The selection of pumps mainly involves the data of working medium, working medium characteristics, head, flow rate and ambient temperature. The suitable pumps not only work smoothly, but also have long service life, and can save the cost to the greatest extent for users.
Introduction to pump selection
Pump is a kind of universal mechanical equipment with a wide range of applications. It is widely used in petroleum, chemical industry, power metallurgy, mining, shipbuilding, light industry, agriculture, civil and national defense departments, and occupies an important position in the national economy. According to statistics, the output of pumps in China has reached 5.256 million units. Pump power consumption accounts for more than 21% of the national power consumption. Therefore, it is of great significance to reduce the energy consumption of pumps for saving energy. In recent years, our pump industry has designed and developed many high-efficiency energy-saving products, such as IHF, CQB, FSB, UHB and other types of pump products, which play a positive role in reducing the energy consumption of pumps.
Necessity of Correct Type Selection of Water Pumps
But at present, in various fields of the national economy, many pumps are in unreasonable operation because of unreasonable selection, low efficiency and waste a lot of energy. Other pumps can not be used at all because of unreasonable selection, or the cost of use and maintenance increases, resulting in low economic benefits. It can be seen that the rational selection of pumps is equally important for energy conservation. The so-called rational pump selection is to take into account the comprehensive technical and economic indicators such as the investment and operation cost of pumping units and pumping stations, so as to make them conform to the principles of economy, safety and applicability. Specifically, there are the following aspects: must meet the requirements of the use of flow and head, that is to say, the pump operation point (the intersection point of device characteristic curve and pump performance curve) is often maintained in the high-efficiency range, which saves power and is not easy to damage the machine parts. The selected pump should be 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 excavation depth of the pump house, but also avoid cavitation of the pump. It runs smoothly and has a long service life. Construction of pumping stations according to selected pumps will result in less investment and lower operating costs.
Steps of pump selection
Pump selection lists basic data:
1. Characteristics of medium: medium name, specific gravity, viscosity, corrosiveness, toxicity, etc.
2. The diameter and content of solid particles in the medium.
3. Medium temperature: (C)
4. The leakage in pipeline system can be neglected in the process flow of industrial pumps, but the influence of process change on flow must be considered. If agricultural pumps use open channel for water conveyance, leakage and evaporation must also be considered.
5. Pressure: suction tank pressure, drainage tank pressure, pressure drop in pipeline system (head loss).
6. Pipeline system data (diameter, length, type and number of pipe accessories, geometric standard from suction tank to pressure tank).
Characteristic curves of the device should also be drawn if necessary. In the design and layout of pipelines, the following points should be paid attention to:
1. Reasonable selection of pipe diameter, pipe diameter, at the same flow rate, fluid flow speed, resistance loss is small, but the price is high, pipe diameter is small, will lead to resistance loss increased sharply, so that the pump head increased, power increased, cost and operating costs increased. Therefore, it should be considered from the perspective of technology and economy.
2. The discharge pipe and its joint shall take into account the maximum pressure they can withstand.
3. Pipeline layout should be arranged as straight as possible, minimizing the accessories in the pipeline and minimizing the length of the pipeline. When turning, the bending radius of the elbow should be 3-5 times of the diameter of the pipeline, and the angle should be greater than 90 C as far as possible.
4. Valves (ball valves or globe valves, etc.) and check valves must be installed on the discharge side of the pump. The valve is used to regulate the working point of the pump. The check valve can prevent the pump from reversing when the liquid is flowing back, and prevent the pump from being hit by the water hammer. (When the liquid flows backwards, a huge reverse pressure will be generated, which will damage the pump.)
Select pump to determine flow head flow:
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 only normal flow rate is given in the production process, a certain margin should be considered. For large flow and low head pumps with NS > 100, the flow allowance should be 5%, for small flow and high head pumps with NS < 50, the flow allowance should be 10%, for pumps with 50 < ns < 100, the flow allowance should also be 5%. For pumps with poor quality and poor operating conditions, the flow allowance should be 10%.
3. If the basic data are only given to the weight flow, it should be converted into volume flow.
