| 摘要 |
The disclosure is directed to a seal forming means in a valve plug for use in a fluid control valve, particularly in high temperature and high pressure fluid applications. The valve plug of the invention generally comprises a main valve plug member and a seal forming member associated therewith. The seal forming member is axially aligned with the main valve plug member and includes an outer wall having a surface that is coincident with an imaginary surface extension of the outer surface of the main valve plug. The seal forming member comprises a durable material having predetermined resilient characteristics, whereby said seal forming member is resiliently compressible within a predetermined range of compression. Moreover, the seal forming member includes an interior space and a finite section of minimum wall thickness formed in the outer wall. A packing material is tightly received and compressed within said interior space and, means are provided for compressing the seal forming member upon valve shut off. In this manner, the seal forming member is resiliently compressed within its predetermined range of compression to thereby compress and urge the packing material toward the finite section of minimum wall thickness of the outer wall. Upon a predetermined amount of compression, the packing material will exert a pressure sufficient to resiliently deform the outer wall into an outwardly extending bulge formation, which bulge formation is arranged to contact the control valve to thereby form a leak tight seal around the valve plug.
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