Back to basics: Getting to the bottom of leaks in your compressed air system

Having a program to find, tag, and fix compressed air leaks will keep them in check, prolong equipment life, and add money back to your bottom line.

By Michael Camber and Waheed Chaudhry, Kaeser Compressors

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Leaks happen. There is quite simply no way around it. They’re in every compressed air system. Even in systems with the newest pipe and the most energy-efficient and most technologically advanced compressors. Due to material thermal stresses, leaks will appear, costing you money. Possibly a lot of money. While it’s sometimes impractical to eliminate them completely, it’s possible to manage them and greatly reduce their impact on your operating costs. Having a program to find, tag, and fix compressed air leaks will keep them in check, prolong equipment life, and add money back to your bottom line. Here’s how.

Begin with buy-in

Many companies make the mistake of starting with a leak-detection audit, but, unless you control all the resources needed to find, tag, and repair the leaks, you need to start with getting buy-in for establishing a sustainable leak-reduction program from those who do. If there is no buy-in, there will be no follow-through. Without buy-in, you will find yourself with a completed leak-detection audit, a list of leaks, and not much else. This is where so many plants fall short. They pay for the audit and tag the leaks, but never fix them. The tags remain attached to the leaks, fade, or get covered in dust, and over time people stop noticing them, or worse they are hastily removed before a high-level plant inspection. Meanwhile, the same existing leaks may worsen as new ones develop.

If, however, you begin by getting everyone on board with a leak-reduction program rather than a leak detection audit, you will have a better chance of successfully managing the leaks and proactively contributing to your plant’s ongoing energy efficiency efforts.

Money talks. Use it to convince colleagues and upper management to back your leak-reduction program. Some managers acknowledge they have leaks but assume they aren’t worth the time and money to fix, given other priorities. But until you get at least a solid estimate of your leak situation, you can’t make an informed decision. The true benefit comes from setting a baseline, following up with leak detections, and making subsequent repairs.

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Figure 1. According to Compressed Air Challenge of the U.S. Department of Energy’s Office of Industrial Technologies, the total cost of 100 psig compressed air has been calculated to be between $0.18/1,000 ft3 and $0.32/1,000 ft3. Fixing a single small leak in a plant quickly pays for itself. (Source: Compressed Air Challenge)
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Figure 2. Leaks commonly occur in hoses and fittings.

While you may not know how much money you are losing each month to leaks, you can make the point by sharing the cost of a single leak (Figure 1). Then point out that leaks are very common. They can occur at every connection from the compressor discharge flange, in dryers and filters, throughout the distribution piping, and on down to the point of use at the FRLs and fittings on the production equipment. Hoses and quick-release fittings are notorious for leaks. So are underground air pipes. Some of the largest leaks are within the production equipment. We’ve seen annual leak losses from $3,000 in a small system to more than $600,000 in large systems. Individual leaks are commonly between $200 and $1,200, but some are much worse (Figure 2).

Finally, point out how much you are paying for power to run the compressors. If you don’t know how much you are paying to run your compressors, you can calculate it:

Compressor input power (kW) x Operating Hours x Energy Cost ($/kWh)

And if you want to know how to calculate the cost of a particular leak for your system, here is the formula:

Leak Rate (cfm) x System Efficiency (kW/cfm) x Operating Hours x Energy Cost ($/kWh)

For many, this will be enough to get the support you need. If not, consider that the U.S. Department of Energy estimates that as much as 25% of all compressed air is wasted through leaks; we’ve seen worse. If possible, take a stroll through the plant when you are not in production and listen — do you hear hissing? If you can hear a leak, you should immediately fix it. It’s that simple.

Are the compressors running when you are not in production? This is another sign of leaks, even if you cannot hear them. Note how many hours they run when they shouldn’t be.

Numerous companies with plans to expand their plant operations have been able to avoid capital expenses simply by fixing their leaks and relying on their existing compressor equipment. So you should definitely assess your leaks before buying more/larger compressors to meet new demand. Another point to make is that more leaks mean more compressor run time, which has cost implications for parts and service in addition to energy. After you have buy-in, you can move forward with getting a thorough leak-detection audit.

Find your “leakness”

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Figure 3. Ultrasonic leak detection is safe and convenient, and it gives concrete data on the leak volume.

There are different methods for leak detection, each with advantages and disadvantages, and each method has a place in an ongoing leak-reduction program. Your hearing, sight, and sense of touch may help clue you in to the fact that you have leaks, but they are limited. For the purposes of gathering concrete, measurable data that you can use to help you prioritize how you want to fix the leaks, ultrasonic leak detection is the most effective.

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