Cavitation prevention for centrifugal pumps? How can I prevent cavitation in my centrifugal pump?

The most susceptible parts of centrifugal pumps to cavitation are: aat the front cover plate with the greatest impeller curvature, near the low-pressure side of the blade inlet edge; b.

the low-pressure side of the volute septum and guide vane near the inlet edge in the extrusion chamber; c.the sealing gap between the outer circle of the blade tip and the housing of the high specific speed impeller without the front cover plate and the low-pressure side of the blade tip; d.The first stage impeller in a multistage pump.

Measures to improve the anti-cavitation performance of centrifugal pumps.

a.Measures to improve the cavitation resistance of the centrifugal pump itself.

1) Improve the structural design from the suction inlet of the pump to the vicinity of the impeller. Increase the overflow area; Increase the radius of curvature of the inlet section of the impeller cover to reduce the sharp acceleration and pressure drop of liquid flow. Appropriately reducing the thickness of the blade inlet and rounding the blade inlet to make it close to the streamlined shape can also reduce the acceleration and depressurization of the head of the flowing blade. Improve the surface finish of the impeller and blade inlet part to reduce the resistance loss; The inlet edge of the blade is extended to the impeller inlet, so that the liquid flow accepts the work in advance and increases the pressure. (2) The pre-induction wheel is used to make the liquid flow work in advance in the pre-induction wheel to increase the liquid flow pressure.

3) Using a double-suction impeller, so that the liquid flow enters the impeller from both sides of the impeller at the same time, the inlet cross-section is doubled, and the inlet flow rate can be doubled. (4) In the design condition, a slightly larger positive angle of attack is used to increase the inlet angle of the blade, reduce the bending at the inlet of the blade, and reduce the blockage of the blade to increase the inlet area; Improve working conditions at high flow rates to reduce flow losses. However, the positive angle of attack should not be too large, otherwise the efficiency will be affected.

5) Adopt anti-cavitation materials. Practice shows that the higher the strength, hardness and toughness of the material, the better the chemical stability and the stronger the resistance to cavitation.

b.Measures to increase the effective cavitation allowance of the inlet device.

1) Increase the pressure of the liquid level in the liquid storage tank before the pump to increase the effective cavitation allowance. (2) Reduce the installation height of the suction device pump. (3) Change the suction device to a backfilling device.

4) Reduce the flow loss on the front pipeline of the pump. For example, in the required range, try to shorten the pipeline, reduce the flow rate in the pipeline, reduce the elbow and valve, and increase the valve opening as much as possible. The above measures can be comprehensively analyzed and appropriately applied according to the conditions of pump selection, material selection and pump use site.

Due to cavitation caused by more air in the middle of the pipeline, the liquid in the pipeline needs to be exhausted before the pump is opened.

Fill the pump with liquid and vent valve at the outlet!

Structural measures: double suction impeller is used to reduce the flow rate through the impeller, thereby reducing the NPSH of the pump; Install a booster pre-pump before the large high-head pump is simply dismantled to increase the inlet pressure; When the gas reaches the high-pressure area, the vapor condenses, the bubble bursts, and the disappearance of the bubble leads to the creation of a local vacuum, and the liquid particles quickly rush to the center of the bubble, and the particles collide with each other, resulting in a high local pressure.

Increase the density of liquids.

The higher the density of the liquid, the smaller the suction height of the pump, when the installed pump that conveys the less dense liquid is used to transfer the denser liquid, the pump may produce cavitation, but when the pump that conveys the denser liquid is used to transfer the less dense liquid, the inlet pressure of the pump is higher and cavitation will not occur.

Increase the temperature of the liquid being delivered.

When the inlet pressure of the centrifugal pump is less than the saturated vapor pressure of the liquid at ambient temperature, a large amount of steam escapes from the liquid potato body and mixes with the gas to form many small bubbles; Cavitation occurs when the temperature of the conveyed liquid rises as the temperature of the conveyed liquid rises, and the pump cavitation occurs.

Factors influencing the occurrence of cavitation

The essential cause of cavitation is that the inlet pressure is less than the saturated vapor pressure at the fluid transport temperature. Cavitation mainly occurs at the outer edge of the impeller blade and cover, vortex shell or several noisy guide wheels, and does not occur at the blade inlet, for example, when the flow rate is greater than the design flow rate, it occurs at the blade front of the blade inlet near the front cover.

When the pressure at the inlet of the impeller drops to the saturated vapor pressure of the liquid to be sent at the working temperature, the liquid will be partially vaporized, and the generated bubbles will enter the high-pressure area with the liquid from the low-pressure area, and the bubbles will shrink and condense sharply in the high-pressure area, and the surrounding liquid rushes to the space occupied by the original bubble at a very high speed, generating a high-intensity shock wave that impacts the impeller and the pump casing, and causes noise and vibration.

Cavitation in centrifugal pumps can affect the performance and life of the pump, so measures need to be taken to prevent and prevent cavitation from occurring.

Here are some ways to prevent and prevent cavitation:

Choose an appropriate pump: The appropriate centrifugal pump should be selected according to the specific conditions and requirements of use. For example, choose the right pump model based on flow and head requirements, and avoid pump models that are too small or too large.

Reduced inlet pressure: If there is a high-velocity flow in the inlet pipe or a sudden contraction of the pipeline, the inlet pressure will decrease, which will lead to cavitation. Therefore, it is possible to reduce the inlet pressure and prevent cavitation by installing a pressure reducing valve or installing a diffuser at the inlet.

