian age in each group, that is, the average 25- and 50-yr-olds of the normal population. Computed values of luminance and illu- minance were rounded off for consistency after the calculations were made. Variations in luminances and illumi- nances for similar tasks and equipment are largely the result of the wide dif- ferences in the conditions under which field measurements were actually taken. In general, high contrast between the task target or critical detail and its background will result in good visibility and relatively lower illuminance levels, while low contrast will result in poorer visibility and relatively higher levels of illuminance. The footnote "Supplemental lighting" on some of the tables refers to illumination added to the scene for certain visual tasks (generally from the direction of normal or existing lighting) to increase the transmittance through the VTE. SURFACE COAL MINES Draglines Draglines are generally very large, mobile, electric-powered excavating ma- chines used to remove and transport over- burden (the earth and rock overlying a coalbed) while operating from the top edge of a nearly vertical pit. Those working on or near a dragline include an operator, an oiler, and a groundman who usually operates a track- or wheel-type bulldozer to maintain a relatively uni- form ground surface around the dragline and handles the trailing cable for relo- cation purposes. For obvious safety rea- sons, good visibility is a necessary concern for tasks on and around the ma- chine. Accordingly, the dragline opera- tor must be able to see the following: the bottom of the pit at the greatest reach and digging depth of the machine, for positioning of the bucket; the point at which the overburden meets the coal, to remove only overburden; the top of the spoil pile or waste dump when disposing of overburden; and on the hoist rope, the bucket-chain assembly including the dump block, to prevent lifting the dump block into the point sheave located at the end of the boom. Other tasks for workers In- clude approaching, boarding, and exiting the machine, routine maintenance, and in- spection. A final task involves handling of the trailing cable during relocation maneuvers. 5 The three draglines observed during field investigations displayed illumina- tion systems consisting of mercury vapor luminaires and some high-pressure sodium vapor luminaires; these were mounted on the boom and around the top edge of the machinery house. Incandescent fixtures were generally located near doorways, walkways, stairways, and ladders, and beneath the mainframe of the machine. Figure 5 shows an illuminated dragline operating at night. Table 1 shows tasks for which visibility was measured, along with the existing and computed illumina- tion and task viewing distances. In addition to the data in table 1, more comprehensive data on the illumina- tion needs for tasks on draglines can be found in a report by Crouch and Vincent. ^ ^Some information contained in this paragraph was obtained from a "rough" draft report of the CIE Subcommittee SC- 4.1 OB, entitled "Recommended Practices For Open Cast Mine Lighting," and com- pleted on Jan. 25, 1983. This report is yet to be published in its entirety and final .form. ^This report documents work performed for the Mine Safety Appliance Co. under Bureau contract H03874024. A copy of the report is available upon request from A. G. Mayton, BuMines, Pittsburgh, PA. FIGURE 5. — Typical lighting on dragline operating during nighttime hours. TABLE 1. - Illumination values resulting from task visibility measurements for coal mine draglines Existing illumi- Viewing distance, ft Computed luminance, fL 1 ' 2 Reflec- tance, % Computed illuminance, fc 1 ' 3 nance, fc 20- to 30-yr- olds 40- to 60-yr- olds 20- to 30-yr- olds 40- to 60-yr- olds DRAGLINE 1 Seen from operator's cab: Tooth of bucket 5.11 100 0.058 0.095 9.00 3.10 5.13 DRAGLINE 2 Seen from operator's cab: 4 2.40 150 0.036 0.058 2.08 1.74 2.80 Lower edge of bucket 4 1.38 105 .371 .743 47.10 .79 1.58 Coal with respect to 4 1.34 150 1.18 2.99 14.18 8.34 21.11 Dump block on hoist 4 2.10 150 .039 .063 2.86 1.36 2.19 Seen from ground level at rear of machine: 1.31 3.7 2.22 6.86 9.92 22.40 69.17 DRAGLINE 3 Seen from operator's cab: Control panel button. . 9.24 1.8 0.037 0.060 34.52 0.11 0.17 Tooth of bucket rest- 1.27 241 1.121 2.193 18.90 5.94 11.61 Seen from landing: Edge of landing to stairs... 3.48 4.7 .014 .022 3.45 .41 .61 Calculated for median age in each group. To convert to candelas per square meter, multiply by 3.426. 3 To convert to lux, multiply by 10.76. Extrapolated from other measurements. Stripping and Loading Shovels The lighting of both stripping and loading shovels was observed and stud- ied, although task visibility measure- ments were obtained only for loading shovels. Personnel and visibility re- quirements are generally the same as those for draglines. Stripping shovels (fig. 6) work in the pit on top of the coalbed and move along the pit by crawler-type conveyance. Like draglines, they remove a highwall of overburden (up to 100 ft or more) and de- posit it on a spoil pile at a distance of the boom's length away. The visibility requirements of the shovel operator and the groundman differ from those of work- ers on the dragline in that a dominant safety concern is the highwall, which must be monitored continually for dangers due to material falling or rolling down the face of the highwall. Loading shovels (fig. 7) operate on the bottom of a bench of broken overburden or coal. Bench heights typically range from 15 to 40 ft. The operating characteris- tics of this type of shovel are the same as those of the stripping shovel, except that the stripping shovel transports the overburden to a spoil pile, while the loading shovel loads overburden or coal into trucks that transport it to a desig- nated dump area or hopper. Visual tasks were identified and vis- ibility was measured for five loading shovels. Illumination of these shovels, like that of the draglines, was provided by a combination of primarily mercury va- por luminaires with high-pressure sodium and incandescent luminaires. Visual tasks for these machines, with computed values of illumination, are shown in ta- ble 2. Additional information on the il- lumination needs for tasks on electric- powered shovels can also be found in Crouch and Vincent. 'See footnote 6. FIGURE 6.— Stripping shovel with typical lighting system. TABLE 2. - Illumination values resulting from task visibility measurements for coal mine shovels Existing illumi- nance, fc Viewing distance, ft Computed luminance, fL 1 ' 2 20- to 30-yr- olds 40- to 60-yr- olds Reflec- tance, % Computed illuminance, fc 1 ' 3 20- to 30-yr- olds 40- to 60-yr- olds SHOVEL 1 Seen from operator's cab: Rear edge of dipper resting on ground . 