A valve in hydraulic elevator oil circuits that automatically closes upon detection of seismic activity above a threshold level, preventing uncontrolled car movement during an earthquake.
Full Definition
The seismic shutoff valve is a safety device in hydraulic elevator installations in seismic zones that detects ground motion acceleration exceeding a set threshold and automatically closes the hydraulic circuit to prevent uncontrolled car movement due to earthquake-induced pipe failure or pump malfunction. Upon seismic detection, the valve closes, stopping car movement and holding the car at its current position. The elevator remains out of service until inspected by a qualified engineer who manually resets the valve and verifies hydraulic system integrity. Some advanced seismic shutoff valves also trigger a preferential landing sequence to bring the car to the nearest floor before closing. Compliance with ASME A17.1 Section 8.4 or equivalent national standards is required in designated seismic zones.
