The pump is a widely used general mechanical equipment. It is widely used in petroleum, chemical industry, power metallurgy, mining, ship selection, light industry, agriculture, civil and defense sectors, and plays an important role in the national economy. According to the statistics of 79 years, the output of the pump in our country reached 1 million 256 thousand. The electric energy consumption of the pump accounts for more than 21% of the energy consumption in the country. Therefore, it is of great significance to reduce the energy consumption of the pump and to save energy.
In recent years, our pump industry has designed many energy-efficient products, such as QBY, IHF, CQB, PF, FSB, UHB, 2XZ, ZW and other pump products, which has played a positive role in reducing the energy consumption of pumps. But in the various fields of national economy, because of the unreasonable selection, many pumps are in unreasonable operation condition, and the efficiency is low, which wastes a lot of energy. Due to the unreasonable selection of the pump, the pump can not be used at all, or the cost of maintenance is increased and the economic benefit is low. Thus, it is also of great significance to choose a reasonable pump for saving energy.
The so-called rational pump selection is to comprehensively consider the comprehensive technical and economic indicators such as the investment and operation cost of pump units and pumping stations, and make them conform to the principles of economy, safety and application. Specifically, there are the following aspects:
We must meet the requirements of traffic and lift. That is to say, the operation point of pump (the intersection of device characteristic curve and the performance curve of pump) is always kept in the efficient range, so that it saves power and is not easy to damage parts.
The selected pumps are small in size, light in weight, cheap in cost, and have good characteristics and high efficiency.
It has good anti cavitation performance, which can not only reduce the depth of the excavation of the pump room, but also do not make the water pump cavitation, running smoothly and long life.
According to the pump station selected by the selected pump, the investment of the project is less and the operating cost is low.
Second section pump selection step
First, list the basic data:
1, the characteristics of medium: medium name, specific gravity, viscosity, corrosiveness, toxicity and so on.
2. The diameter and content of the particles in the medium.
3, medium temperature: (centigrade)
4, the required flow
In general industrial pumps, the leakage in the pipeline system can be ignored in the process flow, but the effect of process changes on the flow rate must be taken into account. If the agricultural pump is used to transport water in a open channel, it is necessary to consider the leakage and the amount of evaporation.
5, pressure: the pressure of the suction pool, the pressure of the drainage pool, the pressure drop in the pipe system (head loss).
6. The data of the pipe system (pipe diameter, length, type and number of pipe accessories, and the high geometry of the sump to the pressure pool).
If needed, the device characteristic curve should also be made.
In the design and layout of the pipeline, the following matters should be paid attention to:
A, a reasonable choice of pipe diameter, pipe diameter, and at the same flow rate, flow velocity is small, small resistance loss, but the price is high, small diameter pipeline will lead to resistance loss increases rapidly, so that the selected pump head increased, with increased power, cost and increased operating costs. Therefore, it should be considered from the point of view of technology and economy.
The B, discharge tube and its pipe joint should consider the maximum pressure to bear.
C and piping layout should be arranged as straight as possible, minimize the accessories in the pipe and minimize the length of the pipeline. When turning, the elbow radius should be 3~5 times the diameter of the pipe, and the angle should be greater than 90 degrees.
The discharge side of the D and pump must be equipped with a valve (ball valve or cut-off valve, etc.) and a reverse check valve. The valve is used to regulate the working conditions of the pump, and the reverse check valve can prevent the reversal of the pump when the liquid flow reverses, and the pump avoids the blow of water hammer. (when the liquid reflows, it produces a huge reverse pressure, causing the pump to be damaged)
Two. Determine the flow head
Determination of flow rate
A, if the minimum, normal and maximum flow rate has been given in the production process, the maximum flow rate should be considered.
B, if the normal flow rate is only given in the production process, some allowance should be taken into consideration.
For ns>100, the large flow rate and its low head pump, the flow allowance is 5%. For the ns<50 small flow and high lift pump, the flow allowance is 10%, 50≤ ns≤ 100, the flow allowance of the pump is 5%, and the flow allowance for the inferior quality and bad running pump should be 10%.
C, if the basic data is only given to the weight flow, it should be converted into volume flow.
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