| 摘要 |
<p>A hydraulically powered triplex pump having at least three pumping units, each operable in a cycle including suction, precompression and discharge phases, with the cycles being out of phase with one another, whereby simultaneous performance of these functions results in a substantially constant pressure and flow of both the pumped fluid and the power fluid. Separate power and cycle control circuits, which may employ different fluids, are provided. Control valve assemblies, each including two sleeve valves communicating with a common chamber, are operated by the control circuit fluid to condition power circuit flow for various phases of the pumping cycle. Precompression valves, a fill valve and a dump valve are operated by the control circuit to provide additional conditioning of power circuit flow to provide the precompression phase and to correct for variations in pumping unit stroke length. A hydraulically operated shut off valve is employed to selectively isolate the multiplex pump from a source of pressurized power fluid. The power end of the pumping units include power cylinders which may be fluid interconnected at their rod ends so that operations in each power cylinder affect operations in the other cylinders.</p> |
