The most comprehensive analysis of pump failures, summarized by an expert

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Analysis of reasons why a water pump fails to discharge water: There is air in the intake pipe and the pump body. (1) Before starting, a self-priming pump isn’t filled with enough water. Sometimes, it seems that the water has overflowed from the vent hole; however, the pump shaft isn’t rotated enough to completely expel all the air. As a result, a small amount of air remains in the intake pipe or the pump body. (2) The horizontal section of the inlet pipe in contact with the water pump should have a downward slope of at least 0.5% opposite to the direction of water flow; the end connected to the pump inlet should be the highest point, and it must not be completely level. If it bends upward, air will accumulate in the inlet pipe, reducing the vacuum level in the pipe and pump, thus affecting water suction. (3) In a single-stage centrifugal pump, the packing has worn out due to long-term use or is too loosely compressed, resulting in a large amount of water spraying out from the gap between the packing and the pump shaft sleeve. As a consequence, external air enters the interior of the pump through these gaps, affecting its ability to lift water. (4) Due to being submerged underwater for a long time, the pipe walls of the water inlet pipe corrode and develop holes; as the water level drops continuously after the pump starts operating, air enters the water inlet pipe through these holes. (5) Cracks at the bends of the water inlet pipe, as well as slight gaps at the connection between the water inlet pipe and the water pump, can both allow air to enter the water inlet pipe. Low speed of the second water pump: (1) Human factors. Some users, due to damage to the original motor, simply replace it with another motor. As a result, this leads to low flow rate, reduced head, or even no water delivery at all. (2) Mechanical failures of the water pump itself. Loose fastening nuts on the impeller and pump shaft, or deformation and bending of the pump shaft, can cause the impeller to shift significantly, resulting in direct friction with the pump casing, or damage to the bearings – all of which can reduce the speed of the water pump. (3) The power machine cannot be repaired. The motor loses its magnetism due to burned-out windings. Changes in the number of winding turns, wire diameter, and wiring method during repairs, or failure to completely eliminate faults during maintenance can also cause changes in the pump’s rotational speed. The permissible suction lift of the three-stage water pump is too limited. Some water sources are quite deep, while in other cases the surrounding terrain near the water source is relatively flat; yet the permissible suction lift of the pump is overlooked. As a result, the pump draws in very little water, or fails to draw any water at all. It should be understood that there is a limit to the degree of vacuum that can be created at the suction inlet of a self-priming centrifugal pump; the suction height achievable in an absolute vacuum is approximately 10 meters of water column, and it is not possible for a water pump to create an absolute vacuum. Moreover, an excessive vacuum level can easily cause the water inside the pump to vaporize, which is detrimental to the operation of the water pump. Therefore, each centrifugal pump has its maximum allowable suction lift, which is generally between 3 and 8.5 meters. When installing a water pump, one must not prioritize convenience and simplicity alone. The resistance loss in the inlet and outlet pipes of the four-flow system is too high. Some users, after conducting measurements, found that although the vertical distance from the reservoir or water tower to the water surface at the source was still slightly less than the head provided by the centrifugal pump, the amount of water pumped was low or no water could be pumped at all. The reason is often that the pipes are too long and have many bends, resulting in excessive flow resistance loss within the pipes. The reason is often that the pipes are too long and have many bends, resulting in excessive flow resistance loss within the pipes. Under normal circumstances, a 90-degree elbow creates more resistance than a 120-degree elbow; each 90-degree elbow results in a head loss of about 0.5–1 meter, while the resistance over every 20 meters of pipe can cause a head loss of around 1 meter. Furthermore, some users arbitrarily choose the diameters of the water inlet and outlet pipes, which also has a certain impact on the head pressure. 