Main application fields of pump

From the performance range of the pump, the flow of the giant pump can reach hundreds of thousands of cubic meters per hour, while the flow of the micro pump is tens of milliliters per hour. Now it has been gradually replaced by aluminum forgings and gradually put into use; The pressure of the pump can be from atmospheric pressure to more than 19.61mpa (200kgf/cm2); The temperature of the transported liquid can reach below - 200 ℃ at the lowest and above 800 ℃. Pumps deliver a wide variety of liquids, such as water (clean water, sewage, etc.), oil, acid-base liquid, suspension, and liquid metal

in the production of chemical and petroleum departments, raw materials, semi-finished products and finished products are mostly liquids. Making raw materials into semi-finished products and finished products requires complex process. In these processes, the pump plays the role of conveying liquid and providing pressure flow of chemical reaction. In addition, the pump is also used to adjust the temperature in many devices

in agricultural production, pump is the main drainage and irrigation machinery. China's rural areas are vast, and a large number of pumps are needed in rural areas every year. Generally speaking, agricultural pumps account for more than half of the total output of pumps

pumps are also the most used equipment in the mining and metallurgical industries. The mine needs to be drained by pumps. In the process of beneficiation, smelting and rolling, pumps are needed to supply water first

in the power sector, nuclear power plants need nuclear main pumps, secondary pumps, tertiary pumps, and thermal power plants need a large number of boiler feed pumps, condensate pumps, circulating pumps and ash pumps

in national defense construction, pumps are needed for the adjustment of aircraft flaps, tail rudders and landing gears, the rotation of warships and tank turrets, and the ups and downs of submarines. High pressure and radioactive liquid, and some require the pump to have no leakage

in the shipbuilding industry, more than 100 pumps are generally used on each ocean going ship, and their types are also various. Others, such as water supply and drainage in cities, water for steam locomotives, lubrication and cooling in machine tools, transportation of bleach and dyes in textile industry, transportation of pulp in paper industry, and transportation of milk and sugar food in food industry, all need a large number of pumps

in short, pumps are needed everywhere, whether in aircraft, rockets, tanks, submarines, drilling, mining, trains, ships, or daily life. That's why the pump is listed as a general machinery, which is an important product in the machinery industry

when designing equipment, the design institute shall determine the purpose and performance of the pump and select the pump type. This choice must start with the selection of the type and form of pump, so what principle should be used to select the pump? What is the basis

1. Understand the pump selection principle

1. Make the type and performance of the selected pump meet the requirements of process parameters such as device flow, head, pressure, temperature, cavitation flow and suction

2. It must meet the requirements of medium characteristics

for pumps conveying flammable, explosive, toxic or valuable media, reliable shaft seals or leak free pumps are required, such as magnetic drive pumps, diaphragm pumps and shielded pumps

for pumps conveying corrosive media, corrosion-resistant materials are required for convection components, such as AFB stainless steel corrosion-resistant pumps and CQF engineering plastic magnetic drive pumps

for the pump conveying the medium containing solid particles, the convection parts shall be made of wear-resistant materials, and the shaft seal shall be washed with clean liquid if necessary

3. High mechanical reliability, low noise and low vibration

4. In terms of economy, we should comprehensively consider that the total cost of equipment cost, operation cost, maintenance cost and management cost is the lowest

5. The centrifugal pump has the characteristics of high speed, small volume, light weight, high efficiency, large flow, simple structure, no pulsation of infusion, stable performance, easy operation and convenient maintenance

therefore, centrifugal pump shall be selected as far as possible except for the following situations:

A. metering pump shall be selected when there are metering requirements

B. when the head requirement is very high, the flow is very small and there is no suitable centrifugal pump with small flow and high head, the reciprocating pump can be selected, and the vortex pump can also be selected if the cavitation requirement is not high

C. axial flow pump and mixed flow pump can be selected when the head is very low and the flow is very large

D. when the medium viscosity is large (greater than 650 ~ 1000mm2/s), rotor pump or reciprocating pump (gear pump and screw pump) can be considered

e, when the medium gas content is 75%, the flow is small and the viscosity is less than 37.4mm2/s, the vortex pump can be selected

F. for occasions with frequent start-up or inconvenient pump filling, pumps with self-priming performance shall be selected, such as self-priming centrifugal pump, self-priming vortex pump and pneumatic (electric) diaphragm pump

II. Know the basic basis of pump selection

the basis of pump selection should be considered from five aspects according to the process flow and water supply and drainage requirements, including liquid delivery capacity, device head, liquid properties, pipeline layout and operation conditions

1. Flow is one of the important performance data of pump selection, which is directly related to the production capacity and conveying capacity of the whole device. For example, the design institute can calculate the normal, minimum and maximum flow of the pump in the process design. When selecting the pump, it is based on the maximum flow and takes into account the normal flow. When there is no maximum flow, it is usually 1.1 times of the normal flow as the maximum flow

2. The head required by the device system is another important performance data for pump selection. Generally, the head shall be selected after enlarging the margin of 5% and 10%

