Misuse of centrifugal pumps

1. High-lift pump for low-lift pumping Many drivers think pumping lower lift, the smaller the motor load. Misleading in this misunderstanding, the purchase of pumps, the pump is often elected head high. In fact, for centrifugal pumps, when the pump model is determined, the size of the power consumption is proportional to the actual flow of the pump. The pump flow will increase with the head decreases, so the higher the head, the smaller the flow, the smaller the power consumption. On the contrary, the lower head, the greater the flow, the greater the power consumption. Therefore, in order to prevent motor overload, the actual requirements of the actual pumping pump head lift of not less than 60% of the nominal lift. Therefore, when the high lift for low lift pumping, the motor is prone to overload and fever, severe motor burn. In case of emergency use, a gate valve (or a small outlet with wooden objects) must be installed on the outlet pipe to reduce the flow rate and prevent the motor from overload. Pay attention to the motor temperature rise, if it is found that the motor overheating, should promptly close the outlet flow or shutdown. This is also prone to misunderstandings, some people think plugging the outlet, forced to reduce the flow, will increase the motor load. In fact, on the contrary, the regular high-power centrifugal pump drainage pipe units are equipped with gate valve, in order to reduce the motor load when the unit starts, the gate valve should be closed before the motor starts and then gradually open the gate is the truth.

2. Large diameter pump with a small pipe pumping

Many drivers think this can improve the actual lift, in fact, the actual head of the pump = total head ~ loss of head. When the pump model is determined, the total head is a certain; loss head mainly from the pipeline resistance, the smaller the diameter of the pipe is obviously the greater the resistance, so the loss of lift the greater, so reducing the diameter, the actual pump not only can not increase the actual lift , But will be reduced, resulting in reduced pump efficiency. Similarly, when a small diameter pump with a large water pipe pumping, it will not reduce the actual lift of the pump, but will reduce the resistance due to pipelines to reduce the loss of lift, so that the actual lift has improved. However, there are also some organic hands who think that when using a large pipe for pump with small diameter, it will inevitably greatly increase the motor load. After the pipe diameter increases, the pressure in the water pipe will greatly increase the pressure on the pump impeller, which will greatly increase the motor load. As everyone knows, the size of the liquid pressure is only related to the level of head, and the size of the cross-sectional area of ​​the water has nothing to do. As long as the lift is certain, the pump impeller size unchanged, no matter how much diameter, the role of the pressure on the impeller is certain. Only the diameter increases, the flow resistance will be reduced, leaving an increase in flow, power consumption also have an appropriate increase. However, as long as the rated head range, no matter how to increase the diameter of the pump are working, and can also reduce the pipeline loss, improve pump efficiency.

3. When installing the water inlet pipe, the horizontal section should be horizontal or upturned

This will make the air inlet tube to gather air, reduce the vacuum degree of water pipes and pumps, so that pump suction head lift to reduce the amount of water. The correct approach is: the horizontal section should be slightly tilted to the direction of the water source, should not level, but not up tilt.

4. Into the water pipe with more elbows

If the inlet pipe in the use of more elbows, will increase the local resistance to water flow. And bend should be turned in the vertical direction, not allowed to turn in the horizontal direction, so as to avoid the accumulation of air.

5 pump inlet and elbow directly connected

This will make the water flow through the elbow into the impeller uneven distribution. When the inlet pipe diameter is larger than the inlet of the pump, eccentric reducer should be installed. Eccentric reducer plane part to be installed in the above, bevel part installed below. Otherwise, gather air, reduce the amount of water or pumping out of water, and a percussion sound. If the inlet pipe and pump inlet diameter equal, should be in the pump inlet and elbow plus a straight tube, straight pipe length of not less than 2 to 3 times the diameter of the pipe.

6. The bottom section of the inlet pipe fitted with a foot valve is not vertical

Such as installation, the valve can not be closed on their own, resulting in leakage. The correct installation method is: equipped with a valve at the end of the inlet pipe, the next section is best vertical. As a result of the terrain conditions can not be vertical installation, the water pipe axis and the horizontal angle should be 60 ° or more.

Inlet water inlet position is wrong

(1) Inlet pipe inlet from the bottom of the pool and pool wall distance is less than the inlet diameter. If the bottom sediment and other dirt, the inlet from the bottom of the pool is less than 1.5 times the diameter, it will cause poor pumping or sucked into the sediment debris, plug the inlet.

(2) Inlet pipe inlet water depth is not enough, it will cause the water around the inlet pipe whirlpool, affecting water, reduce the amount of water. The correct installation method is: small and medium-sized pumps into the water depth of not less than 300 ~ 600mm, large pumps shall not be less than 600 ~ 1000mm.

8. The outlet pipe in the pool above the normal water level

If the outlet above the normal level of the water pool, although the increase in the pump head, but reduces the flow. As a result of the terrain conditions, the outlet must be above the water level out of the pool, you should install the elbow and short tube in the nozzle to make the water pipe siphon, reducing the height of the outlet.

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