A is a cutaway sketch of a wood split box for treating a vertical wire rope with lubricant. Note the arrangement of metal clamp straps and tightening wedge, also the sloping interior which insures continuous contact of lubricant with the rope. B is a wood box for treating a horizontal rope. This is not a split box. The rope is passed through suitable slots that are guarded by wedge-shaped ends to prevent leakage of lubricant during impregnation. Note the burlap wiper at the outlet end of the box. C is a wood box for use on a sloping rope. To permit insertion of the rope, the upper part is removable, as shown, and is provided with hasps for subsequent locking. Note the wiper at the outlet end. D is a sketch of a metal split box for vertical wire-rope treatment. Note the interlocking sides. The burlap wiper or collar similar to that employed with a wood box is shown in cutaway detail. E is a view of a metal split box of construction similar to D for use on a horizontal wire rope. F shows a box similar to D for use when the rope is on an angle. G is a sectional view of an immersion vat for applying lubricant to wire cables. Note the manner in which immersion of cables is controlled by suitable pulleys, the cable wipeoff, and the installation of steamheating coils to insure adequate fluidity of lubricant. A hoisting rope failed in a metal-mine shaft while a double-deck cage with two loaded cars was being lowered from one level to another. The rope was 8-inch, 6 by 19 plow steel, 1,000 feet long. The rope had been in service for about 18 months on moderate single-shift duty when it broke suddenly under normal use. Hoisting in the 1,000-foot shaft was mainly between levels in the lower 400 feet, where the shaft was wet. Examination of the broken ends revealed that the rope had been weakened by corrosion and wear of the individual wires, which had reduced the overall diameter to thirteen-sixteenths inch. Crown wires had been worn to approximately 47 percent of their diameter. The hemp center of the rope was dry and had received no lubricant from the drip lubricator placed above the sheave wheel. The cold oil drip had not penetrated between the strands, particularly on the lower part where the break occurred. The safety catches functioned, but the cams did not hold, although they wore a deep groove in the guides for 36 feet, until the space between the teeth of the cams became filled with wood. This accident illustrates the necessity for efficient lubrication and thorough inspection of hoisting ropes and of making tests of safety catches with the cage fully loaded. INSPECTION who Hoisting ropes require preshift inspection at least once a day; their condition should be noted and recorded by a competent man, must be held responsible for the condition of the ropes. For daily inspection he should stand at the collar or head of the shaft, where he can see the rope as it is hoisted past him at a speed of not more than 50 feet per minute. He must inspect one rope at a time, examining it and its connections carefully. Special attention should be given the rope just above the socket or clamps and the safety clamps if they are used; where the rope rests. on the sheave; where it leaves the drum when the cage or skip is at the collar of the shaft and the active working levels; and at the place where a layer of cable begins to overlap other layers on the drum. Thorough inspection should be made when ropes are turned endfor-end. Spot checks with a caliper, set equal to the diameter of the circle that will enclose the rope, will indicate any sudden change in diameter where weakness has developed. The life of a rope under heavy service probably will be estimated by the tonnage hoisted, while a rope used intermittently or on light duty will be estimated by the length of time it has been in use. Accurate records of the performance of hoisting ropes at a given shaft or slope make possible an accurate forecast of the probable life of ropes of similar construction. Thorough checks of the condition of any rope should be made at intervals determined by the service it is to perform. Such inspection should be more frequent after the rope has been in service for an appreciable part of its estimated life and after any unusual strain that may have damaged it. DISCARDING ROPES All progressive mining companies reverse, change, or discard hoisting ropes before the expiration of their calculated lives, predicated upon past experience under specific operating conditions. If there has been excessive wear or if, for any other reason, expected usability has been decreased, they are changed immediately. No exact method has been developed to determine when a rope is no longer safe for use as a hoisting rope, but the following recommendations are considered to be good practice: 1. For ropes of standard construction, when there are 6 broken wires in any 1 rope lay. 2. When wires on the crown are worn to 65 percent of their original diameter. 3. When there is a sudden decrease in the diameter of the rope. 4. When marked corrosion appears. 5. When the safety factor is 3.6 or less. Whatever practices are adopted, they should always err on the side of safety rather than on the side of long life for the rope. The following are actual practices of mining companies in changing or discarding hoisting ropes. Company A Cage Ropes.-Cage ropes are changed to skips after 6 to 9 months use (depending on use of cage). Skip Ropes. Skip ropes are discarded when the wires on the crown are worn to 65 percent of their original diameter; or when 6 wires are broken in any 1 rope lay, or when wear is 30 percent with 3 broken wires in a lay, or when wear is 20 percent with 4 broken wires in a lay, or when wear is 10 percent with 5 broken wires in a lay, or when marked corrosion appears. Company B Cage Ropes.-Cage ropes very seldom are used more than 6 months and then, if in good condition, are used for skip or counterweight. Skip Ropes. Skip ropes are discarded when the number of breaks in any running foot of said rope exceeds 10 percent of the total number of wires composing the rope, or when the wires on the crown of the strands are worn to less than one-half of their original diameter, or when the specified inspections required show marked signs of corrosion. Company C Cage Ropes.-Cage ropes are discarded when weekly visual inspection discloses broken or corroded main wires in a portion of the rope that cannot be cut off, also when weekly calipering discloses any necking down of rope. Ropes are also discarded after a predetermined length of service. (Decision to discard rope is made by district master mechanic.) Skip Ropes.