| 摘要 |
<p>The valve comprises a hollow body (1) connected (2,3) at either end to the piping, and containing a transverse partition (4) with a central hole (5). Fitted in this hole is a shut-off spool (8) movable parallel to the fluid flow through the valve between a shut-off position when a portion (15) contacts a fixed area (16) on the partition surface, and an open position when the shut-off is moved away. The shut-off terminates in identical pistons (11,12) operating in chambers (13,14) situated coaxially on the valve body and are isolated from the core of the valve. The valve is normally held off its seat by pressure introduced into the chamber via a pilot valve, which when released allows the spool to close the flow by spring (19) action.</p> |