5. Influence of other factors (1) The bottom valve cannot be opened. It is usually because the water pump has been left unused for too long, causing the gasket of the bottom valve to stick; a bottom valve without a gasket may also rust. (2) The bottom valve filter screen is clogged ； Or the bottom valve may cause clogging of the filter screen within the muddy layer underwater. (3) The impeller is severely worn. The impeller blades wear out over time, affecting the performance of the water pump. (4) If the check valve of the gate valve is faulty or blocked, it can result in a reduced flow rate or even an inability to draw water in. (5) Leaks in the export pipeline can also affect the water extraction volume. Six common simple methods for equipment fault diagnosis. The common simple methods for condition monitoring include auscultation, tactile inspection, and observation. 1. Auscultation: When the equipment is operating properly, the sounds produced always have a certain rhythm and pattern. By becoming familiar with and mastering these normal melodies and rhythms, one can use their auditory sense to detect any abnormal noises such as heavy, noisy, strange, or chaotic sounds coming from the equipment, and thus identify potential issues like looseness, collisions, or imbalance inside the equipment. By tapping the part with a hammer and listening for any cracking noises, it is possible to determine whether cracks have formed. An electronic stethoscope is a vibration acceleration sensor. It converts the vibration conditions of the equipment into electrical signals and amplifies them; workers use headphones to listen to the vibrations of the operating equipment, thereby enabling qualitative measurement of those sounds. By measuring the signals at the same measurement point at different times, under the same rotational speed and under the same operating conditions, and comparing them, it is possible to determine whether there is a fault in the equipment. When a crisp and high-pitched noise occurs in the headphones, it indicates a relatively high vibration frequency; this is usually caused by local defects or tiny cracks in components that are relatively small in size but high in strength. When the headphones produce a muffled, low-frequency noise, it indicates that the vibration frequency is low; generally, this is due to large cracks or defects in components that are relatively large in size and have relatively low strength. When the noise coming from the headphones increases compared to normal, it indicates that a fault is developing; the louder the sound, the more severe the fault. When the noise coming from the headphones appears in a random and intermittent manner, it indicates that a component or part is loose. 2. Touch sensing method: The tactile sense of the human hand can be used to monitor changes in the equipment’s temperature, vibration, and clearance. The nerve fibers in the hands are sensitive to temperature, allowing them to detect temperatures down to 80°C with relative accuracy. When the temperature of the component is around 0°C, it feels icy to the touch; prolonged contact can cause a piercing pain. At around 10°C, it feels cool to the touch, but it is generally tolerable. At around 20°C, it feels slightly cool to the touch; as contact time increases, it gradually becomes warmer. At around 30°C, it feels slightly warm to the touch, providing a comfortable sensation. At around 40°C, it feels warm to the touch, with a slight burning sensation. At around 50°C, it feels quite hot to the touch; if one presses with the palm for an extended period, sweating will occur. At around 60°C, it feels very hot to the touch, but it can generally be tolerated for about 10 seconds. At around 70°C, it feels scorching hot to the touch; one can generally only tolerate it for about 3 seconds, and the area touched by the hand turns red very quickly. When touching, touch it first and then feel it more carefully to estimate the temperature rise of the component. By shaking the component by hand, it is possible to sense the gap size of 0.1mm–0.3mm. By touching the components with your hand, you can sense changes in the intensity of vibration and whether shocks are generated, as well as the movement of the slide. Using a thermometer equipped with a surface thermocouple probe to measure the surface temperature of components such as rolling bearings, sliding bearings, spindle boxes, and motors offers the advantages of rapid identification of locations with thermal abnormalities, accurate data, and a convenient measurement process. 