The outlet pressure drop is one of the common failures of the D-type horizontal multistage centrifugal pump, which will directly affect the working performance and efficiency of the pump. There are many reasons for the outlet pressure drop of the multistage centrifugal pump. If this happens, generally from the following Check the multi-stage pump in all aspects.
Reasons for the drop in outlet pressure of D-type horizontal multistage centrifugal pump
(1) Motor reverse
Due to the wiring, the rotation direction of the motor will be opposite to the actual rotation direction of the pump. In this way, the rotation direction of the pump should be observed first when starting. If the rotation direction is reversed, any two wires on the terminal of the motor should be exchanged.
(2) Working condition point shifts to large flow and low head
Under normal circumstances, D-type horizontal multi-stage centrifugal pumps have a continuous downward performance curve, and the flow rate gradually increases as the head decreases. In the process of operation, due to some reasons, the pump back pressure is reduced, and the working point of the pump passively shifts to the low-lift and large-flow point along the device curve, which will cause the head to decrease. In fact, this is due to external factors such as the device. The result of the change has nothing to do with the pump itself. At this time, the problem can be solved by increasing the back pressure of the pump, such as closing the outlet valve a little.
(3) Speed reduction
The important factors that affect the head of the D-type horizontal multistage centrifugal pump are the outer diameter of the impeller and the speed of the pump. Under other conditions unchanged, the head of the pump is proportional to the square of the speed, which shows the influence of speed on the head. It is very large, sometimes due to some external reasons that reduce the speed of the pump, it will reduce the pump head accordingly. At this time, check the speed of the pump. If the speed is indeed not enough, check the cause and solve it reasonably.
(4) Cavitation at the entrance
If the suction pressure of the pump is too low, lower than the saturated vapor pressure of the pumped medium, cavitation will form. At this time, check whether the inlet piping system is blocked or the inlet valve opening is too small, or increase the liquid level of the suction pool.
(5) Internal leakage occurred
When the gap between the rotating part and the static part of the pump exceeds the design range, it will cause internal leakage, which is reflected in the drop in the discharge pressure of the pump, such as the gap between the impeller orifice and the interstage gap of the multi-stage pump. At this time, the corresponding disassembly and inspection should be carried out, and the parts that cause the excessive clearance should be repaired or replaced.
(6) Impeller flow passage is blocked
If part of the flow passage of the impeller is blocked, it will affect the work of the impeller and cause the outlet pressure to drop. Therefore, it is necessary to disassemble the pump to check and remove foreign objects. To prevent this problem from recurring, if necessary, a filter device can be installed before the pump inlet.
D-type horizontal multistage centrifugal pump outlet pressure drops due to many reasons, please check the above reasons one by one.