6.84 28 0.381 0.765 16.52 2.31 4.63 SHOVEL 2 Seen from operator's cab: Rear edge of 1.41 .70 2.00 50 25 24.6 0.038 .251 .080 ■ 0.061 .478 .139 4.26 10.00 10.00 0.89 2.52 .80 1.43 Rock on slope of Rear edge of dipper resting on ground. . 4.78 1.39 SHOVEL 3 Seen from operator's cab: Top rear edge of 4 1.40 30 0.240 0.453 10.00 2.40 4.53 Top edge of empty Top edge of truck 4 1.20 4 1.30 4 1.70 20 25 30 .062 .513 .045 .103 1.08 .074 10.00 34.62 1.76 .62 1.48 2.58 1.03 3.12 Height of load in 4.20 Seen from ground level at rear of machine: .23 3.5 .020 .031 17.39 .12 .63 SHOVEL 4 Seen from operator's cab: Top rear edge of loaded dipper. . . . 12.60 25 1.30 3.39 10.00 13.06 33.91 SHOVEL 5 Seen from ground level at rear of machine: Bottom rung of boarding ladder.... 2.09 2.3 0.140 0.248 12.92 1.08 1.92 5th rung of boarding ladder used as 2.83 1.3 .003 .005 .71 .46 .66 Toi...i.» n j e~— _.ji._ . Calculated for median age in each group. To convert to candelas per square meter, multiply by 3.426. 3 To convert to lux, multiply by 10.76. Extrapolated from other measurements. 10 FIGURE 7. — Typical illumination on loading shovel. FIGURE 8.— Typical lighting system on loader. 11 TABLE 3. - Illumination values resulting from task visibility measurements for coal mine loaders Existing illumi- nance, fc Viewing distance, ft Computed luminance, fL 1 ' 2 Reflec- tance, % Computed illuminance, fc 1 ' 3 20- to 30-yr- olds 40- to 60-yr- olds 20- to 30-yr- olds 40- to 60-yr- olds LOADER 1 Seen from ground level at boarding ladder: 4 0.78 4 .02 1.01 .39 .37 2.3 1.4 1.4 3.6 15 0.017 .016 .017 .068 .031 0.026 .024 .026 .114 .050 1.28 50.00 1.98 10.26 10.81 1.33 .03 .86 .66 .29 2.06 .05 Seen from plate-metal landing outside oper- ator's cab: 1.33 Edge of landing to Seen from operator's cab: Height of load 1.11 .46 LOADER 2 Seen from operator's cab: Left end of 2.65 15 0.028 0.046 1.89 1.51 2.41 LOADER 3 Seen from operator's cab: Top rear edge 8.78 13 0.162 0.294 17.08 0.95 1.72 Calculated for median age in each To convert to candelas per square 3 To convert to lux, multiply by 10, Supplemental lighting required to group. meter, multiply by 3.426. 76. make measurements. Loaders A wheel-tractor loader is a very common machine around a surface mining pit. It can be used in a number of ways at a min- ing operation, but its most important function is to remove overburden or coal and load it into trucks or railroad cars for transport to a designated dump area. Loader operators must have good visi- bility to board and exit the equipment via boarding ladders and cab decks or landings. The operators must be able to see the immediate areas adjacent to ei- ther end of the bucket, determine when the bucket is full, detect any loose or falling material when near the highwall, determine the position of the truck or railroad car to be loaded with respect to the loader bucket, and see other moving vehicles and hazards when traveling from one location to another within the mine. Illumination systems on loaders usual- ly consist of regular incandescent or, in some cases, quartz halogen luminaires. Figure 8 shows the lighting system on a typical loader. Table 3 shows existing and computed illumination values for var- ious tasks of loader operators. Haul Trucks There are basically two types of haul- age trucks used at surface coal mines: 12 the rear dump, used primarily for trans- porting overburden, and the center (bot- tom) dump, used for transporting coal. Illumination of haul trucks consists typ- ically of high- and low-beam headlights and a set of rear-mounted backup lights (on rear dumps only). In some instances, mine operators have mounted an additional floodlight behind the cab of rear-dump trucks for dumping purposes. The visi- bility required by truck drivers includes the following: seeing the ladders and handrails when boarding and exiting the truck, viewing the area near the shovel or loader at a loading site, viewing the berm or edge of the dump and general area of the dumping site, and readily detect- ing hazards and other moving equipment on haulage roads when driving from place to place within the mine. Driver visibility was measured for various tasks on five haul trucks. These tasks are shown in table 4 with the existing and computed levels of illumination. Figure 9 shows a typical rear-dump haul truck at a dump site. Blasthole Drills Rotary blasthole drills are an impor- tant facet of the overburden removal pro- cess. Drills are used to bore vertical or angled holes into the overburden. The holes are then filled with explosives and detonated to break up the overburden into fragments that can easily be removed by the excavating equipment. The illumina- tion of drills includes mercury vapor luminaires that are mounted on the top of the operator's cab to illuminate the mast and the drill table or deck through which the drill pipe passes down to the hole. Some drills are also equipped with high- pressure sodium vapor luminaires at the rear and sides of the machines and incan- descent fixtures to illuminate doorways to the house, the main walkway, and the boarding stairs or ladders. Figure 10 shows the typical illumination on a drill. In most cases, two people work on a drill, an operator and an oiler. The visibility required for these workers includes the ability to see the area FIGURE 9. — Haul truck dumping load at waste dump. 13 TABLE 4. - Illumination values resulting from task visibility measurements for coal mine haul trucks Existing i 1 lumi - nance, fc Viewing distance, ft Computed luminance, flJ.2 20- to 30-yr- olds 40- to 60-yr- olds Reflec- tance, % Computed illuminance, fc 1 ' 3 20- to 30-yr- olds 40- to 60-yr- olds TRUCK 1 Seen from driver's cab: Pile of debris in 0.50 .54 130 55 0.107 .018 0.186 .029 14.81 1.85 0.72 1.00 1.25 1.55 Seen from ground level at boarding ladder: 4 1.21 4 .61 2.2 1.3 .018 .043 .028 .070 1.65 8.20 1.10 .53 1.71 .85 TRUCK 2 Seen from driver's cab: Left curb at 1.02 35 0.620 1.37 6.86 9.04 19.97 TRUCK 3 Seen from driver's cab: Edge of berm at 0.91 32.5 0.025 0.041 1.10 2.27 3.71 Body-down indicator. 4 .31 3 .069 .115 6.45 1.08 1.78 TRUCK 4 Landing at head of boarding ladder: Handrail of landing. Edge of landing 0.10 .54 1.8 3.6 0.022 .016 0.035 .026 20.00 1.80 0.11 .89 0.18 1.45 TRUCK 5 Seen from driver's cab: 5 Tire track at load- ing shovel 6 Sloped waste pile at base of bench highwall 6 Rear (shadowed) edge of loading shovel 6 . 3.15 1.48 1.90 99.3 138 99.3 0.432 .198 .781 0.886 .367 1.78 8.89 1.35 10.00 4.86 14.67 7.81 9.97 27.18 17.80 Calculated for median age in each group. To convert to candelas per square meter, multiply by 3.426. To convert to lux, multiply by 10.76. Supplemental lighting required to make measurements. Left side-view mirror used. Positioning and/or maneuvering mark. 14 FIGURE 10.