Leak Detection and Repair
After your Compressed Air System has been optimized, leak detection and repair should occur as often as it makes financial sense. This could be every 3 months in some plants and once a year in others. A guideline for determining how often to do leak detection and repair is the cost of 1 scfm of Compressed Air use in your plant per year.
Once you’ve determined how often you need to detect and repair leaks, here are the steps to take:
Find the leaks.
Leaks can be found in any component the compressed air passes through, including piping, valves, and equipment. You can find your system’s leaks yourself, or you can engage an independent leak expert or consultant to find them for you. If you do it yourself, you can find the leaks by listening or using an ultrasonic leak detector.
Listening. Leaks make noise. They hiss at different decibel levels depending on their size and the pressure of the air passing through them. Much has been written about the limitations of the human ear for leak detection but, as a start, it’s an excellent tool. When Compressed Air Consultant's performs an audit in a noisy environment, such as a cement plant, we can usually find two thirds of the leaks just by using our ears even though we wear ear plugs during much of the investigation. Some companies have claimed that if you can hear a leak, it must be at least 6 scfm. In our experience, leaks much smaller than that can be heard with the ear.
Ultrasonic leak detectors. Even though careful, experienced listening can give you a good idea about the location and strength of Compressed Air leaks, for speed and efficiency it often pays to get an ultrasonic leak detector. This detector transforms leak sounds so that leaks undetectable to the human ear become audible.
Record, tag, and quantify them.
It’s not always possible to fix a leak as soon as it’s discovered, but it’s important to record it immediately so that it isn’t forgotten. Record the leak location with the leak’s description, including its size and estimated repair cost. Size can be denoted simply as small, medium, or large; however, if you know your plant’s cost for 1 scfm of air per year, then quantifying the leak in terms of scfm has value for determining whether the repair should be made or not. For example, if the cost of air in your plant is $150 per scfm per year and you have a 2-scfm leak, a $5 repair should be done quickly, but a $900 repair might be postponed because it will cost you more to repair it than you can save in a year by doing it.
If at all possible, put a tag on the leaking spot. If the specific leak source isn’t clear, hang or tape the tag near where you believe the leak is occurring and mark it with the same description you’ve written in your report. If you have a lot of leaks, prioritize them in your report. As soon as possible, transfer the information in the report to a spreadsheet or other document that can be passed on to those responsible for the repair.
Prioritize and schedule the repairs.
When you’re ready to schedule the repairs, review your leak report. Here are some things to look for:
Is there a common source or reason for many of the leaks? In such a case, it usually makes sense to design that problem out of the system. For example, CAC worked at one plant where there were roughly 30 solenoid valves in a hot area, but the valves weren’t designed to operate in such an environment so they leaked. The air lost through the leaks cost more than $27,000 per year; the cost of fixing the problem was replacing a simple $10 seal in each solenoid valve. So if the problem is a repeating one, find the reason and consider whether it makes sense to eliminate that cause from your system.
Which leaks are in applications that can be shut down? If a shutdown is easy to schedule, consider the ROI for repairing these leaks. In some cases it makes sense to fix smaller leaks, while in others you must fix the larger ones. Your schedule should be based on money saved, not air lost.
Which leaks feed critical pieces of equipment and can only be repaired when the line is down? As with other leaks, the decision of when to repair should be based on the cost to repair versus the cost not to repair.
Repair the leaks.
The important issue here is attitude. Nike’s “Just do it” slogan is what to keep in mind. Once you’ve made the decision to repair the leaks, do it quickly. CAC recently did a plant audit where we found 3-year- old leak tags attached to various equipment components. In one case, a simple hose replacement costing less than
$100 would have taken care of the leak. The cost of air lost through the leak since the first tag was put in place was over $750. What a waste!
Maintain low leak loads.
Even though you may have designed common leak problems out of your system, this can only get you so far. Plan to do regular leak detection and repair — typically about every 3 to 6 months.
Ultimately your operators will be your first line of defense. It’s critical to educate them about the real cost of Compressed Air and the importance of catching leaks in their infancy when the repair costs are slight. This will keep the leak loads to a minimum. When you hire new operators, taking 5 minutes to educate them will go a long way to keeping your leak loads low.
There’s no doubt that fixing leaks is an important component in optimizing your Compressed Air System. It’s equally important to take a business approach to the problem — deciding when to repair the leaks based on real data from a detailed compressed-air system audit.