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Difference Between Powered Pumps And Positive Displacement Pumps
- Dec 06, 2016 -

Power pump main features are: ① must pump in the lift generated by a certain speed limit. Work flow and shaft power depends on the system and the pump connection (error, pressure differential and piping losses). Head change with the flow (Figure 2). Work stability, conveying a continuous, flow, and pressure pulsation-free. ③ without self-absorption capacity, you will need to pump to fill liquid or pipeline vacuum before beginning work. ④ pump discharge pipe valve closed position start, Vortex pumps and axial-flow pump starts under the valve fully open, in order to reduce the starting power. ⑤ suitable for high-speed motor and turbine of centrifugal pump, direct drive, simple structure, low cost, easy maintenance. ⑥ applicability to a wide range of centrifugal flow from a few to hundreds of thousands of m 3/h, head from a few meters to thousands of meters generally applies to a large flow of axial flow pump with low head (20 meters). Centrifugal and axial-flow pump efficiency below 80%, high up to 90%. ⑦ suitable for conveying clean liquid viscosity is very small (for example, water), specially designed pump can transfer slurry, sewage or water to solids. Power pump is mainly used for water supply, drainage, irrigation, process, liquid transfer, power storage, hydraulic and marine jet propulsion.

Positive displacement pump features: ① must pump at a certain speed or flow under reciprocation number of times is certain, almost no change over pressure. Working pressure system connecting with the pump and shaft power depends on the situation, so when the pump is in the discharge pipe through (the equivalent resistance is infinite) under operation, and shaft power will increase its pressure to the pump or motor damage, so you must set the relief valve to protect the pump (direct steam or compressed air-driven pump). ② the flow and pressure of reciprocating pumps have a greater pulse fluctuation mitigation measures need to be taken; Rotary pump pulsation-free or only small ripples. ③ with self-priming capacity, immediately after the pump starts pumping air into the liquid in the pipe. ④ When starting the pump discharge pipe valves must be fully open. ⑤ reciprocating pump is a low-speed machines, large size, manufacture and installation costs; Rotary pump speed is higher, up to 3000 rpm. ⑥ reciprocating pump for high pressure (up to 350 MPA) and low flow (100.3-meter/hour); Rotary pump for small and medium flow (400.3-meter/h) and high pressure (35 MPA). In General, the positive displacement pump efficiency is higher than the power pump and high efficiency efficiency curve wider. Reciprocating pump efficiency is generally 70~85%, high above 90%. ⑦ reciprocating pumps are suitable for cleaning liquid or vapor-liquid mixture, some pumps are diaphragm pumps for slurry, sewage and other, mainly used to supply high pressure liquid source and water supply, metering and delivery. Rotary pumps are suitable for lubrication of clear liquids, and liquid-gas mixture, especially high viscosity liquid, mainly for oil, food and liquid delivery and hydraulic transmission.