Centrifugal pumps are widely used in industrial applications and are prone to various malfunctions during operation. Therefore, it is necessary to conduct planned inspections, repairs, and maintenance to prevent problems before they arise. Our editor has specially compiled a list of common malfunction types of centrifugal pumps. Let's take a look together!

The preferred operating range of a centrifugal pump is determined in engineering design to ensure high efficiency and low vibration values during operation. Generally, it is required that the operating point fall within 70% to 120% of the flow rate at the best efficiency point.

If the operating point of a centrifugal pump deviates from the preferred operating range and falls between the extreme operating range and the preferred operating range, it can still operate safely for a long period of time, but its efficiency will decline rapidly. Generally, a centrifugal pump has a maximum allowable flow rate and a minimum continuous stable flow rate.

Common faults and their solutions:

1. The pump cannot be started or the starting load is high

(1) The prime mover or power source is abnormal.

Solution: Check the power supply and the prime mover.

(2) The pump is stuck.

Handling method: Manually rotate the coupling for inspection, and disassemble it for inspection if necessary to eliminate faults in the rotating and stationary parts.

(3) The packing is pressed too tightly

Treatment method: Loosen the packing material.

(4) The discharge valve is not closed.

Treatment method: Close the discharge valve and restart.

(5) The balance pipe is not unobstructed.

Solution: Dredge the balance pipe.

2. The pump cannot be started or starts with a high load

(1) Insufficient filling of the pump (or gas inside the pump has not been completely discharged).

Solution: refill the pump.

(2) The pump is not rotating in the correct direction.

Solution: Check the rotation direction.

(3) The pump speed is too low.

Solution: Check the rotational speed and increase it.

(4) The filter screen is clogged, and the foot valve is malfunctioning.

Solution: Check the filter screen and remove any impurities.

(5) The suction height is too high, or there is vacuum in the suction tank.

Solution: Reduce the suction height; check the pressure of the suction tank.

3. Pump stops after discharging liquid

(1) Air leakage in the suction pipeline.

Treatment method: Inspect the connection of the suction side pipeline and the sealing condition of the packing box.

(2) The gas on the suction side was not fully discharged during pump priming.

Solution: It requires re-priming the pump.

(3) The suction side is suddenly blocked by a foreign object.

Solution: Stop the pump to remove the foreign object.

(4) Inhaling a large amount of gas.

Treatment method: Check whether there is a vortex at the suction inlet and whether the submergence depth is too shallow.

4. Insufficient traffic

(1) Same as b and c.

Handling method: Take corresponding measures.

(2) The system static head increases.

Troubleshooting method: Check the liquid level and system pressure.

(3) Increased resistance loss.

Solution: Check the pipeline and check valve for any obstructions.

(4) The wear of the shell and the impeller wear ring is excessive.

Treatment method: Replace or repair the wear-resistant ring and impeller.

(5) Leakage from other parts.

Treatment method: Check the shaft seal and other parts.

(6) Blockage, wear, and corrosion of the pump impeller.

Handling methods: cleaning, inspection, and replacement.

5. Insufficient lift

(1) Same as (1), (2), (3), (4) of b, (1) of c, and (6) of d.

Treatment method: Take corresponding measures.

(2) The impeller is installed reversely (double-suction impeller).

Treatment method: Inspect the impeller.

(3) The liquid density and viscosity do not match the design conditions.

Treatment method: Check the physical properties of the liquid.

(4) The flow rate is too high during operation.

Solution: Reduce traffic.

6. Power consumption during operation

(1) There is friction between the impeller and the wear-resistant ring, as well as between the impeller and the shell.

Solution: Check and repair.

(2) The same as item (4) of e.

Solution: Reduce traffic.

(3) The density of the liquid increases.

Treatment method: Check the density of the liquid.

(4) The packing is pressed too tightly or there is dry friction.

Treatment method: Loosen the packing and inspect the water seal tube.

(5) Bearing damage.

Solution: Inspect, repair, or replace the bearing.

(6) The rotational speed is too high.

Troubleshooting method: Check the driver and power supply.

(7) The pump shaft is bent.

Solution: Correct the pump shaft.

(8) The axial force balancing device has failed.