3. Observation method: Human vision can be used to check whether there is any looseness, cracks, or other damage to the components on the equipment ； It is possible to check whether the lubrication is proper, as well as to detect any signs of dry friction or leaks ； It is possible to examine the quantity, size, and characteristics of metal particles in the fuel tank sediment in order to assess the wear level of related components ； It is possible to monitor whether the device is moving properly and to detect any abnormal phenomena ； It is possible to view the various gauges installed on the device, which indicate its operating status, in order to understand how the data changes. By using measurement tools and by directly observing the surface condition, it is possible to assess the quality of the product and determine the device’s operating condition. By comprehensively analyzing various observed pieces of information, it is possible to determine whether there is a malfunction in the equipment, the location of the fault, its severity, and the cause. The magnetic plug method is a simple way to monitor the wear condition by using an instrument to observe the wear particles collected from the equipment’s lubricating oil. Its principle involves inserting a magnetic plug into the lubricating oil to collect the iron particles generated by wear; by using a reading microscope or simply observing with the naked eye, the size, quantity, and shape of these particles are examined in order to determine the degree of wear on the surface of mechanical parts. The magnetic plug method can be used to observe the larger particle sizes that appear in the later stages of wear of mechanical parts. During inspection, if small abrasive particles are found in small quantities, it indicates that the equipment is operating normally ； If large abrasive particles are found, it is necessary to pay close attention and closely monitor the operating condition of the equipment ； If large particles are repeatedly found consecutively, it is a precursor to an impending malfunction. The machine should be shut down immediately for inspection, to identify and rectify the fault. It was explained in great detail; accurate judgment using these diagnostic methods requires a long period of experience accumulation. As a supplement: For auscultation, you can use the tip of a screwdriver (or a metal rod) to point at the area to be examined; hold the screwdriver with your hand and listen carefully. Doing this can filter out some noise. Temperature touch sensation assessment training: Using a nodular thermometer, measure the metal surface at temperatures of 50 degrees, 60 degrees, 70 degrees, and 80 degrees. For lower temperatures, timing is used to determine how long it is possible to touch the surface, and the temperature is inferred based on this duration. When the higher temperature is too hot to touch, a few drops of water can be sprayed to observe the evaporation process, and then these states should be remembered. Used when diagnosing equipment, it enables more accurate judgments. I came across the method of determining temperature by touch in the book \"Comprehensive Guide to the Installation, Commissioning, Operation, Inspection, Fault Diagnosis, and Maintenance Management of Modern Mechanical and Electrical Equipment.\" However, I think everyone’s tolerance level may vary, so it’s more accurate to use the method suggested by the moderator to make an actual assessment on one’s own. Troubleshooting of tripping faults in seven water pumps 1: Fault symptoms Since the commissioning of the 125 MW unit at the power plant, the water pumps have occasionally experienced a situation where they trip immediately upon being energized, with no signal relays getting activated. After ruling out faults in the switching mechanism, the cables, secondary circuit connections, as well as all relays and their settings were checked using conventional methods, and they were found to be normal; restarting the system then often succeeded. It was later suspected that it was caused by a software fault in the DCS system, but the same issue occurred even when operations were performed on the control panel. 2: Experiment to determine the cause. To identify the reason for this phenomenon, observe the changes in various gauges during the process of closing the switch, so as to determine what caused it to trip. In the test, the voltmeter is used to monitor the microcomputer-based tripping circuit, the milliammeter is used to monitor the operation of differential relays 1cj and 2cj, and the ammeter is used to monitor the thermal protection circuit. After connecting the meters, the feed water pump was started. After a period of testing, there was finally one instance where the pump tripped immediately upon startup. At the same time, it was observed that the pointer of the milliammeter deflected slightly; no other monitoring instruments showed any response. The newly installed XJL-0025/31 type integrated-circuit signal relay 1XJ also operated and its trip indicator activated, indicating that the trip was caused by the operation of the differential protection. 