An energy-absorbing device installed at the base of the elevator pit beneath the car and counterweight travel path to limit impact forces in the event of over-travel beyond the lowest landing.
Full Definition
Buffers are classified as energy-storage (spring or polyurethane pad) or energy-dissipation (oil-hydraulic). Spring buffers return energy after impact and are permitted for elevator speeds up to 1.0 m/s. Oil-hydraulic buffers absorb energy through controlled oil flow in a damper cylinder; they are required for speeds exceeding 1.0 m/s and are mandatory for all installations above this threshold under EN 81-20. The car buffer is sized for the car at rated load; the counterweight buffer for the counterweight mass. After buffer impact (a safety activation event) the buffer must be inspected and restored to its normal extended position before the elevator re-enters service. Hydraulic buffers have a minimum stroke calculated from the rated speed (≥stroke = v²/2 × 2 per EN 81-20) and must be reset after compression. Buffer condition (oil level, corrosion, clearances) is checked at every periodic maintenance visit.
