| 摘要 |
Apparatus for hydraulic control of a stack of subsea operators using only a pair of hydraulic pressure lines (28,35) includes a rotary actuator (17) movable by hydraulic operation to a plurality of positions corresponding to different states of operation of valves (18-24) contained in the operators. In particular the actuator is hydraulically stepped through a series of positions and automatically reversed by mechanical means at each end of the series.
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