Water pump in operation, often appear abnormal noise: First, the cavitation noise is the pump when the cavitation occurs when the sound is generally crackling crackling sound. Second, loosening noise that is by the rotor components on the shaft loose sound. This sound often comes with periodicity. Such as circulating pump impeller, shaft sleeve on the shaft loose (gap is even 1 to 3 mm), will send out a slightly rustling impact sound. If the pump shaft is bent at this moment, the collision sound will be greater because the impeller and the bushings have a tendency to sag on the shaft, and the gap appears below the shaft. However, when the curved surface of the convex to the top, it will impact the impeller upward movement, not waiting for the impeller to move up, the pump shaft convex down to the bottom, the impact impeller down. After that, the convexity of the pump shaft turns to the top again, and the impeller is re-struck to move upwards, thus giving a periodic sound. It must be pointed out that pumps running in such conditions are dangerous and that, apart from the leakage of air into the pump due to the swinging of the rotor parts, the impeller is more severely cracked and the shaft breaks (at the edge of the mating area), etc. . Some rolling bearing spacer sleeve, because it is not bearing pressure, there will be intermittent operation of the shaft and the impact of the sound. Due to the gap between the spacer and the shaft is large, when it is not pressed in the axial direction, the gap will appear below the shaft. But occasionally the reason will bring the gap to the top, due to their own weight, the distance sleeve to go down, issued a slight impact with the shaft. Third, the small flow abnormal noise is mainly on the volute pump. The noise of the small flow is similar to the cavitation sound, but some are larger, as if they were thrown on the pump casing. This is mainly the design of pump tongue position. Fourth, the rolling bearing noise 1, the new change of rolling bearings, due to radial load assembly is too large, rolling body rotation difficult, will issue a lower buzz. At this point bearing temperature will rise. 2, if the bearing body oil shortage, running rolling bearings will be issued a uniform whistle. 3, the rolling body and the spacer gap is too large, the operation can be issued a larger sizzling sound. 4, the rolling bearing inner and outer ring raceway surface or rolling surface peeling, the operation will be issued intermittent impact and beating. 5, if the rolling bearing damage (including the isolated frame broken, rolling body broken, broken inside and outside the ring, etc.), the operation has cracked crackling sound.