초록 ▼

An improved heat responsive backseat for gate valves which includes a rotating valve stem (50) carried by a bonnet assembly (14) for actuation of a gate member (40). A fusible stem ring (126) supports the valve stem at an outer portion thereof (68) within a roller bearing chamber (56) of the bonnet

An improved heat responsive backseat for gate valves which includes a rotating valve stem (50) carried by a bonnet assembly (14) for actuation of a gate member (40). A fusible stem ring (126) supports the valve stem at an outer portion thereof (68) within a roller bearing chamber (56) of the bonnet assembly. The valve stem (50) moves axially outward from the valve chamber (20) when the fusible stem ring (126) melts due to an external fire condition to bring a valve stem backseat portion (64) into sealing engagement with a bonnet seat portion (54). The valve stem (50) moves axially outward from the valve chamber (20) independently of roller bearings (74, 76) contained within roller bearing chamber (56) such that the roller bearings (74, 76) remain axially fixed with respect to the bonnet assembly before, during and after the shifting of the valve stem. Therefore, the valve stem may be easily rotated after the fire condition has been extinguished without the occurrence of cocking or wedging between the bearing means and valve stem. Accordingly, a secondary metal-to-metal seal is provided between the valve stem (50) and bonnet assembly (14) such that if the primary packing (104) is destroyed by the fire condition the gate valve will not leak flowline fluid exteriorly of the gate valve.

대표청구항 ▼

A gate value comprising: a valve body having an open ended valve chamber and inlet and outlet fluid passages communicating with the valve chamber, a valve seat positioned about each said inlet and outlet fluid passages adjacent the valve chamber; a bonnet assembly forming a closure for the valve cha

A gate value comprising: a valve body having an open ended valve chamber and inlet and outlet fluid passages communicating with the valve chamber, a valve seat positioned about each said inlet and outlet fluid passages adjacent the valve chamber; a bonnet assembly forming a closure for the valve chamber and having a central bore therein communicating with the valve chamber, the central bore having a seat portion facing in a direction toward the valve chamber and an enlarged diameter bore portion axially spaced from the seat portion in a direction away from the valve body; an axially rotatable non-rising valve stem carried within the central bore of the bonnet assembly and having a threaded end section extending into the valve chamber, a backseat portion facing toward the bonnet assembly and positioned in a normally spaced relationship to the seat portion of the bonnet assembly, and a valve stem shoulder positioned within the enlarged diameter bore portion facing in an upwardly direction away from the valve chamber; packing means positionable within the central bore of the bonnet assembly between the seat portion and enlarged diameter bore portion surrounding the valve stem for sealing between the valve stem and bonnet assembly; a gate member disposed in the valve chamber and movable between open and closed positions relative to the fluid passages to control fluid flow through the valve, the gate member having an externally threaded extension with a longitudinal bore therein for receiving the threaded end section of the valve stem; a stem connection means positioned in the valve chamber for providing a connection between the threaded end section of the valve stem and the gate member extension, the stem connection means translating rotational movement of the valve stem into longitudinal movement of the gate member; roller bearing means including an upper roller bearing and a lower roller bearing separated by a spacer positioned in an axially fixed relationship within the enlarged bore portion of the central bonnet assembly bore for supporting and providing for axial rotation of the valve stem within the gate valve, the roller bearing means further including a key positioned between the valve stem and spacer for rotationally fixing the valve stem to the spacer such that upon rotation of the valve stem, the spacer rotates between the upper and lower bearings; and a fusible stem spacing element of a preselected temperature degradable material positioned between the upper roller bearing and lower roller bearing, the spacing element acting as a spacer separating the upwardly facing valve stem shoulder and a portion of the axially fixed roller bearing means for normally maintaining the valve stem in a fixed axial position relative to the bonnet assembly and normally maintaining the upwardly facing valve stem backseat portion in a spaced relationship to the downwardly facing bonnet seat portion, the fusible stem spacing element being adapted to relax its spacing function upon reaching the preselected temperature condition so that the valve stem is allowed freedom to move axially upward to a limited extent relative to the upper and lower roller bearings and the bonnet assembly allowing the valve stem backseat portion to sealingly contact the bonnet seat portion to provide a secondary metal-to-metal seal between the valve stem and bonnet assembly in a fire situation, the upper roller bearing and lower roller bearing remaining in a fixed axial position relative to the bonnet assembly before, during and after shifting of the valve stem so that rotation of the valve stem after the fire situation has been extinguished will not be affected such that the gate member may continue to be easily opened or closed with respect to the inlet and outlet fluid passages.