— Typical illumination on blast hole drill. around the drill for different operating maneuvers; walkways, stairs, and ladders for boarding and exiting; and -areas imme- diately adjacent to the operator's and rear sides of the machine to relocate the machine for drilling the next hole. The visibility for various tasks was measured on six blasthole drills; the tasks are shown in table 5 with corresponding illu- mination levels. Explosives Trucks Explosives trucks (figs. 11-12) are used for transporting a bulk explosive mixture or packaged explosives to the lo- cation of previously drilled blastholes. Here the driver of the truck loads the blastholes with the explosives and pre- pares the holes for firing during the next day shift. General visibility re- quirements include being able to see the general area around the drilled holes, steps and handles for entering or exiting the truck, and hazards or other vehicles while traveling from one location to another in the mine. Specific tasks and corresponding light levels for two explo- sives trucks are shown in table 6. Scrapers Wheel-tractor scrapers are another type of excavating equipment used in surface coal mines. They are used primarily for removing and transporting topsoil or very shallow overburden. Illumination, like that on haulage trucks, is primarily ac- complished with headlights that have the high- and low-beam feature. If the ma- chine design permits, mine operators will sometimes add incandescent floodlights to better illuminate the area to the front of a scraper. One other incandescent lu- minaire is mounted on the rear of the driver's cab to provide illumination for the pan. Figure 13 shows a typical scraper with incandescent lighting. 15 TABLE 5. - Illumination values resulting from task visibility measurements for coal mine blasthole drills Existing illumi- nance, fc Viewing distance, ft Computed luminance, fL 1 ' 2 20- to 30-yr- olds 40- to 60-yr- olds Reflec- tance, % Computed illuminance, fc 1 ' 3 20- to 30-yr- olds 40- to 60-yr- olds DRILL 1 Seen from operator's cab: Shovel (marker) to align machine for drilling 27.24 15.10 16.53 60 8 12 0.226 .128 .081 0.423 .227 .137 16.52 4.44 15.12 1.37 2.89 .54 2.56 Stem lock against drill 5. 11 Paint mark on hoist chain .91 DRILL 2 Seen from landing at head of boarding ladder: Edge of landing to descend stairs 2.40 3.7 0.063 0.106 4.17 1.52 2.55 DRILL 3 Seen in operator's cab: Pointer of pressure gauge. 1.51 1.5 0.012 0.018 56.95 0.02 0.03 DRILL 4 Seen from operator's cab: Edge of box (marker) to align machine for drill- 1.43 21 0.568 1.22 6.99 8.12 17.45 Edge of deck bushing 9.18 4.5 .533 1.13 5.45 9.78 20.71 Rope with weighted end 4 23.30 20 .336 .663 4.25 7.91 15.61 Seen from ground level at operator's cab: Boarding 2.16 4.5 .028 .045 4.63 .60 .96 DRILL 5 Seen from operator's cab: Edge of deck bushing without drill pipe Edge of pipe rack against drill pipe Seen from ground level at boarding stairs: Bottom step Handrail 2.14 4.43 4.50 1.31 2.1 1.8 0.147 .091 .032 .095 ,262 ,156 ,0T1 ,163 2.34 10.38 8.22 8.40 6.27 .88 .38 1.13 11.21 1.50 .62 1.94 DRILL 6 Seen from operator's cab: Edge of deck bushing 1.48 5 0.304 0.588 25.00 1.22 2.35 .93 4.3 .029 .041 13.98 .65 1.00 Drop pin in drill pipe 55 6 .790 1.81 21.82 3.62 8.30 Pointer of pressure gauge 6 1.4 .616 1.35 62.17 .99 2.17 2.85 4 .458 .948 32.28 1.42 2.94 Calculated for median age in each groupc To convert to candelas per square meter, multiply by 3.426. To convert to lux, multiply by 10.76. Supplemental lighting required to make measurements. 16 FIGURE 11. — Flatbed truck for transporting packaged explosives. ■■llillilll WMilH li ii il iHWhrtliiHP FIGURE 12.— Tank- or drum-type truck for transporting bulk mixture of explosives. 17 Visibility required by scraper opera- tors includes the ability to see hazards or other moving vehicles while moving from one location to another, the mate- rial to be loaded and the general area where loading takes place, the cutting edge of the pan to begin loading, the material level in the pan when filled, and the general area where loaded mate- rial is being deposited. Visibility was measured for a number of tasks on two scrapers. Table 7 shows the tasks and task viewing distances with existing and computed illumination levels. TABLE 6. - Illumination values resulting from task visibility measurements for coal mine explosives trucks Existing illumi- nance, fc Viewing distance, ft Computed luminance, fL 1 ' 2 20- to 30-yr- olds 40- to 60-yr- olds Reflec- tance, % Computed illuminance, fc 1 ' 3 20- to 30-yr- olds 40- to 60-yr- olds TRUCK 1 Seen from ground level at rear of truck: Edge of bagged 1.84 3 1.04 2.53 29.35 3.54 8.64 Detonating cord 2.30 1.3 .188 .347 27.83 .68 1.25 Hole slot in primer. 2.28 1.3 .258 .493 32.46 .79 1.52 Black digit on tape 20.70 4.3 .718 1.62 9.90 7.25 16.37 TRUCK 2 Seen from ground level at rear of truck: Edge of blasthole. . . . 4 150 4.5 0.312 0.612 9.93 3.14 6.16 Calculated for median age in each group. To convert to candelas per square meter, multiply by 3.426, To convert to lux, multiply by 10.76. Supplemental lighting required to make measurements. FIGURE 13.— Typical lighting on scraper. 18 TABLE 7. - Illumination values resulting from task visibility measurements for coal mine scrapers Calculated for median age in each group. "To convert to candelas per square meter, multiply by 3.426. To convert to lux, multiply by 10.76. Extrapolated from other measurements. 'Supplemental lighting required to make measurements. Computed Computed Existing Viewing luminance, Reflec- illumi nance , illumi- nance, distance, ft fL 1 ,2 tance, % fc 1 ,3 20- to 40- to 20- to 40- to fc 30-yr- 60-yr- 30-yr- 60-yr- olds olds olds olds SCRAPER 1 Seen from operator's cab: Cutting edge of pan. 1.96 16 2.15 6.49 18.88 11.40 34.39 .77 39.6 .635 1.40 20.78 3.06 6.74 .45 47 1.47 3.97 17.78 8.26 22.32 Top rear edge of 4 8.20 14 .204 .378 9.76 2.09 3.87 Seen from ground level at rear push bumper: 5 12.24 2 .012 .019 2.53 .49 .76 Hand bar for 5 1.79 1.3 .776 1.79 14.52 5.34 12.30 SCRAPE R 2 Seen from operator's cab: Cutting edge of 54.0 19 0.028 0.046 12.52 0.23 0.36 Bulldozers Graders Track- or wheel-type tractors or simply dozers are indispensable items of equip- ment for surface mine operators, because of the power they possess to push or pull other machines, objects, etc. Although they can be used in many ways, their main function is to redistribute overburden at dump sites and at dragline and shovel working areas. The illumination system of a typical dozer generally consists of incandescent floodlight luminaires that are mounted in the front and rear, and in some cases, on top of the operator's cab. A track dozer with Incandescent lighting is shown in figure 14. Table 8 shows the results of task visi- bility and illumination measurements for 11 dozers. Motor graders are used to maintain haul roads leading to dump areas and access roads in and around the pit area. Illu- mination systems are similar to those of loaders and dozers, in that they are mainly incandescent floodlights mounted on the