Wire Rope and Sheave Wear on a Freight Elevator
A 15-year-old freight elevator in a warehouse has a 4,000 lb capacity, 100 fpm, geared traction machine, four 5/8-inch 6x19 IWRC suspension ropes, and a counterweight. The annual inspection finds: rope A has three broken wires in one strand within one lay and several valley breaks; rope B has one broken wire; rope C shows heavy corrosion and a diameter of 0.605 inch; rope D looks clean. The traction sheave grooves show visible wear and the ropes are not seated uniformly. The building runs two shifts, and the owner wants to replace only rope A to avoid downtime. The mechanic has a rope gauge and a caliper but no magnetic flux detector on site.
1. How would you evaluate the rope findings against replacement criteria, and why is broken-wire count alone not enough?
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The rope condition must be judged against the adopted code and the rope manufacturer's criteria, using distribution, type, and location of defects rather than a single count. Rope A has broken wires concentrated in one strand plus valley breaks; valley breaks and strand concentration are more serious than isolated crown breaks because they indicate internal fatigue. Rope C has heavy corrosion and a measured diameter below the nominal 5/8 inch, which is a separate condemnation concern because corrosion and diameter loss reduce strength. Rope B's single broken wire may not alone condemn the rope, but it must be evaluated with the rest of the set. Rope D looking clean does not prove it is acceptable. The worn and non-uniform sheave grooves mean the ropes are not sharing load equally, so replacing only rope A would put a new rope against worn grooves and uneven tension. The mechanic should recommend evaluating the entire rope and sheave system, not just the worst rope.
2. What additional measurements and inspections would you perform before making a recommendation?
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Measure each rope diameter at several points along its length, including at the most worn section, and compare it with the nominal diameter and the code's rejection limit. Measure lay length and check for unusual stretch or uneven lay. Inspect the full length of each rope, especially over the sheaves and at end connections, and record broken-wire locations by rope, lay, and strand. Check rope tension and equalization, since unequal tension accelerates wear on the tightest rope. Inspect the traction sheave groove profile and the deflector sheave grooves for wear, and compare rope seating across all four grooves. Check the counterweight guide shoes, rope attachments, and shackle rods. If a magnetic flux detector is not on site, arrange a nondestructive examination or have a qualified inspector perform one. The goal is to determine whether the problem is isolated to one rope or is a system-wide wear condition.
3. What recommendation and documentation would you give the owner, including downtime and safety?
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Recommend replacing all four suspension ropes as a set and correcting the sheave condition before returning the elevator to freight service. Replacing only rope A is not acceptable because the new rope would run on worn, non-uniform grooves and would not match the stretch and tension of the old ropes. The sheave should be inspected and re-machined or replaced according to the manufacturer's limits; new ropes on a worn sheave will wear rapidly and may not seat properly. Plan the downtime around the two-shift schedule and provide a written scope that includes rope replacement, sheave evaluation, tensioning, and load testing. Document the inspection findings, measurements, photographs, and the basis for condemning the set. The owner should be told that the elevator must remain out of service until the work is complete and the installation is tested. This is a strength and safety issue, not a maintenance preference.