What does an elevator speed governor do?

It continuously measures car speed through a rope-driven sheave. At overspeed it first opens an electrical contact to drop the drive and apply the machine brake, and if the car keeps accelerating it grips the governor rope so the safety gear clamps the car to the rails.

At what speed does an elevator governor trip?

Under EN 81-20 the mechanical trip occurs at not less than 115% of rated speed. For instantaneous safety gear the trip speed must not exceed 0.8 m/s; progressive gear allows a higher, speed-dependent limit. The electrical contact must always open before the mechanical trip.

How often should an overspeed governor be tested?

The governor is trip-tested at commissioning and then at every statutory periodic inspection — annually in normal practice — together with a safety-gear drop test. The calibration seal must be intact; if it is broken the governor must be re-calibrated and re-certified.

What is the governor tension weight for?

The pit tension weight keeps the governor rope taut so the sheave turns at true car speed. Its frame carries a slack/broken-rope switch that stops the lift if the rope goes slack, breaks or stretches beyond the allowed travel.

Can a speed governor be repaired on site?

Only the rope, sheave bearings, switch and tension assembly are serviced on site. The trip mechanism itself is a sealed, type-tested certified component — if it fails or the seal is broken, it is replaced or returned for factory re-calibration.

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Parts · PRT-07

Elevator Safety Speed Governors

Overspeed governors with electrical trip and mechanical rope grip, calibrated and sealed to EN 81-20.

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DZ-XS24B elevator overspeed governor with sealed calibration plate and spring-loaded rope grip, supplied and trip-tested to EN 81-20 in Karachi, Lahore and Islamabad — PRT-07 · Elevator Safety Speed Governors

PRT-07

In short

An elevator speed governor is the safety device that detects car overspeed. It opens an electrical contact to cut the drive and brake circuit, and if the car continues to accelerate its mechanical jaws grip the governor rope, which pulls the safety-gear linkage and clamps the car onto the guide rails. Mechanical tripping must occur at no less than 115% of rated speed under EN 81-20.

Engineering overview

The overspeed governor is the sensing half of the elevator's fall-protection system. A governor rope, looped from the car safety-gear linkage over the governor sheave and down to a tension weight in the pit, spins the governor at car speed. When speed exceeds the set trip point, the governor first opens an electrical contact to drop the drive and brake, and if the car keeps accelerating it grips the rope mechanically to set the safety gear.

EN 81-20 fixes the trip window: the electrical contact opens before mechanical tripping, and mechanical tripping occurs at not less than 115% of rated speed and below the ceiling defined for the safety-gear type — 0.8 m/s for instantaneous gear, and a speed-dependent limit for progressive gear. Governors are factory-calibrated, sealed and stamped with the trip speed; a broken seal invalidates the certificate.

Liftech Global supplies governors matched to car speed and safety-gear type, plus the pit tension weight assembly with its slack/broken-rope switch, and performs the on-site overspeed trip test at commissioning and at every statutory re-test.

Types & variants

Uni-directional governor
Trips on downward overspeed only — standard for lifts without unintended-movement duty on the up direction.
Bi-directional governor
Trips in both directions; required where the safety gear also protects against upward overspeed (EN 81-20 §5.6.6).
Centrifugal flyweight type
Classic flyweight mechanism with adjustable sealed trip setting, 0.5–2.5 m/s.
High-speed governor
Damped flyweight design with reduced trip scatter for 2.5–4.0 m/s installations.
Remote-reset / electric-reset governor
Allows reset from the machine space after a trip, used in MRL installations.
Tension weight assembly
Pit-mounted sheave and weight with slack-rope and broken-rope safety switch.

Technical specifications

Rated speed range	0.5 – 4.0 m/s
Electrical trip	≥ 100% and before mechanical trip
Mechanical trip	≥ 115% of rated speed
Instantaneous gear ceiling	≤ 0.8 m/s trip speed
Governor rope	Ø 6 / 8 / 10 mm, 6×19 or 8×19 steel
Sheave diameter	200 / 240 / 320 mm
Rope safety factor	≥ 8 (EN 81-20 §5.6.2)
Gripping force	≥ 300 N or twice the force to set the safety gear
Calibration	Factory sealed and stamped; re-test at commissioning and annually