| 摘要 |
<p>A valve unit for permitting or preventing communication between two pipelines, wherein two coaxially arranged valve members (22, 24) are mounted for guided movement towards and away from a valve seat (12) having opposed seating surfaces against which the valve members are urged closed by the product pressures in the respective pipelines and cylinder/piston sub-assembly (40) is operative for simultaneously opening the valve at both seating surfaces in order to put the pipelines into communication.</p> |
