The reason why the pump does not get water may be that the user has not installed it correctly. The correct installation and use method is that a bottom valve must be installed at the bottom of the water pump suction pipe. Before starting, the entire pump body and inlet pipe must be filled with water and before starting. It is necessary to close the water outlet valve, and then slowly open the water outlet valve after starting the water pump. Each centrifugal water pump has different self-priming performance according to different models. It is necessary to understand the cavitation of each single-stage centrifugal pump model when selecting the model. With the margin, you can know the effective self-priming height of the centrifugal pump.
The reason why the single-stage centrifugal pump does not fill water is also possible that the self-priming height exceeds the effective self-priming height of the centrifugal pump. The self-priming height of the conventional single-stage centrifugal pump is within 3 meters. If the height exceeds this height, it should be changed to suction. Centrifugal pump or high suction self-priming pump with vacuum assist. The reason why the single-stage water pump in use cannot pump water may also be caused by the blockage of debris in the pump cavity, impeller, bottom valve, pipeline and other places. If the single-stage centrifugal water pump leaks from the seal, the centrifugal pump cannot pump water. The reason why the newly installed centrifugal pump fails to pump water may also be the wrong direction of the motor. If it is the wrong direction, you need to switch off any two power cords after shutting down.
There are four reasons why the water pump does not supply water. The main reasons why the centrifugal water pump does not output water are as follows:
One, the pump speed is too low
(1) Human factors. Some users arbitrarily equipped with another motor to drive because the original motor was damaged, resulting in the consequence of small flow, low lift or even no water supply.
(2) The power machine is not repaired properly. The motor loses its magnetization due to the burnt windings. Changes in winding turns, wire diameter, and wiring methods during maintenance, or failure to completely eliminate factors during maintenance can also change the pump speed.
(3) The mechanical failure of the centrifugal water pump itself. The impeller and pump shaft fastening nut loose or the pump shaft is deformed and bent, causing the impeller to move too much, directly rubbing against the pump body, or bearing damage, which may reduce the speed of the pump.
2. There is air in the water pump inlet pipe and pump body
(1) Holes appear in the inlet pipe due to long-term potential underwater and corrosion of the pipe wall. After the multi-stage centrifugal pump works, the water surface drops continuously. When these holes are exposed to the water surface, air enters the civil inlet pipe from the holes.
(2) The packing of the multi-stage centrifugal water pump has worn out due to long-term use or the packing is too loose, causing a large amount of water to be ejected from the gap between the packing and the pump shaft sleeve. As a result, external air enters the pump from these gaps. The inside of the water pump is affected.
(3) The horizontal section of the water inlet pipe that is in contact with the water pump should have a descending slope of more than 0.5% against the flow direction. The end connected to the water pump inlet is the highest, not completely horizontal. If it is tilted upwards, air will remain in the water inlet pipe, which reduces the vacuum in the water pipe and the water pump and affects water absorption.
(4) The water pump is not filled with enough water before starting. Sometimes it seems that the filled water has overflowed from the vent hole, but the pump shaft is not rotated and the air is completely discharged, resulting in a little air remaining in the water inlet pipe or pump body.
(5) Cracks appear at the elbow of the inlet pipe, and there is a tiny gap between the inlet pipe and the water pump, which may cause air to enter the inlet pipe.
Three, the resistance loss in the inlet and outlet pipes of the water pump flow is too large
Some users have measured that although the vertical distance from the reservoir or water tower to the water surface is slightly less than the lift of the centrifugal pump, the water lift is still small or unable to lift water. The reason is often that the pipe is too long, the water pipe has many bends, and the resistance loss of the water flow in the pipe is too large. The reason is often that the pipe is too long, the water pipe has many bends, and the resistance loss of the water flow in the pipe is too large. In general, the resistance of a 90-degree elbow is greater than that of a 120-degree elbow. The head loss of each 90-degree elbow is about 0.5-1 meters, and the resistance of every 20 meters of pipe can cause a head loss of about 11 meters. In addition, some users also arbitrarily choose the diameter of the inlet and outlet pipes of the pump, which also have a certain influence on the head.
Fourth, the pump suction stroke is too large
Some water sources are deeper, and some water sources have relatively flat outer terrain, and ignore the allowable suction stroke of the centrifugal pump, which results in little or no water absorption. It is necessary to know that the degree of vacuum that can be established at the suction port of the water pump is limited. The suction range of an absolute vacuum is about 10 meters water column height, and it is impossible for a centrifugal pump to establish an absolute vacuum. Moreover, if the vacuum is too large, it is easy to vaporize the water in the pump, which is unfavorable to the operation of the pump. Therefore, each centrifugal pump has its maximum allowable suction stroke, generally between 3-8.5 meters. When installing a water pump, it must not be simple and convenient.
5. The influence of other factors
(1) The bottom valve cannot be opened. It is usually because the centrifugal pump is left for too long, the bottom valve gasket is stuck, and the bottom valve without gasket may rust.
(2) Leakage of the outlet pipe will also affect the water extraction volume.
(3) The failure or blockage of the gate valve and the check valve will cause the flow to decrease or even fail to pump water.
(4) The filter screen of the bottom valve is blocked; or the bottom valve is blocked in the sludge layer in the potential water.
(5) The impeller inlet and flow passage are blocked
