FIGURE 22.-Frequency Trend of Injuries From Machinery at Opencut Metal and Nonmetallic Mines, 1932-54. total and frequency rates of each, at opencut metal and nonmetallic mines for 1932-54. These injury rates are shown graphically in figure 22. The injury-frequency trend from machinery at opencut mines (fig. 22) was upward, with an increase of 43.6 percent, during 1932-54. During the 23-year period there were 34 fatal and 2,278 nonfatal injuries (total, 2,312), or 12 percent of the total injuries from all causes. TABLE 6.-Injuries from machinery at opencut metal and nonmetallic mines, 1932-54 (Prepared by the Branch of Accident Analysis, Division of Safety) During 1950-54 the trend was downward, with a decrease of 34.1 percent. During the 5-year period there were 10 fatal and 596 nonfatal injuries (total, 606), or 13.9 percent of the injuries from all causes. (See table 6.) EXAMPLES OF MECHANICAL ACCIDENTS These accounts of accidents from mechanical equipment at mines in all parts of the country are selected from reports issued by State mine inspectors, from accounts given by company officials to safety associations, and from reports by Bureau engineers. Typical examples of accidents from the most common causes are described as a basis for such conclusions as may be drawn regarding hazards and possible remedies. In reopening an old drift the old timber was being pulled out of the muckpile by a cable attached to the timber and to a mucking machine. A miner stood in front of the mucking machine to watch the tightening of the cable; but he gave the machine too much air, and the bucket swung and caught his leg against the rock, breaking it. This accident, like many others connected with the use of cables to move objects, resulted in injury to a man remaining in a dangerous place. Although the work may thus be made easier, the risk is unjustified in ordinary tasks. A laborer at a crushing plant attempted to move a conveyor belt mounted on a track over the ore bins. The method in use was to attach a rope to the skids on which the track was mounted and wrap several turns of the rope around a spool on the main drive shaft. This man, who had seen the regular attendant move the belt, tried to do it while substituting on the job. He was caught in the rope and wound about the spool. He died soon after arrival at the hospital. After the accident a winch was installed to move the belt and track. The practice being followed at the plant was unsafe, and this man was not given needed instruction or supervision. A mill helper was found dead suspended by one leg with his head and shoulders immersed in the fluid in a flotation cell. The cuff of his overalls had caught on a dustcap on the cell agitator shaft, and he had been carried around by it, breaking many bones. The overload cutout on the 5-horsepower motor had stopped the motor. The victim had been cleaning the drive shaft while it was operating. The work on the drive shaft was not unduly hazardous if a suitable place to stand had been provided; without a platform it was necessary to stand on the edge of the cell and on the bearing supports close to the shaft. Loose clothing was also at fault in this accident. * Two men had barred down after blasting in a stope and put up the block to scrape out the rock. One man stayed in the breast, and the other went back to operate the hoist; as he could not see the breast from the hoist he shouted to ask if his partner was in the clear and heard him answer that he was. The man at the breast then yelled to wait a minute and went to adjust the scraper block just as the slusher hoist was started. The man at the hoist did not hear the second call, and the other man's hand was drawn into the block, resulting in the loss of two fingers. In repairing or adjusting machinery reliance should not be placed in directions given by word of mouth or by signals that can be misinterpreted or be given accidentally. The cable of a scraper hoist jumped from one drum while it was being operated in a stope. The operator threw out the clutch and reached out to pull the cable back onto the drum without shutting off the electric power; his fingers were caught under the cable when the drum turned because he unwittingly pressed against the clutch lever. Parts of three fingers were cut off. Power should be cut off before cables are handled. A millman who had worked at the same plant for 15 years was killed when he attempted to replace a leather belt on an 8-inch steel pulley attached to the shaft of a 50-horsepower motor. The motor was being momentarily started and stopped to assist in putting on the belt. This man failed to release his hold on the belt in time after one of the starts; he was caught and pulled around the shaft, striking his head on the motor base and fracturing his skull. Belts should not be