[Q&A Question 232] 2018.08.26
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【Q&A Question 232】August 26, 2018: Briefly describe the causes of cavitation in centrifugal pumps and the methods to address it. Symptoms: 1. The pressure gauge at the pump outlet shows large fluctuations in reading. 2. The pump emits abnormal squealing noises during operation. 3. Vibration increases while the pump is running. 4. Sealing leaks are severe. Causes: 1. Low liquid level at the inlet, insufficient priming volume, resulting in cavitation. 2. Air present inside the pump. 3. Blockage in the inlet pipe or impeller. 4. Water present in the medium, which vaporizes. Solutions: 1. Raise the liquid level at the inlet. 2. Stop the pump, refill it with liquid, and then restart it. 3. Switch to another pump, address the issue with the inlet pipe, or contact a mechanic to repair the pump. 4. Remove water from the inlet pipe. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) Correct: 3 wealth, Incorrect: 1 wealth ； Mass posting of posts – rated based on the lowest score ； Replies that are unrelated to the answer are considered spam and will be deleted immediately. For management purposes, if you need to view content from a few days ago, please go to https://bbs.hcbbs.com/home.php?mod=space&uid=3862647&do=thread&view=me&from=space through the summary post below
Reasons for vacuum formation in centrifugal pumps: blockage in the pump inlet pipeline, the flow path not being reversed and the pump inlet valve not opened, blockage of the pump impeller, severe air leakage due to poor sealing at the pump inlet, excessively low oil temperature, high resistance at the suction inlet, blockage of the pump inlet filter, air remaining inside the pump that has not been removed, low liquid level in the buffer tank, and high temperature of the incoming fluid which can lead to vaporization. Solution: Clean the pipeline at the pump inlet or use a high-pressure pump truck to clear it. Conduct a thorough inspection of the entire system before starting the pump, remove any blockages at the inlet of the pump impeller, adjust the seal packing gland so that the leakage from the seal packing is within the specified limits. If the packing is severely worn, it needs to be replaced. Increase the temperature of the oil flowing into the pump, inspect and clean the filter at the pump inlet, release all gas from inside the pump at its outlet, and also release any gas from the pump inlet at the filter tank. Raise the level of liquid in the buffer tank and lower the temperature of the liquid flowing into the pump.
Reason: (1) Air entrainment in the pump inlet pipe； (2) Motor reversal ； (3) Insufficient pump inlet pressure ； (4) Gas inside the pump ； (5) High temperature of the medium at the pump inlet ； (6) Inlet pipe blockage ； (7) Sealing oil with water ； (8) When starting the backup pump, the two pumps compete for flow rate ； (9) Damage to the impeller and internal grinding ring. Solution: (1) Check and eliminate air leakage ； (2) Contact the electrician for adjustment ； (3) Increase inlet pressure ； (4) Refill the pump ； (5) Coordinate with relevant departments for adjustments ； (6) ； Clean the inlet pipeline; (7) Strengthen oil sealing and dehydration ； (8) First close the outlet valve of the operating pump, then gradually open the outlet valve of the standby pump ； (9) Contact the fitter for handling.
Reason: (1) Air entrainment in the pump inlet pipe； (2) Motor reversal ； (3) Insufficient pump inlet pressure ； (4) Gas inside the pump ； (5) High temperature of the medium at the pump inlet ； (6) Inlet pipe blockage ； (7) Sealing oil with water ； (8) When starting the backup pump, the two pumps compete for flow rate ； (9) Damage to the impeller and internal grinding ring. Solution: (1) Check and eliminate air leakage ； (2) Contact the electrician for adjustment ； (3) Increase inlet pressure ； (4) Refill the pump ； (5) Coordinate with relevant departments for adjustments ； (6) ； Clean the inlet pipeline; (7) Strengthen oil sealing and dehydration ； (8) First close the outlet valve of the operating pump, then gradually open the outlet valve of the standby pump ； (9) Contact the fitter for handling.
Phenomena: 1. The pressure gauge at the pump outlet shows large fluctuations in reading. 2. The pump emits abnormal squealing noises during operation. 3. Vibration levels increase while the pump is running. 4. Sealing leakage is severe. Causes: 1. Low liquid level at the inlet; insufficient filling leads to cavitation. 2. Air is present inside the pump. 3. The inlet pipe or impeller is blocked. 4. Water is present in the medium and vaporizes. Solutions: 1. Raise the liquid level at the inlet. 2. Stop the pump, refill it, and then restart it. 3. Switch to another pump, address the issue with the inlet pipe, or contact a mechanic to repair the pump. 4. Remove water from the inlet pipe.
Reasons: 1. Blockage in the inlet pipeline, resulting in increased pipe resistance. 2. Breakage in the inlet pipeline, causing severe air leakage. 3. The liquid level in the tank containing the inlet medium is too low. 4. The filter is blocked. 5. The inlet valve is not fully open. 6. The outlet valve is opened too wide, leading to low outlet pressure. 7. The temperature of the medium entering the system is too high.
