What is the purpose of an elevator buffer?

A buffer sits in the pit under the car and counterweight and absorbs the kinetic energy of an overtravelling car, decelerating it within safe limits. It is the final mechanical protection after the terminal limit switches and the safety gear.

When is an oil hydraulic buffer required instead of a spring or PU buffer?

Energy-accumulation buffers — polyurethane and spring — are permitted up to 1.0 m/s, or 1.6 m/s if they have buffered return. Above that, EN 81-20 requires an energy-dissipation oil hydraulic buffer, which has no rated-speed ceiling.

How is buffer stroke calculated?

Stroke is derived from the impact speed (115% of rated speed for energy accumulation) and the permitted deceleration of 1 g average, with peaks up to 2.5 g for no longer than 0.04 s. Total mass of the car or counterweight sets the buffer capacity rating.

How often should elevator buffers be inspected?

Buffers are checked at every routine maintenance visit for corrosion, damage and correct alignment with the strike plate. Oil buffers additionally need oil-level checks, plunger-return switch testing and periodic oil replacement per the manufacturer's schedule.

What happens if the buffer oil level is low?

A low oil level reduces the buffer's energy absorption and can allow the plunger to bottom out. The oil-level indicator must be topped to the mark with the specified grade, and the plunger-return switch tested, before the lift is returned to service.

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Parts · PRT-09

Elevator Safety Buffers

Polyurethane, spring and oil-hydraulic buffers sized to rated speed and total mass.

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Aodepu OH-80 oil hydraulic elevator buffer with return spring, plunger-return switch and EN 81-50 qualification certificate, supplied by Liftech Global in Karachi Pakistan — PRT-09 · Elevator Safety Buffers

PRT-09

In short

An elevator buffer is a pit-mounted energy-absorbing device beneath the car and counterweight that stops them safely if they overtravel the lowest landing. Polyurethane and spring buffers (energy accumulation) are used up to 1.0 m/s, and oil-hydraulic buffers (energy dissipation) are required above 1.6 m/s.

Engineering overview

Buffers are the last line of protection in the pit. If the car or counterweight overtravels past the terminal limit, the buffer absorbs the kinetic energy and brings the mass to a controlled stop within a limited deceleration.

EN 81-20 splits them into energy-accumulation buffers — polyurethane and coil spring, permitted up to 1.0 m/s (1.6 m/s with buffered return) — and energy-dissipation oil-hydraulic buffers, which are mandatory above 1.6 m/s and have no speed ceiling. Oil buffers must carry a plunger-return switch and an oil-level indicator, and the lift must not restart until the plunger has fully returned.

Sizing is a calculation, not a stock pick: stroke follows from impact speed (115% of rated speed for energy accumulation) and the permitted deceleration — 1 g average with a maximum 2.5 g for no more than 0.04 s. Liftech Global supplies the buffer with its pedestal and pit channels, verifies pit depth and clearance, and issues the stroke calculation with the handover dossier.

Types & variants

Polyurethane (PU) buffer
Moulded cellular PU cone, maintenance-free, 0.3–1.0 m/s, home and low-rise lifts.
Coil spring buffer
Steel compression spring with guide tube, 0.5–1.0 m/s, common on freight and counterweight.
Oil hydraulic buffer
Orifice-damped plunger with return spring, plunger-return switch, 1.0–6.0 m/s.
Reduced-stroke oil buffer
Used with certified terminal-speed monitoring to shorten pit depth in tight retrofits.
Buffer pedestal and pit channels
Fabricated steel bases to align buffer height with the car and counterweight strike plates.

Technical specifications

PU / spring speed limit	≤ 1.0 m/s (1.6 m/s with buffered return)
Oil buffer speed	1.0 – 6.0 m/s (no upper limit by type)
Typical strokes	50 / 65 / 90 / 135 / 210 / 350 mm and up
Impact speed	115% of rated speed (energy accumulation)
Average deceleration	≤ 1 g
Peak deceleration	≤ 2.5 g for ≤ 0.04 s
Oil buffer switch	Plunger-return switch in safety circuit
Load range	500 – 12 000 kg total mass per buffer set
Type test	EN 81-50 §5.5 certified with data plate