placed on pulleys or removed from them while the pulleys are in motion, unless by mechanical means. * * * A plant employee was injured while putting dressing on a moving belt. His right hand was pulled between the belt and pulley and badly mashed. Belt dressing should be applied to a belt as it leaves the pulley or preferably while the belt is not in motion. * The operator of a large scraper hoist was injured while filling grease cups on the drumshaft bearings of the hoist. At the time of the accident a level boss was in the operator's seat at the hoist; upon receiving a signal from the scraper man at the breast of the stope the boss started the hoist, causing the hoist operator's hand to be caught in the gears, with the resultant loss of the hand. The boss did not know that the man was putting grease in the cups, but he should have made certain that the operator was not around before starting the hoist. The mine rules provide that greasing must be done at the beginning of the shift. * * * When the operator of a 15-ton scraper hoist pulled back on a brake lever, his left foot slipped off a journal box against which he had braced himself and was caught between the countershaft gear and the motor housing. His leg was amputated below the knee. The gear was protected with a top shield, but this accident proved the need for a shield that would cover it completely. A mechanic was pouring oil in a cup on the gear bearings of a large hoist while it was in motion. He was standing on the bedplate, and when he reached over to pour the oil his foot slipped; as he attempted to catch himself his left hand was caught in the gears. The loss of his hand prevented his continuing at skilled work. Long-established rules forbade the greasing, oiling, or adjusting of machinery in motion, but this man had not been trained to observe them. Enclosed gears and oil or grease cups placed so that they are safely accessible should be a standard requirement. * A carpenter at a mine shop was putting a board through a ripsaw driven by a 15-horsepower motor. After the board had been cut for half its length he put his hand on the part that had been cut to guide the board. The board hung in the saw and kicked back, pulling his hand into the saw and cutting off the four fingers. A guard to prevent injury from such a kickback was placed on the saw after this accident. ** * * An employee at a crusher plant attempted to clean sticky ore from a conveyor belt and from pulleys, using a short piece of strap iron. The iron was caught; he was pulled by the belt and his body squeezed between a pulley and a cross brace in the supporting structure. He was crushed fatally. He had been instructed to clean spilled ore from a platform alongside the belt (a job he had done on numerous occasions), using a long-handled shovel. A safety rule at the plant provided that belts or pulleys should not be cleaned while in motion; however, to prevent similar accidents the conveyor belt and the return and idler pulleys at this location were completely enclosed with a screen guard. * A miner was hoisting a timber from the level below to the sublevel on which he was working. While operating the air throttle of the tugger hoist with his right hand he tried to guide the cable on the drum with his left hand and arm. His arm was caught between the cable and the drum, crushing it so that it had to be amputated. The number of accidents of this type show that it is dangerous to attempt to control the movement of cables with the hand or foot as the drum is turned. As the operator of a mechanical shovel was cleaning up broken muck in a drift, his hand slipped off the travel lever; the shovel turned and caught him against a close place in the side of the drift, causing several broken ribs. The accident was due to a slip by the operator, but it is a question whether enough attention has been given to providing a safe place for the operator in the design of shovel loaders. * * While a mechanic was packing the cylinder of a plunger pump his finger was caught between the piston and follower, causing permanent injury to the finger. The injured man failed to release the air pressure from the cylinder or to use packing hooks instead of his finger. * ** When a miner was removing a valve from an air line the air pressure blew it off, striking him in the face and injuring him so that he was off work for 6 months. He did not release the air pressure from the line before unscrewing the valve. A foreman at an opencut mine reached through the guard at a conveyor transfer point to examine the surface of the rotating-drive pulley by moving his hand over it. His fingers were drawn in the pinch point, and his arm was pulled from the shoulder socket. His life was saved because a shovel operator nearby, who had taken Bureau of Mines first-aid training, reached