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What’s the best way to avoid Pump Cavitation during brewing beer

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What’s the best way to avoid Pump Cavitation during brewing beer

Pumps play an important role for medium transfer in a brewery. In the real brewing operation, there always have a risk to meet pump cavitation and damage pump seal, it will delay your brewing. Then how to prevent pump cavitation in a Brewery
Cavitation is not a new phenomenon that impacts a pump system in a brewery, but it is an issue that occurs far too often. It occurs when air bubbles are generated inside of pump due to the partial pressure drop of the flowing liquid, resulting in a tiny air bubble. The air bubbles move, pressure is increased and the air bubbles instantaneously implode. The collapse of the vapor bubbles erode the impeller surface and pump casing. If strong cavitation occurs at the pump inlet, pump performance decreases, which can lead to premature pumping failure. The pump cavitation is normally found in a centrifugal pump, for example at whirlpool process. So it is extremely important to understand the different types of pump cavitation and steps that should be taken to prevent it at all costs.
1. Air Aspiration Cavitation
Air is unpredictable and can sometimes be sucked into a brewhouse pump through failing valves or other weak components. The air will eventually start to form bubbles that then gets popped under pressure by the pump impeller. Some operations we can do on brewery pumps:
Check all O-Rings and mechanical seals
Ensure all piping is crack-free
Make sure joint rings have not perished on any suction piping
Regularly checking any components that will likely fail at some point
2. Internal Re-Circulation
This type of cavitation prevents the pump from discharging at your desired rate, meaning that the liquid will re-circulate around the impeller. The liquid travels through low and high pressure zones resulting in heat and high velocity, which in turn creates vaporized bubbles. So what we can do in brewery to protect the pump?
Open a restricted discharge valve on the pump
Operating too close to shut-off head
A closed discharge valve
An over-pressurized header
Unclog the downstream filter
Assess pressure at the discharge line
3. Turbulence
Any kind of turbulence in a brewhouse pump is never a good sign. If the system has been designed with parts that are inadequate for the amount of liquid you’re trying to pump, it will in turn create vortexes in said liquid. These vortexes will become turbulent and experience major pressure differences throughout the system. This all leads to erosion of solid materials over time. So how to eliminate turbulence in your brewing system?
Design pump suction piping and routing to avoid excess turbulence
Have sufficient NPSHa
Respect maximum allowable flow limits
Increase pump suction line size
4. Vane Syndrome
This cavitation occurs if the pumps impeller uses too large of a diameter or the housing coat is too thick. Both problems here create less space throughout the pump housing. The pump will then have an increased velocity in the liquid from the small amount of free space available, which in turn leads to lower overall pressure. This is where you will see cavitation bubbles because the lower pressure is now heating the liquid. Some tips to prevent this cavitation include:
Free space between the impeller blade tips
Ensure the free space between your impeller and its housing is 4% of the impeller’s diameter or more
5. Vaporization
Also called inadequate NPSHa (Net Positive Suction Head Available) cavitation – this is the most common form. This type of cavitation occurs when a centrifugal pump imparts velocity on a liquid as it passes through the eye of the impeller. Liquid gets vaporized quickly if the impeller is not functioning correctly, which then creates tiny shock waves. Some solutions for your brewery:
NPSHa > NPSHr + 3 ft or more safety margin
Lower temperature
Raise liquid level in suction vessel
Change out pump type
Reduce motor RPM
Use impeller inducer
Increase diameter of the eye of impeller

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