| 摘要 |
A valve unit for installation in a vent to atmosphere from an upper end of a shipboard storage tank for liquids. The valve has a housing with a closure seat, a normally open closure member, and an actuator for automatically closing the closure member against the seat to prevent the passage of liquids out from the tank if and when the ship sinks. The actuator includes a sealed reference chamber and a restricted orifice leading into a housing surrounding the sealed chamber, so that if the ship sinks, water enters the orifice, fills the housing around the sealed chamber and exerts pressure substantially greater than that inside the sealed reference chamber. A trigger is actuated by movement resulting from the pressure in the housing exceeding that inside the reference chamber. The invention also provides for a safety by-pass. A by-pass conduit leads around the closure seat, and a relief valve in the by-pass conduit opens only when the pressure in the main valve, i.e., below the closure seat is a predetermined amount higher than the pressure in the vent conduit above the closure seat. The by-pass conduit is in a housing that is freely detachable from the valve housing and which is secured to it by a pivotally mounted locking clamp device. Detachment results in mechanical locking of the closure member against its seat and also enables salvage of the contents with either positive or negative pressure after the ship has sunk.
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