Principle of Pump Selection

Principle of Pump Selection
Pump selection is according to the pump's working environment and conditions, normal operation of pump required performance parameters, as well as the physical and chemical properties of the medium to be delivered comprehensively considering technical performance index of pump unit in the system, material selection, the matching of the motor and pump seal reliability and energy saving, use comprehensive economic indicators, such as the maintenance requirements, Select the most appropriate pump type and model specifications in the stereotyped pump products.


Reasonable selection of pump principle, but also comprehensive consideration of pump unit and pump station investment and operating costs and other comprehensive technical and economic indicators, so that it conforms to the principle of economy, safety and applicability. Specifically, there are the following aspects:
 

1. must meet the requirements of flow and head, pressure, temperature, NPSH, suction and other process parameters, that is, the operating condition of the pump (the intersection of the device characteristic curve and the pump performance curve) often keep running in the high efficiency range, so as to save power and not easy to damage part
2. The selected water pump should not only be small in size, light in weight, cheap in cost, but also have good characteristics and high efficiency; Low investment, low operation and maintenance costs. Is advanced technology, reasonable economy, mature and reliable products, and has a high flexibility, that is, to meet the needs of the operation mode.
3. It has good anti-cavitation performance, which can reduce the excavation depth of pump house, and does not make the pump cavitation, stable operation, long life, high reliability, low noise, small vibration.
4. The total cost is minimal, taking into account initial procurement costs, operating costs, maintenance costs and management fees.
5. Must meet the requirements of medium characteristics.

For the delivery of flammable, explosive, toxic or valuable medium pump, the shaft seal is required to be reliable or use no leakage pump, such as magnetic drive pump, diaphragm pump, shield pump.

1. For the pump conveying corrosive medium, the flow parts are required to use corrosion resistant materials. A, the flow parts and shaft seals should meet the corrosive (pH) requirements of the liquid to be transported; B. Non-metallic materials should be selected for liquid flow parts with strong corrosion, such as fluorine plastics, ceramics, glass fiber reinforced plastics, graphite, etc.; C. In general, metal pumps have better abrasion resistance, pressure resistance and high temperature resistance than non-metal pumps, while non-metal pumps have better corrosion resistance than metal pumps.
2. For the delivery of corrosive liquid containing solid particle medium pump, the flow part should be selected both corrosion resistant and wear-resistant metal corrosion resistant material manufacturing, such as high silicon cast iron, duplex stainless steel, nickel-chromium alloy, special alloy steel. If necessary, the shaft seal should be washed with clean liquid.
3. According to the size and proportion of fixed particles contained in the liquid to choose different flow parts. A, the delivery of liquid containing solid particles is larger, more, can choose non-blocking design of flow parts pump, such as cyclone pump, single channel impeller pump; B, according to the hardness, content and corrosiveness of solids contained in the liquid to choose the material of the flow parts.
4. For toxic, flammable, explosive, odor liquid, precious medium, aseptic transportation, vacuum transportation should comply with the principle of not allowing leakage, the sealing part of the pump is safe and reliable or choose shield pump, magnetic pump, diaphragm pump, etc.
5. Contains long fiber liquid: A, the flow parts with tearing, cutting structure, to ensure that the impeller is not wound by long fiber; B, the choice of non-blocked passage type, open type or single blade impeller; C. Consider the mechanical characteristics of the motor (overload capacity, etc.).
6. High temperature and high pressure liquid: flow parts selection of high temperature and high pressure material, can be selected in turn ductile iron, cast steel, chromium steel production. A. Mechanical strength and thermal expansion requirements of flow components under high temperature and high pressure have been considered; B. Select shaft seal and cooling device with high temperature and high pressure resistance.
7. When the characteristics of the pump medium is determined, you can choose the specific pump series, structural form and production materials according to the process parameters and medium characteristics.

Installation requirements of the site environment must be met:

1. For the pump installed in the presence of corrosive gas, anti-atmospheric corrosion measures are required.
2. For the pump installed in the outdoor environment temperature below -20℃, the cold and brittle phenomenon of the pump should be considered, the use of low temperature resistant materials, and the structure of the cylindrical double shell centrifugal pump.
3. Environmental noise: the pump has low noise requirements, to consider the selection of sliding bearing structure and hydraulic low noise design, and with low noise motor.
4. relative humidity: in the use of high humidity environment, should consider the pump to take anti-rust measures; Also consider the protection and insulation level of the motor.
5. Power grid conditions: whether the capacity is enough; Frequency of power grid (domestic 50Hz, foreign 60Hz and frequency conversion usage); Ac and DC power supply; Power grid voltage three-phase (380V), single-phase (220V), or different voltage (including high voltage above 660V), the range of power supply voltage change; Voltage drop between power supply and pump use point (long distance cable transmission).
6. For a year of maintenance of the pump, the continuous operation cycle of the pump should not be less than 8000 hours, should comply with GB5656-2008 (ISO5199) or ANSIB73.1m standard. Petroleum, petrochemical, chemical and other industries require three years of maintenance of the pump, should comply with API610(10th edition) standard provisions, continuous operation for at least 3 years.
7. The pump installed in the explosion area, should be based on the explosion area grade, the corresponding grade of explosion-proof motor.
8. to have special requirements of the use of occasions, such as vacuum transport, high temperature and high pressure transport, low temperature transport should choose special pump class.

When determining the pump model and manufacturing plant, pump performance, efficiency, quality, energy consumption, reliability, installation and maintenance, price and manufacturing specifications and other factors should be considered comprehensively. Choose a pump with high speed, small volume, light weight, high efficiency, large flow, simple structure, transfusion without pulsation, stable performance, easy operation and convenient maintenance and other characteristics. When all parameters are in line with the selection standards of more than two specifications, to the comprehensive index of high for the final selection of the model. Specifically, the following parameters can be compared: high efficiency is optimal, light weight is optimal, and low price is optimal.


In addition to the following circumstances, centrifugal pumps should be selected as far as possible

1. When there are metering requirements, choose metering pump.
2. the head requirements are very high, the flow is very small and there is no suitable small flow and high head centrifugal pump can be selected, the reciprocating pump can be selected; If cavitation requirements are not high, vortex pump can also be used.
3. When the head is very low and the flow is very large, axial flow pump and mixed flow pump can be used.
4. the medium viscosity is larger (more than 650~1000mm2/s), can consider the use of rotor pump or reciprocating pump (gear pump, screw pump).
5. When the gas content of the medium is more than 5%, the flow rate is small and the viscosity is less than 37.4mm2/s, the vortex pump can be used.
6. on the occasion of frequent start or inconvenient irrigation pump, should choose a pump with self-priming performance, such as self-priming centrifugal pump, self-priming vortex pump, pneumatic (electric) diaphragm pump.