Troubleshooting methods for horizontal centrifugal pumps

Fault form Cause of occurrence Elimination method

1-1 Horizontal centrifugal pump does not discharge water

a. The inlet and outlet valves are not open, the inlet and outlet pipelines are blocked, and the flow path and impeller are blocked. Check and remove the blockage.

b. The motor rotation direction is incorrect, the motor is missing a phase and the speed is very slow. Adjust the motor rotation direction and tighten the motor terminal block.

c. The suction pipe leaks air. Tighten all sealing surfaces and remove air.

d. The pump is not filled with liquid. There is air in the pump cavity. Open the pump cover or open the exhaust valve to remove all air.

e. Insufficient water supply at the inlet, too high suction lift, and leakage of the bottom valve. Stop the machine for inspection and adjustment (this phenomenon is prone to occur when connected to the municipal water supply network and used with suction lift).

f. Excessive pipeline resistance. Improper pump selection. Reduce pipeline bends and reselect the pump.

1-2 Insufficient flow of horizontal centrifugal pump

a. Check the causes in 1. and eliminate them first.

b. Partial blockage of the pipeline, pump flow path and impeller, water scale deposition, and insufficient valve opening. Remove the blockage and readjust the valve opening.

c. Low voltage. Stabilize the voltage.

d. Impeller wear. Replace the impeller.

1-3 Excessive power of horizontal centrifugal pump

a. Exceeding the rated flow. Adjust the flow by closing the outlet valve.

b. Excessive suction lift. reduce

c. Pump bearing wear - Replace the bearing

1-4 Horizontal centrifugal pump noise and vibration

a. Unstable pipeline support - Stabilize the pipeline

b. Liquid mixed with gas - Increase suction pressure and vent

c. Cavitation occurs - Reduce vacuum degree

d. Damaged bearing - Replace the bearing

e. Motor overload and overheating - Adjust operation as per 5.

1-6 Horizontal centrifugal pump motor overheating

a. Excessive flow, overloaded operation - Close the outlet valve partially

b. Contact and rubbing - Check and eliminate

c. Damaged motor bearing - Replace the bearing

d. Insufficient voltage - Stabilize the voltage

1-7 Horizontal centrifugal pump leakage

a. Worn mechanical seal - Replace

b. Sand holes or cracks in the pump body - Weld or replace

c. Uneven sealing surface - Rectify

d. Loose installation bolts - Tighten 

2. Operating Steps of Centrifugal Pumps 

2-1 Inspection Before Starting a Centrifugal Pump 

(1) Check if the motor wiring is correct, whether the coupling is fixed properly, and if the protective cover is complete.

(2) Inspect the inlet and outlet pipelines of the pump and the associated pipelines, flanges, and valves to ensure they are installed as required. Check if the anchor bolts and grounding wires are in good condition and if the coupling is properly installed.

(3) Turn the pump by hand to check if it rotates smoothly.

(4) Check if the lubricating oil level is normal. Add oil if necessary and inspect the quality of the lubricating oil (grease).

(5) Open the cooling water valves and check if the pipelines are unobstructed. Note that the cooling water should not be too large or too small. Excessive water will cause waste, while too little will result in poor cooling. Generally, the cooling water should flow in a line.

(6) Open the inlet valve of the pump, close the outlet valve, and open the pressure gauge hand valve.

(7) Check the sealing condition of the centrifugal pump and the opening degree of the oil seal.

Note: For hot oil pumps, they should be evenly preheated before starting. 

2-2 Starting of Centrifugal Pumps 

(1) Fully open the inlet valve, close the outlet valve, and start the motor.

(2) When the pump outlet pressure is greater than the operating pressure, check that all parts are running normally and gradually open the outlet valve.

(3) When starting the motor, if it fails to start or makes abnormal sounds, immediately cut off the power supply for inspection. Only start it again after eliminating the fault.

(4) When starting, be sure not to face the coupling to prevent injury from it flying out. 

2-3 Centrifugal Pump Shutdown Procedure 

(1) Gradually close the outlet valve of the pump.

(2) Cut off the power supply to the motor.

(3) Close the hand valve of the pressure gauge.

(4) After the pump stops, the cooling water should not be stopped immediately. The water can be stopped only when the temperature of the pump drops below 80 degrees.

(5) According to the need, close the inlet valve and empty the pump body. 

2-4 Operation and Maintenance of Centrifugal Pumps in Operation 

When the centrifugal pump is in normal operation, the following items should be carefully inspected:

(1) Check the outlet pressure, flow rate, current, etc. of the pump and motor, ensure they are not overloaded, and accurately record the current, pressure and other parameters.

(2) Listen to the sounds to distinguish the operation sounds of the pump and motor, and determine if there are any abnormalities.

(3) Check the vibration of the pump, motor and pump base. If the vibration is severe, replace the pump for inspection.

(4) Check the temperature of the motor housing and the bearing box of the pump. The temperature of the bearing box should not exceed 65 degrees Celsius, and the temperature of the motor should not exceed 95 degrees Celsius.

(5) Ensure the normal quality of the lubricating oil and the liquid level in the lubricating oil tank. When there is a scale on the oil tank, the liquid level should be based on the scale; when there is a sight glass (oil gauge) but no scale, the oil level should be maintained between 1/3 and 1/2. When the oil level is normal, the leakage of the lubricating oil should not exceed 5 drops per minute. For pressure oiling, follow the machine instructions.

(6) Check for leaks in the pump seal, flanges, plugs, cooling water, and oil seal joints.

(7) Check the standby status of the standby pump and turn it by hand once a day. 

Switching Operation of Centrifugal Pumps 2-5 

To ensure that the parameters such as flow rate and force remain basically unchanged and without fluctuation when switching pumps, two people should operate simultaneously.

(1) Make all the preparations before starting the standby pump.

(2) One person should first start the standby pump. After the pump operates normally and stably, slowly open the outlet valve. At this time, as the outlet valve of the pump is opened, the outlet pressure of the pump will slightly decrease, but the motor current will increase. Meanwhile, the other person should slowly close the outlet valve of the pump to be stopped. When the flow rate of the operating pump is large enough, completely close the outlet valve of the pump to be stopped, cut off the power supply, and then carry out the normal pump shutdown procedure. 

Precautions for Operating Centrifugal Pumps 2-7 

(1) Centrifugal pumps should avoid idling during operation.

(2) Do not run the pump for a long time with the outlet valve closed.

(3) Never use water to rinse the motor.

(4) The motor of a centrifugal pump should be started with the outlet valve closed.