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Working principle: When the centrifugal pump starts, the pump shaft drives the impeller to rotate at high speed, forcing the liquid pre-filled between the blades to rotate. Under the effect of inertial centrifugal force, the liquid moves radially from the center of the impeller toward the periphery. Centrifugal pumps have prominent advantages such as small size, simple structure, easy operation, uniform flow rate, long service life, and low purchase and operating costs. As the liquid flows through the impeller, it gains energy; its static pressure increases and its flow velocity rises. After the liquid leaves the impeller and enters the pump casing, it slows down due to the gradually widening flow channels within the casing; part of its kinetic energy is converted into static pressure energy. Finally, it flows tangentially into the discharge pipe. Therefore, the volute casing is not only a component that collects the liquid flowing out of the impeller but also an energy conversion device. As the liquid is flung from the center of the impeller toward the periphery, a low-pressure area forms at the center of the impeller. Due to the difference in total potential energy between the liquid surface in the tank and the center of the impeller, the liquid is drawn into the center of the impeller. Thanks to the continuous rotation of the impeller, the liquid is continuously drawn in and discharged. The mechanical energy obtained by the liquid in a centrifugal pump is ultimately manifested as an increase in static pressure energy. Faults and solutions: 1. The pump does not draw in water. Fault analysis: There are debris in the suction valve or it is not open, or the suction pipe is blocked; the sealing of the piping system is poor; air is being drawn in from the shaft seal; there is a fault in the pumping system. Solutions: Open the suction valve, remove any debris, and clear the suction pipe. Seal leaks in the inspection pipeline, especially at the flanged connections during sectional pressure testing. Replace the shaft seal and tighten the packing seal; inspect and repair the filling pump system. 2. The pump will not start. Fault analysis: There is a problem with the prime mover (including the power supply) ； The pump is stuck ； The stuffing box is tightened too much ； The discharge valve is not closed. Solution: Check the power supply and prime mover ； Rotate the shaft again to check the condition of the coupling ； Relaxing filler ； www.dsc86.com manages import and export valves; restarting. 3. Pump does not discharge fluid – Fault analysis: Insufficient priming (or gas remaining inside the pump) ； The pump is not rotating in the correct direction ； The pump speed is too low ； Clogged filter and suction pipe ； The suction height is too high, or the liquid supply to the suction port is insufficient, resulting in a suction vacuum. Solution: Refill the pump ； Confirm the pump’s rotation direction again ； Check the no-load speed of the motor, examine the reduction ratio of the reducer, and determine whether the pump speed matches the designed speed ； Clean the filter and unclog the intake pipe ； Adjust the suction line to be above the pump’s inlet, and modify the liquid supply system at the top of the pump to ensure adequate supply of the medium. 4. Pump discharge stops after operation. Fault analysis: Air leakage in the suction line ； The gas on the suction side was not fully exhausted during pump filling ； The inhalation side is suddenly blocked by a foreign object, or the inlet filter is clogged ； The suction pipe is dehydrated, resulting in excessive gas intake. Solution: Check the sealing condition of the connections on the suction side as well as the stuffing box ； Re-priming the pump ； Stop the pump, clean the filter element, and clear the suction line ； Check whether the suction line is broken and whether the valve on the parallel inlet line is open (lines that are not used frequently). 5. Insufficient flow – Fault analysis: Increase in the system’s net head ； Increased resistance loss ； Excessive wear of the mouth ring and impeller ； Leakage in other areas ； Clogging, wear, and corrosion of the pump impeller. Solution: Check the liquid level and system pressure ； Check for any faults in the piping, check valves, etc ； Replace the mouth ring and impeller ； Check areas such as shaft seals ； Clean, inspect, replace. 6. Insufficient head. Fault analysis: Impeller installed in the wrong direction (double-suction pump) ； The liquid density and viscosity do not match the design conditions ； The operation traffic is too high. Solution: Check the impeller ； Check the relevant physical properties ； Regulate valves, reduce sulfur content. 7. Overload operation – Fault analysis: Poor quality of the motor, friction between the stator and rotor ； Friction occurs between the impeller and the wear ring, as well as between the impeller and the pump casing ； Increase in liquid density ； The filler is compressed too tightly or there is dry friction ； Bearing damage ； Too high rotation speed ； Pump shaft bent ； Axial force balance device failed ； Poor coupling alignment or too small axial clearance ； The viscosity of the liquid being transported is too high or its density is too great. Solution: Check and replace the motor ； Inspect the components inside the pump and repair them ； Check density ； Loosen the packing and check the water seal tube ； Inspect and replace bearings ； Prosecution prime mover speed and power supply ； Align the pump shaft ； Check whether the balance pipe and return pipe are blocked ； Inspect the coupling and adjust its alignment ； Replace the high-power motor. 8. Excessive pump vibration or noise. Fault analysis: Loose foundation bolts or defective base welding ； The pump suffers from flow erosion (excessive flow rate, increased suction resistance, or too high liquid operating temperature) ； The pump is experiencing surging (the system’s net head pressure is higher than the pump’s shut-off pressure); the impeller is damaged or there are foreign objects present. Solution: Tighten the foot bolts, recheck the welding of the base, and if necessary, weld the base again ； Check the cause and eliminate the obstruction ； Check whether the discharge pressure is also too high ； Disassemble the pump body for inspection, and replace or remove any foreign objects. 9. Bearing overheating – Fault analysis: Improper bearing assembly ； Insufficient lubricating oil, poor oil quality, or oil aging ； Insufficient cooling water volume or circuit interruption. Solution: Check and adjust ； Add more oil or change the oil ； Increase the water volume after checking. 10. Overheating of shaft seal – Fault analysis: The packing seal is too tight ； The mechanical seal is faulty. Solution: Adjust the sealing pressure ； Inspect, repair, or replace the mechanical seal.