Remedies: 1. Clear the blockages in the pipeline. 2. Repair the leaks promptly. 3. Keep the liquid level in the tank at a sufficient height to ensure safety. 4. Clean the filter. 5. Open the inlet valve fully. 6. Reduce the opening degree of the outlet valve to adjust the outlet pressure. 7. Lower the temperature of the medium in the inlet pipeline; if insulation or heating is in use, reduce the flow of heat steam
Remedies: 1. Clear the blockages in the pipeline. 2. Repair the leaks promptly. 3. Keep the liquid level in the tank at a sufficient height to ensure safety. 4. Clean the filter. 5. Open the inlet valve fully. 6. Reduce the opening degree of the outlet valve to adjust the outlet pressure. 7. Lower the temperature of the medium in the inlet pipeline; if insulation or heating is in use, reduce the flow of heat steam
Reason: (1) Air entrainment in the pump inlet pipe； (2) Motor reversal ； (3) Insufficient pump inlet pressure ； (4) Gas inside the pump ； (5) High temperature of the medium at the pump inlet ； (6) Inlet pipe blockage ； (7) Sealing oil with water ； (8) When starting the backup pump, the two pumps compete for flow rate ； (9) Damage to the impeller and internal grinding ring. Solution: (1) Check and eliminate air leakage ； (2) Contact the electrician for adjustment ； (3) Increase inlet pressure ； (4) Refill the pump ； (5) Coordinate with relevant departments for adjustments ； (6) ； Clean the inlet pipeline; (7) Strengthen oil sealing and dehydration ； (8) First close the outlet valve of the operating pump, then gradually open the outlet valve of the standby pump ； (9) Contact the fitter for handling.
Reason: (1) Air entrainment in the pump inlet pipe； (2) Motor reversal ； (3) Insufficient pump inlet pressure ； (4) Gas inside the pump ； (5) High temperature of the medium at the pump inlet ； (6) Inlet pipe blockage ； (7) Sealing oil with water ； (8) When starting the backup pump, the two pumps compete for flow rate ； (9) Damage to the impeller and internal grinding ring. Solution: (1) Check and eliminate air leakage ； (2) Contact the electrician for adjustment ； (3) Increase inlet pressure ； (4) Refill the pump ； (5) Coordinate with relevant departments for adjustments ； (6) ； Clean the inlet pipeline; (7) Strengthen oil sealing and dehydration ； (8) First close the outlet valve of the operating pump, then gradually open the outlet valve of the standby pump ； (9) Contact the fitter for handling.
Reason: (1) Air entrainment in the pump inlet pipe； (2) Motor reversal ； (3) Insufficient pump inlet pressure ； (4) Gas inside the pump ； (5) High temperature of the medium at the pump inlet ； (6) Inlet pipe blockage ； (7) Sealing oil with water ； (8) When starting the backup pump, the two pumps compete for flow rate ； (9) Damage to the impeller and internal grinding ring. Solution: (1) Check and eliminate air leakage ； (2) Contact the electrician for adjustment ； (3) Increase inlet pressure ； (4) Refill the pump ； (5) Coordinate with relevant departments for adjustments ； (6) ； Clean the inlet pipeline; (7) Strengthen oil sealing and dehydration ； (8) First close the outlet valve of the operating pump, then gradually open the outlet valve of the standby pump ； (9) Contact the fitter for handling.
Reason: (1) Air entrainment in the pump inlet pipe； (2) Motor reversal ； (3) Insufficient pump inlet pressure ； (4) Gas inside the pump ； (5) High temperature of the medium at the pump inlet ； (6) Inlet pipe blockage ； (7) Sealing oil with water ； (8) When starting the backup pump, the two pumps compete for flow rate ； (9) Damage to the impeller and internal grinding ring. Solution: (1) Check and eliminate air leakage ； (2) Contact the electrician for adjustment ； (3) Increase inlet pressure ； (4) Refill the pump ； (5) Coordinate with relevant departments for adjustments ； (6) ； Clean the inlet pipeline; (7) Strengthen oil sealing and dehydration ； (8) First close the outlet valve of the operating pump, then gradually open the outlet valve of the standby pump ； (9) Contact the fitter for handling.
Phenomena: 1. The pressure gauge at the pump outlet shows large fluctuations in reading. 2. The pump emits abnormal squealing noises during operation. 3. Vibration levels increase while the pump is running. 4. Sealing leakage is severe. Causes: 1. Low liquid level at the inlet; insufficient filling leads to cavitation. 2. Air is present inside the pump. 3. The inlet pipe or impeller is blocked. 4. Water is present in the medium and vaporizes. Solutions: 1. Raise the liquid level at the inlet. 2. Stop the pump, refill it, and then restart it. 3. Switch to another pump, address the issue with the inlet pipe, or contact a mechanic to repair the pump. 4. Remove water from the inlet pipe