front and rear of the machine and on the top of the operator's cab. An ex- ample of a motor grader with an incandes- cent lighting system is shown in figure 15. General visibility requirements for the grader operator include the ability to see obstacles, hazards, and other ve- hicles when traveling throughout the mine; the areas adjacent to either end of the blade; the wind row of material being pushed; and the ladder-type steps and hand bars needed for boarding and getting 19 TABLE 8. - Illumination values resulting from task visibility measurements for coal mine bulldozers Existing illumi- nance, fc Viewing distance, ft Computed luminance, fL 1 ' 2 20- to 30-yr- olds 40- to 60-yr- olds Reflec- tance, % Computed illuminance, fc 1 ' 3 20- to 30-yr- olds 40- to 60-yr- olds BULLDOZER 1 Seen from operator's cab: Dirt at left blade end Dirt above blade when pushing load. 0.80 135.70 23 16 0.054 .002 0.088 .003 1.25 .02 4.32 10.00 7.05 15.00 BULLDOZER 2 Seen from operator's cab: Dirt at right blade end Seen from ground level: Hand bar above trunnion arm for boarding Edge of trunnion arm step for boarding.. 1.56 .41 .44 20 1.6 1.6 0.063 2.96 .021 0.014 10.27 .033 1.92 34.15 4.54 3.26 8.65 .46 5.43 30.09 .72 BULLDOZER 3 Seen from operator's cab: Power cable of dragline 0.47 42.2 0.492 1.03 21.28 5.25 11.00 BULLDOZER 4 Seen from ground level: Edge of bottom rung of boarding ladder. 0.06 .03 2.1 1.4 0.018 .086 0.028 .146 16.67 100.0 0.11 .09 0.17 .15 Seen from operator's cab: Top edge of blade against load 42.65 14 .421 .864 4.99 8.43 17.30 BULLDOZER 5 Seen from operator's cab: Left blade end against load pushed. « 0.86 15 0.325 0.637 30.23 1.08 2.11 BULLDOZER 6 Seen from operator's cab: Left blade end against load pushed. « 4 122.40 15.6 0.085 0.145 3.34 2.54 4.34 BULLDOZER 7 Seen from operator's ■ - ■ - — ■ ■ ■ ■■ 1 cab: Left blade end against load pushed.. 4 12.60 15.3 0.188 0.344 23.81 0.79 1.45 See footnotes at end of table. 20 TABLE 8. - Illumination values resulting from task visibility measurements for coal mine bulldozers — Continued Existing illumi- nance, fc Viewing distance, ft Computed luminance, fL 1 ' 2 20- to 30-yr- olds 40- to 60-yr- olds Reflec- tance, % Computed illuminance, fc 1 ' 3 20- to 30-yr- olds 40- to 60-yr- olds BULLDOZER 8 Seen from ground level at rear of machine: Edge of grouzer (step) for boarding. . 4 42.20 2.1 0.001 0.002 0.02 5.00 10.00 BULLDOZER 9 Seen from operator's cab: Left blade end against muddy load pushed 1.51 17.5 0.035 0.056 4.64 0.76 1.20 BULLDOZER 10 Seen from operator's cab: Top of blade against load pushed. . 6.35 13.3 0.132 0.234 8.66 1.52 2.70 Seen from ground level at boarding ladder: 4 36.80 2.5 .008 .012 .46 1.78 2.57 1.32 1.3 .057 .093 61.36 .09 .15 BULLDOZER 11 Seen from operator's cab: Left blade end against ground 1.39 3.26 1.33 14.8 14.5 3.3 0.572 .081 .200 1.23 .138 .368 17.27 8.28 32.33 3.31 .98 .62 7.12 Top right blade end against ground 1.67 Edge of deck outside Seen from ground level: 1.14 Edge of trunnion arm (step) for boarding Hand bar above .39 1.7 .010 .015 2.56 .39 .60 trunnion arm for .93 2.8 .005 .007 2.15 .23 .35 v, ~—~..._ To convert to candelas per square To convert to lux, multiply by 10 Supplemental lighting required to group. meter, multiply by 3.426. 76. make measurements. 21 FIGURE 14.— Typical lighting on bulldozer. • ^ ^ ■■ -■■-■. BHi^,7^^^BB L *w i ^Jz I I i ■1 ■■**■. ■ j tl ^< • ... ,.,'. . ' PWI "™^^^^^W^" II '■ill IIP.'I! UIWIH'lHil II I'll ^s, -. W**** - ii|8i^itir;^ M ^ fe6t ~ J '"'- FIGURE 15.— Typical illumination system on motor grader. off the machine. Table 9 shows the illu- mination levels with corresponding tasks for four motor graders. Service Vehicles Various types of service vehicles are an essential part of coal mining pit operations. Fuel and lubrication trucks (figs. 16-17), which may work in pairs, are used to maintain equipment in the pit area. As their names imply, they are used in replenishing diesel fuel, greas- ing appropriate parts, and checking and replacing various filters on mobile die- sel equipment. 22 TABLE 9. - Illumination values resulting from task visibility measurements for coal mine motor graders Computed Computed Existing Viewing luminance, Reflec- illumi nance, illumi- nance, distance, ft fL ,2 tance, % fc 1 ,3 20- to 40- to 20- to 40- to fc 30-yr- 60-yr- 30-yr- 60-yr- olds olds olds olds GRADER 1 Seen from operator's cab: 4 0.31 85 2.57 8.43 29.03 8.84 29.05 Top of wind row at right blade end.... 1.04 14.6 .106 .184 4.81 2.20 3.82 Top of left blade 6.26 .44 10.7 65 .014 .492 .021 1.03 .96 22.73 1.46 2.16 2. 16 4.53 Clumped dirt at right blade end.... 1.35 14.7 5.41 25.76 28.15 19.20 91.51 Seen from ground level at boarding ladder: 4 .63 1.9 .024 .037 4.76 .50 .78 4 .11 1.4 .009 .014 9.09 .10 .15 GRADER 2 Seen from operator's cab: 5.63 13.4 0.014 0.021 1.06 1.30 2.02 7.23 9.4 .123 .216 14.38 .86 1.50 Seen from ground level at boarding ladder: 2.74 1.9 .320 .625 5.84 5.48 10.70 GRADER . 3 Seen from operator's cab: Bottom of left blade 2.99 1.23 1.23 .36 13.3 8.7 7.8 2 0.008 .007 .027 .041 0.012 .010 .043 .067 0.67 .81 7.32 22.22 1.14 .87 .37 .18 1.76 1.23 Top of left blade .58 Seen from ground level at boarding ladder: .30 GRADER 4 Seen from operator's cab: 2.26 9 0.012 0.019 1.33 0.94 1.45 2.45 13.4 .080 .135 5.31 1.50 2.54 Seen from ground level at boarding ladder: 1.67 1.7 .052 .085 4.19 1.23 2.02 Calculated for median age in each "To convert to candelas per square To convert to lux, multiply by 10. Supplemental lighting required to group. meter, multiply by 3.426. 76. make measurements. 23 FIGURE 16. — Truck used for refueling and lubricating equipment. FIGURE 17. — Luminaires mounted on top rear section of lubrication truck. Illumination for these vehicles is sup- plied by incandescent luminaires mounted on the truck or handheld lamps or cap lamps. In some cases, quartz halogen lu- minaires are used. Also, these vehicles rely a great deal on the illumination systems of the equipment which they ser- vice for the lighting needed to do their work. General visibility requirements for op- erators of these vehicles are basically the same as those for operators of other mobile mining equipment. Tasks involve detecting hazards or other vehicles while driving to and from different working areas within the mine and seeing hand- holds, handles, and steps when getting in and out of the service vehicles or on and off equipment being serviced. Selected tasks for two fuel trucks and three lu- brication trucks are shown in tables 10 and 11 with corresponding illumination levels for each task. Another type of service vehicle is the water truck, which is used to sprinkle or spray water onto haulage and access roads to allay dust. The primary illumination for watering vehicles, as for some of the vehicles previously mentioned, is the standard high- and low-beam headlights. 