Frequently Asked Questions — Elevator Safety Gears / Clamps
What is the difference between progressive and instantaneous safety gears?
Instantaneous safety gears engage abruptly, gripping the guide rail with a rigid jaw or rollers, producing a rapid stop with high deceleration forces — acceptable at speeds up to 0.63 m/s per EN 81-20. Progressive safety gears use a brake mechanism that produces a controlled, graduated stopping force within defined deceleration limits (between 0.2g and 1g), making them suitable and required for rated speeds above 1 m/s. At intermediate speeds (0.63–1 m/s), either type may be used if the deceleration requirements are met.
How are safety gears triggered?
Safety gears are triggered by the overspeed governor — a centrifugally-operated device mounted in the machine room or hoistway that trips at a defined overspeed threshold (typically 115% of rated speed for the car gear, and higher for counterweight devices). The governor activates a mechanical linkage — the governor rope and tension device — which engages the safety gear jaws against the guide rail. Some systems also include electrical contacts that cut the safety circuit before or upon gear engagement, initiating a controlled stop.
When should safety gears be tested and serviced?
EN 81-20 and TS EN 13015 require safety gear testing during initial commissioning, after any modification to the suspension system, and as part of the periodic mandatory inspection programme. In Turkey, authorized inspection bodies test safety gear operation at defined intervals, typically every 5 years for commercial elevators. The sliding guide shoes and gear jaw surfaces must be inspected and lubricated (or de-lubricated, as some designs require dry contact) at each maintenance visit.
Can safety gears be retrofitted or upgraded during modernization?
Yes — safety gear replacement is common during modernization, particularly when upgrading to higher speeds, changing the guide rail profile, or when the existing gear has reached end of service life. The replacement gear must be rated for the new speed and load conditions and compatible with the existing governor rope pull force. A new type examination certificate and commissioning test is required after installation.