Stop Distance Out of Tolerance After Governor Rope Replacement
A maintenance crew replaces the governor rope on a 1,600 lb (725 kg) geared traction passenger elevator in a six-story office building. Rated speed is 350 fpm (1.78 m/s). After reassembly the mechanic runs the car at rated speed and trips the governor by hand while the car is descending. The measured stopping distance from the point of governor trip to full stop is 71 in (1,800 mm). The car is empty. The mechanic also notices the governor rope tension sheave at the pit does not move freely and the rope has visible slack. The building manager needs the car back in service the same afternoon. The mechanic has the original acceptance test record showing a prior measured stop of 44 in (1,120 mm) with the same machine and brake.
1. How should the mechanic interpret the 71 in (1,800 mm) result, and what does the change from the prior 44 in (1,120 mm) record tell you?
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The first step is to recognize that the result is a change against a documented baseline, not an isolated number. A stop that grew from 44 in to 71 in on the same machine and brake points to a change in the stopping system rather than normal wear scatter. Three candidate causes should be separated:
- Governor rope tension. The tension sheave is not free and the rope is slack. A slack governor rope can let the governor jaw grip late or unevenly, and the tension sheave is what keeps the rope taut enough for the governor to act predictably. This is a mechanical defect that must be corrected before any retest is meaningful.
- Brake condition. The brake may be contributing, but the prior record was taken with the same brake, so brake wear alone does not explain a 27 in increase unless something changed in adjustment or lining.
- Test method. Confirm the trip was made at rated speed with the car descending and that the measurement point is consistent with the prior record.
The mechanic should not sign the car back into service on the strength of a single out-of-family number. The correct judgement is: fix the tension sheave and rope slack first, re-run the test under the same conditions as the baseline, and compare against the baseline again. If the stop remains well above the prior value, escalate to a full brake and governor inspection before returning the car to service.
2. The building manager pressures the mechanic to put the car back in service because 'it still stops.' What is the defensible position, and what documentation should exist before the car carries passengers again?
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'It still stops' is not the standard. The relevant question is whether the stopping means is functioning as designed under the code requirements that apply to this unit, and the mechanic has affirmative evidence that it is not behaving as it did at acceptance. The defensible position is:
- The car stays out of service until the governor rope tension and slack are corrected and the stop is re-measured under repeatable conditions.
- The retest must reproduce the original test conditions (rated speed, descending, same measurement definition) so the comparison is valid.
- If the corrected stop is still materially above the baseline, the brake and governor get a full inspection before release.
Documentation before return to service should include: the defect found (tension sheave binding, rope slack), the corrective action taken, the retest speed and direction, the measured stop distance, and the comparison to the prior acceptance value. The mechanic's signature on the return-to-service record is the accountability point; a verbal assurance to the manager is not a substitute.