Emergency Shutdown System

The CNG station Emergency Shutdown (ESD) System uses fail safe closed valves, strategically located to shut off gas flow in an upset scenario.

The ESD valves are located in piping systems near pressure vessels, compressor suction and discharge lines, and inside CNG dispensers. Most ESD valves use either pneumatic, spring return operators or spring return electric solenoid actuators.

The means of initiating valve closure include:

  • Loss of electric power
  • Manually depressing ESD push buttons located in various station locations
  • Seismic activity detection devices
  • Proximity or limit switch devices sensing motion of impacted equipment
  • Vibration sensing equipment
  • Gas, fire and heat detectors
  • Loss of pneumatic control pressures from plastic air line ruptures caused by fire.