Do you know how to ID compressed air leaks?

Insights on finding compressed air leaks

• Eric Bessey discusses the identification of compressed air leaks and suggests various methods, including acoustic imaging, to efficiently detect leaks and save energy.
• Tom Taranto emphasizes the importance of eliminating inappropriate uses of compressed air, illustrating a case where adjusting controls and using a low-pressure source resulted in significant energy savings.

Air leaks cause equipment to cycle more frequently, thereby increasing the running time of the air compressors, which leads to additional maintenance requirements and possible increased unscheduled downtime. Watch the educational webcast “Energy efficiency: Focus on compressed air systems” and then read this transcript for additional details. This has been edited for length and clarity.

Learn about compressed air leaks from:

• Tom Taranto, Principal Engineer and Owner, Data Power Services LLC, Baldwinsville, New York
• Eric Bessey, President, TTed Solutions, Beaverton, Oregon

Eric Bessey: Compressed air leaks: How do we go about finding those leaks?

No. 1, spend your time wisely. How do we find about it? What kind of areas are good candidates to find leaks? Well, you can see that piston glands, cylinders leak. Hoses, you know those red rubber hoses that droop across the floor? Well, forklifts drive over them and they can leak.

Any point of connection — quick release connections, for instance, even threaded connections — and various types of fittings can leak. They’re good candidates to just snoop around. Regulators, they blow. They are a leak in and of itself, that’s how they work. Blown diaphragms can really present a problem. Then flange gaskets, you can have a blowout.

How do you find these compressed air leaks? Well, one way you can do it is just with your ear. If the plant is down over the weekend or on a holiday, you can walk around and you’ll hear some big leaks. Believe it or not, sometimes some of those leaks can be difficult to locate.

If you can hear it by not find it, the next best thing to do then is soapy water. But soapy water, of course, can be messy and in environments like food production, you wouldn’t want that.

Ultrasonic leak detection is good at finding the general location of a leak and it’s even good at giving you a sense of how big the leak is in terms of small, medium and large. But the latest, greatest thing that’s come out is called acoustic imaging, which is really cool.

Figure 6: There are three main ways to find compressed air leaks. Courtesy: CFE Media and Technology

In Figure 6, lower left, you can see a picture of this guy’s holding one. Basically, it consists of a lot of little microphones that read into a device. The device then transmits that sound pressure level or decibels in the frequencies that they’re at. You can see in the middle picture, you can see there’s a leak there on a connect. That’s like a quick release connect.

It then shows you the intensity of the leak off to the right and the frequencies. Most of us know that humans don’t hear much above about 20 kilohertz. These devices can hear up in the upper range of 50,000 hertz. You can see in this instance that this leak has a very high intensity just above 20 kilohertz. You wouldn’t hear it, but the leak detector can find it.

It’s a very, very handy tool that they can be expensive, but if a company buys one, they’re good for many years. They will pay themselves back tenfold very, very quickly.

Tom Taranto: Eliminating waste in terms of inappropriate uses. Most facilities have leaks and artificial demand. Now we’re going to talk about inappropriate use of compressed air. I was called into a factory that makes glass tubing. As the glass tubing comes to the end of the cooling bed, it gets cut into lengths. There can be glass chips on the end of the tube that they want to be sure don’t get packaged with the tubes. They had a set of six nozzles blowing air at the end of the tubes as they went by, so that the glass chips would be removed. They were supplying it with 100 psi compressor and they had a ball valve there. I asked the operator, “Well, how far do you open the ball valve?”

He said, “Well, I open the ball valve until it just starts to blow the tubes off the conveyor and then I close it a little bit.” I said, “Well, let’s get a pressure gauge and see what is the pressure you’re actually feeding the nozzles at.” It was only 3 psi. We’re using 100 psi compressed air source to supply a 3 psi air demand. What did we do?

We said, “Let’s take a regenerative blower capable of 8 psi and then you can throttle your valve down to 3 psi. Same thing you’re getting previously.” What do we find? We find that the air consumption of the nozzles is 72 cfm each. Among eight production lines, that’s 576 cfm, which is 128 hp air compressor.

That air compressor is going to consume a lot more energy than that. If you take 8,000 hours a year times the 128 horsepower, convert it to kilowatt-hours, the power consumption is much greater and the cost is $49,400 a year.

If you supply that same amount of air from a low-pressure source, which is more appropriate than using compressed air, now you’re down to 32 kW with the blowers. At 8,000 hours a year, you’re down to $16,800.

They’re saving a lot of money every year and the blowers cost a fraction of what an air compressor would cost. The original reason they asked me to come in and look at their system was they wanted to know what size air compressor they needed to have because they were running out of capacity.

Eric Bessey: When readjusting your controls, whenever you’re out in the plant you can make corrections to piping, improve pressure distribution, reduce the airflow consumption, fix leaks, reduce artificial demand with pressure and eliminate potentially nonideal or inappropriate uses.

You have to come back to the compressor room. As a big example, if you fix leaks out in the plant, how much energy are you going to save? The answer is zero. The compressor’s simply going to blow off more. You must go back, readjust controls and make sure that your supply side gets being managed in the best way to meet the demand. Supply and demand and that’s what this is all about.

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