① The self-priming pump is not filled with enough water before starting. Sometimes it seems that the water has overflowed from the vent hole, but the pump shaft is not rotated to allow the air to be completely discharged, causing a small amount of air to remain in the water inlet pipe or pump body. ② The horizontal section of the water inlet pipe in contact with the water pump should have a downward slope of more than 0.5% against the direction of water flow, with the end connected to the water pump inlet being the highest. Do not be completely horizontal. If it tilts upward, air will remain in the water inlet pipe, reducing the vacuum in the water pipe and the water pump, affecting water absorption. ③ The packing of the single-stage centrifugal pump has been worn out due to long-term use or the packing has been pressed too loose, causing a large amount of water to spray out from the gap between the packing and the pump shaft sleeve. As a result, external air enters the interior of the water pump through these gaps, affecting water pumping. ④ The water inlet pipe has been submerged in water for a long time, and holes appear on the pipe wall due to corrosion. After the water pump is working, the water level continues to drop. When these holes are exposed to the water surface, air enters the water inlet pipe through the holes. ⑤ Cracks at the bend of the water inlet pipe or tiny gaps at the connection between the water inlet pipe and the water pump may allow air to enter the water inlet pipe.
① Human factors: Some users randomly install another motor to drive the machine because the original motor is damaged, resulting in small flow, low head or even no water supply. ② Mechanical failure of the water pump itself: the fastening nuts between the impeller and the pump shaft are loose or the pump shaft is deformed and bent, causing the impeller to move too much, directly rubbing against the pump body, or the bearing is damaged, all of which may reduce the speed of the water pump. ③ Poor maintenance of the power machine: The motor loses its magnetism due to burning of the windings. Changes in the number of winding turns, wire diameter, and wiring methods during maintenance, or failure to completely eliminate the fault during maintenance will also cause the pump speed to change.
