24 Pneumatic diaphragm pumps, rotary vane vacuum pumps, vortex pumps, slurry pumps... Common faults and solutions

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Common faults and solutions for pneumatic diaphragm pumps. Fault causes and troubleshooting methods: Failure to start or slow operation – The filtration, pressure regulation, and lubrication devices as well as the air inlet filter may be clogged; check and clean them. The air valve might be blocked by debris; remove the valve and clean it thoroughly. If there are scratches on the piston inside the valve, replace the piston and the “O” rings. Low flow rate – The inlet pressure is not appropriate; reduce the pump’s operating speed to handle liquids with high viscosity or concentration. The valve ball is stuck; replace it with a suitable valve seat. The liquid being pumped does not match the material of the valve ball; use a valve ball and valve seat made of a suitable material. The inlet pipe is blocked; check and clear it. The outlet liquid contains many bubbles; the diaphragm is damaged; replace the diaphragm. There are leaks in the pump body and pipes; check and seal them. Liquid leaks from the exhaust port of the gas chamber; the diaphragm is damaged; replace the diaphragm. The diaphragm is not installed or secured properly; install and secure it correctly. Common faults and solutions for rotary vane vacuum pumps: Causes of faults and methods to eliminate them. Decreased vacuum level: 1. Air leakage in the system; 2. Insufficient oil volume; 3. Severe contamination of the pump oil; 4. Cracked or detached exhaust valve plates; 5. Blocked oil return holes on the exhaust valve seat; 6. Excessively high temperature of the gas being pumped; 7. Wear of parts due to long-term use; 8. Aging of pump seals. Check for leaks, repair them, fill the tank with oil to the specified level, replace the oil, replace the exhaust valve plates, clear the oil return holes, cool the gas, replace worn parts, and replace seals. Excessive oil discharge: 1. Too much oil; 2. Detached oil traps or plates; 3. Excessively high suction pressure. Drain the oil to the specified level, reinstall or replace it with a larger-sized pump. Oil leakage: 1. Worn oil seals; 2. Damaged oil tank gaskets; 3. Aging of O-rings on the stator and end faces; 4. Loose drain plugs or damaged gaskets. Replace the oil seals, gaskets, and O-rings, or tighten/replace the gaskets. Difficult start-up: 1. Low oil temperature; 2. Missing phase in the motor; 3. Loose belt; 4. Foreign objects inside the pump. Heat the pump oil before starting, check the motor, adjust its position, and remove any foreign objects. Common faults and solutions for vortex pumps: Causes of faults and solutions. No water output after the pump starts: 1. No liquid inside the pump; 2. Air leakage in the suction pipeline; 3. Blockages in the impeller and pipelines; 4. Incorrect rotation direction of the pump; 5. Suction height exceeds the specified limit (4-5 m). 1. Fill the pump tank with liquid; 2. Eliminate air leakage; 3. Check and clean the pipelines; 4. Check and correct the motor wiring; 5. Reduce the geometric installation height of the pump or shorten the length of the suction pipe. Excessive power consumption: 1. Head pressure exceeds the allowable range; 2. Too small a gap between the pump body, pump cover, and impeller. 1. Reduce the pump’s head pressure; 2. Adjust the gap to the specified range. Excessive leakage from the sealing device: 1. Misalignment of the stationary and rotating rings in the mechanical seal; 2. Aging of rubber seals; 3. Presence of solid impurities in the water; 4. Loose springs in the mechanical seal. 1. Repair or replace it to meet requirements; 2. Replace the rubber seals; 3. Install a proper filter; 4. Replace the springs. Reduced displacement: 1. Lower rotational speed; 2. Blockages in the impeller or pipelines; 3. Pipeline resistance exceeding the specified value; 4. Excessively large gaps between the impeller and the pump body/pump cover. 1. Increase the rotational speed to the rated value; 2. Check and clean out debris; 3. Check the pipeline installation, minimizing bends and valves; 4. Adjust the gaps. Common faults and solutions for slurry pumps: Causes of faults and solutions. 1. Difficult start-up: 1. The pump chamber is not filled with liquid, resulting in high friction resistance; 2. The packing gland is tightened too much, causing excessive friction between the shaft and the packing. 