The boiling point of a liquid decreases as the ambient pressure drops;under standard atmospheric pressure,the boiling point of water is 100°C,and it will drop significantly in low-pressure environments.A low-pressure zone forms inside the pump during operation.When the local pressure falls below the saturated vapor pressure of the liquid at its current temperature,the liquid vaporizes and generates a large number of bubbles.After the bubbles enter the high-pressure zone with the fluid,they collapse instantaneously,and the released high-frequency impact force continuously strikes the metal surface.Long-term action will form pitting erosion pits and trigger secondary failures such as seal failure and bearing damage.From a quantitative perspective,available net positive suction head(NPSHa)being lower than required net positive suction head(NPSHr)is the core criterion for cavitation occurrence.

-Bonve Pump Cam Type Double Rotor Pump-

As a positive displacement pump,the lowest pressure point of the cam rotor pump is located in the suction-side working chamber before the rotors enter meshing.During operation,the cam rotors disengage from meshing,and the chamber volume expands rapidly to form negative pressure.Bubbles will be generated if the pressure drops below the saturated vapor pressure of the medium.After the bubbles are transferred to the high-pressure zone on the discharge side along with the rotors,they collapse and erode the rotors and the inner wall of the pump chamber.For rotors with a coating layer,the rubber layer may peel off,accompanied by abnormal noise and vibration,which eventually leads to reduced volumetric efficiency and premature failure of seals and bearings.Compared with centrifugal pumps,cam rotor pumps feature lower rotational speed and gentler flow velocity inside the chamber,with slightly weaker cavitation sensitivity.However,targeted prevention and control are still essential under working conditions of high suction lift,high temperature and high viscosity.

The core of cavitation prevention and control is to ensure that NPSHa is always higher than NPSHr.The widely accepted industry safety margin requires that NPSHa shall be no less than 1.1 times of NPSHr,and the prevention and control can be implemented in four aspects:

1.Reasonable matching of pump type and working conditions

Pump selection is the core of source prevention and control.Parameters including flow rate and medium characteristics shall be fully considered in the selection process to ensure that the system's NPSHa is always higher than the pump's NPSHr.Pipeline loss,medium viscosity and tank liquid level shall be fully calculated to avoid hidden dangers caused by the mismatch between pump type and actual working conditions.

2.Inspection and rectification of discharge side working conditions

Excessive pressure on the discharge side will cause high-speed circulation of fluid inside the pump chamber,triggering discharge cavitation.Clogged filters and pipeline sediments shall be cleaned promptly,and reducers shall be installed as close to the pump body as possible.If necessary,control valves shall be added on the discharge side to avoid bag-shaped pipeline structures that are prone to gas-liquid accumulation.

3.Normalized operation and maintenance management

Daily operation and maintenance is the key to sustained cavitation prevention and control.The suction-side filter shall be cleaned regularly to prevent excessive filtration resistance from causing increased suction pressure drop.The pump operation curve shall be checked against actual working conditions periodically,pressure sensing devices shall be calibrated,and pipeline faults shall be investigated to ensure smooth and stable flow channels.

4.Standardized installation and pipeline design

During the installation phase,key attention shall be paid to pipeline and equipment positioning:the pump shall be installed below the tank liquid level as far as possible to maintain suction pressure by gravity,and be placed close to the fluid source to shorten the pipeline length.A straight pipe section equivalent to 5-10 times the pipe diameter shall be reserved before the pump inlet to reduce resistance components such as elbows and valves.The pipe diameter on the suction side should be 1-2 specifications larger than the pump inlet,and the flow velocity shall be controlled within 2 m/s to reduce friction loss.The suction lift height shall be restricted,and pipe supports shall be adopted to bear the pipeline weight so as to avoid additional pressure load on the pump body.

Cavitation is a widespread fluid phenomenon in pump equipment.Through full-process management and control,its occurrence probability can be greatly reduced,and the stable operation cycle of the equipment can be effectively extended.

Bonve pump always adheres to the philosophy of "Wholeheartedly Making Good Rotor Pumps," committed to providing global customers with customized conveying and mixing solutions. If you have technical inquiries, selection needs, case references, or other cooperation intentions related to Bonve rotor pumps, please feel free to contact us.  

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Official Website: www.bvpumps.com  

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We look forward to working with you to drive efficiency and innovation in industrial fluid transmission with precision technology.