There are many reasons why self priming pumps ca n’t suck water. The most common reason why self-priming pumps do n’t suck water is due to leaks in the inlet pipe of the self-priming pump. of. So when the self priming pump cannot suck water, what are the reasons?
The reason that the self-priming pump is not on the water is divided into the following types
1. There is air in the inlet pipe of the self-priming pump and the pump body
(1) The self priming pump is not filled with sufficient water before it starts. Sometimes it seems that the filled water has overflowed from the vent hole, but the air is completely discharged without turning the pump shaft, leaving a small amount of air remaining in the water inlet pipe or pump body.
(2) The horizontal section of the inlet pipe that is in contact with the self-priming pump should be applied with a descending slope of more than 0.5% against the direction of the water flow. The end connected to the inlet of the self-priming pump is very high and should not be completely horizontal. If it is tilted upward, air will remain in the water inlet pipe, which reduces the vacuum in the water pipe and the self-priming pump and affects water absorption.
(3) The packing of the self-priming pump has been worn out due to long-term use or the packing has become 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 self-priming from these gaps. The inside of the pump affects the water extraction. Mechanically sealed pump mechanical seal is damaged and leaking.
(4) The water inlet pipe has holes due to long-term potential underwater corrosion. The water surface continuously drops after the self-priming pump works. When these holes emerge from the water surface, air enters the private water inlet pipe from the hole.
(5) A crack appears at the bend of the water inlet pipe, and a small gap appears at the connection between the water inlet pipe and the pump, which may cause air to enter the water inlet pipe.
self priming pump speed is too low
(1) Human factors. Due to the damage of the original motor, some users are randomly equipped with another motor to drive it. As a result, the flow is low, the head is low, or the water is not supplied.
(2) Mechanical failure of the self-priming pump. Loose fastening nuts of the impeller and the pump shaft or deformation and bending of the pump shaft will cause the impeller to move more, friction with the pump body of the self-priming pump, or damage to the bearings may reduce the speed of the self-priming pump.
(3) The maintenance of the power machine is not working. The motor is demagnetized due to burned windings. Changes in winding turns, wire diameters, wiring methods during maintenance, or failure to be repaired during maintenance will not cause the pump speed to change.
3, the suction stroke of the self-priming pump is too large
Some water sources are deeper, and some water sources have a flatter periphery, and the allowable suction range of the self-priming pump is ignored, which results in less or no water absorption. It must be known that the degree of vacuum that can be established at the suction port of a self-priming pump is limited. The suction distance of a vacuum is about 10 meters high, and the vacuum that a self-priming pump cannot establish. In addition, the vacuum is too large, which easily vaporizes the water in the pump, which is disadvantageous to the operation of the self-priming pump. Therefore, self-priming centrifugal pumps have their allowable suction range, generally between 3 and 8.5 meters. When installing the self-priming pump, don't just figure it out for convenience.
The suction stroke of the self-priming pump is also related to the pressure at the inlet of the pump. A decrease in pressure will also lead to the self-priming effect of the self-priming pump. Among them, the reducer is used at the inlet, and the elbow at the inlet is dense, which will typically be incorrectly installed.
Fourth, the resistance loss in the water inlet and outlet pipes is too large
Some users have measured that although the vertical distance from the reservoir or water tower to the water source surface is still slightly smaller than the pump head, it still has a small amount of water or no water. The reason is that the pipeline is too long, there are many bends in the water pipe, and the resistance loss of the water flow in the pipe is too large. The reason is that the pipeline is too long, there are many bends in the water pipe, and the resistance loss of the water flow in the pipe is too large. Generally, the resistance of a 90-degree bend is greater than that of a 120-degree bend. Each 90-degree bend has a head loss of about 0.5-1 meters. Every 20 meters of the pipe resistance can cause a head loss of about 11 meters. In addition, some users also arbitrarily pump the diameter of the pipe into and out of the pipe, which also has a certain impact on the lift.
Fifth, other factors that the self-priming pump is not on the water
(1) the bottom valve filter network is blocked; or the bottom valve causes the filter network to be blocked in the sludge layer in the water.
(2) The impeller is severely worn. Impeller blades wear out after long-term use, affecting the performance of the pump.
(3) Gate valve can be non-return valve failure or blockage will reduce flow or even pumping water.
(4) Leakage from the outlet pipeline will also affect the water withdrawal.
(5) The foot valve cannot be opened. Usually because the pump is left for too long, the foot valve gasket is stuck, and the foot valve without gasket may rust and die.
(6) The cavitation phenomenon occurs when the water inlet pipe of the pool and the water inlet pipe of the self-priming pump interact with each other. The air flowing into the pool water from the water inlet pipe of the pool generates bubbles, which are sucked into the inlet pipe of the self-priming pump and cause cavitation.
In addition, it is necessary to inform the users of self-priming pumps. The length of self-priming pump after being filled with water depends on the self-priming performance of the self-priming pump and the length, height, and pipeline size of the self-priming pump inlet pipe. Related, many people who use it are worried that the self-priming pump will be damaged for a long time. We have to share with you as long as there is water in the pump body and the pump body is not hot and you can not touch it. In the case of long-term operation, the pump will not be affected, so if you encounter high self-priming height and long distance, you can run it for a while after filling it with water. If the pump body is a little hot, you can run it while filling the water inlet. Go in to play the role of cooling, help the self-priming pump to improve self-priming capacity.