VALVE WITH HEAT RESPONSIVE BEARING ASSEMBLY PROVIDING BACK SEAT ARRANGEMENT

摘要

The bearing assembly of a normally non-rising stem gate valve is provided with an annulus of fusible material. Upon subjection to a preselected temperature level, the fusible body melts out of the way, permitting the stem to raise slightly, making up a metal-to-metal seal between the valve stem and bonnet. This forms another line of defense against consequences from loss of the sealing normally provided by the valve stem packing.