| 摘要 |
In accordance with the present invention, the bottom operable tank car valve assembly described in U.S. Pat. No. 3,981,481 is simplified and improved and a supplemental sealing arrangement is provided. In the improved design, the valve body includes a flange portion which is attached to a standard tank car universal flange and an inwardly extending circumferential portion upon which a valve closure seats in closed position. The valve closure includes a keeper which maintains a circumferential elastomeric seal in place engaging the closure. Clearance is provided between the closure operator, and the valve closure so that if the circumferential seal softens, melts or burns, the closure can move vertically downwardly relative to the closure operator, and the valve closure will engage the valve seat on the valve body in place of the circumferential seal, to substantially prevent escape of lading from the tank.
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