24 TABLE 10. - Illumination values resulting from task visibility measurements for coal mine fuel trucks Existing illumi- nance, fc 4 Viewing distance, ft Computed luminance, fL 1 - 2 20- to 30-yr- olds 40- to 60-yr- olds Reflec- tance, % Computed illuminance, fc 1 ' 3 20- to 30-yr- olds 40- to 60-yr- olds TRUCK 1 Seen from ground level: Black digit of fuel meter Boarding step of cab Hand bar for boarding Seen from corner of walkway behind driv- er's cab: Edge of walkway along fuel t ank 0.58 .30 1.65 .24 2.3 2.7 1.3 4.6 0.109 .038 .026 .007 0.190 .061 .041 .010 8.62 13.33 6.67 4.17 1.27 .29 .39 .17 2.20 .46 .62 .25 TRUCK . 2 Seen from ground level: Black digit of fuel 0.70 1.02 1.03 1.3 1.5 3 0.178 .167 .010 0.325 .304 .015 7.03 17.65 .97 2.54 .95 1.03 4.63 Nozzle of fuel hose. Boarding step of cab 1.72 1.59 Calculated for median 2 To convert to candelas To convert to lux, mul Supplemental lighting age in each group. per square meter, multiply by 3.426. tiply by 10.76. required to make measurements. In many cases, water trucks are modified forms of other equipment, such as bottom- dump haul trucks or scrapers. In gen- eral, visibility is needed for many of the same types of tasks as required for the above vehicles. Selected tasks for one water truck are shown in table 12 with corresponding existing and computed illumination levels. SURFACE METAL AND N0NMETAL MINES Surface methods are used to mine a num- ber of M-NM ores besides coal. The types of mines visited during this program in- cluded iron ore, phosphate, limestone, and granite quarries. With a few excep- tions, most of these mines are operated in much the same way as the surface coal mines with similar equipment and visibil- ity requirements for machinery operators. The two iron ore mines are large, open pit mines. The ore is mined by the benching method using loading shovels and haul trucks, which transport the ore to a primary crusher. From there it is con- veyed by belt to a secondary crusher and then processed into pellets at a plant located adjacent to the mining pit. The five phosphate mines employ drag- lines for excavating this very soft non- metallic ore. The draglines, which are essentially the only type of mobile equipment in operation during nighttime hours, dump the phosphate ore into small pits equipped with high-pressure water guns, which in turn wash the phosphate down into a "well." The slurry formed is 25 TABLE 11. - Illumination values resulting from task visibility measurements for coal mine lubrication trucks Existing illumi- nance, Viewing distance, ft Computed luminance, fL 1 ' 2 20- to 30-yr- olds 40- to 60-yr- olds Reflec- tance, % Computed illuminance, fc 1,3 20- to 30-yr- olds 40- to 60-yr- olds TRUCK 1 Seen from ground level at rear of truck: Nozzle of grease hose. Chain link of boarding 1.21 12.80 358 1.3 2 3.5 0.054 .029 .064 0.089 .046 .108 9.09 9.22 .22 0.59 .32 29.32 0.98 .50 49.02 TRUCK 2 Seen from ground level at grease fitting of haul truck wheel: Noz- 314 2.1 0.040 0.064 6.30 0.63 1.02 TRUCK 3 Seen from ground level: Nozzle of grease hose. 33.2 1.6 0.068 0.114 3.46 1.96 3.28 Boarding step of cab. . 1.19 2 .022 .035 9.24 .24 .38 Hand bar for boarding. 1.63 1.5 .004 .006 3.07 .13 .19 i _ 4. _~~V „ _ _„ , To convert to candelas per square To convert to lux, multiply by 10 Supplemental lighting required to group. meter, multiply by 3.426. ,76. make measurements. TABLE 12. - Illumination values resulting from task visibility measurements for coal mine water truck Existing illumi- nance, fc Viewing distance, ft Computed luminance, fL'» 2 20- to 30-yr- olds 40- to 60-yr- olds Reflec- tance, Computed illuminance, fc'' 3 20- to 30-yr- olds 40- to 60-yr- olds Seen from operator's cab: Vertical stream of wa- ter at fillup point.. Top of berm at right side of road Water-filled pothole.. Rock on road Seen from ground level at boarding ladder: Bottom rung Handhold (rung) 0.94 117 .69 88 1.13 110 .64 110 4 2.04 2.5 4 1.81 1.3 0.103 .009 .104 .103 ,016 .181 0.177 .013 .181 .177 .025 .330 5.32 1.45 5.31 7.81 .98 11.05 Calculated for median age in each To convert to candelas per square To convert to lux, multiply by 10. Supplemental lighting required to group. meter, multiply by 3.426. 76. make measurements. 1.93 .61 1.97 1.31 1.66 1.64 3.33 .92 3.40 2.27 2.57 2.98 26 then pumped through a pipeline to flota- tion plants where the sand is separated from the phosphate. Investigations at these mines did not include measurements of task visibility. The six limestone and calcite quarries operate with equipment such as loading shovels, loaders, haul trucks, and unit trains. Task visibility measurements at two of these mines are not included in the report because the VTE was later found to be out of calibration. Circum- stances did not permit measuring task visibility at one other of the quarries. The two granite quarries are rather unique compared with the types and meth- ods of mining previously discussed. The prominent item of equipment is the wire saw, which is used to cut huge slabs of granite from a massive face or wall. The saw consists of helical-shaped steel "wires," roughly 9/32 in. in diameter, which are strung over large sheaves re- sembling bicycle wheels. The sheaves are mounted on steel tower-like carriages lo- cated in channels cut out of either end of the working face. The wire of the saw is one continuous length, up to nearly 1 mile strung around and across the quarry pit, and back and forth across the face to provide for as many as ten 1—1/2 — f t cuts. The wires, propelled at speeds up to 45 mph, are used to transport a water slurry consisting of silicon carbide granules fed into the cut from secondary reservoirs on the top of the face. The carbide granules ate the "blade" that ac- tually cuts the stone. Once the cut is made to the bottom of the quarry floor, the giant slab of granite (as large as 125 by 1.5 by 100 ft) is broken into smaller size slabs or blocks with drills, jackhammers, regular hammers, shims, and wedges. The slabs are hoisted with cranes and placed on flatbed railroad cars that transport them to a cutting and finishing plant located at or very near the quarry. The wire saw is the focus of work ac- tivity during nighttime hours. Visibil- ity requirements include the inspection of: wires and sheaves at carriages, slurry pumps (at the bottom of each chan- nel) and slurry reservoirs (main and sec- ondary), and the general area on top of the granite face. Data on task visibil- ity were obtained but not included in the report because the VTE was later found to be out of calibration. Tables 13, 14, and 15 summarize the measurements of task visibility at sev- eral of the above M-NM mines. These ta- bles show various visual tasks with ex- isting and computed illumination levels for shovels, blasthole drills, and load- ers, respectively. CONCLUSIONS AND RECOMMENDATIONS This study shows that the type and ex- tent of illumination varies from