Troubleshooting method: Check whether the balance hole and the return pipe are blocked.

(9) Poor alignment of the coupling or too small axial clearance.

Treatment method: It involves checking the alignment and adjusting the axial clearance.

7. Pump vibration or abnormal noise

(1) Same as items (4) of c, (5), (7), and (9) of f.

Treatment method: Adopt corresponding measures.

(2) The vibration frequency ranges from 0 to 40% of the working speed. Excessive bearing clearance, loose bearing shells, impurities in the oil, poor oil quality (viscosity, temperature), oil foaming caused by air or process fluid, poor lubrication, and bearing damage may occur.

Treatment method: After inspection, take corresponding measures, such as adjusting the bearing clearance, removing impurities from the oil, and replacing the oil with new one.

(3) The vibration frequency ranges from 60% to 100% of the working speed. The issues related to bearings are the same as those mentioned in (2), or it may be due to excessive seal clearance, loose retainer, or worn seals.

Treatment method: Inspect, adjust, or replace the seal.

(4) Vibration frequency is twice the working speed. Misalignment, loose coupling, friction in the sealing device, deformation of the housing, damaged bearing, support resonance, damaged thrust bearing, bent shaft, poor fit.

Handling method: Inspect, take corresponding measures, repair, adjust, or replace.

(5) The vibration frequency is n times the working speed. Pressure pulsation, misalignment, shell deformation, seal friction, support or foundation resonance, pipeline and machine resonance.

Treatment method: Same as (4), reinforce the foundation or pipeline.

(6) The vibration frequency is excessively high. This may be attributed to factors such as shaft friction, imprecise sealing, bearings, bearing vibration, and poor shrink fit.

Treatment method: same as (4).

8. Bearing heating

(1) The scraping and grinding of the bearing tile do not meet the requirements.

Treatment method: Repair the bearing tile or replace it.

(2) The bearing clearance is too small.

Treatment method: It involves readjusting the bearing clearance or performing scraping and grinding.

(3) Insufficient lubricating oil and poor oil quality.

Solution: Increase the oil volume or replace the lubricating oil.

(4) Poor assembly of the bearing.

Treatment method: Inspect the assembly of the bearing as required and eliminate factors that do not meet the requirements.

(5) Cooling water circuit is broken.

Treatment method: inspection and repair.

(6) Worn or loose bearings.

Treatment method: Repair the bearing or discard it. If the bolts are loose, retighten the relevant bolts.

(7) The pump shaft is bent.

Solution: Correct the pump shaft.

(8) The oil slinger is deformed, cannot rotate, and cannot absorb oil.

Solution: Replace the oil slinger.

(9) Poor alignment of the coupling or too small axial clearance.

Treatment method: Check the alignment and adjust the axial clearance.

9. Axle seal heating

(1) The packing is pressed too tightly or there is friction.

Solution: Loosen the packing and inspect the water seal tube.

(2) Misalignment between the water seal ring and the water seal tube.

Solution: Recheck the alignment.

(3) The flushing and cooling are effective.

Solution: Check and flush the cooling circulation pipe.

(4) The mechanical seal is faulty.

Solution: Check the mechanical seal.

10. Large rotor runout

(1) Improper operation, with operating conditions far from the design conditions of the pump.

Treatment method: Strictly follow the operation procedures to ensure the pump operates near its design operating conditions at all times.

(2) The balance is not smooth.

Solution: Dredge the balance pipe.

(3) The material of the balancing disc and its base does not meet the requirements.

Solution: Replace the balance disc and its seat with those made of the required material.

11. Water hammer occurs

(1) Due to a sudden power outage, system pressure fluctuates, causing negative pressure to be discharged from the system. Bubbles dissolved in the liquid escape, resulting in the presence of gas inside the pump or pipeline.

Treatment method: The gas should be completely discharged.

(2) Due to a sudden power outage, the high-pressure liquid column rapidly flows backward, impacting the check valve plate at the pump outlet.

Treatment method: The approach involves modifying the layout of the pipes and pipe fittings in the pump's unreasonable discharge system.

(3) The valve of the outlet pipeline is closed too quickly.

Handling method: Close the valve slowly