How does a pump prevent cavitation?

It is generally impossible to completely avoid this phenomenon, as when a centrifugal pump rotates at high speed, negative pressure is generated in the central area, causing the gas to separate into small bubbles. The pressure near the periphery of the impeller, where the liquid collects, increases sharply; as a result, the liquid crushes these bubbles, and the voids created by them are filled quickly by the liquid. The cavity filling process near the outer peripheral surface of the impeller can damage the impeller surface, unless the liquid contains no gaseous components and does not evaporate under a certain negative pressure. 1. Avoid the formation of internal bubbles. There are various factors that can cause bubbles to form: such as air being drawn in at the inlet, high temperature of the medium, low inlet pressure, and so on. 2. You can try increasing the inlet pressure. Such as increasing the backflow height, etc. 3. The impeller is made of a material with good cavitation resistance.

A funnel with a valve is installed at a high position in the suction section of the centrifugal pump; each time the pump is started, water is first poured in until the water level is above the impeller of the centrifugal pump, after which the valve is closed and the pump is started. Also, check the suction section of the centrifugal pump to ensure there are no leaks, in order to prevent gas from being drawn in due to negative pressure.

Thank you. What are the specific measures?

If the pump has already been manufactured, the way to prevent cavitation is to reduce the pump’s suction lift, thereby giving the fluid being pumped a greater net positive suction head and ensuring that cavitation does not occur

Cavitation is not inevitable. It is necessary to clarify the causes and processes behind its formation: After the liquid is drawn in at the pump’s suction inlet due to negative pressure, the pressure does not rise immediately; once it reaches the inlet of the impeller, the pressure drops further. The lowest pressure point is usually found on the back side, slightly behind the tip of the blade. If the pressure here is lower than the vaporization pressure of the liquid, the liquid will vaporize, resulting in the formation of many bubbles. As the bubbles flow with the liquid to areas of higher pressure, they burst, causing mechanical and electrochemical damage to the flow channel; this is cavitation. Therefore, cavitation will not occur as long as the pressure at the lowest point in the pump flow channel remains above the vaporization pressure of the liquid. This post was last edited by liyong*n on 2008-1-27 17:22]

Cavitation is generally difficult to avoid in centrifugal pumps. The following methods can usually be employed: 1. The pipeline or tank at the pump inlet should be filled with the fluid, with a high liquid level; 2. The pump’s flow rate should be designed taking into account the amount of fluid that needs to be transported at the inlet; 3. Valves can be added at the pump inlet to regulate the flow rate. The above information is provided for reference only.

One is to improve the structural parameters or design of the pump itself, so that the pump requires as little net positive suction head as possible； Another approach is to properly design the device placed before the pump and its installation location, so as to ensure a sufficiently large effective net positive suction head at the pump inlet. The first method is one that can be changed by the pump manufacturer, such as by using a pre-inducer wheel, a double-suction impeller, selecting a slightly larger positive draft angle for operating conditions, or using more resistant materials, and so on ； The second method can be adjusted on-site, for example by reducing the installation height of the suction device in front of the pump, shortening the pipelines, and decreasing the flow velocity within the pipelines.

Increase the pressure difference between the liquid level and the pump inlet, and lower the pump’s position!

Power plants often use pre-pumps.....

Therefore, accumulators and expansion tanks must be added to reduce and eliminate cavitation and water hammer effects

1. First, remove the residual gas from the pump； 2. When installing the pump, try to minimize the suction vacuum level as much as possible ； 3. In terms of operation, the temperature at which the liquid is heated should be kept as low as possible ； 4. Reduce resistance losses in the pipelines ； 5. Minimize hydraulic losses in the suction pipe so that the pressure at the pump’s inlet is much higher than the saturated vapor pressure of the liquid. 6. Reducing the speed at which liquid enters the impeller, that is, lowering the pump’s rotational speed and flow rate, can also prevent cavitation. 7. Using an inducer wheel can also improve the cavitation of the pump.

Our factory has added a level switch tank in front of the pump; if the liquid level in the tank drops too low, an interlock is triggered

When the pump is in operation, gas is generated at the inlet of the impeller due to a certain vacuum pressure. The vaporized bubbles, driven by the impact of liquid particles, cause erosion on metal surfaces such as those of the impeller, thereby damaging them. This vacuum pressure is known as the vaporization pressure. The net positive suction head is the excess energy per unit weight of liquid at the pump’s inlet, above the vaporization pressure. The unit is indicated in meters, denoted as (NPSH) r. The suction lift is equivalent to the required net positive suction head Δh: it represents the vacuum level at which the pump can draw in liquid, or in other words, the maximum installation height allowed for the pump, measured in meters.

Both electric feedwater pumps and steam-driven feedwater pumps have pre-pumps

1. Avoid the formation of internal bubbles. There are various factors that can cause bubbles to form: such as air being drawn in at the inlet, high temperature of the medium, low inlet pressure, and so on. 2. You can try increasing the inlet pressure. Such as increasing the backflow height, etc. 3. The impeller is made of a material with good cavitation resistance. :handshake

1. Reduce the suction height. 2. Adjust the inlet and outlet valves to control flow rate. 3. Install a pipeline pump on the inlet pipe