| 摘要 |
A dual seal valve having a bubble-tight primary seal and a metal-to-metal secondary seal for sealing engagement with a rotating valve element. The primary seal is preferably a composite seal comprising a relatively hard, high lubricity element bonded to a relatively soft, resilient elastomeric element. The elastomeric element biases the hard element into sealing engagement with the valve element. Several embodiments of the primary seal are disclosed. Tapered inserts are positioned on opposite sides of the valve element, and a seal groove is provided on a tapered outer surface of the insert and adapted for receiving a seal therein. The groove has an enlarged portion which provides a seal relief, allowing deformation and unsealing disengagement of the seal when pressure thereon exceeds a predetermined level. While plug valve embodiments are disclosed, the dual seal arrangement and seal relief are also applicable to ball valves, spherical plug valves, and other valve types having rotating valve elements.
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