mine to mine and seems to be influenced by sev- eral factors including mine size, ton- nage, and management philosophy. Al- though operators of surface mines and quarries have generally made positive strides toward providing adequate machine lighting, the results of the study in- dicate there are some instances where higher levels of illumination are re- quired than are available. The lighting and/or visibility for the visual tasks of machinery operators could be improved in several specific working areas on or about equipment including, among others, draglines, shovels, dozers, loaders, and haul trucks. Some examples and suggested improvements are as follows: 1. The power cable on draglines or shovels must be handled when relocating these machines. Because the cable is frequently dragged along the ground dur- ing these procedures, it can become dis- colored so that it blends with the sur- face of the ground. In a previous study, Crouch and Vincent 8 reported that by in- creasing the contrast of the task detail as seen against its background, the visi- bility of a task can be increased, re- sulting in lower illumination require- ments. The visibility of the power cable in this case could be improved by apply- ing material such as reflective tape, to increase the cable's contrast as seen against its background, the ground surface. °See footnote 6. 27 TABLE 13. - Illumination values resulting from task visibility measurements for noncoal mine shovels Existing illumi- nance, fc Viewing distance, ft Computed luminance, fL 1 ' 2 20- to 30-yr- olds 40- to 60-yr- olds Reflec- tance, % Computed illuminance, fc 1 ' 3 20- to 30-yr- olds 40- to 60-yr- olds SHOVEL 1 Seen from operator's cab: Bottom rear of dipper 4.43 30 0.050 0.083 10.38 0.49 0.80 Edge of loaded truck bed. 7.22 20 .072 .123 10.39 .70 1.19 SHOVEL 2 Seen from ground level at boarding ladder: Handhold (rung) 1.31 1.3 0.004 0.007 6.11 0.07 0.11 SHOVEL 3 Seen from operator's cab: Bottom rear of dipper resting on ground 1.28 59.8 0.045 0.073 42.97 0.10 0.17 SHOVEL 4 Seen from operator's cab: Bottom rear of dipper Seen from landing outside door to house: 3.23 2.48 1.68 .54 .35 52 1.6 3.7 2.6 1.3 0.101 .030 .034 .080 .075 0.173 .048 .054 .135 .125 20.43 1.61 22.62 20.37 5.71 0.49 1.88 .15 .39 1.31 0.84 2.98 Edge of landing to de- .24 Seen from ground level at boarding stairs: .66 2.19 SHOVEL 5 Seen from operator's cab: Bottom rear of dipper resting on ground Seen from ground level at boarding ladder: Bottom rung . Handhold (rung) 8.98 4.40 4.55 22.8 2.4 1.5 0.070 ,045 .006 0.119 .073 .010 15.37 25.45 .66 0.46 .18 .98 0.77 .29 1.50 SHOVEL 6 Seen from operator's cab: Bottom rear of dipper resting on ground Seen from ground level at boarding ladder: Bottom rung Handhold (rung) 4.19 1.12 .95 23 3.9 1.8 0.027 .220 .202 0.043 .411 .373 23.63 26.78 30.53 Calculated for median age in each group. To convert to candelas per square meter, multiply by 3.426. To convert to lux, multiply by 10.76. 0.11 .82 .66 0.18 1.54 1.22 28 TABLE 14. - Illumination values resulting from task visibility measurements for noncoal mine blasthole drills Existing illumi- nance, fc Viewing distance, ft Computed luminance, fL 1 ' 2 ' Reflec- tance, % Computed illuminance, fc 1 ' 3 20- to 30-yr- olds 40- to 60-yr- olds 20- to 30-yr- olds 40- to 60-yr- olds DRILL 1 Seen from ground level: 4 Wooden marker to align machine for drilling 0.54 .66 10.51 1.42 3.47 30 41.3 8 2.2 32 0.093 .425 .090 .022 .150 0.160 .871 .154 .035 .270 16.67 9.09 9.99 9.15 2.59 0.56 4.68 .90 .24 5.79 0.96 9.58 Straw to mark hole 1.54 .39 10.43 DRILL 2 Seen from operator's cab: Stem lock against drill pipe Red digit of pressure gauge Cardboard cylinder to maintain opening of blasthole Seen from ground level at boarding stairs: Bottom step Handrail Seen from landing at head of boarding stairs: Edge of land- ing to descend stairs.. 5.28 6.57 1.18 2.62 2.28 2.24 7 1.3 10 3.4 2.2 3.7 0.093 .486 .050 018 ,105 .026 0.159 1.02 .081 ,028 ,183 .041 41. 66. 67 67 11.02 53 51 1.78 ,40 .73 .45 16 99 1.47 2.42 1.53 .73 1.82 5.20 2.30 DRILL 3 Seen from operator's cab: Deck bushing (dust-coated) against drill pipe Seen from landing out- side door to house: Handrail 13.90 3.24 7.2 1.3 0.029 .037 0.045 .060 10.50 10.80 0.27 34 0.43 .56 Calculated for median age in each group. To convert to candelas per square meter, multiply by 3.426. To convert to lux, multiply by 10.76. Operator worked alone and relocated the machine by remote control while standing on ground near operator's cab. 29 TABLE 15. - Illumination values resulting from task visibility measurements for noncoal mine loaders Existing illumi- nance, fc Viewing distance, ft Computed luminance, fL 1 ' 2 Reflec- tance, % Computed illuminance, fc 1 ' 3 20- to 30-yr- olds 40- to 60-yr- olds 20- to 30-yr- olds 40- to 60-yr- olds LOADER 1 Seen from operator's cab: Top rear edge 4.47 12 0.080 0.134 25.28 0.32 0.53 LOADER 2 Seen from operator's cab: Top rear edge 1.35 13 0.053 0.086 25.92 0.20 0.33 Calculated for median age in each group. To convert to candelas per square meter, multiply by 3.426. To convert to lux, multiply by 10.76. 2. On dozers and loaders, there is a need to improve visibility and illumina- tion in viewing areas immediately ahead of the machines and adjacent to either end of the blade or bucket, so that the overburden material sliding off to the right or left can be seen. Improvements in these areas can be made by assuring the proper aiming of the light beams of luminaires and/or replacing existing lamps with those of higher intensity. 3. Two other examples involve machin- ery working near the highwall of the min- ing pit. A principal danger associated with the highwall is the potential for rocks and other loose material to fall or roll off these nearly vertical walls of overburden onto equipment, such as shov- els or loaders, working in the pit below. The danger at waste dumps or stockpiles is the potential for haul trucks to top- ple over the edge of the highwall and into the pit when dumping waste material. Illumination levels can be increased and the required visibility attained in these cases by using portable light plants (fig. 18), which are available at nearly all mines. The light plants, however, should be placed in locations that would minimize glare for equipment operators working in the areas. The use and application of the in- strumentation, methods, and equations presented in this report will enable a surface mining company to improve its ex- isting levels of luminance and illumi- nance on or about its mining equipment. Due to the wide variation in lighting at the different mines, the limited time available to take measurements on operat- ing equipment, and the limitations of the instruments used, the data given in the tables are only an indication of the luminances, illuminances, and reflectance factors needed for equipment operators to carry out required tasks safely and efficiently. The results of this study should pro- vide data useful in efforts to establish illumination standards for surface mines. Additional field work should be done to establish more rigid guidelines. 