1. Use pipe wrenches to turn the pump shaft 3–6 times: 2. Adjust the packing gland. 2. No liquid is discharged after startup: 1. A large amount of air has been drawn in; 2. The motor is rotating in the wrong direction; 3. The viscosity of the liquid is too high. 1. Check whether the liquid level at the suction inlet is too low, and whether there are leaks in the suction pipe. 2. Connect any two phases of the motor’s power supply. 3. Thin out the material liquid. 3. The pump experiences significant vibration or noise. 1. The motor and pump shaft are not aligned properly; 2. Air is being drawn into the pump, or the liquid contained within it has a high amount of air. – 1. Re-adjust the alignment of the shafts; 2. Check the liquid level and take measures to remove any air from the liquid being pumped in. 4. During operation, the flow rate decreases significantly. 1. Wear of the bushings leads to an increased gap; 2. Reduced rotational speed; 3. Damage to the universal joint or shaft, resulting in transmission failure; 4. Insufficient depth of liquid in the suction pipeline, allowing air to enter the pump. 1. Replace the bushings; replace the screw if necessary; 2. Check the power supply and motor; 3. Stop the machine for maintenance, and replace the shaft joint or shaft; 4. Reduce the suction height Increase the immersion depth to remove air from the liquid being pumped. 5. Motor overload: 1. The head pressure is too high compared to the pump’s capacity; 2. The viscosity of the liquid is too high; 3. The voltage is too low. 1. Minimize the head loss in the pipelines, or replace it with a pump with a higher head capacity. 2. Dilute the solution: 3. Check the cause. Increase the voltage to the specified value. 6. Severe leakage at the shaft seal packing: 1. Overly loose gland; 2. Worn packing; 3. Incorrect inlet and outlet positions. 1. Adjust the gland: 2. Replace the packing: 3. Use the middle flange as the suction inlet. Common faults of mud pumps and their solutions. Fault causes and solutions: The pump fails to draw in water due to insufficient water supply, air remaining inside the pump, air leakage in the suction pipe, or a large gap between the front liner and the impeller. Continue to supply water, check for air leaks in the pipelines, and adjust the gap between the impeller and the front shroud. Low discharge pressure, low flow rate; air in the pump; large gap between the impeller and the front liner; poor clutch engagement; worn impeller or liner. Evacuate air from the pump, adjust the gap to regulate the clutch friction plate clearance, and replace the impeller or liner. The slow water filling of the pump is due to a large gap between the front liner and the impeller, as well as the inability of the outlet pipe to prevent air from entering. Adjust the gap, adjust the water discharge pipe, install the vacuum pumping device. Pump vibration: The pump shaft is not aligned with the diesel engine (or motor), the impeller is unbalanced, or the bearings are damaged. Adjust concentricity, perform balance testing on the impeller, and replace the bearings. Pumps wear out quickly due to a poor construction environment (large particles), long transportation distances, and long inlet pipelines; changing the sand site, adding booster units, and shortening the length of the inlet pipes can help reduce cavitation. The impeller journal wears out quickly, the high-pressure water pump has a low head, the gaskets are misaligned, and the pump shaft is not aligned with the rear cover. Replace the high-pressure pump with one that has a higher head than that of the mud pump, replace the packing, and adjust the concentricity. Causes and Solutions for Submersible Pump Failures
Cause Solution
Oil leakage – Sealing box is severely worn; replace the sealing box.
Electric leakage – Water enters the pump body; dry it in a drying room or use a 100–200W incandescent bulb for drying. If the insulation resistance is infinite, replace the mechanical seal.
Low pump impeller speed – The head cannot be achieved due to incorrect wiring; swap the live wires. If this does not resolve the issue, replace the pump.
Impeller does not rotate after power is applied – The rotor is stuck; replace the bearings.
Weak water output and low flow rate – The lower shaft and bearings are loose, causing the rotor to move downward; use appropriate shims between the rotor and bearings to lift the rotor upward.

