| 摘要 |
An emergency shutdown check valve (10, Fig. 1) having a check plate (34) which pivots about an axis (40) to open and close a bore (18) through the valve housing (12) to limit fluid flow through the valve (10) to one direction only (from direction 14 to 16) during functioning as a check valve during which plate 34 occupies generally the figure 1 position. The check plate (34) can be lifted clear of the bore (18) by a plate-lifting mechanism (42 - 50) to the figure 2 position to allow bi-directional flow and/or the passage of a pig. In its raised position (Fig. 2), the check plate (34) can be latched up by a latch mechanism (52 - 66) whose operation requires constant pressurisation of a linear actuator (60). A built-in spring (68) biasses the latch mechanism (52 - 66) to a delatched state in which plate 34 falls through gravity, as a result of its displaced mass from pivot axis 40, to the figure 1 position to provide for automatic fail safe reversion to check valve functioning. The valve (10) is particularly applicable to the protection of submarine hydrocarbon pipelines and facilities connected thereto. <IMAGE>
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