3: Root cause analysis – When differential protection trips, a fault inside the protected equipment is suspected first. Through routine inspections, the water pump motor and its cables are in good condition; the differential relay has been properly calibrated, and the polarity connections of the current transformers are correct. After ruling out causes such as equipment malfunction and wiring errors, the differential protection operated during the motor startup process, indicating that the differential current in the differential circuit exceeded the setting value of the differential relay during this process. Under normal conditions, there are mainly two reasons that cause a differential current in the differential circuit: first, the transformation ratio errors of the current transformers on the two ends of the motor differ from each other, resulting in a small differential current; this differential current is less than 5% of the motor’s rated current Id. Secondly, the difference in the secondary loads of the current transformers at the beginning and end also leads to a difference in their transformation ratios, resulting in a differential current. The difference in load on the current transformers in the differential protection circuit of the water pump motor is merely due to the difference in length of the secondary cables, which is about 50 m; at the rated current, the power consumption of the differential relay is no more than 3 VA, so the secondary load is not heavy. The inspection revealed that the current transformers used for the differential protection of the feedwater pump motor on both the primary and secondary sides are all of the LMZBJ-10 type; they are rated for 15 times the rated current, have a transformation ratio of 600/5, and a capacity of 40 VA, which is more than sufficient to meet the requirements of the secondary circuit loads. The above analysis is based on normal operating conditions; the situation is different when the motor starts. When the motor starts, the current is very high, and the current transformers on the left and right sides may become saturated. At this time, due to the different magnetization characteristics of the various current transformers, the secondary differential current can be quite large. According to the setting instructions for the LCD-12 differential relay manufactured by Acheng Relay Factory, the set value of the relay’s operating current is calculated as follows: izd = △i1 × kk × in/n = 0.06 × 3 × 356/120 = 0.534 A. Here, △i1 represents the maximum error between the current transformers at the beginning and end under normal operating conditions; this value ranges from 0.04 to 0.06 ； kk—reliability coefficient, 2–3 ； in—rated motor current ； n—Current transformer turns ratio. It should be set at the 1.0a position. When using Class B current transformers, with the operating current of the differential relay set at 1.5 A and a braking coefficient of 0.4, the differential protection still operates occasionally during motor startup. This is because Class B current transformers have a lower saturation point in their magnetization characteristics and weaker resistance to saturation, which fails to meet the requirements of the differential relay. Typically, Class D current transformers are required for the current transformers in differential protection circuits. Class D transformers have a higher saturation point; they are less prone to saturation, thereby reducing the differential current flowing through the differential circuit during motor startup. After replacing it with a Class D current transformer, setting the operating current of the differential relay at 1.0 A, and setting the braking coefficient at 0.4, no further occurrences of the fault where the circuit breaker tripped immediately upon closing have been reported. Treatment and Discussion on Mechanical Seal Failures in Eight Water Pumps. A mechanical seal, also known as an end-face seal, relies on the pressure of springs and the sealing medium to generate an appropriate compressive force on the contact surfaces of the rotating moving ring and the stationary ring, thereby ensuring that these two end faces are in close contact. A very thin layer of oil film is maintained between the end faces; the resistance to the flow of the medium is high, which prevents liquid leakage and thus achieves sealing. At the same time, it provides lubrication for both the moving ring and the stationary ring. With proper adjustment, there can be absolutely no leaks. 