| 摘要 |
<p>A shut-off device (1) of the double block-and-bleed type comprising a flow passageway (3) accommodating two shut-off members (26,46) provided with through cavities, and a drain means (11). The flow passageway (3) is provided with an inlet (4) and an outlet (5). Each of the shut-off members may be moved between a position in which the flow passageway (3) is open and a position in which the flow passageway (3) is closed. In association with the shut-off members (26,46) two auxiliary chambers (29,49) are communicating with cavities (27,47) of the shut-off members. The chambers 29,49 are formed between faces 33,53 of the casing and body portions 35,55 abutting the faces 33,53. Vents (33,54, figure 3) extend between the flow passageway 3 and the faces 33,53. Excess pressure in the cavities 27,47 may cause the body portions 35,55 to lift slightly off their abutment faces allowing fluid to pass into the vents 33,54. The shut-off device is formed of a single undivided casing (2). The shut-off members (26,46) are truncated cone-shaped and mounted in matching truncated cone-shaped recesses (28,48,68,88) in the common casing (2). As a result, the overall length of the shut-off device may be reduced compared to prior art. Moreover, the tightness at high pressure, e.g. above 100 ato. is enhanced.</p> |
