| 摘要 |
The housing (12) of a valve is internally provided with a valve cavity- to-throughbore bypass conduit (62) on its upstream side. A relatively vulnerably-placed body (134) of heat- activated material normally forces a bypass valve (93) to close this conduit. In the event of a fire in the vicinity of the protected valve, the heat-activated body (134) loses its forcing capability and the bypass valve (93) opens, moving off a first metal- to-metal seat (78) and making a second metal-to-metal back seat (98). Any fluid that had previously leaked from the throughbore (14) of the protected valve into the valve cavity (23) may then pass to the upstream side of the protected valve, instead of becoming dangerously highly pressurized in the valve cavity. <IMAGE> |