1 Characteristics of pump mechanical seals. The main advantage of pump mechanical seals is their reliable sealing performance, with very little leakage over a long service life ； It has a long service life, typically lasting around 5 years ； The maintenance cycle is long. However, mechanical seals have a complex structure, require high precision in manufacturing and installation, are costly, and demand high technical skills from maintenance personnel. Since the mechanical seals used in oil pipelines are of the internal type, repairing them often involves disassembling the oil pump, which entails a lot of work. Therefore, it is very important to ensure the reliable operation of mechanical seals and extend their service life. 2 Common problems of water pump mechanical seals: During use, the main issues that arise with mechanical seals are excessive leakage and high temperatures. Touch the mechanical seal gland with your hand; if you cannot keep your hand on it, it indicates that the temperature is too high. The leakage rate on each side should not exceed 60 drops per minute; if liquid flows in a linear pattern, it indicates an excessive leakage rate, and it is then possible to determine whether to continue observing the operation ； If oil is spraying outward, the machine should be stopped immediately for inspection. 3 Control measures taken 3.1 Ensuring the quality of components Mechanical seals must undergo seal performance tests before leaving the factory, and must come with a certificate of conformity. After long-term operation, mechanical seals experience wear of the rotating ring and the stationary ring, corrosion and wear of the springs and shaft, as well as wear, aging, and deformation of the sealing rubber rings – all of which can lead to leakage. In such cases, the seal must be repaired or replaced with new parts. The sealing surfaces of the moving ring and the stationary ring must be free of cracks, chipped corners, scratches, pitting, burrs, and uneven wear; scratches and pitting must not extend across the entire sealing surface. When using the repaired stationary and rotating rings, the sum of the heights of their protrusions should be at least 3 mm, with each individual protrusion having a height of at least 1 mm, in order to avoid affecting heat dissipation. After installation, the moving ring should be able to move freely on the shaft; when pressed against the spring, it should be able to spring back freely, thereby maintaining the perpendicular and parallel alignment between the moving and stationary rings. The specifications of the sealing rubber rings for the rotating and stationary rings comply with the requirements specified in the drawings; the surfaces must be free from any damage, uneven thickness, or uneven hardness. The sealing rubber rings should be replaced during major overhauls. The outer surface of the springs is clean and free of rust. Before use, they should be inspected for length and shape as well as subjected to pressure tests. The pressure difference at the specified compression length for each set of springs must meet the required standards, and the pressure error at that same compression length also needs to be within acceptable limits. The tolerance for the free length shall not exceed 0.5 mm, and the compression amount should not be too large or too small; the allowable error is ±2 mm. The sealing sleeve and the pump shaft cannot be made of the same material; the tolerance for the parallelism of their end faces, as well as the tolerance for their deviation from being perpendicular to the axis, must not exceed ±0.20 mm. 3.2 Ensure adequate cooling and lubrication: Adjust the opening degree of the control valves in the cooling circuit to ensure that the cooling circuit for the mechanical seal remains unobstructed. When operating the tank pump, open the drain valve to remove all gas from the seal chamber. 3.3 Ensuring installation accuracy: When disassembling or assembling the mechanical seal of a water pump, the stationary and rotating rings must be cleaned thoroughly, and a small amount of clean lubricant should be applied to the friction surfaces. Attention must be paid to both the high-pressure side and the low-pressure side; impact must be strictly avoided. When installing the static ring gland, apply even force to avoid misalignment; use a feeler gauge to check that the deviation in the up, down, left, and right directions is no more than 0.05 mm ； Check the fit clearance between the gland and the outer diameter of the shaft; it should be uniform around the perimeter, with the allowable deviation at each point not exceeding 0.1 ram. The radial runout of the pump shaft at the location where the mechanical seal for the water pump is installed shall not exceed 0.05 mm. Before installing the pump cover and the sealing end cap, it is necessary to carefully verify the installation positioning dimensions of the mechanical seal. If these dimensions do not meet the requirements, steel shims can be used for adjustment between the shaft sleeves; however, the precision of these shims must be high, with a thickness difference of no more than 0.01 mm. The radial runout of the mechanical seal sleeve and the end-face runout of the sealing surface meet the requirements. For mechanically sealed units that have been in operation and where the gland loosening has caused the sealing surfaces to shift, the stationary and rotating ring components must be replaced; it is absolutely not permissible to retighten them and continue using the unit. Because after such loosening, the original motion path of the friction pair changes, and the sealing performance of the contact surface is easily compromised. 