Elevator Compensation Chain: Rope Weight Imbalance, Chain vs Tension Pulley Rope, EN 81-20 and Pit Snubber

On high-rise elevator installations, the weight of the suspension ropes themselves (typically 3–6 ropes × 20–60 m × rope weight per metre) becomes significant relative to the rated load — up to 15–20% of the rated load weight difference. As the car travels from the bottom to the top landing, the rope weight shifts from the car side to the counterweight side, creating an increasing imbalance. Compensation systems: (1) Compensation chain — steel link chain suspended from the car sling at the bottom and from the counterweight at the bottom, hung in a U-shape below both; provides mass compensation but produces noise at speed; used at speeds up to ~2 m/s; (2) Compensation rope with tension pulley — quieter alternative for higher speeds (>2 m/s); a separate set of ropes (smaller diameter than suspension ropes) runs between the car bottom and counterweight bottom, guided by a tensioning sheave at the pit; (3) Compensating cable — used in some MRL designs. EN 81-20 requires compensation for any installation where the rope weight difference between the car and counterweight sides exceeds a specified threshold. Compensation also applies to the trailing cable (travelling cable) weight if the installation is very tall. At the pit, a snubber device prevents the compensation chain from flying up during safety gear actuation.

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