Compressed Air System

How to make your vacuum system more efficient, from levels to leaks

Four takeaways from the recent Plant Services webinar "The 5 Myths of Vacuum Systems" live Q&A session.

Darren Cartney is the vacuum business line manager for Quincy Compressor and has been with them for five years. Before joining Quincy Compressor, Darren worked in custom pharmaceutical packaging and robotics, providing extensive experience in both the vacuum and compressed air processes.

During the live Q&A portion of the on-demand webinar "The 5 Myths of Vacuum Systems," Darren tackled several attendee questions related to vacuum system optimization.

PS: Can the vacuum level in the vacuum pump be regulated or is it just start/stop control?

DC: Yes, you can regulate. Much like compressed air, you can add a vacuum pump regulator, but this is not always terribly efficient. This leads back to what technology you're using. Like many industries out there, we have moved towards offering some type of VFD or variable frequency drive control so that we can actually set a very specific point.

Let's say that your process requires 26 inches of vacuum. With a VFD and a properly sized vacuum, you can enter in 26 inches of mercury, and if that is a properly sized unit, you should be able to hold 26 inches of mercury with no issue. Maybe you have different processes that require different levels but you want to run a centralized system. You could still use the VFD along with a vacuum regulator as well.

PS: How do you determine the required vacuum level for your system?

DC: Determining the required vacuum level can be a little bit tricky. It’s often very reliant on your process. I have been in the vacuum world for some time, so if you tell me what the process is, I can give you a general window of where that vacuum pump is operating. The things that we can do above and beyond that to tweak that a little bit is coming back down to a VFD. For instance, we may know that we need to work at 26 to 28 inches, but we’re not really sure within that range what would get our best quality.

That’s where the point control would give us a huge advantage because we could do some tests in house. Unfortunately there is no blanket answer; it’s going to be a little bit different for each process. But with the new technologies that are out there, it’s pretty easy to refine the process and figure out what that number is.

PS: Is there a way to measure and data log vacuum flow for a plant-wide system?

DC: Yes, you can measure and data log. We often call it doing an audit. There are some different levels to what we consider an audit. As part of Quincy Compressor, we do a fairly introductory level audit. It’s called our EQ Plus. We go in and measure amp output of the vacuum and then we monitor the pressure. Then we have to do some behind the scenes calculations with the technology so we can identify if it’s a rotary screw, a dry vane, or a flooded vane. We can do some calculations there to see what is actually being used.

Above that are some very intensive audits. They do end up costing substantially more, but you can get a ton of great information out of those audits. And if you have a large system, it would be worth your time and money to invest in a good vacuum audit.

PS: How is leakage determined?

DC: Leakage is a little bit more difficult. We can use leak detection, we have subsonic leak detectors, we can follow pipe. Unfortunately, it’s much more difficult to identify leakage in the vacuum world than in the compressor world. In the compressor world, bad leaks are often audible so we can hear them very easily. In the vacuum world, air is getting pulled inward instead of outward, but it is still possible to do leak detection.

For instance, if you're using a black steel threaded pipe in a system that’s been in place for many years, there is probably pretty substantial leakage anywhere from 20 to 30%. If you're running something that’s a little bit newer with an aluminum pipe that’s O-ring sealed, those systems generally last a little bit longer and their leak percentage is much lower. Knowing the failure rate of your piping system is half the battle.

It’s a Catch-22. You could spend a lot of money doing leak detection, which is often going to determine that you have lot of leaks. There may be so many leaks that repiping is probably the best method. If you know that your system is quite old and needs to be updated, it might be worth your time and money to just go to a new, more modern piping system.

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