Line Pressure Operated (LPO) Surface Safety Systems are hydraulically operated flow line control valves, arranged to protect a facility from the effects of pipeline failures. The primary function of the Line Pressure Operated Surface Safety System is to detect any abnormal high or low flow line pressure deviations and respond to it, by shutting down the streamline.

This valve is an actuated gate valve controlled by hydraulic pressure fed from the pipeline stream, thus it is well-suited for remote unattended locations. LPO is normally closed, preventing the flow from the up stream to down stream, and it will open only if the pressure amount of the upstream side falls within a specific pressure range. This pressure range is defined by two pressure sensors, one for high pressure sensing (High Pressure Pilot) and one for low pressure sensing (Low Pressure Pilot).

Each pilot has its own technical function and its set pressure knob.