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Preventing Cavitation in Your Pumping Applications
•ABB Motors and Drives US•Season 1•Episode 16
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Pumping applications are in almost every industry. On this week’s episode, host Mike Murphy is joined by Kevin Dunn, ABB business development manager for drive products, to discuss cavitation and how it can impact the integrity of your equipment. Tune in to hear Kevin talk about what cavitation is and how to prevent it.
Welcome to the ABB solutions podcast where we address challenges faced in our industry. I'm your host, Mike Murphy, coming to you from Greenville, South Carolina. I have with me today Kevin Dunn, Business Development Manager for drive products. Kevin is here to speak with us on Cavitation. Thanks for being here, Kevin.
Kevin Dunn:
Hey, it's great to be here. Michael excited about sharing what I know about this subject.
Mike Murphy:
Yeah, it's great having you. Okay, so pumping applications aren't just in the food and beverage industry, but they're in about every industry, I keep hearing talk about cavitation. So Kevin, can you explain to me and our listeners, what is cavitation?
Kevin Dunn:
Sure. In short, cavitation occurs when fluid or water at a centrifugal pump starts to vaporize and vapor bubbles are created. So looking at the problem in more detail helps us better understand how to cope with it, provides solutions and in many cases, we can even prevent it. So for example, where cavitation might occur would be inside a typical centrifugal pump. And if you look at the design of the pump, there's an impeller inside and that impeller will create a vacuum on the suction side, what's also called the inlet side. So when that impeller spins, it creates high pressure on the front side of the impeller blades. But unfortunately, there's also low pressure on the backside of the blades as part of the function of the pump. And under some operating conditions, the water vaporizes and actually creates bubbles. For example, if the vacuum gets too large, the water starts to boil and the fluid or water goes from liquid to vapor, essentially steam. These vapor bubbles reach high pressure and they collapse back into liquid form. And when these steam bubbles collapse to liquid again cavitation occurs. The real trick is to avoid the suction pressure getting so low, that we get this transformation from liquid to vapor. So ensuring that there's sufficient pressure in the front of the pump is really key. Actually, many people will tell you, Michael, that they know when cavitation is occurring. interesting enough by a sound like rocks that are moving inside the pump. A cracking or rumbling sound is what people will say they hear. This is the actual rapid implosion of all the vapor bubbles reaching areas of high pressure and then collapsing back into liquid form. This produces damaging shock waves to the pump system unfortunately. Open pumping systems are subject to cavitation if the inlet pressure drops below the NPSH, or the net positive suction head, and that NPSH is quoted in meters or feet. It's the measure of the pressure experienced by fluid on the suction side of that centrifugal pump. It's volume dependent and provided by the pump manufacturer as a specific value for each pump.
Mike Murphy:
Okay, so Kevin, you mentioned one of the tells is the sound of rocks in the pump system. So that sounds like that can do some, some nasty things to the facility, to the equipment in that facility. So what really can happen to a user's equipment? Yeah, it's really can be detrimental. And it's important that facilities address this issue. That shockwave from each individual implosion during cavitation may be tiny, but unfortunately, they occur in large numbers which has immediate negative impact on the pump performance and can be detrimental over time or even catastrophic to the pump. Okay, so what can a user do to avoid cavitation?
Kevin Dunn:
Well, we know that cavitation increases the risk of downtime and results in higher maintenance costs. And these increased costs go beyond frequent replacement of pumps because in some cases, the cost of sending a maintenance team with heavy lifting equipment to a remote pumping site can be several times the cost of the pump. So to your question earlier, I just want to emphasize that cavitation will eventually damage the impeller, the pump housing, the other components in the pumping system through wear and metal fatigue. And it can easily cut the life of a pump by as much as 50%. Some pumps with cavitation issues have even been destroyed in just a matter of minutes. So left unchecked, it'll cause disruption to pumping operations as well as requiring pumps to be repaired and replaced at high cost, therefore, make sense that people would be looking for a solution right.
Mike Murphy:
Kevin, can you tell me more on the solution that ABB can provide to help users minimize cavitation?
Kevin Dunn:
Yeah, sure. Michael. ABB has a smart VFD, also known as an Intelligent Variable Ffrequency Drive that has cavitation detection and control software built into it. And this allows you to monitor online variation in torque or speed., pick up on potential flow issues immediately by changes in the torque on the shaft, automatically reduce speed to mitigate cavitation, control a pump motor more precisely, and you can actually set up warnings to be issued. So the benefits of this solution that ABB provides in this Intelligent VFD with the cavitation detection and control software built in, is you solve that cavitation locally within the drive in real time. There's a cost saving as no extra components are needed and no extra installation work is required. There are fewer production stops for the customer's location, you have increased production volume, it doesn't require additional hardware and it doesn't require additional installation work. So Michael, we believe the ABB VFD Intelligent Drive with this cavitation detection and control software is really one of the best solutions available out there as it makes it possible to address that cavitation without any additional cost or complexity.
Mike Murphy:
Okay, great. So we're going to stop right here. Remember, if you would like more information, contact your local ABB sales representative or visit us at www.ABB.com. If you have any questions or ideas on future podcasts, email us at us- solutions@abb.com Thanks and have a great rest of your day.
