How to prevent air locking and cavitation in water pumps
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In the abnormal operating conditions of the water pump； Gas entrapment and cavitation: What are their symptoms and how can they be prevented?
Ensure all preparations are in place before starting; perform multiple exhaust venting sessions, and avoid running the machine idly for too long
It is recommended to slightly open the outlet valve after starting the water pump for the air-cooling tower, so as to maintain a pressure slightly higher than that in the air-cooling tower. Once the nozzles are filled with water, the pressure will rise naturally; this can be achieved by gradually opening the outlet valve. Use the outlet valve to control the desired flow rate.
Gas application ensures airtightness, while cavitation increases the inlet pressure and reduces the inlet temperature!
Reply to 2# gader: What phenomena are there?
1: Reduce the installation height of the pump. 2: All sealing points are airtight and leak-free. 3: Slightly open the high-point vent valve, and close it once normal operation is achieved.
Before starting the pump, fill it properly and remove all air; after starting, maintain the outlet pressure!
Before starting, close the outlet valve, fully open the inlet valve and control the exhaust valve to allow gas to be discharged. If necessary, rotate the pump to drive it into operation; if there is a backflow valve, open it to ensure that all gas is completely expelled. After startup, the outlet valve is opened to control the amount of liquid pumped, thereby preventing excessive current and pressure in the motor, as well as regulating the inlet water temperature to avoid vapor formation inside the pump.
Before starting, close the outlet valve and open the inlet valve; use the exhaust valve to remove all air from inside the pump to prevent gas from remaining within it. After starting, control the temperature of the water entering the pump to avoid vaporization of the liquid
Cavitation is a process that damages pumps. During operation, the pressure inside the impeller varies; if the temperature of the liquid entering the pump is higher than the vaporization temperature corresponding to the inlet pressure, part of the liquid will vaporize, forming bubbles. When these bubbles are carried to areas with higher pressure, they burst rapidly. Due to the large difference in density between gas and liquid, the surrounding liquid rushes towards the bubbles at high speed, causing intense shock within the liquid. This results in very high pressures and shock frequencies, as well as extremely high temperatures at the point of impact. Symptoms include loud noise, vibration of the pump body, and a significant drop in flow rate, pressure, and efficiency. Consequences include high-frequency shocks and high-temperature corrosion, which together cause cavities to form on the surface of the impeller, leading to its destruction. Preventive measures include avoiding prolonged operation of the pump without liquid, and immediately venting air when cavitation occurs, or even shutting down the pump.
Essentially, it is still about increasing the inlet pressure and following the procedures outlined in the operating instructions. Generally, the outlet valve must be closed before starting a centrifugal pump; after the motor starts, the outlet valve should be opened gradually until the desired flow rate is achieved, after which it should be stopped. However, during normal operation, the opening degree of the outlet valve must be greater than 1/3; if it is less than 1/3, a bypass pipeline must be installed.