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Pump belongs to a kind of fluid machinery, which refers to the mechanical equipment with fluid as working medium and energy carrier. According to the direction of energy transfer, fluid machinery can be divided into original ideas (turbine, steam turbine) and working machines (pump, fan, compressor). Pump belongs to the working machine, that is, energy-consuming machinery.

From the function range of the pump, the flow rate of the giant pump can reach more than hundreds of thousands of cubic meters per hour, while that of the micro-pump can be less than tens of milliliters per hour; the pressure of the pump can be from normal pressure to 19.61 Mpa (200 kgf/cm2); the temperature of the transported liquid can be as low as - 200 degrees Celsius, and the highest can be more than 800 degrees Celsius. There are many kinds of pumps to transport liquids, such as water (water purification, sewage, etc.), oil, acid and alkali liquids, suspensions, and liquid metals.

In the production of chemical and petroleum parts, raw materials, semi-finished products and finished products are mostly liquid. It is necessary to make semi-finished products and finished products from raw materials through complex process. In these processes, pumps play the role of transporting liquid and providing pressure and flow of chemical reaction. In addition, pumps are used to regulate temperature in many devices.

Operating Principle, Structure and Classification of Pumps

1) The working principle can be divided into blade type, volume type and other forms.

(1) Vane pump, depending on the dynamic action of the rotating impeller on the liquid, transfers energy to the liquid continuously, which increases the kinetic energy (mainly) and pressure energy of the liquid, and then transforms kinetic energy into pressure energy through the extrusion chamber, which can be divided into centrifugal pump, axial flow pump, departmental flow pump and scroll pump.

(2) Volumetric pumps, depending on the periodic change of the volume of the sealed working space containing liquid, transfer energy periodically to the liquid, increase the pressure of the liquid to forced discharge of the liquid, and can be divided into reciprocating pumps and rotary pumps according to the movement form of working elements.

(3) Other types of pumps transmit energy in other forms. For example, jet pump relies on high-speed jet working fluid to mix the fluid to be conveyed after suction pump, so as to improve the performance exchange to transfer energy; water hammer pump uses the departmental water during braking to transfer energy to a certain height; electromagnetic pump is to make the electrified liquid metal produce lively movement under the action of electromagnetic force and realize transportation. In addition, pumps can also be classified according to the nature, driving method, structure and use of the conveying liquid.

2) Classification according to the number of working impellers

Single stage pump: that is, there is only one impeller on the pump shaft.

(2) Multi-stage pump: that is, there are two or more impellers on the shaft of the pump. At this time, the total lift of the pump is the sum of the lift generated by n impellers.

3) Classification according to work pressure

(1) Low pressure pump: water column with pressure less than 100 meters;

(2) Medium pressure pump: pressure between 100-650 m water column;

(3) High-pressure pump: pressure higher than 650 meters water column. (Multistage centrifugal pump can reach 2800m)

4) Classification according to impeller intake mode

(1) Unilateral intake pump: also known as single suction pump, that is, there is only one intake on the impeller;

(2) Bilateral intake pump: also known as double suction pump, that is, there is a water intake on both sides of the impeller. Its flow rate is twice as large as that of a single suction pump. It can be approximately considered that the impellers of two single suction pumps are placed back to back together.