4.4 Adjusting the end-face specific pressure The end-face specific pressure is an important parameter that affects the sealing performance and service life; it is related to the design of the seal, the size of the spring, and the pressure of the medium. Excessive end-face specific pressure will damage the friction pair ； If the specific pressure is too low, leakage is likely to occur; manufacturers usually specify an appropriate range, with the specific pressure at the end faces typically being between 3 and 6 kg/cm2. Adjusting the specific pressure means adjusting the compression size of the spring. The free length of the spring is denoted by A, the load that the spring stiffness can withstand for a unit amount of compression is denoted by k, and the required specific pressure is denoted by P; these are all parameters specified by the manufacturer. If the dimension after compression is denoted by B, then P/A – 13 = k, which gives 13 = A – e/k; this is the dimension of the spring after it has been compressed and installed. If the size after the spring is installed is too large, the thickness of the adjustment shims between the spring seat and the spring can be increased; if it is too small, the thickness of the shims should be reduced. The thickness of the adjustment shims is measured using a micrometer. 9. Diagnosis and Remedial Measures for Pump Failures During maintenance, the diagnosis of pump failures is a crucial step. The following outlines several common failures along with their corresponding remedial measures, to help in carrying out accurate diagnoses of pump failures. 1. No liquid is supplied, or the supply of liquid is insufficient or the pressure is low. (1) The water pump is not filled with water or proper venting has not been carried out. Remedial measure: Check whether the pump casing and inlet pipes are completely filled with liquid. 2) The pump speed is too low. Remedy: Check whether the motor wiring is correct, whether the voltage is normal, or whether the steam pressure of the turbine is normal. 3) The head pressure in the water pump system is too high. Remedy: Check the head pressure of the system (especially friction losses). 4) The pump’s suction head is too high. Solution: Check the existing net head (very small or long inlet pipes can cause significant friction losses). 5) Clogging of the water pump impeller or pipelines. Remedy: Check for any obstructions. 6) The rotation direction of the water pump is incorrect. Solution: Check the rotation direction. 7) Air is generated by the water pump or there is a leak in the inlet pipeline. Remedial measure: Check the inlet pipeline for cavitation and/or air leaks. 8) Wear of the packing or seal in the water pump’s stuffing box allows air to leak into the pump casing. Remedial measures: Check the packing or seal and replace it as necessary, and verify that the lubrication is functioning properly. 9) Insufficient suction head when the water pump pumps hot or volatile liquids. Solution: Increase the suction head; consult the manufacturer. 10 Water pumps) The bottom valve is too small. Solution: Install a bottom valve of the correct size. 11) The submersion depth of the water pump’s bottom valve or inlet pipe is insufficient. Solution: Consult the manufacturer for the correct submersion depth. Use baffles to eliminate vortices. 12) The clearance of the water pump impeller is too large. Remedy: Check whether the clearance is correct. 13) Damaged water pump impeller. Remedy: Inspect the impeller and replace it as required. 14) The diameter of the water pump impeller is too small. Solution: Consult the manufacturer for the correct impeller diameter. 15) The water pump pressure gauge is in the wrong position. Remedy: Check whether the position is correct, and inspect the outlet nozzle or pipe. 2. The water pump stops operating after running for a while. 1) The suction lift is too high. Solution: Check the existing net head (very small or long inlet pipes can cause significant friction losses). 2) Clogging of the impeller or pipeline. Remedy: Check for any obstructions. 3) Air is generated or there is a leak in the inlet pipeline. Remedial measure: Check the inlet pipeline for cavitation and/or air leaks. 4) Wear of the packing or seal in the stuffing box allows air to leak into the pump casing. Remedy: Inspect the packing or seal and replace it as necessary. Check whether the lubrication is normal. 5) Insufficient suction head when pumping hot or volatile liquids. Remedy: Increase the suction head; consult the manufacturer. 