| 摘要 |
A passage (18) in the housing (1) runs between an inlet and outlet (5, 6) at opposite housing ends. A chamber (16) in the latter is connected to the passage and contains a plug (16) working against the housing via seals (3, 4), being moved between the open and shut positions by handle passing out of the housing through a passage (8). At the side of the seal (4) furthest from the inlet, the chamber (16) is connected to a system (14, 15) generating excess pressure in it. The plug can be ball-shaped, working against sealing rings on the inlet and outlet side. The space between the rings is supplied with the excess pressure, typically via a drilling (14) in the handle connected between an external pressure source and the housing chamber.
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