30 FIGURE 18— Typical portable lighting unit. REFERENCES 1. Federal Register. U.S. Mining En- forcement and Safety Administration (Dep. Interior). Illumination. V. 2, No. 9, Jan. 13, 1977, pp. 2805-2807. 2. Blackwell, H. R. Development of Procedures and Instruments for Visual Task Evaluation. Ilium. Eng. (N.Y.), v. 65, 1970, pp. 267-291. 3. . Instructions for Use of the Blackwell VTE Model 5 Visibility Meter. Aug. 1983, 10 pp.; available upon request from A. G. Mayton, BuMines, Pittsburgh, PA. 4. Merritt, J. 0., T. J. Perry, W. H. Crooks, and J. E. Uhlaner. Recommen- dations for Minimal Luminance Require- ments for Metal and Nonmetal Mines (con- tract J0318022, Perceptronics, Inc.). BuMines OFR 65-85, 1983, 236 pp.; NTIS PB 85-215689. 5. Kaufman, J. E. (ed.). IES Lighting Handbook. Illuminating Engineering Soc. , New York, ref. v., 1981, 577 pp. 6. Hitchcock, L. C. Development of Minimum Luminance Requirements for Under- ground Coal Mining Tasks (contract H0111969, U.S. Dep. Navy). BuMines OFR 12-74, 1973, 288 pp.; NTIS PB 230 447. 7. Commission Internationale de l'Eclairage (CIE), Technical Committee 3.1 (Paris). An Analytic Model for De- scribing the Influence of Lighting Param- eters Upon Visual Performance. V. 1, Technical Foundations; v. 2, Summary and Application Guidelines. (TC-3.1), 1981, 235 pp. 8. Blackwell, H. R. Laboratories). Private June 1985, 6 pp.; available upon request from A. G. Mayton, BuMines, Pittsburgh, PA. 9. Kaufman, J. E. (ed.). IES Lighting Handbook. Illuminating Engineering Soc, New York, 5th ed. , 1972, pp. 3-14, 3-15, 3-16. CIE Rep. 19/2 (Visioneering communication, 31 APPENDIX A. --GLOSSARY OF TERMS. ABBREVIATIONS, AND SYMBOLS 1 TERMS Equivalent contrast — a measure of the visibility of a visual task representing the luminance contrast of the reference task with both the visual task and refer- ence task having the same visibility at the background luminance level of the visual task. Illuminance — density of light flux ar- riving at a surface. Illumination — the act of illuminating or state of being illuminated. Luminance — a measure of the character- istic of being luminous, formerly called brightness. Luminance contrast — the difference in luminance of a visual task's critical de- tail and its immediate background, ex- pressed as a proportion of the background luminance. Reflectance — generally speaking, the ratio of the light flux leaving a surface to the light flux striking a surface. Threshold contrast — the value of lu- the visibility at mmance contrast threshold. Transmittance — the ratio of the light passing through a medium to the light striking the medium (illuminance). Visibility — the quality or state of be- ing perceived by the eye. References 5 and 7 were primarily used Visibility level — a measure of the ex- tent to which the equivalent contrast of a visual task exceeds the visibility threshold of an observer for the same display at the same level of task back- ground luminance. Visibility reference function — values of threshold contrast as a function of reference luminance for the visibility reference task, obtained by the reference observer. Visibility reference task — a 4 ' lumi - nous disk shown in a pulse train of 0.2-s exposures when used to establish the visibility reference function. Visibility threshold — the setting on a contrast-reducing visibility meter at which the critical detail of a visual task can barely be seen, such as detec- tion of presence, recognition of spatial detail, recognition of meaning. Visual performance — generally speaking, the speed and accuracy with which a vis- ual task is performed. Visual task — the critical detail of ob- jects or surfaces that must be seen to perform a given activity and the imme- diate background of the objects or surfaces. Visual task evaluator — an optical in- strument that enables an observer to mea- sure visibility by varying the contrast of objects or surfaces seen through the instrument. in defining the terms and symbols. 32 ABBREVIATIONS AND SYMBOLS NOTE. — This list does not include the unit of measure abbreviations listed at the front of this report. C Luminance contrast C Threshold contrast CC Contrast control CIE Commission Internationale De L'Eclairage (International Commission on Illumination) C re f Reference equivalent contrast C re f Reference threshold contrast CT Contrast transmittance DVM Digital voltmeter — a numerical value corresponding to the measurement of a level of contrast with the Blackwell model 5 VTE. E Illuminance IES Illuminating Engineering Society of North America k j Correction constant for VTE model 5 k Q VTE operator calibration constant L Standard population luminance Lb Background luminance L re f Reference luminance L-t Target (critical detail) luminance mi Visibility threshold multiplier for age M-NM Metal and nonmetal R Reflectance RCS re f Relative contrast sensitivity VL Visibility level VL/\ Adjusted visibility level VLr Raw visibility level VTE Visual task evaluator APPENDIX B. —CALIBRATION AND ANALYSIS PROCEDURES 33 CALIBRATION FOR THE VTE USER The following discussion is excerpted in part from Blackwell (8). 1 In order to adjust visibility data for differences in the sensitivity between a VTE user and the average 20- to 30-yr-old of the nor- mal population, a calibration constant, k , was determined for the Bureau VTE user. In the Bureau's illumination labo- ratory, a series of 10 tests was con- ducted using a black, matte, circular target on a white, matte-paper back- ground. The size of the target was ad- justed to the size of a 4' disk by in- creasing the distance of the user from the target. The adjustment was made by the formula 4' target = j (3,436), where x = diameter of target, in; (B-l) and d = user distance, in. C = Lt L b (B-3) where Lb = luminance of the background; and L-t = luminance of the target. Then, the VTE user's threshold contrast for a 4' disk target under VTE model 5 conditions is C = (C)(CT). (B-4) Using the external luminance (Lb from above) and the graph in figure B-2, the threshold contrast C np can be obtained for the average normal user in the 20- to 30-yr-old age group. Note that the graph takes into account the overall transmit- tance (0.08) of VTE model 5. The user's calibration constant is given then by ko - Cnp/C( (B-5) Once the test target was set up, a to- tal of 10 VTE readings were taken (that is, the contrast control dial was set to visibility threshold 10 times). Values in degrees were read from the contrast control of the VTE and were converted to digital voltmeter units (DVM) by the equation CC = 350 - 40 DVM, (B-2) where CC = contrast control reading, deg; and DVM = unit of measure of threshold contrast. The DVM values were summed, averaged, and then used in conjunction with the graph in figure B-l to obtain a value of CT. The luminance contrast C was determined for each test by the equation Underlined numbers in parentheses re- fer to items in the list of references preceding appendix A. .004 I 2 3 4 5 6 7 DIGITAL VOLTMETER READING (DVM) FIGURE B-1 .