A wide range of general mechanical equipment, which is widely used in oil, chemical industry, power metallurgy, mine, ship selection, light industry, agriculture, civil and national defense departments. The selection of water pump mainly involves the data of the working medium, the characteristic of the working medium, the lift, the flow and the ambient temperature. The suitable pump not only works smoothly, but also has a long life, and it can save the cost for the user's maximum.
A wide range of general mechanical equipment, which is widely used in oil, chemical industry, power metallurgy, mine, shipbuilding, light industry, agriculture, civil and national defense departments, occupies an important position in the national economy. According to statistics, the output of the pump in China is up to 5 million 256 thousand. The power consumption of the pump accounts for more than 21% of the national electricity consumption. Therefore, vigorously reducing the energy consumption of pumps is of great significance for saving energy. In recent years, our pump industry has designed and developed many high efficiency and energy saving products, such as IHF, CQB, FSB, UHB and other types of pump products, which have played an active role in reducing the energy consumption of the pump.
However, in various fields of national economy, because of unreasonable selection, many pumps are in unreasonable operation condition, low efficiency, and waste a lot of energy. Some of the pumps can not be used because of unreasonable selection, or the use of maintenance costs increases, and economic benefits are low. It can be seen that reasonable selection of pumps is also of great significance for energy conservation. The so-called rational selection of pumps is to comprehensively consider the investment and operating costs of pump units and pumping stations and other comprehensive technical and economic indicators, so that it is in line with the principles of economic, safety and application. Specifically, there are the following aspects: it is necessary to meet the requirements of the use of flow and lift, that is, the operation point of the pump (the intersection point of the characteristic curve of the device and the performance curve of the pump) is often kept in the high efficiency interval, so that the engine is not easy to be damaged and the machine is not easily damaged. The selected pump should be small in volume, light in weight and cheap in cost, and also has good characteristics and high efficiency. It has good anti cavitation performance, which can not only reduce the excavation depth of the pump room, but also make the pump cavitation, stable operation and long life. According to the selected pump station, the project investment is low and the operation cost is low.
Basic data of pump selection:
1, medium characteristics: media name, specific gravity, viscosity, corrosion, toxicity and so on.
2. The diameter and content of solid particles contained in the medium.
3, medium temperature: (centigrade)
4. The amount of flow in the pipeline system can be ignored in the process flow, but the effect of process change on the flow rate must be taken into account. If agricultural pumps are to use open channels for water conveyance, leakage and evaporation must also be considered.
5, pressure: suction tank pressure, drain pool pressure, pipe system pressure drop (head loss).
6, piping system data (diameter, length, type and number of pipe accessories, suction tank to the pressure tank of the geometric high).
If necessary, the device characteristic curve should also be made. When designing piping, attention should be paid to the following:
1. Reasonable selection of pipe diameter, large pipe diameter, low liquid flow speed, low resistance loss under the same flow rate, high price and small pipe diameter will lead to a sharp increase of resistance loss, increase the lift of the selected pump, increase the power of the matching belt, increase the cost and operating cost. Therefore, we should consider comprehensively from the perspective of technology and economy.
2, discharge pipe and its joints should consider the maximum pressure that can be sustained.
3, the pipe arrangement should be arranged as far as possible, as far as possible to reduce the accessories in the pipe and minimize the length of the pipe. When the bend must be turned, the bending radius of the elbow should be 3~5 times the diameter of the pipe, and the angle is as much as 90 degrees as far as possible.
4, the pump must be installed on the discharge side of the valve (ball valve or globe valve, etc.) and check valve. The valve is used to adjust the working point of the pump, and the check valve can prevent the pump from reversing when the liquid reverses, and prevents the pump from hitting the water hammer. (when the liquid reversing, there will be a huge reverse pressure to damage the pump).
The determination of the flow head:
1, if the minimum, normal and maximum flow rate has been given in the production process, the maximum flow rate should be considered.
2, if the normal flow rate is only given in the production process, there should be some allowance. For the large flow and low lift pump of ns>100, the flow allowance is 5%. For the small flow high lift pump of ns<50, the flow allowance is 10%, 50 less than ns < 100, the flow allowance is also 5%. The flow allowance should be 10% for the poor quality and poor operating conditions.
3, if the basic data is only given to the weight flow, it should be converted into volume flow.