Installing an air valve or inlet pipe: Installing an air valve or air intake pipe can effectively prevent cavitation. This allows gas to be introduced to fill the air in the duct after the pump is stopped, preventing air and water from mixing and thus preventing cavitation.

Change the installation position of the pump: If the inlet pipe of the pump is too long or too high, it will also cause the inlet pressure to decrease, which can lead to cavitation. The inlet pressure can be increased by changing the installation position of the pump or increasing the diameter of the inlet pipe to prevent cavitation.

Regular maintenance and inspection: Regular maintenance and inspection of centrifugal pumps, including cleaning debris inside the pump and regularly replacing worn parts, can ensure the normal operation of the pump and prevent the occurrence of cavitation. Li Yunqi.

1. The installation height of the centrifugal pump must be lower than the allowable suction height of the pump.

2. Reduce the resistance of the suction pipeline, such as making the suction pipeline as short and straight as possible, increasing the pipe diameter, reducing pipeline accessories, low valves, elbows, gate valves, etc.

3. The purpose can be achieved by increasing the booster pump, increasing the gas phase pressure of the storage tank, and reducing the temperature of the fluid, that is, reducing the vaporization pressure head. However, it is more difficult to change stupidity in practice, and the increase cost is large.

4. In addition, the different performance characteristics of the centrifugal pump are considered in the gear selection quietly, so that it meets the requirements of the working environment conditions, so that it can work reliably at the high efficiency point.

In short, during the operation of the centrifugal pump, it is necessary to pay attention to whether there is abnormal noise, observe whether the pressure gauge is normal, and regularly check the heating of the bearing and shaft seal, and pay attention to whether there is abnormal leakage at the lubrication and shaft seal.

The main cause of cavitation in centrifugal pumps is because the gas or vapor in the fluid reaches a saturated state, and when the pressure drops, the gas or vapor will precipitate out of the liquid and form cavitation. Methods to address cavitation in centrifugal pumps include:

1.Increase the inlet pressure: Increase the inlet pressure by increasing the height of the inlet pipe or installing an inlet vacuum pump to reduce the occurrence of cavitation.

2.Reduce the flow rate of liquids: Reduce the flow rate of liquids by adjusting the diameter of the pipe, increasing the length of the pipe, etc., so as to reduce the occurrence of cavitation.

3.Change the structure of the pump: use a pump with good cavitation performance, such as deep well pump, self-priming pump, submerged pump, etc.

4.Increase the liquid level height: By increasing the liquid level height, the liquid pressure can be increased, which reduces the occurrence of cavitation.

5.Increase the outlet pressure of the pump: By increasing the degree of closure of the outlet valve of the pump, the outlet pressure of the pump can be increased, thereby reducing the occurrence of cavitation.

In short, to prevent cavitation of centrifugal pumps, it is necessary to start from many aspects, including increasing the inlet pressure, reducing the liquid flow rate, changing the structure of the pump, increasing the liquid level height and increasing the outlet pressure of the pump.

Hello dear! The main causes of cavitation in centrifugal pumps include the following:1

The inlet pressure of the centrifugal pump is too low. If the inlet pressure of the centrifugal pump is too low, it will cause vacuum bubbles to appear in the pump chamber, which will cause the liquid to boil instantaneously and produce gas, which will reduce the pump efficiency or fail to work normally. 2.

The design of the pump inlet pipeline is not reasonable. Improper pipeline design will lead to unstable liquid flow in the pipeline, which is easy to produce liquid oscillation and aggravate the generation and diffusion of bubbles. 3.

Centrifugal pump impeller or housing is worn or corroded. Abrasion or corrosion of the impeller or casing can lead to an unstable flow of liquid in the pump chamber, creating an area of low pressure that promotes gas formation and diffusion. 4.

The liquid level is too low when the centrifugal pump is running. If the liquid level is too low, the liquid in the pump chamber will be thin, and the gas will easily dissolve into the liquid to form bubbles, which will cause cavitation. 5.

Centrifugal pumps use liquids that contain gases or dissolved gases. The presence of gases or dissolved gases in liquids further promotes gas dissolution and evaporation, which can lead to cavitation.

Centrifugal pump cavitation refers to the cavitation phenomenon at the suction end of the centrifugal pump, which leads to the decline of pump performance, increased noise, burial and even damage of the pump, affecting the normal operation of the equipment. The causes of cavitation of centrifugal pumps mainly include the following aspects:1

Too high suction pressure: If the suction pressure of a centrifugal pump is too high, it will cause the liquid to boil, resulting in cavitation. 2.

Gases in liquids: If there is too much gas in the liquid, cavitation can form at the suction end of the centrifugal pump. 3.

Liquid temperature is too high: If the temperature of the liquid being conveyed is too high, it will cause the liquid to boil and produce cavitation. 4.

Unreasonable design of centrifugal pump: If the design of centrifugal pump is unreasonable, such as too long inlet pipe and too many elbows, it will increase the resistance of the pump and cause cavitation. The above are the main reasons for cavitation of centrifugal pumps, and it is necessary to pay attention to the comprehensive consideration and control of these factors when using centrifugal pumps to avoid cavitation.

In summary, the causes of cavitation in centrifugal pumps include excessive suction pressure, gas in the liquid, excessive liquid temperature and unreasonable centrifugal pump design. The comprehensive consideration and control of these factors can effectively avoid the cavitation phenomenon of centrifugal pumps. I'm glad to answer for you, and I hope I can help you.

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