Patent ID: 7575016

Claim:
A system disconnector for physically disconnecting an upstream liquid system having an inlet pressure from a downstream liquid system having an outlet pressure with a pressure drop between said upstream and said downstream system and thereby generating a flow from said upstream towards said downstream liquid system, said system disconnector comprising a casing, an upstream backflow preventer ( 40 ), said inlet pressure occurring upstream from said upstream backflow preventer ( 40 ), a downstream backflow preventer ( 64 ), said outlet pressure occurring downstream of said downstream backflow preventer ( 64 ), a release valve ( 34 ) with a valve seat ( 32 ) and an opening and a closing direction, said release valve ( 34 ) being adapted to disconnect in response to said pressure drop between said upstream and said downstream liquid system and comprising a release valve body ( 18 ) in the form of a piston which is, regarding said flow, arranged between said backflow preventers ( 40 , 64 ), and has an effective pressurized surface (d), a middle pressure space ( 66 ) between said release valve body ( 18 ) and said downstream backflow preventer ( 64 ) with a middle pressure, a spring ( 60 ) biasing said release valve body in said opening direction and counteracting a pressure difference between said inlet pressure and said middle pressure, a hollow space ( 74 ) connected to the middle pressure space ( 66 ) and defined between said release valve body ( 18 ) and said casing, wherein said effective pressurised surface (d) of said release valve body ( 18 ) is smaller than said surface effective for said inlet pressure, and wherein a shiftable seat ( 76 ) is provided in said hollow space ( 74 ) which is adapted to be moved in said opening or closing direction of said release valve body, a casing fixed stop ( 84 ) is provided upstream of said valve seat ( 32 ) in said casing said shiftable seat movable with respect to said release valve body up to said casing fixed stop ( 84 ).