-Skip ropes are discarded for the above reasons, except that skip ropes are retired after a predetermined tonnage rather than length of service. SHAFT SINKING Shafts should be equipped with safety gates at the collar and at shaft stations. The gates should be so constructed that materials will not go through or under them and into the shaft. Safety gates should be kept closed when the skip or cage is not at the landing. Positive stopblocks or derails should be placed on all tracks leading to a shaft collar or level landing. If stopblocks or derails are not provided, the gates should be constructed strong enough to stop a runaway car from reaching the shaft. The gate should be made to close automatically when the cage or skip is not at the landing. Figure 9 shows an H-beam on a shaft gate and a car stop at the cage landing. FIGURE 9.-Reinforced Gate and Car Stop at Cage Landing in Shaft. The gate is reinforced with an H-beam, and the car stop is counterbalanced and has to be held open to allow a car to enter the cage; a car coming off the cage kicks the derail open, and when the car passes it returns to an upright position. The shaft guides should be thoroughly inspected at weekly intervals by a competent person. The inspection should include examination of the physical condition of the guides, the fit of the guide shoes, joints, and alinement of guides. With the advent of newer shaft sinking or deepening methods, hoisting is done by means of auxiliary equipment placed as close as possible to the sinking operations. Hoisting is done from relatively shallow depths and beneath a substantial bulkhead. Preformed hoisting ropes used for this purpose eliminate bucket spin. The use of buckets for hoisting men much over 200 feet is unnecessary. These methods and practices offset the positive hazard of a crosshead used to prevent the sway of the bucket; its only advantage under these circumstances would be to support a protecting bonnet. The ever-present possibility of a crosshead hanging in the shaft and subsequently falling is a greater hazard than that occasioned from falling objects while riding a bucket for a short distance without a protecting bonnet. The old sinking method (bucket, guides, and crosshead) is used in many mining districts. The laws and regulations of some mining States define the steps that must be taken to protect workers engaged in shaft sinking or deepening a producing shaft. The following safe practices should be regarded as a minimum standard in those States that do not have more stringent regulations and laws.10 A substantial, well-constructed bulkhead that covers all but the passageway for the hoisting bucket or skip and manway and that will protect the workers should be provided in sinking vertical and inclined shafts when no hoisting operations are carried on from the upper levels. Some State laws require bulkheads to be erected when shafts or slopes are sunk steeper than 20° from the horizontal. A substantial, well-constructed, rock-filled bulkhead or a rock pentice, at least 10 feet thick, should be required in every shaft that is being deepened while hoisting operations from the upper levels are in progress. The opening through the bulkhead should be as small as possible and yet permit the sinking bucket to pass freely. Derail switches should be installed above the bulkhead in all inclined shafts or slopes to insure against the bucket, skip, or trip of cars entering the passageway in the bulkhead if the hoisting rope breaks. Vertical-shaft bulkheads should be provided with a heavy trapdoor over the opening for the sinking bucket. The door should be closed when the bucket is above it. The sinking bucket should never be lowered directly to the bottom of the shaft. It should be stopped 15 feet above the shaft bottom and held there until a second signal is received before it is lowered to the bottom of the shaft. The shaft timbering should be carried close enough to the bottom of the shaft to prevent falls of rock from the sides of the shaft; or temporary timber sets may be used when there is danger of damage from blasting. The timbers below the bulkhead should be cleaned of loose material after blasting in the shaft before work is resumed in the bottom of the shaft. Permanent, substantial ladders should be maintained as near the shaft bottom as is practicable. Chain or wire-rope ladders that will withstand blasting should be maintained from the bottom of the shaft to the permanent ladder. The hoisting-signal devices should be kept within easy reach of the men on the shaft bottom. Adequate ventilation should be provided to clear the smoke and gas from below the bulkhead after each blast before the men are permitted to return to work in the shaft. Electric blasting is recommended in shaft sinking. Adequate provisions should be made to protect the blasting circuits from being accidentally energized. Sectional switches should be used. Blasting circuits should not be grounded. If caps and fuse are used in shaft blasting, the hoisting engineer should be required to answer the blasting signal by raising the bucket a few inches and then lowering it. He should be prohibited from accepting any other signal of any kind until the men in the shaft have been hoisted to safety after receiving the blasting signal. 10 Harrington, D., and East, J. H., Jr., Safe Practices in Mine Hoisting: Bureau of Mines Miners' Circ. 61, 1946, 55 pp. CAGES, SKIPS, AND BUCKETS Cages and skips recently installed in at least two metal-mining districts of the United States are of aluminum-alloy construction; thus the weight of equipment has been materially decreased. Operational safety is increased because of lessened wear and tear on hoists, hoisting rope, sheaves, and shaft guides. Other installations have been designed where steel instead of wood guides are used in vertical shafts. The initial cost of steel-guide installation is greater than that for wood guides, but maintenance costs are less, and the effective stopping power of the cage and skip cams (safety catches), if rope fails, is greater than that usually noted where cage and skip cams engage wood guides. Cages for hoisting and lowering men should be of the safety type, with bonnets and four fully enclosed sides, strongly constructed of metal and equipped as follows: 1. Safety gates constructed of metal extending at least 5 feet above the floor. 2. Overhead or side bars that will provide each man with an easy and secure handhold. 3. Safety catches strong enough to hold the cage with its maximum load at any point in the shaft if the hoisting rope should break. 4. Provisions for signaling the hoisting engineer from within the cage at any point in the shaft. Although a completely enclosed man-cage is less hazardous than the 34-front enclosure in figure 10, a door to the height that will not |