The centrifugal pump has become the most widely used water pump in agriculture and industry because of its simple structure, convenient use and maintenance, and high efficiency. However, it is also troublesome because sometimes the centrifugal water pump cannot be lifted. Now analyze the cause of the failure of the centrifugal pump to lift water.
Air in the inlet pipe and pump body
(1) Some users are not filled with enough water before the pump starts; sometimes it seems that the water has overflowed from the venting hole, but the air is not completely discharged from the pump shaft, so that a little air remains in the inlet pipe or pump body. .
(2) The horizontal section of the inlet pipe that is in contact with the water pump applies a downward slope of more than 0.5% in the direction of the water flow, and the end connected to the inlet of the water pump is the highest, not completely horizontal. If it is lifted up, air will remain in the inlet pipe, which will reduce the vacuum in the water pipe and the water pump and affect the water absorption.
(3) The packing of the centrifugal pump has been 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 bushing. As a result, external air enters the inside of the pump from these gaps. , affecting the water.
(4) Due to the long-term potential of the inlet pipe, the hole in the pipe wall is corroded. After the pump works, the water surface continuously drops. When these holes are exposed to the water surface, the air enters the inlet pipe from the hole.
(5) Cracks appear at the inlet pipe bends, and slight gaps appear at the connection between the inlet pipe and the pump, which may cause air to enter the inlet pipe.
Pump speed is too low
(1) Human factors. A considerable number of users are randomly equipped with another motor to drive the original motor, resulting in less flow, low lift or even water.
(2) The belt is worn. There are many large-sized off-water pumps that use belt transmission. Due to long-term use, the belt is loose and worn, causing slippage, which reduces the speed of the pump.
(3) Improper installation. The center distance between the two pulleys is too small or the two shafts are not parallel. The tight side of the transmission belt is installed on the top, which makes the wrap angle too small, the calculation of the diameter of the two pulleys and the eccentricity of the two shafts of the coupling drive are large. The change in pump speed.
(4) Mechanical failure of the pump itself. The impeller and the pump shaft fastening nut are loose or the pump shaft is deformed and bent, causing the impeller to move more, directly rubbing against the pump body, or the bearing is damaged, which may reduce the rotation speed of the pump.
(5) Improper maintenance of the power machine. The motor is de-excited due to the burning of the windings. The number of winding turns, the wire diameter, the wiring method change during maintenance, or the failure to completely eliminate the fault during maintenance will also cause the pump speed to change.
Pump suction is too large
Some water sources are deeper, and some of the water sources have a flatter outer surface, ignoring the allowable suction of the pump, resulting in less or no water absorption. It is necessary to know that the vacuum that can be established at the suction port of the pump is limited. The suction in absolute vacuum is about 10 meters high, and the pump cannot establish an absolute vacuum. Moreover, the degree of vacuum is too large, which makes it easy to vaporize the water in the pump, which is detrimental to the operation of the pump. Therefore, all kinds of centrifugal pumps have their maximum allowable suction stroke, generally between 3 and 8.5 meters. When installing the water pump, it must not be simple and simple.
Excessive resistance loss in the water inlet and outlet pipes
Some users have measured that although the vertical distance from the reservoir or water tower to the water source is slightly smaller than the pump lift, it is still small or impossible to lift. The reason is often that the pipeline is too long, there are many bends in the water pipe, and the water flow is excessively lost in the pipeline. The reason is often that the pipeline is too long, there are many bends in the water pipe, and the water flow is excessively lost in the pipeline. Under normal circumstances, the 90 degree bend is more resistant than the 120 degree bend, and the loss of each 90 degree bend is about 0.5 to 1 meter. The resistance of each 20 meter pipeline can cause the head loss to be about 1 meter. 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.