Reasons for the decrease of outlet pressure of centrifugal pump

(1) Motor reverse

Due to wiring, the steering of the motor will be opposite to the actual required steering of the centrifugal pump. Generally, observe the steering of the pump when starting. If the steering direction is opposite, replace any two wires on the motor terminal.

(2) The working point moves to high flow and low head

Generally speaking, the centrifugal pump has a continuous downward performance curve, and the flow increases gradually with the decrease of head. During operation, due to some reason, the back pressure of the pump decreases, and the working point of the pump passively moves to the low head point flow with the curve of the device, which will lead to the reduction of head. In fact, this is caused by external factors such as changes in equipment, which has no special relationship with the pump itself. At this time, as long as the back pressure of the pump increases, such as closing the outlet valve a little. The problem can be solved.

(3) Slow down

The important factors affecting the pump head of centrifugal pump are impeller outer diameter and pump speed. When other conditions remain unchanged, the pump head is directly proportional to the quadratic power of speed. It can be seen that the speed has a great influence on the pump head. Sometimes, if the speed of the pump is reduced due to some external reason, the pump head will be reduced accordingly. At this time, check the speed of the pump. If the speed is not enough, check the cause and solve it reasonably.

(4) Cavitation at inlet

If the suction pressure of the centrifugal pump is too low and lower than the saturated vapor pressure of the pumped medium, cavitation will be formed. At this time, check whether the inlet pipeline system is blocked, or whether the opening of the inlet valve is too small, or raise the liquid level of the suction tank.

(5) Internal leakage

When the gap between the rotating part and the stationary part of the centrifugal pump exceeds the design range, internal leakage will occur, which is reflected in the decrease of the discharge pressure of the pump, such as the gap between the impeller port ring and the interstage gap of multi-stage pump. At this time, corresponding disassembly and inspection shall be carried out to repair or replace the parts causing excessive clearance.

(6) Impeller passage blocked

If part of the flow passage of the impeller is blocked, the operation of the impeller will be affected and the outlet pressure will drop. Therefore, it is necessary to disassemble the pump to check and remove foreign matters. In order to prevent this problem from happening again, if necessary, a filtering device can be added in front of the inlet of the centrifugal pump.
roots vacuum pump of vacuum water diversion steps