Oil Loss From Cylinder Causes Elevator to Shake and Drop

Incident Overview

A mechanical failure caused misalignment with the hydraulic system resulting in the elevator shaking and rapid but controlled decent.

Failure Scenario(s)

There was oil loss from one of the cylinders as a result of a deteriorated internal packing gland and uneven pressure due to a clogged check valve. The sensors, located within the system, detected that the pistons were not within the tolerances set by the manufacturer and proceeded to resync the jacks to ensure that both pistons were within equal positions. Resyncs usually occur at night but in this case it occurred during the day when there was an occupant in the elevator.

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