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What is a reciprocating pump

What is a reciprocating pump?

Reciprocating pump includes piston pump, metering pump and diaphragm pump, commonly known as reciprocating pump. It is a kind of positive displacement pump, which is widely used. Reciprocating pump is a conveying machine that directly provides energy to liquid in the form of pressure energy through the reciprocating motion of piston. According to the driving mode, reciprocating pumps are divided into motor-driven pumps (motor-driven) and direct acting pumps (steam, gas or liquid driven).

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The main features of reciprocating pump are:

  • ① High efficiency and wide efficiency area.
  • ② It can reach a very high pressure, and the pressure change hardly affects the flow, so it can provide a constant flow.
  • ③ With self-priming capacity, it can transport liquid and gas mixtures, and specially designed can also transport mud, concrete, etc.
  • ④ The flow and pressure have large pulsation, especially in single acting pump. Due to the acceleration of piston movement and the discontinuity of liquid discharge, the pulsation is greater. It is usually necessary to set an air chamber on the discharge pipeline (sometimes on the suction pipeline) to make the flow more uniform. The use of double acting pump and multi cylinder pump can also significantly improve the non-uniformity of flow.
  • ⑤ The speed is low, the size is large, the structure is more complex than that of centrifugal pump, special pump valve is required, and the manufacturing cost and installation cost are high.

Piston pump is mainly used for water supply. Manual piston pump is a widely used domestic water pump. Plunger pump is used to provide high-pressure liquid source, such as high-pressure water supply of hydraulic press. It and piston pump can be used as drilling mud pump and oil well pump in oil field. The diaphragm pump is especially suitable for conveying highly toxic, radioactive and corrosive liquids, precious liquids and liquids containing abrasive solids. Diaphragm pump and plunger pump can also be used as metering pumps.
Features of reciprocating pump:

  • 1. Strong self-priming ability;
  • 2. The theoretical flow has nothing to do with the working pressure, but only depends on the speed, the size of the pump cylinder and the number of actions;
  • 3. The rated discharge pressure is independent of the size and speed of the pump;
  • 4. Uneven flow;
  • 5. The speed should not be too fast;
  • 6. Not very sensitive to liquid pollution;
  • 7. The structure is complex and there are many vulnerable parts.

Structure and working principle of reciprocating pump

Main components
Pump cylinder, piston, piston rod, suction valve and discharge valve.
Working principle

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Electric reciprocating pump
When the piston moves from left to right, negative pressure is formed in the pump cylinder, and the liquid in the storage tank enters the pump cylinder through the suction valve. When the piston moves from right to left, the liquid in the cylinder is squeezed and the pressure] increases, which is discharged by the discharge valve. The piston reciprocates once, sucking and discharging liquid once, which is called a working cycle; This kind of pump is called single acting pump. If the piston goes back and forth once, and each sucks and discharges liquid twice, it is called double acting pump. The movement of the piston from one end to the other is called a stroke.

Installation and flow of reciprocating pump

The reciprocating pump does not need to be filled with liquid when starting. Because the reciprocating pump has self-priming capacity, but its suction vacuum height also changes with the atmospheric pressure, liquid properties and temperature in the pump installation area, the installation height of the reciprocating pump is also limited. The flow of the reciprocating pump cannot be adjusted by the valve on the discharge pipeline, but should be realized by using the bypass pipe or changing the reciprocating times and stroke of the piston. The valve in the discharge pipeline must be opened before the reciprocating pump is started. The piston of the reciprocating pump is connected with the prime mover by the connecting rod crankshaft. The prime mover can be either an electric] engine or a steam engine. The reciprocating pump is suitable for the transportation of high-pressure head, small flow and high viscosity liquid, but it is not suitable for the transportation of corrosive liquid. Sometimes it is directly driven by the steam engine to transport flammable and explosive liquids.
The flow of reciprocating pump has nothing to do with the pressure head, but is related to the size of pump cylinder, piston stroke and reciprocating times. The theoretical flow of single acting pump is QT = ASN. The actual flow of reciprocating pump is smaller than the theoretical flow and decreases with the increase of pressure head, which is caused by leakage. The pressure head of reciprocating pump has nothing to do with the flow and geometric size of the pump, but is determined by the mechanical strength of the pump, the power of the prime mover and other factors.

Advantages of reciprocating pump

  • (1) High discharge pressure can be obtained, and the flow is independent of pressure. The suction performance is good and the efficiency is high. Among them, the steam reciprocating pump can reach 80% ~ 95%;
  • (2) In principle, it can transport any medium, almost not limited by the physical or chemical properties of the medium;
  • (3) The performance of the pump does not change with the change of pressure and viscosity of conveying medium.

Other pumps do not have the above outstanding advantages of reciprocating pumps, but they have the advantages of simple structure, convenient operation, small volume, light weight, uniform flow and serial mass production.

Disadvantages of reciprocating pump

The flow is not very stable. Larger than centrifugal pump at the same flow; Complex organization; Large amount of funds; Difficult to maintain, etc.

Application characteristics of reciprocating pump

  • 1. Wastewater discharge of enterprises.
  • 2. Discharge system of urban sewage treatment plant.
  • 3. Subway, basement, civil air defense system sewage pump system drainage station.
  • 4. Sewage discharge from hospitals, hotels and high-rise buildings.
  • 5. Sewage pump is used for sewage drainage station in residential area.
  • 6. Discharge of thin mud in municipal engineering and construction site.
  • 7. Water supply device of waterworks.
  • 8. Farm sewage discharge and rural farmland irrigation.
  • 9. Supporting exploration mine and water treatment equipment.
  • 10. The sewage pump can replace the shoulder to carry the human arm to suck and deliver river mud.

Source: China Pipe Fitting Manufacturer – Yaang Pipe Industry (

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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