Maintenance ROPING ESSENTIALS

All hoist ropes are lubricated during the manufacturing process. The core is fibre or nylon to which lubricant is applied to make the internal wires smooth; this prevents entry of moisture and protects the rope against corrosion and rust while in use. Head ropes for friction hoists are dressed with a special lubricant which provides extra corrosion protection and reduction in slippage. It is impossible to introduce lubricant into the core after the rope has been in service because the lubricant cannot migrate through the interstices to the core. Ropes should be stored in a clean dry indoor area and the reels should be rotated periodically to prevent leakage of the internal lubricant.

At installation, the rope surface is lubricated and, from time to time, dry sections are redressed. The frequency depends on shaft and winding conditions. When dressing friction hoist ropes, the lubricant must be applied in limited amounts to prevent slippage on the wheel. With balance ropes, the dressing can only be done in the lower area of the shaft where there must be easy access, good lighting and some form of headcover to protect workers from falling objects.

All ropes, while in service, must be inspected daily for broken wires and deformities throughout their working length. At the same time, the quality of lubrication can be checked.

The ropes are tested electromagnetically six months after installation and every four months thereafter. Additional tests are made if the degree of deterioration warrants. The results indicate the approximate breaking strength remaining. They are compared to the destructive tests that are made every six months at the government rope test laboratory. Balance rope and guide rope testing frequencies vary.

On drum hoists, the rope is cut above the clamps every six months, and an 8-ft test piece is taken. The wires are subjected to bending tests to determine the quality of the rope after which the piece is discarded. After 18 months, another piece is removed and sent to the government laboratory for a complete analysis. The breaking load is compared with the result when the rope was manufactured.

Hoist ropes are discarded when the number of broken wires in one lay length reaches 5% of the total number of wires in the rope (for example, six wires in 6×19 round strand construction); the breaking strength falls to 90% of the original; the extension of the test pieces falls to 60% of the original; and the electromagnetic test indicates a 10% loss of strength.

Each time rope test pieces are taken, the U-bolt clamps are examined before re-use. Periodically, they are given a non-destructive test to expose flaws. In practice, the attachment is never in place more than six months at one time. The same regulation applies to the wedge-type cappels and spelter sockets when used for drum hoist terminations.

On friction hoists, the cappels must be dismantled every six months, and the part of the rope within the wedge must be examined for broken wires. After 18 months, the position of the rope within the wedge must be moved by cutting off a short section at the safety socket. Cappels and sockets are given ultrasonic or magnetic particle tests and discarded if found defective.

A problem common to stranded ropes, particularly high-tensile ropes, is torque buildup. This is evident in flattened strand ropes where the strands tend to turn and will feel sharp to the touch.

Another indicator is the early appearance of broken wires. Ultra- high tensile wire is susceptible to this. To release torque, the conveyance is banked at the collar, the thimble pin is removed, and the rope is allowed to spin out under control until it goes dead. A special clamp on the rope is needed to prevent it from lashing about when it is first disconnected.

Ropes that are wound on more than two layers on the hoist drum will wear at the dead turns and at the crossovers. The position of the wear points are changed by removing a small section of the rope at the drum end. When rewinding the rope on to the drum, it should be under enough tension to prevent movement of the dead turns during hoist operation.