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How to choose a water pump? The selection principle and steps of the pump.

Data: 2020-12-29


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How to choose a water pump? The selection principle and steps of the pump.

Water pump is a kind of general-purpose machinery with a wide range of applications. It is very important to choose the type and model of the pump correctly. This is directly related to whether the pump can meet system design requirements, pump reliability and service life, pump purchase cost and total life cycle cost. 

The selection of the pump needs to be carried out carefully, and the advantages and disadvantages of different schemes are repeatedly compared to ensure the normal operation of the pump. The following are the principles and steps for selecting a pump:

The principle of pump selection:

1. Meet the requirements
 The performance of the selected pump should meet the process design requirements.

2. Choose the pump simpler
The pump with a simple structure is preferred. Compared with a pump with a simple structure, a pump with a simple structure has the advantages of high reliability, convenient maintenance, and low total cost during the life cycle. For example: single-stage pumps and multi-stage pumps, vane pumps and reciprocating pumps.

3. Optimal centrifugal pump
The centrifugal pump has the characteristics of high speed, small size, light weight, simple structure, no pulsation of infusion, stable performance, easy operation and convenient maintenance. Therefore, in addition to the following conditions, centrifugal pumps should be used as much as possible:

(1) When there are metering requirements, use metering pumps;

(2) For small flow and high head, choose vortex pump and reciprocating pump;

(3) When the flow rate (pressure) is required to have no pulsation, the vortex pump should be selected; (the definition of the high and low head of the large and small flow)

(4) For large flow and low head, choose axial flow pump or mixed flow pump;

FSB-L centrifugal pump produced by Paragon

(5) When the medium contains 75% air, the flow is small and the viscosity is less than 37.4mm2/s, the vortex pump is used;

(6) When the medium viscosity is large (greater than 650~1000mm2/s), use rotor pumps and reciprocating pumps (gear pumps, screw pumps);

(7) For occasions with frequent start-up or inconvenient pumping, use pumps with self-priming performance, such as self-priming centrifugal pumps, self-priming vortex pumps, and diaphragm pumps;

(8) When there are special needs, use other pumps, such as jet pumps, hose pumps, etc.

4. Special requirements
For pumps installed in explosive areas or special occasions, explosion-proof motors or other effective measures should be adopted according to the level of the explosive area.

The steps of pump selection:

1. Confirm the environmental conditions, including environmental temperature, relative humidity, atmospheric pressure, air corrosivity, hazardous area grade, dustproof and waterproof requirements.

2. Confirm the operating conditions. 

Refers to the liquid surface pressure (absolute) on the suction side of the liquid, the liquid surface pressure on the discharge side, intermittent or continuous operation, fixed or movable positions, and ease of installation and maintenance.

3. Confirm the properties of the medium, including medium name, temperature, density, viscosity, saturated vapor pressure, solid particle diameter and content, gas content, corrosiveness, volatility, flammability, and toxicity.

4. Select the material of the pump wetted parts
According to the physical and chemical properties of the pumped medium, the following aspects are mainly considered:

(1) Corrosiveness of the medium
The corrosion resistance of the pump's flow-through components only needs to meet the requirements of use. Do not pursue excessive corrosion resistance, otherwise, the purchase cost of the pump will be greatly increased.
Centrifugal pump for sale
(2) Whether the medium contains solid particles
Because the hardness and content of solid particles are directly related to the durability of the pump wetted parts.

(3) The temperature (pressure) of the medium. The higher the temperature (pressure) of the medium, the higher the material strength of the pump wetted parts. Generally, when the temperature is >250℃, steel castings or steel parts should be used.

(4) For media with sanitary or non-pollution requirements, select the corresponding wetted parts material. In addition, the structure of the pump should be easy to clean.

5. Select the pump installation type 

According to the pipeline layout and installation site, choose horizontal, direct, vertical and other types (right-angle, variable-angle, corner, double, and easy-to-disassemble).

6. Determine the number of pumps and reserve rate
Generally, only one pump is used for normal operation. Because a large pump is equivalent to two small pumps working in parallel (referring to the same head and flow), the efficiency of the large pump is higher than that of the small pump, so it is better to choose one from the perspective of energy saving. A large pump is used instead of two small pumps, but in the following situations, two pumps can be considered in parallel cooperation:
China sells centrifugal pumps
(1) The flow is very large, and a pump cannot reach this flow.
(2) For pumps that require a 50% standby rate, they can be configured as two-purpose and one-backup, with a total of three configurations.
(3) For some large pumps, pumps with 70% flow requirements can be used for parallel operation, instead of standby pumps. When one pump is overhauled, the other pump still bears 70% of the production capacity.
(4) For pumps that must be operated continuously for 24 hours, one pump should be operated, one standby, and one repaired, totaling three. When necessary, the pump provider can assist in the selection.

The above is provided by Paragon, a supplier of centrifugal pumps. For more detailed information, please click here.