| 摘要 |
<p>PURPOSE: To flow a fluid to a valve chamber side through a seal part without damaging an elastic seal member by providing a releasable actuating device reducing contact pressure of a secondary seal loaded on a gate by a secondary seal assembly. CONSTITUTION: A secondary seal assembly structure can relieve contact pressure of a secondary seal at the time of opening and closing of a gate 15, and the pressure relief device is provided with a spring member 40 arranged between a seal support ring 31 and a space ring 38. The spring member 40 is allowed to have a spring constant selected in consideration of fluid pressure, so that when a seal retaining body 36 is pressurized and contacted on the gate 15 to form the secondary seal, a suitable contact pressure is continually kept between the seal retaining body 36 and the gate 15. However, when pressure more than a prescribed degree is applied on the seal retaining body 36 by the fluid pressure of an upper stream side (a flow path 26 side), the spring member 40 is compressed, and if largely compressed, the seal retaining body 36 is separated from the gate 15 to prevent the breakdown of an elastic seal member 36a.</p> |
