【 Weak current College 】 principle of centrifugal pumps and major components

Present in all areas of the national economy, since selection is not reasonable, many of the pump is not reasonable health, low efficiency, waste a lot of energy. A selection of the pump as unreasonable, would not be able to use, or maintenance costs increase, economic efficiency is low. This shows that a reasonable selection of pumps on saving energy also has important significance.
The so-called reasonable selected pump was to be considered pump and pump station of investment and operating costs, and so on comprehensive technical and economic indicators, bring it into line with economic, safety, the applicable principles. Specifically, the following areas:
1 must meet the use flow rate and head's request that the requirements of the pump operating point (device characteristic curve and the pump performance curve of intersection points) are kept in high interval running, so that both provincial power and not easily damaged parts.
2 choose pump to small volume, light weight, low cost, but also has good characteristics and high efficiency.
3 excellent resistance to cavitation performance, so that both can reduce the depth of excavation, pump room and do not make the pump cavitation, smooth running, long service life.
4 press the selected pump pumping station construction, engineering, low investment, low running cost.
Selection procedure
First, the lists of basic data:
1, media: media names, specific gravity, viscosity, corrosive, toxic, etc.
2. media containing solid particle diameter, content.
3, medium temperature (℃)
4, the flow of general industrial pumps in technological process can ignore the pipeline system leakage, but must take into account technological changes to flow in. Agricultural pumps if used is the open-channel water, must also consider the seepage and evaporation.
5. pressure: sump pond discharge pressure, pressure, the pressure in the piping system is poor (head loss).
6. piping system data (diameter, length, piping attachment types and numbers of the sump to pressure tank geometric standard advanced). If you want to make a device should also be the characteristic curve. In designing the layout of the pipeline, you should be aware of the following matters:
A reasonable choice, pipe diameter, pipe diameter, in the same flow, flow rate, pressure loss is small, but the price is high, the pipe diameter is small, can cause a dramatic increase in resistance loss such that the pump head, equipped with power increase, costs and operating costs are increasing. So from a technical and economic point of view.
Exhaust pipe and B, fitting should consider can bear the pressure of Max.
C, piping layout should, as far as possible, arranged the straight pipe, minimize pipeline accessories and minimize the pipe length, must turn, bend bend radius should be pipe diameter 3-5 times, as far as possible, greater than 90 ° angle.
D, pump discharge side must be fitted with a valve (ball valve or valves, etc.) and non-return valve. Valve is used to adjust the pump operating point, when the liquid back check valve to prevent pump reversal, and the pump to avoid water hammer blow. (When the liquid flow backwards, will produce great reverse pressure pump damage)
Second, determine flow head flow determination
A production process, if you have been given minimum, normal, maximum flow rate should be considered the maximum flow.
B, if the production process only gives the normal flow, you should consider to stay there. For ns > 100 high-traffic low lift pumps, flow margin for 5% of the ns < 50 small high-lift pump, flow margin by 10%, 50% ≤ 100 ns ≤ pump, flow margin also take 5% on poor quality and operating conditions of pump, flow margin should take 10%.
C, if basic data only to the weight of traffic, you should convert volume flow.