—Contrast control calibration for VTE model 5. (Courtesy H. R. Blackwell, Visloneerlng Laboratories) 34 o 10 LU CO a: < •— • z o o Q o t 1 1 r t r i 1 r -i r fc—x- -1.5 J L J I L J L i I i J L 1.0 1.5 2.0 2.5 LOG [EXTERNAL LUMINANCE, cd/m 2 , x0.08] 3.0 FIGURE B-2 — Normal population data to determine calibration constant for users of VTE model 5. (Courtesy H. R. Blackwell, Visloneering Laboratories) A sample of calculations to determine k D for 1 of the 10 laboratory tests follows: L>t and Lb were measured with a Pritchard photometer and found to be 2.11 fL and 40.6 fL, respectively. The task contrast is calculated as C = 40.6 - 2.11 40.6 = 0.948. The VTE's contrast control dial was set to visibility threshold 10 times, to give an average value of 1.88. From figure B-l , at DVM = 1.88, CT = 0.073. The VTE user's threshold contrast is then C = (0.948)(0.073) = 0.0692. Next, the external luminance (Lb) is changed to SI units: (40.6 fL) (3.426 C ^ m j = 139.1 cd/m 2 . Taking into account the 8% transmission of the VTE and taking the logarithm gives (139.1)(0.08) = 11.13; log 11.13 = 1.05 From figure B-2 the log of the external luminance equal to 1.05 corresponds to log -1.19 for C np . The antilog of this value is 0.0646. Then k = "0*0592 ' = 0.9335. Thus, this value and those calculated for nine other lab tests gave an average val- ue of 0.97 for k . 35 -3 -2 -I +1 t2 +3 LOG [EXTERNAL LUMINANCE, cd/m 2 ,xQ08] FIGURE B-3.— Correction constant for VTE model 5. (Courtesy H. R. Blackwell, Visioneering Laboratories) +4 ANALYSIS OF FIELD DATA The field data, which included raw visibility level (VLr) values for the different mining tasks, were adjusted further to take into account the difference between the visual conditions of the model 5 VTE and the single-glimpse conditions used in CIE Report 19/2. The differences are the reduction in luminance imposed by the VTE and the use of long exposures rather than 0.2-s pulses. Using the graph in figure B-3 with the logarithm of the external luminance measured for each task in the field, a correction constant for the VTE model 5, kj, was determined. Then the adjusted visi- bility level values (VLa) were calculated by VL A = VLr (£> (B-6) The visibility data collected during mine visits were analyzed according to the indirect method of CIE Report 19/2. The illumination levels for each mining task were computed by the equations that follow. Their use is shown in a set of sample calculations. A full explanation of the method can be found in CIE Report 19/2. C ref = 0.05936 1.639 \ ' 4 L ref J + 1 2.5 (B-7) VL = Cref/Cref. ~ f RCSref \ VL - L re f ^ 0.0923 m, ) (B-8) (B-9) 36 Age: 20-42 yr, mi = 1.000 + 0.00795 (A-20) , 42-64 yr, m, = 1.175 + 0.0289 (A-42), (B-10) where m] = the visibility threshold multiplier, and A = age, yr. T / 1.639 \°» 4 1 " 2 « 5 > r8 f = 1.555 [ { ±Z jf 1 ) + 1 " (B-ll) RCSr Using the equations above, the illumination levels for each mining task were calcu- lated, as illustrated in the following sample calculations. The L^, measured for each mining task is first converted to candelas per square meter and then can be used in equation B-7 for L re f to obtain a value of C re f» In this case, Lb was equal to 0.03426, so: C ref =0.5936 [(^§39_)°- 4 + l] 2 - 5 = 4.6. Using equation B-8 with this value of C re f and a value of 2.2 for VL (equivalent to VLa), C re f can be found. Cref = (2.2X4.6) = 10.1. This value of C r ef is subsequently inserted into equation B-9 with VL = 8.0 and mi = 1.040 (from equation B-10, where A ■ 25) to determine the appropriate value of RCSpef . 2 wpc (0.0923)(8.0)(1.040) RCS ref - (10>1) - = 0.076. The luminance of the task is then calculated by substituting the resulting value of RCS re f into equation B-ll, which is rearranged to solve for L. L = 1.639 \ 0.076 J 0.4 - 1 -2.5 = 0.195 cd/m 2 , or (0.195 cd/m 2 )(0.292) = 0.057 fL. This is the luminance level of the task for the average 25-yr-old user of the nor- mal population. — . ■'A VL of 8 is the visual performance criterion used in the IES method for prescrib- ing illumination (9). 37 The illuminance or the amount of illumination on the task is computed by using the luminance or reflectance factor (R) of the task background under actual lighting conditions (also reference conditions). In this instance, R is 1.25%. Since the surfaces are largely diffusing, the equation describing a basic law of lighting can be used: L R = (B-12) where L = luminance; and E = illuminance. Inserting the values produces E = 0.057 fL or 0.0125 = 4.56 fc, (4.56 fc)(10.76) = 49.1 lx. The level of illumination was also calculated for the most commonly found older worker. A random sample of 81 equipment operators was collected from 7 surface coal mines during the study. Of this total, 38% were found to be in the 40- to 60-yr age group. Using equation B-10, and 50 yr as the average age of this group, the factor mj is determined as follows: mi = 1.175 + 0.0289 (50 - 42), = 1.406. A new value of RCS re f is then calculated with this value of mi and the previously determined C re f. pro (0.0923)(8.0)(1.406) RCS re f = r^r— ^ — — > (10.1) = 0.103. As shown in the previous calculations for the 20- to 30-yr age group, this value of RCS re f is entered in equation B-ll to obtain the task luminance, which in this case was 0.304 cd/m 2 or 0.089 fL. Then, once again with 1.25% as the reflectance, 7.12 fc or 76.6 lx was calculated as the illumination on the task. Note that the preceding calculations for illumination did not account for other factors (discussed in CIE Report 19/2) that affect task visibility and, consequently, illumination, such as contrast rendition, disability glare, and transient adaptation effects. Inclusion of these additional factors in calculating illumination required additional measurements that were beyond the scope of this study. 10783 96 INT.-BU.OF MINES,PGH. ,PA. 28563 U.S. Department of the Interior Bureau of Mines-Prod, and Distr. Cochran* Mill Road P.O. Box 18070 Pittsburgh. Pa. 15236 OFFICIAL BUSINESS PENALTY FOB PRIVATE USt $300 ["""] Do not wi sh to recoi ve thi s material, please remove from your mailing lists ~^2 Address change* Please correct as indicated* AN EQUAL OPPORTUNITY EMPLOYER A> ... <-& .T? ... «*» A> . . . <-6 _^ - . • 'U A> . . . 0> -^ J>u • A. V %6 o '-*«SV * v « -WW / ^ vwSV * v ^ -WW «F ** v^V * v ^ -WW «? L*^L% ^ ^o< o. ,« ,0 V \3 % .. .* A > v *v. r *°+'??rs? J v**^r«\^ p °+'??rr- % j>' .. v^^r-\^ °**^-* < * •• S* ..* o ? %;^-y v^*^ \'^-> %-">\.V ! ^'^ p % 4 V** -^^*- \-/ •«- V** -A X/ -K- ^ .v ^°-