| 摘要 |
<p>@ An improved gate valve has a body (12) with an inlet (16) into the valve chamber (14) and an outlet (18) from the chamber. A gate (26) is disposed in the chamber. A bonnet (20) with an opening therethrough is secured to the body and a stem (34) connected to operate the gate extends through the bonnet opening. A seat (38) is provided in the bonnet, a shoulder (40) is formed on the stem and heat responsive means (58) hold the stem out of back seating position during normal operation and release to back seat in response to excess heat. Body bushings (30, 32) surround the inlet and outlet and seal against the gate, each of the bushings having resilient sealing means and a sealing lip for sealing against a sealing surface on said body.</p> |
