The Dresser Excess Flow Valve (EFV) is a device that automatically limits the flow of gas when a condition of excess flow occurs.  It is generally used for residential natural gas service lines to minimize escaping gas in the event of third party damage and other types of line ruptures. Dresser Excess Flow Valves offer simplicity of design with only two moving parts - the poppet and the spring. EFV's reset automatically so there’s no need to excavate or manually re-pressurize line. Dresser EFV's are 100% production-tested per ASTM F1802 test methods assuring trip and bypass flow rates per CFR Title 49 D.O.T.192.381, MSS-SP-115 and ASTM F2138 governing standards