Common Failures and Solutions for Screw Pumps
Cause Solution
Decreased flow rate:
1. Blockage or air leakage in the suction line.
2. Wear of the screw and pump casing.
3. The safety valve spring is too loose, or the valve disc does not fit tightly against the valve seat.
4. Insufficient motor speed.
Solution:
1. Remove blockages or air leaks in the suction line.
2. Repair or replace worn parts.
3. Adjust the safety valve to ensure proper sealing.
4. Check for missing phases or replace the motor to increase its speed.

Pump fails to draw in oil:
1. Blockage or air leakage in the suction line.
2. The suction height exceeds the allowable vacuum level.
3. The motor is running in reverse.
4. The viscosity of the fluid is too high.
Solution:
1. Eliminate blockages or air leaks in the suction line.
2. Adjust the suction height.
3. Realign the phase wires.
4. Use heating to reduce the fluid’s viscosity.

Severe oil leakage from the mechanical seal:
1. Incorrect assembly position.
2. The sealing gland is not pressed properly.
3. Damage to the sealing surfaces of the rotating or stationary ring.
4. Damaged sealing rings on the rotating or stationary ring.
Solution:
1. Re-adjust the assembly.
2. Press the sealing gland properly again.
3. Grind or replace the rotating or stationary ring.
4. Replace the sealing rings.

Overheating of the drive shaft or motor bearings: This can be caused by a lack of lubrication or damaged bearings. Fill with lubricant or replace the bearings. Severe vibration or noise from the pump body: the pump is not installed properly or is installed too high; the ball bearings of the motor are damaged; the pump’s main shaft is bent, or it is not aligned or parallel to the motor’s main shaft. Replace the motor’s ball bearings; straighten the bent pump shaft or adjust the relative position of the pump and the motor. Common faults and solutions for self-priming pumps. Fault cause – Solution: No response after power is connected; short circuit in the power plug, power leads, or motor windings – Check and fix the wiring issues. Difficult to start or unable to start, with a \"buzzing\" sound: 1. Damaged starting capacitor or starting winding; 2. Motor stuck – 1. Replace with a capacitor of the same capacity or repair the starting winding ； 2. Check for mechanical faults in the motor and pump head, such as damaged bearings or stuck impellers. If the motor can run, but at a low speed, with the casing overheating and a burnt smell present, it may indicate a short circuit in the motor windings; repairs should be carried out using methods such as welding, bypassing, isolation, or rewinding, depending on the extent of the damage. Excessive noise and vibration during operation may be caused by damaged bearings or an improper fit between the bearings and the casing; the motor should be disassembled for inspection, and if the bearings are damaged, they need to be replaced ； If the bearing runs on the outer circumference, the mating surface of the pump casing can be treated with chiseling ； If the bearing wears against the inner surface, the worn area of the motor shaft can be treated with fretting. In cases of severe wear, the area can be repaired by first performing welding and then machining it. Low water output or no water output at all: 1. Leakage in the suction inlet gasket or impeller cover gasket, as well as air leaks in the pipelines; 2. Damaged impeller; 3. Increased gap between the impeller and the pump casing. Solutions: 1. Repair or replace the affected components; 2. Replace the impeller; 3. Depending on the worn parts, repair or replace the impeller ring or the impeller itself. If the water seal on the motor casing is damaged, water can seep into the motor through the motor shaft, thereby deteriorating the motor’s insulation properties. Solution: Replace the water seal and dry the motor. Common faults and solutions for multi-stage centrifugal pumps: Fault – Cause – Solution: The pump fails to draw in water, and the pressure gauge pointer fluctuates violently. There isn’t enough priming water; there are air leaks at the connections between the pipes and instruments. Check whether the bottom valve is leaking; fill it with water and tighten or repair the leaky area. No water comes out; the vacuum gauge indicates a high level of vacuum. The foot valve is not open or is clogged; the suction pipe resistance is too high; the suction height is excessive. Check the bottom valve, replace the water pipes, and reduce the water suction height. Insufficient water output is caused by too much resistance in the outlet pipe, incorrect rotation direction, clogged impeller, or insufficient pump speed. Inspect or shorten the water pipe. Inspect the motor, remove debris from the impeller, and increase the pump speed. The flow rate is below the design requirement. The pump is clogged, the sealing ring is excessively worn, and the rotation speed is insufficient. Clean the water pump and pipelines, replace the sealing ring, and increase the pump speed. The pump consumes too much power. The stuffing box is too tight and heats up; the impeller is worn, and the pump flow rate has increased. Adjust the tightness of the stuffing box; check whether the pump shaft is bent; replace the impeller; increase the discharge resistance to reduce the flow rate. There is an abnormal sound inside the pump, and it cannot pump water. The suction pipe resistance is too high, there is air leakage in the suction line, and the temperature of the liquid being transported is too high. Inspect the suction