| 摘要 |
<p>A "fire-safe" packing arrangement (104) for a valve stem (72) which extends through a packing chamber in a valve bonnet bore (42) to a valve chamber (50) in a valve body (12). The packing arrangement (104) comprises a low temperature packing assembly (112)positioned within the packing chamber between the stem (72) and the wall of the bonnet bore (42) for sealing therebetween at normal temperatures and resting on an inner annular shoulder (62) provided in the bonnet bore (42). A metal spacer ring (116) is positioned within the packing chamber axially outward of the low temperature packing assembly (112) with respect to the flow passage (18, 20) through the valve. The spacer ring (116) has a lower side or inner end (140) thereof resting on the low temperature packing assembly (112). The packing arrangement includes a high temperature packing assembly (114) positioned within the packing chamber between the stem (72) and the wall of the bonnet bore ( 42) and axially outward of the spacer ring (116) with respect to the flow passage (18, 20). The high temperature packing assembly (114) is sandwiched between the outer end portion (138) of the spacer ring (116) and a retainer (106) seated on an annular shoulder (58) provided in the bonnet bore (42). The high temperature packing seals between the stem (72) and the valve body (12) at above normal temperature conditions of the valve body (12) which are destructive of the low temperature packing assembly (112). The packing arrangement (104) effectively seals throughout the range of low and above normal temperatures without imposing frictional drag on the valve stem.</p> |