into the shoulder socket and grasped the ends of the arteries and thereby stopped the flow of blood. Regulations forbade manipulation, maintenance, or adjustment of conveyor pulleys when in operation. The foreman elected to disregard the rules and lost one arm. The presence of a man familiar with first aid saved his life. A truck driver driving a loaded truck attempted to start the 22-ton-capacity truck by having it pushed down a grade into the opencut mine. The truck traveled approximately 3,000 feet, the last 600 of which was down a 71⁄2-percent grade. At this point, the converter flywheel exploded into numerous pieces. The driver suffered a fractured right leg that required amputation above the knee. Examination of the truck showed no evidence of the possibility of the starter gear sticking. The consensus of opinion as to the immediate causes of the accident follows: a. That the clutch was not engaged at any time up to the accident, otherwise oil pressure would have been obtained to operate the steering booster. b. That at the moment of the accident the driver removed his foot from the 22- by 3-inch plate which operates an air valve that engages the clutch. This action caused a sudden torque to the clutch and flywheel far in excess of what the equipment was designed to take. At 20 miles per hour the clutch spline shaft and clutch disk would be revolving at 14,000 r.p.m. in first gear. Engine-governed speed is only 2,100 r.p.m. * * A shovel oiler was fatally injured when he was caught and squeezed between the shovel pads and counterweight of a 34-cubic yard shovel. The oiler had completed greasing the tumbler shaft bearings, except for some plugged grease fittings. He was between the rear shovel pads changing a fitting on the drive shaft bearing. The shovel operator was loading a truck, and as the shovel swung from left to right the oiler was struck by the left side of the shovel housing and squeezed between the shovel pads and the counterweight. The oiler's body was pulled across the top of the left shovel pads and dropped to the ground on the outside of the pads. Clearance between the shovel pads and counterweight is 6 inches. CAUSES OF MECHANICAL ACCIDENTS AND INJURIES Probably everyone who had had any experience with mining operations knows of some accidents from machinery used in the work with which they were connected. Knowledge of the nature of mechanical hazards gained in this way may emphasize the dangers of the machinery that was involved and of certain unsafe practices that have developed in its use. On the other hand, long familiarity with machinery that can be used without accident by persons trained to avoid its known hazards may cause the existence of those hazards to be forgotten as long as the necessary care is exercised in machinery operation. Even when there is a slip in judgment or a departure from the safe methods whose use is assumed to be customary, any resulting injury is likely to be held due to failure of the individual to use enough care rather than the fact that the machinery in question has some dangers. It is not always recognized that, wherever possible, mechanical protection should be provided rather than to place reliance on individual care and skill to avoid mishaps. In industries that are almost entirely mechanized, as are thousands of manufacturing plants, the process of safeguarding machine operation has been carried much farther than it has in mining, construction work, and similar industries where the process is not and possibly cannot be standardized. As is done by Phelps-Dodge Corp.21 and doubtless by other companies a comprehensive study should be made for each operation in and around mines and plants, especially where mechanical equipment is used. The data should be analyzed by a capable person and a code of safe practices formulated for the guidance and use of each supervisor, operator, or workman for the particular operation in order that his duties may be performed safely and efficiently. A study of the reports on accidents from machinery in the sources from which the selected examples were obtained shows that most of them can be grouped under a few general causes. These causes and the approximate frequency of accidents in each group were found to be as shown in the following subheadings. GREASING, OILING, OR ADJUSTING WHILE IN MOTION The accidents in this group involve greasing and oiling gears and bearings, applying dressing to belts and pulleys, and cleaning spilled material from around conveyor belts and pulleys. Although nearly all of the accident reports stated that there was a company rule against performing any of these duties while the machinery was running, they 21 Bureau of Mines, Accident Prevention in Nonferrous-Metal Processing Plants. 2. Mills and Concentrators (Appendix): 1954, 380 pp. |