Patent ID: 8286937

Claim:
A valve ( 1 ) comprising a tubular housing ( 2 ) extending along an axis; a first valve seat ring ( 14 ) extending along said axis in said housing and movable in axial direction; a second valve seat ring ( 26 ) encircling said first valve seat ring and movable in axial direction; a valve closure member ( 39 ) axially movable toward and away from the valve seat rings ( 14 , 26 ) to close and open said valve seat rings ( 14 , 26 ); means for adjusting the axial position of the valve closure member ( 39 ) in said housing; and a locking arrangement ( 22 , 24 , 35 , 36 ) associated with the valve seat rings ( 14 , 26 ) in order to selectively lock said valve seat rings in a prespecified position.