What Are The Reasons For The Decrease Of Pump Head?
What are the reasons for the decrease of pump head?
Centrifugal pump in the work may have a variety of problems, such as flow does not meet the requirements, head reduction, motor failure and so on. Today, we will analyze the reasons for the lower head reduction.
(1) Impeller passage blocked
If the flow passage of the impeller is blocked, the work of the impeller will be affected and the outlet pressure will drop. Therefore, it is necessary to dismantle the pump to check and remove foreign matters. In order to prevent this problem from happening again, if necessary, a filter device can be added in front of the pump inlet.
(2) Internal leakage occurred
When the clearance between the rotating part and the stationary part of the pump exceeds the design range, it will lead to internal leakage, which is reflected in the decrease of the discharge pressure of the pump, such as the clearance between the impeller ring and the interstage of the multistage pump. At this time, the corresponding disassembly and inspection should be carried out to repair or replace the parts that cause excessive clearance.
(3) Cavitation at inlet
If the suction pressure of the pump is too low, which is lower than the saturated vapor pressure of the pumping medium, cavitation will be formed. At this time, check whether the inlet pipeline system is blocked or whether the inlet valve opening is too small, or increase the liquid level height of the suction tank.
(4) Speed reduction
The important factors affecting the pump head are the outer diameter of the impeller and the speed of the pump. When other conditions remain unchanged, the head of the pump is in direct proportion to the quadratic power of the speed. It can be seen that the influence of speed on the head is very large. Sometimes, due to some external reason, the speed of the pump decreases, and the head of the pump will be reduced accordingly. At this time should check the speed of the pump, if the speed is not enough, should check the reason, reasonable solution.
(5) The operating point is shifted to large flow and low head
In general, centrifugal pumps have a continuous downward performance curve, and the flow rate gradually increases with the decrease of the head. In the process of operation, due to some reason, the back pressure of the pump decreases, and the working point of the pump passively shifts to the low head and large flow point with the curve of the device, which will cause the head to decrease. In fact, this is caused by external factors such as the change of the device, which has no special relationship with the pump itself. At this time, as long as the pump back pressure is increased, such as closing a little outlet valve, the problem can be solved.
(6) Motor reversal
Because of the wiring, the motor's turn will be opposite to the actual requirement of the pump. In this way, the pump's turn should be observed before starting. If the turn is reversed, any two wires on the motor's terminal should be exchanged.