3. Liquid properties, including the name of liquid medium, physical properties, chemical properties and other properties. Physical properties include temperature C, density D, viscosity u, solid particle diameter and gas content in the medium, which involves the head of the system, the calculation of effective cavitation allowance and the type of appropriate pump: chemical properties, mainly referring to the chemical corrosivity and toxicity of liquid medium, It is an important basis for the selection of pump materials and the type of shaft seal

4. The pipeline layout conditions of the device system refer to the liquid delivery height, liquid delivery distance, liquid delivery direction, some data such as the lowest liquid level on the suction side and the highest liquid level on the discharge side, as well as the pipe specification and its length, material, pipe fitting specification and quantity, so as to calculate the comb head and check the NPSH

5. There are many operating conditions, such as liquid operation T, saturated steam force P, suction side pressure PS (absolute), discharge side vessel pressure PZ, altitude, ambient temperature, whether the operation is intermittent or continuous, and whether the pump position is fixed or movable

III. specific operation of pump selection

according to the principle and basic conditions of pump selection, the specific operations are as follows:

1. According to the layout, terrain conditions, water level conditions and operation conditions of the device, determine to select horizontal, vertical and other types of pumps (pipeline type, submersible type, underwater type, non blocking type, self-priming type, gear type, etc.)

2. According to the properties of liquid medium, determine whether the clean water pump, hot water pump or oil pump, chemical pump or corrosion-resistant pump or impurity pump, or use non clogging pump. The pump installed in the explosion area shall adopt corresponding explosion-proof motor according to the grade of the explosion area

3. Select single suction pump or double suction pump according to the flow; According to the lift, select single-stage pump or multi-stage pump, high-speed pump or low-speed pump (air conditioning pump), and the efficiency of multi-stage pump is lower than that of single-stage pump. If both single-stage pump and multi-stage pump can be used, select single-stage pump first

4. Determine the specific model of the pump

after determining the series of pumps to be selected, the specific model can be determined on the type spectrum or series characteristic curve according to the maximum flow (when there is no maximum flow, usually 1.1 times of the normal flow can be taken as the maximum flow), taking the two main performance parameters of the head amplified by 5% and 10%. The operation is as follows:

use the pump characteristic curve to find the required flow value on the abscissa and the required head value on the ordinate, and lead the vertical line or horizontal line upward and right respectively from the two values. If the intersection of the two lines just falls on the characteristic curve, the pump is the pump to be selected, but this ideal situation is generally rare, and the following two situations are usually encountered:

First: the intersection is above the characteristic curve, This indicates that the flow meets the requirements, but the head is not enough. At this time, if the head difference is not much, or the difference is about 5%, it can still be selected. If the head difference is much, the pump with larger head shall be selected. Or try to reduce the resistance loss of the pipeline

the second type: the intersection point is below the characteristic curve and within the fan-shaped trapezoid range of the pump characteristic curve. Then, determine whether to cut the impeller diameter according to the difference in head.

if the difference in head is very small, do not cut. If the difference in head is very large, cut the impeller diameter according to the required Q, h, NS and cutting formula. If the intersection point does not fall within the fan-shaped trapezoid range, choose the pump with smaller head. When selecting the pump, sometimes the production process requirements must be considered and the Q-H characteristic curves of different shapes shall be selected

5. After the pump model is determined, for the pump or the pump with physical and chemical medium similar to water, it is necessary to go to the relevant product catalogue or sample, and calibrate it according to the performance table or performance curve of the model to see whether the normal working point falls in the area where the pump gives priority to work and continuously improves the localization rate of civil aircraft materials? Whether the effective NPSH is greater than (NPSH). In turn, NPSH can be used to correct the geometric installation height

6. For the liquid pump conveying viscosity greater than 20mm2/S (or density greater than 1000kg/m3), the characteristic curve of the water experimental pump must be converted into the performance curve of the viscosity (or density), especially the suction performance and input power should be carefully calculated or verified

7. Determine the number of pumps and standby rate:

A. introduce the normal operation of the oil cylinder of the testing machine. Generally, only one pump is used, because one large pump is equivalent to two small pumps working in parallel (referring to the same head and flow), and the efficiency of the large pump is higher than that of the small pump. Therefore, from the perspective of energy saving, it is better to choose one large pump instead of two small pumps, but in case of the following situations, the parallel cooperation of two pumps can be considered: large flow, One pump cannot reach this flow

B. for large pumps requiring 50% standby rate, two smaller pumps can be changed to work, and two standby (three in total)

C. for some large pumps, pumps with 70% flow requirements can be selected for parallel operation without standby pumps. When one pump is overhauled, the other pump still undertakes 70% of the production

D. for pumps that need to operate continuously for 24 hours, three pumps shall be standby, one for operation, one for standby and one for maintenance

8. Generally, customers can submit their basic conditions for selecting pumps, and our company will select or recommend better pump products. If the design institute has determined the model of the pump when designing the device and equipment, it shall be configured according to the requirements of the design institute

IV. pump maintenance and management

the pump should be divided into two aspects: electricity and machine. For the machine, it is mainly necessary to transfer the previous maintenance records and compare them. The second is the aspect of electricity. We should understand the power of each pump motor and have a certain understanding of its control system