6) Insufficient immersion depth of the foot valve or inlet pipe. Remedial measure: Consult the manufacturer for the correct immersion depth, and use baffles to eliminate vortices. 7) Damage to the pump casing gasket. Preventive measures: Inspect the condition of the gasket and replace it as required. 3. Excessive power consumption by the water pump. 1) Incorrect rotation direction. Remedial measures: Check the rotation direction. 2) Impeller damage. Remedy: Inspect the impeller and replace it as required. 3) Rotating components seize. Countermeasures: Check whether the clearance of internally worn components is normal. 4) Shaft bending. Remedial measures: Straighten the shaft or replace it as required. 5) Too high speed. Countermeasure: Check the winding voltage of the motor or the steam pressure supplied to the turbine. 6) The head is below the rated value. Too much liquid is being pumped out. Solution: Consult the manufacturer. Install the throttle valve and cut the impeller. 7) Liquid is heavier than expected. Remedial measures: Check the specific gravity and viscosity. 8) The stuffing box does not have proper packing (insufficient packing, improper insertion or seating, or packing that is too tight). Remedial action: Check the packing and refill the stuffing box. 9) Incorrect bearing lubrication or bearing wear. Remedial action: Inspect and replace as required. 10) The operating clearance between the wear rings is incorrect. Remedy: Check whether the clearance is correct. Replace the pump casing and/or impeller wear rings as required. 11) The stress on the pipes on the pump casing is too high. Remedy: Relieve the stress and consult the manufacturer’s representative. After stress relief, check the alignment. 4. Excessive leakage in the pump’s stuffing box. 1) Bent shaft. Remedial measure: Straighten the shaft or replace it as required. 2) Misalignment of the coupling or between the pump and the drive unit. Remedial action: Check the alignment; realign if necessary. 3) Incorrect bearing lubrication or worn bearings. Remedy: Inspect and replace as required. 5. Excessively high bearing temperature 1) Bent shaft. Remedy: Straighten the shaft or replace it as required. 2) Misalignment of the coupling or between the pump and the drive unit. Remedial action: Check the alignment; realign if necessary. 3) Incorrect bearing lubrication or worn bearings. Remedy: Inspect and replace as required. 4) The stress on the pipes on the pump casing is too high. Remedy: Relieve the stress and consult the manufacturer’s representative. After stress relief, check the alignment. 5) Excessive lubricant. Remedy: Remove the plug to allow the excess grease to drain out automatically. If it is an oil-lubricated pump, drain the oil to the correct level. 6. Overheating of the water pump stuffing box 1) The packing or seal in the water pump stuffing box is worn, allowing air to leak into the pump casing. Solution: Inspect the packing or seal and replace it as necessary. Check whether the lubrication is normal. 2) The water pump stuffing box does not have the proper packing (insufficient packing, not properly inserted or not properly seated, or the packing is too tight). Remedial action: Check the packing and reinstall it in the stuffing box. 3) There are design issues with the water pump packing or mechanical seal. Remedy: Consult the manufacturer. 4) Damage to the mechanical seal of the water pump. Remedy: Inspect and replace it as required. Consult the manufacturer. 5) Scratches on the water pump shaft sleeve – Remedial measures: Repair, re-machine, or replace as required. 6) The pump packing is too tight or the mechanical seal is not properly adjusted. Remedy: Check and adjust the packing, and replace it as required. Adjust the mechanical seal (refer to the manufacturer’s instructions provided with the water pump or consult the manufacturer). 7. Difficult rotation or friction in rotating components 1) Bent water pump shaft. Remedy: Straighten the shaft or replace it as required. 2) The operating clearance between the wear rings of the water pump is incorrect. Remedial measure: Check whether the clearance is correct. Replace the wear rings of the pump casing or impeller as required. 3) The stress on the pipes on the water pump casing is too high. Remedy: Relieve the stress and consult the manufacturer’s representative. After stress relief, check the alignment. 4) Excessive wobbling of the water pump shaft or impeller ring. Remedial measures: Inspect the rotating components and bearings; replace any worn or damaged parts as required. 5) There is dirt between the water pump impeller and the wear ring of the pump casing, as well as inside the wear ring of the pump casing. Remedial action: Clean and inspect the wear rings, and replace them as required. Isolate and eliminate the sources of dirt