| 摘要 |
A top entry trunnion ball valve is provided having a valve body forming seat recesses (76, 78) with seat members (92, 94) movable disposed therein and urged towards sealing engagement with a spherical valve member (22) by spring members (126, 128) and by differential pressure induced force. A seat retractor mechanism is movably disposed within the valve body and is movable by an externally controlled tool into retracting engagement with the seat members (92, 94). The seat members and the seat retractor element have cooperative cam surfaces (162, 164, 166) that cause camming movement of the seat members away from the valve member upon linear movement of the seat retractor. Upper and lower portions of the seats may be subect to simultaneous camming activity. The valve member defines a face-to-face dimension smaller than the diameter of the spherical surface thereof and the seat retractor is capable of moving the seat members to a spaced relation slightly greater than the face-to-face dimension of the valve member. This permits the valve member to be removed when the seat members are retracted. A rotatable actuator stem member (50) supported by the bonnet (26) closure of the valve has interengaging driving relation with a trunnion member (46) of the valve element and is orientated so that the stem member (50) is not subjected to side thrust forces upon rotation of the valve member or in its closed position. A fire safe seal and spring chamber (124, 125) is in communication with a relief passage having volumetric closure plugs (150, 152) permitting introduction of solvent or other softening agent into the spring chambers for removal of any accumulation of foreign material therein. |