pipe and bottom valve, seal any leaks, reduce the water suction height, and lower the water temperature. Vibration, bearing overheating. The motor and pump are out of alignment, or the bearings are lacking oil or are worn out. Adjust the coaxiality of the motor shaft and the pump shaft, and lubricate or replace the bearings. Common problems and solutions for magnetic pump issues. Cause and solution for malfunctions: Insufficient flow – 1. Damaged impeller; 2. Insufficient rotation speed; 3. Excessively high head; 4. Obstructions inside the pipes, etc. Solutions: 1. Repair or replace the impeller; 2. Change the motor’s rotation speed; 3. Adjust the head; 4. Perform maintenance and clean the pipes. Insufficient head – 1. Air present in the medium being transported; 2. Damaged impeller; 3. Insufficient rotation speed; 4. Excessively high specific gravity of the liquid being transported; 5. Excessive flow rate. 1. Eliminate air leakage points ； 2. Replace the impeller ； 3. Replace the motor. 4. Adjust the process medium. 5. Adjust the operating conditions of the process. Damaged bearings, impurities inside the pump, install a filter in the inlet pipeline. Broken pump shaft, dry friction of bearings, prevent the pump from running idle, inability to pump liquid: 1. Air leakage in the suction pipeline; 2. Obstructions in the suction pipeline; 3. Pump running in reverse; 4. Excessively high suction height; 5. Broken shaft; 6. Demagnetization of the magnets. 1. Eliminate the air leakage points; 2. Inspect and remove obstructions; 3. Reorder the phases of the motor; 4. Adjust the suction height; 5. Replace the shaft; 6. Replace the magnets. Common faults and solutions for deep well pumps: Fault cause, Solution: Broken shaft: 1. The well pipe is not straight; 2. Severe rusting at the bearings and on the pump shaft, drive shaft, and impeller housing. 1. Dig deeper to increase the diameter of the well; 2. Before starting, turn the drive wheel a few times using a wrench to check for any abnormalities in the transmission. Reduced flow rate and decreased efficiency: 1. Excessive axial clearance, causing the impeller to operate in an abnormal position. 2. The impeller and shroud suffer from severe cavitation or wear. 3. Loose impeller, sliding key. 4. The suction pipe is blocked, there are debris on the impeller, and there is debris between the guide vanes. 5. The rated speed is not achieved, mainly due to belt slippage and improper pulley matching. 6. The well pump is not properly matched, resulting in insufficient water inflow. 7. Increase the head arbitrarily. 1. Adjust the axial clearance. 2. A new part should be replaced. 3. Improve the assembly method. 4. Maintenance and cleaning. 5. The belt should be of appropriate tension; it should not operate if it is too loose, and belt oil (wax) should be applied regularly. 6. Select a suitable deep well pump. 7. It should be corrected in accordance with the instructions. Vibration exceeds limits: 1. The drive shaft is not straight, and the bearings are over-worn. 2. The axial clearance of the bearing is large. 3. The well pipe is not vertical. 4. Not installed correctly as required. 1. Align the drive shaft and replace bearings that are excessively worn. 2. Adjust the axial clearance to correct any upward or downward deviation of the impeller’s working portion. 3. Use well workovers or switch to deep-water pumps with a smaller diameter to address the issue of non-vertical well pipes. 4. Install it correctly as required. The pump pipe is loose, the well tube is not straight, and the well wall is not smooth. 2. The couplings (sleeves) are not concentric. 3. Due to improper fastening ； 4. After shutdown, the effect of water sag causes the shaft to rotate in the opposite direction, resulting in the threads loosening. 1. Well workover solution ； 2. The coupling (sleeve) is properly adjusted as required ； 3. Tighten properly, align the threads correctly, and tighten appropriately ； 4. Solve it by reducing the backflow speed of water in the pipes after shutdown. Causes and solutions for faults in ZW-type self-priming non-clogging sewage pumps
Causes & Solutions:
The self-priming sewage pump does not discharge water:
1. Insufficient or no liquid stored in the pump chamber.
2. Air leakage in the suction pipeline.
3. Low voltage.
4. Excessive suction lift or too long suction pipeline.
5. Severe leakage from the mechanical seal.
Solutions:
1. Add enough liquid.
2. Eliminate air leakage in the pipeline.
3. Adjust the voltage.
4. Reduce the suction lift or shorten the pipeline.
5. Repair or replace the mechanical seal.

Insufficient water discharge from the self-priming sewage pump:
1. Blockage in the impeller flow channel or suction pipeline due to improper use.
2. Severe wear of the impeller.
3. Insufficient power resulting in low rotation speed.
Solutions:
1. Remove the blockages.
2. Replace the impeller.
3. Adjust the rotation speed to the rated value.

Excessive noise and vibration in the self-priming sewage pump:
1. Unstable foundation.
2. Severe wear of the bearings.
3. Misalignment between the pump and the motor shaft.
Solutions:
1. Strengthen the foundation.
2. Replace the bearings.
3. Adjust the alignment.

Excessively high temperature of the bearings in the self-priming sewage pump:
1. Degraded or dried lubricant.
2. Damaged bearings.
Solutions:
1. Replace the lubricant.
2. Replace the bearings.

Leakage from the self-priming sewage pump:
1. Loose connection bolts.
2. Worn seals.
Solutions:
1. Tighten the bolts.
2. Replace the seals