Principle of centrifugal pump

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Troubleshooting of centrifugal pumps – Problems with centrifugal pumps: The pump will not start or starts with high load. The causes and solutions are as follows: (1) The prime mover or power supply is not functioning properly. The solution is to check the power supply and the prime mover. (2) The pump is stuck. The treatment method is to manually rotate the coupling for inspection; if necessary, disassemble it for inspection in order to eliminate faults in the moving and stationary parts. (3) (The filler is pressed too tightly.) The solution is to loosen the filler. (4) The discharge valve is not closed. The solution is to close the discharge valve and restart. (5) The balance tube is not unobstructed. The solution is to clear the balance tube. Reasons why pump B does not discharge liquid and the corresponding solutions are as follows: (1) Insufficient priming of the pump (or residual gas inside the pump). The solution is to refill the pump. (2) The pump is turned in the wrong direction. The solution is to check the rotation direction. (3) The pump speed is too low. The solution is to check the speed and increase it. (4) The filter screen is clogged, and the bottom valve is not functioning properly. The solution is to check the filter screen and remove any debris. (5) The suction height is too high, or a vacuum has formed in the liquid suction tank. The solution is to reduce the suction height ； Check the suction tank pressure. The interruption after discharge by pump C is due to the following reasons and solutions: (1) Air leakage in the suction pipeline. The solution is to check the connections of the suction side pipes as well as the sealing condition of the stuffing box. (2) The gas on the suction side was not completely exhausted during pump filling. The solution is to request a pump refilling. (3) The inhalation side is suddenly blocked by a foreign object. The solution is to stop the pump in order to remove the foreign object. (4) Inhaling a large amount of gas. The solution is to check whether there are vortices at the inlet and whether the submersion depth is too shallow. The reasons for insufficient d traffic and the solutions are as follows: (1) Same as b, c. The solution is to take appropriate measures. (2) The system’s static head increases. The solution is to check the liquid level and system pressure. (3) The resistance loss increases. The solution is to check for obstructions such as pipes and check valves. (4) Excessive wear of the casing and impeller wear rings. The solution is to replace or repair the wear ring and impeller. (5) Leakage in other areas. The solution is to check areas such as the shaft seal. (6) Clogging, wear, and corrosion of the pump impeller. The treatment methods are cleaning, inspection, and replacement. The head is insufficient. The reasons and solutions are as follows: (1) Same as (1), (2), (3), (4) for b, and (1) for c, (6) for d. The solution is to take appropriate measures. (2) Impeller installed in reverse (double-suction impeller). The solution is to check the impeller. (3) The liquid density and viscosity do not match the design conditions. The solution is to check the physical properties of the liquid. (4) The flow rate is too high during operation. The solution is to reduce the traffic. The high power consumption during operation of f is due to the following reasons and solutions: (1) Friction between the impeller and the wear-resistant ring, as well as between the impeller and the casing. The solution is to check and repair it. (2) Same as item (4) of e. The solution is to reduce the traffic. (3) The liquid density increases. The solution is to check the liquid density. (4) The filler is pressed too tightly or there is dry friction. The solution is to loosen the packing and check the water seal tube. (5) Bearing damage. The solution is to inspect, repair, or replace the bearing. (6) Excessively high rotational speed. The solution is to check the drive and power supply. (7) Pump shaft bent. The solution is to correct the pump shaft. (8) The axial force balance device has failed. The solution is to check the balance hole and whether the return water pipe is blocked. (9) Poor coupling alignment or too small axial clearance. The solution is to check the alignment and adjust the axial clearance. Reasons for and solutions to vibration or abnormal noises in the g pump are as follows: (1) Same as items (4) of c, (5), (7), and (9) of f. The solution is to take appropriate measures. (2) The vibration frequency is 0~40% of the operating speed. Excessively large bearing clearance, loose bearing shells, impurities in the oil, poor oil quality (viscosity, temperature), foaming of the oil due to air or process fluids, inadequate lubrication, and damaged bearings. The solution involves conducting inspections and taking appropriate actions, such as adjusting the bearing clearance, removing impurities from the oil, and replacing it with fresh oil. (3) The vibration frequency is 60%~100% of the operating speed. Regarding bearing issues, see 5 (2); it may be due to an excessive seal gap, a loose retainer, or worn seals. The solution is to inspect, adjust, or replace the seal. (4) The vibration frequency is twice the operating speed. Misalignment, loose couplings, friction in the sealing devices, deformation of the housing, damaged bearings, support resonance, damaged thrust bearings, bent shafts, and poor fit. The approach is to conduct inspections, take appropriate measures, and repair, adjust, or replace as necessary. (5) The vibration frequency is n times the operating speed. Pressure pulsations, off-centering, shell deformation, sealing friction, resonance of supports or foundations, resonance of pipelines or machinery – the treatment methods are the same as those in (4): reinforce the foundation or pipelines. (6) The vibration frequency is very high. Shaft friction, sealing issues, bearings that are not precise, bearing vibration, poor fit due to shrinkage, etc. The treatment method is the same as (4). The reasons for heat generation in the H bearing and the corresponding solutions are as follows: (1) The bearing shells were not lapped to the required standard. The solution is to repair the bearing shells again or replace them. (2) The bearing clearance is too small. The solution is to readjust the bearing clearance or perform scraping. (3) Insufficient amount of lubricating oil and poor oil quality. The solution is to increase the oil volume or replace the lubricant. (4) Poor bearing assembly. The solution is to check the bearing assembly as required and eliminate any factors that do not meet the specifications. (5) Cooling water circuit breaker. The treatment method is inspection and repair. (6) Bearing wear or looseness. The solution is to repair the bearing or discard it. Wasmatsu Kyō, retighten the relevant bolts. (7) Pump shaft bent. The solution is to correct the pump shaft. (8) The oil slinger is deformed; it cannot rotate and thus cannot transfer oil. The solution is to replace the oil slinger ring. (9) Poor coupling alignment or too small axial clearance. The solution is to check the alignment and adjust the axial clearance. Reasons for and solutions to heating of the I-axis seal are as follows: (1) The packing is too tight or there is friction. The solution is to loosen the packing and check the water seal tube. (2) The water seal ring is out of alignment with the water seal tube. The solution is to recheck the alignment. (3) Good for rinsing and cooling. The solution is to check the flushing and cooling circulation pipe. (4) The mechanical seal is faulty. The solution is to check the mechanical seal. The reasons for large rotor play and the corresponding solutions are as follows: (1) Improper operation, with operating conditions far from the pump’s design conditions. Solution: Operate strictly to keep the pump running near its designed operating conditions at all times. (2) The balance is not smooth. The solution is to clear the balance tube. (3) The material of the balance disc and its seat does not meet the requirements. The solution is to replace the balance disc and its holder with materials that meet the requirements. The causes and solutions for water hammer in k are as follows: (1) A sudden power outage leads to fluctuations in system pressure, resulting in negative pressure in the discharge system; bubbles dissolved in the liquid escape, causing gas to accumulate within the pump or pipes. The solution is to vent the gas completely. (2) The high-pressure liquid column rushes back rapidly due to a sudden power outage, impacting the valve plate of the pump’s check valve. The solution is to modify the layout of the pipes in the pump’s improper discharge system as well as the pipe fittings. (3) The valve of the outlet pipeline was closed too quickly. The method of handling this is to slowly close the valve