| 摘要 |
Methods and apparatus for controlling fluid flow wherein, according to the methods, a pressure-actuated main valve is conditioned to operate by fluid pressure actuation of a pilot valve, which closes a fluid flow passage through the main valve so that the main valve may then be actuated by fluid pressure. The apparatus is a self-piloting check valve apparatus, disclosed in three embodiments, wherein dual valves are provided. One of the valves serves as a pilot valve and is shown in the form of a spring-biased check valve, closing of which permits closing of a main ball valve adapted to withstand highly elevated pressures. The sealing elements of the valve are fully protected during flow periods whereby fluid erosion is prevented. Full opening flow passages are provided through the valves in each embodiment of the apparatus.
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