Double-seat valve

Claim 1

A double-seat valve, comprising a housing, a movable shaft; means forming a first and second valve seat in said housing; one valve member fixedly mounted on said shaft in one mounting point; another valve member fixedly mounted also on said shaft in another mounting point and having a sealing element which forms a seating face arranged to abut against said first valve seat when said shaft together with said valve members moves to a closed position and to be lifted from said first valve seat when said shaft together with said valve members moves to an open position of the valve, said other valve member being movable independently of and relative to said one valve member and being variable so that said seating face of said other valve member is displaceable relative to the other mounting point and abuts against said one valve member to thereby form a hollow chamber between said valve members, said sealing element of said other valve member being so deformable that after a predetermined stroke of said other valve member in one direction, said seating face of said other valve member first abuts against said one valve member to thereby form said hollow chamber between said valve members, and thereafter said other valve member and said one valve member are lifted from said first and second valve seat respectively; and a draining conduit communicating with said hollow chamber prior to the valve members being lifted toward said open position so that fluid leaking into said chamber flows out of the latter outwardly of the valve.