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Posted by: Norrie on 2008-10-23, 15:21:50
The cylinder of a double acting pump is fitted with Suction and Discharge valves at each end. On the 'Forward' stroke of the piston, the discharge valve at the forward end opens and the suction valve closes. At the same time, the Suction valve at the other (rear) end opens and the Discharge valve closes. The piston forward stroke is now discharging fluid at the forward end and pulling in fluid behind the piston at the rear end. On the return (Back) stroke, the valves reverse their operation and the forward end now takes in fluid with the discharge closed. At the rear end, the discharge has opened and the suction has closed. (The valves are like spring loaded 'Non-return Valves' (also called 'Check Valves) and operate against the springs by the ΔP between the suction and discharge pressures. This reciprocating action provides a smoother (less pulsating) discharge flow and pressure. This type of pump, as you have in your question is a 'Double Acting 'Duplex' Reciprocating' piston pump. (Piston pumps can have single or multiple cylinders depending on the requirements. (Single acting Simplex with a single cylinder; Double acting Simplex with 2 Cylinders; Single acting Duplex (and Double acting Duplex as above. Triplex and more are also available). Unfortunately, sketches are not possible in 'Answers'. When training Nationals in the Sahara, I wrote a number of basic booklets for their use which included one on types of pumps and their operation together with notes on Bearings, Seals and Lubrication...with full colour diagrams. You are welcome to e-mail me and I can send you a copy in Adobe pdf format (No charge). |
