| 摘要 |
The apparatus includes upstream and downstream check valve assemblies 13, 14 with a zone 15 between them, a relief valve 16 venting the zone 15 to atmosphere under predetermined pressure conditions. The upstream check valve assembly has a valve poppet 28 urged towards a valve seat 25 by a spring 33, said spring acting to create a pressure drop through the upstream check valve assembly when said valve poppet is initially moved away from said seat by fluid pressure in the inlet passage 17. An aspirator means 44 receiving fluid from said inlet when said valve poppet has separated from said valve seat acts to reduce the pressure in a chamber 53 to oppose the action of said spring 33 to thereby reduce the pressure drop across the upstream check valve assembly when full flow takes place. <IMAGE> |
