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The service life of a pump depends on regular inspections. The inspection process primarily involves assessing the pump’s condition based on its external operating performance, in order to detect any abnormalities in the pump. Most of the abnormalities are not irreversible damage to the water pump. If the fault can be diagnosed and repaired promptly, the water pump can return to normal operation. There are mainly five types of abnormalities in water pumps: abnormal noise, abnormal vibration, abnormal performance, abnormal temperature rise, and other abnormalities. Today, we will explain the abnormal noise among these five types of abnormalities. Abnormal noise mainly refers to loud or sharp noises generated during the operation of the water pump. This noise may not be sufficient to cause noise pollution in the environment, but it indicates an issue with the water pump system that requires prompt inspection. The causes of noise can be roughly summarized as follows: the mixing of gas and liquid is a common phenomenon in vertical pumps, as the outlet of such pumps is usually not at the highest point of the pump body. When exhaust gas is not discharged or gas is generated within the system, the gas accumulates at the top of the pump. This accumulated gas causes periodic pressure (volume) changes as the pump operates, resulting in abnormal noise from the pump. In this case, it is necessary to completely drain the water pump. If gas is generated by the system, check the cause of the gas generation to prevent it from occurring. Cavitation refers to the shock phenomenon that occurs when, during water pumping, the inlet pressure drops below the saturated vapor pressure, causing the water to vaporize. Water containing bubbles comes into contact with the surface of the impeller; once pressurized by the impeller, the bubbles dissipate, and the water surrounding them quickly fills the space where the bubbles were. It is usually a high-frequency metallic striking sound from the pump head side, like beans exploding. Cavitation can be checked by manually reducing/closing the outlet valve of the water pump. When the valve is reduced in size/closed, the noise disappears significantly, indicating cavitation. Solving the cavitation problem is very troublesome. First, minimize the resistance in the intake pipe and appropriately increase the intake pressure. The friction of the pump body refers to the contact friction within the mechanical structure. Most cases are due to improper assembly of the impeller or pump body, resulting in axial or radial contact, or no contact during assembly but an axial distance that is less than the bearing clearance. When the pump is operating, the impeller inlet is under negative pressure, resulting in axial displacement and friction. This friction noise is caused by periodic or continuous metal friction; it can be checked by turning it by hand after the machine is stopped. The maintenance method involves removing the water pump, reassembling the incorrect components, and reworking those with poor dimensions; if the bearings are damaged, they need to be replaced. The intrusion of foreign objects refers to the situation where, during the installation or operation of a water pump, foreign objects enter the pump’s flow channels and cause friction or impact on the impeller. The noise is usually the sound of metal rubbing, and when turning it by hand after shutting it down, intermittent or continuous resistance can be felt. The repair method involves disassembling the water pump, removing foreign objects, and checking for damage to components such as the impeller and pump body. When the damage is severe, parts need to be replaced. The bearings may rust; small-volume pumps do not have bearings on the pump head side, and are supported by the bearings of the motor, such as those in models CM, PT, etc. Due to the heavy load, some high-capacity pumps are equipped with side bearings on the pump head. Regardless of where the bearing is located, the grease can fail; it will rust when exposed to water or moisture, and a rusty bearing can cause operational noise. To address the issue of bearing rust, it is necessary to disassemble the bearing area, replace the bearings, and check whether other parts are also rusted and need to be cleaned. Dry grinding of bearings is different from bearing rusting; in some environments, the bearing area remains dry at all times. However, due to high temperatures in the bearings or the failure to replenish lubricant regularly, there is a lack of lubrication, which increases friction within the bearings, generates a large amount of heat, and is accompanied by noise during rotation. Externally, this is manifested as high frictional resistance when manually turning the pump shaft while it is stopped; in cases of severe wear, increased axial movement may occur, and in such situations the water pump needs to be disassembled to replace the bearings. Most fan-driven water pumps use air-cooled motors, with the fan blades being the main components for dissipating heat from the motor. When the fan cover is deformed or misaligned due to external forces, it may come into friction with the fan blades; or when the fan blades are misaligned, it may come into friction with the rear cover of the motor. Regardless of the type of friction, noise will be abnormal. The fan blades are mostly made of plastic, so although the noise frequency is high and continuous, the tone of the noise is not sharp. When encountering such a problem, it is necessary to check the friction points and adjust the installation position of the fan cover or fan blades in order to eliminate the friction. When the flow rate is too high, or if the system is not properly designed or if there are significant constrictions in the pipes, the water system may generate sharp noises at such points, similar to the high-speed flow and vibration of air passing through a whistle. This kind of noise usually occurs in the water pump pipes, rather than on the pump itself. This can be eliminated by reducing the flow rate or improving the tapered pipe. Air vibration, also known as air pocketing, occurs when the foundation on which the water pump is installed has low strength and is semi-enclosed, allowing a large amount of air to exist. When the water pump vibrates, the air in the foundation vibrates as well, similar to resonance, resulting in low noise. Holding the water pump or its base with your hands, or lifting the pump and separating it from the base, can reduce or eliminate noise. This procedure can be used to diagnose the cause of the noise. The solution is to adjust the basic structure, increase strength, or add openings to allow air to escape. Electromagnetic noise refers to the sharp whistling sound that occurs when a frequency converter is used to drive a water pump, due to incompatibility between the parameters of the frequency converter and the hardware of the pump’s motor. This does not indicate anything about the quality of a particular series of frequency converters or pump motors, nor does it mean that those products are incompatible with each other; it is simply a case of incompatibility in this specific combination. This noise can be diagnosed by starting the water pump at line frequency or by adjusting the carrier frequency (switching frequency) of the inverter. The solution is also to adjust the carrier frequency (switching frequency); this frequency is typically a parameter that can be set on the inverter, and there is an built-in adjustment gradient – by changing to the next frequency value, it may be possible to eliminate the noise. Does a water pump make noise when it is operating normally? Of course there will be noise. Under normal operation, noise is generated by the friction of water flow inside the water pump, by the mechanical friction in the motor rotor, and by the airflow from the motor fan used for cooling. Of these three types of noise, the first two are negative feedback related to the system’s requirements; they are directly associated with the pump parameters and motor power specified by the system. The third type of noise stems from the need for effective motor cooling. To address this issue, the centrifugal pumps developed by RICITE feature optimized fan blades that help reduce wind noise, thereby lowering the overall noise level generated by the pump during operation. Richter (Zhejiang) Technology