| 摘要 |
<p>A valve seat ring (20) for a ball or other plug valve comprises an annular body of elastomeric material having formed therein pressure relief passageways (28, 29) to enable excess fluid pressure generated, for example by heat from a fire, to be vented in the upstream direction. The pressure relief passageways extend completely through the valve seat between its front and rear faces and comprise two groups of passageways. The first group of passageways (28) are located adjacent the outer periphery of the seat (20). The passageways in the second group are located radially inwardly of those of the first group, and extend between the rear face of the seat and a curved sealing surface on the front face of the seat. The interior seat support surfaces in the valve housing have machined annular recesses (30) adjacent the central fluid passageway (22) of the valve assembly to facilitate lip flexure of the seats. The overall arrangement provides a bidirectional valve which seals on the downstream side only of the valve, and which relieves excess cavity pressure in the valve past the upstream seat. The seats may be provided with chamfered outer rear corners (31) to facilitate pressure operation at the upstream side of the valve under conditions of extremely rapid cavity pressure generation.</p> |
