| 摘要 |
A subsea actuator and method is disclosed that includes all moving components mounted in a compact, concentric configuration. The subsea actuator is highly reliable and will operate at depth even with zero valve body cavity pressure. A preferably cup-shaped spring pusher is provided in telescoping relationship to the hydraulic chamber. A piston position indicator is provided which is connected externally to the hydraulic piston cylinder to avoid the possibility of hydraulic leaks due to the piston indicator. A manual override may be provided with a manual override indicator. The manual override indicator has a shorter travel length than the manual override operating stem to thereby reduce the overall length of the manual override assembly. The driving stem provides a removable connection to the hydraulic piston from the top of the actuator housing and a quick disconnect permits disconnection of the driving stem from the valve stem. In a preferred embodiment, upper and lower t-slot connections are utilized in the driving stem assembly. In a preferred embodiment, two back seat valves are removably secured to the driving stem to engage respective seats and provide additional sealing around the driving stem so as to prevent leakage between the valve chamber and actuator housing chamber. The high tension spring does not need to be removed to perform maintenance, and all wear items and seals are readily accessible. Change or replacement of the stem packing is made from the top of the bonnet to avoid dissasembling the bonnet to valve body connection. Pre-load bolts are used to adjustably preload the tension in the return spring. The height/weight of the actuator is significantly reduced as compared to prior art subsea valve actuators.
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