We all hear it time and time again, leakage reduction is one of the first things we can do to reduce compressed air system electrical costs. Yet almost every industrial compressed air system assessment finds high levels of leakage, and too often plant maintenance staff are fully aware they have a problem but fail to act. 

This condition is so very common it results in millions of dollars of wasted power all across the world. This article discusses leak assessments and the barriers to effective leak management.  Some best practices will be discussed as suggested tips to help you get the most of your leakage reduction efforts, should you choose to act.

Leakage Levels of 80% Not Uncommon

Many years ago, detailed studies of hundreds of industrial sites were done by the U.S. Department of Energy and it found that only 50% of all the compressed air produced in the average plant is used wisely. The other 50% is consumed through higher airflow caused by high pressure (called artificial demand), lost through inappropriate use, and wasted by general leakage. The average leakage level was found to be between 20 and 30 percent of the total. (Source: https://www.compressedairchallenge.org/.) Experienced leak auditors will tell you some plants waste far more than average, with leakage levels of over 80% not uncommon.

Typically, plants with very large compressed air systems, ones that might be oversized for the current production levels, have less worry about large leakage levels because they have more capacity to waste. For this type of plant, levels of 40 to 50 percent or higher will not usually affect the compressed air system pressure at all, because they have lots of spare capacity.

Leakage accounts for between 20 and 30 percent of the total compressed air demand in an average plant. Experienced auditors report levels of up to 80% in some poorly performing plants. Image source: Compressed Air Challenge.

It is very common to see industrial plants with extremely tight maintenance budgets and a shortage of maintenance staff. As a result, routine maintenance falls by the wayside and only priority breakdown maintenance is done. Leakage management becomes a lower priority because the wasted compressed airflow typically does not cause any immediate problem unless it becomes extreme. Many times, there is no regularly scheduled leakage management program programmed into the plant work management system. And often the employees responsible for any leakage repair have little or no awareness of the high cost of the  compressed air waste, nor are they aware of the changes to this airflow month-to-month.

The Cost of Leakage

Compressed air is a very costly way to transmit energy to industrial machines and processes. It usually takes between seven and eight horsepower (hp) of input energy to produce one hp of work at the end use. This high cost also makes it very costly to waste compressed air. For a compressed air system running at its peak efficiency, 24 hours/day, seven days a week, consuming electricity worth 10 cents per kilowatt hour, even a leak sized at 1/16th of an inch, which is a hole smaller than the head of a match, will consume over $1,000 worth of electricity per year.

This cost becomes even greater if the system pressure is jacked up to overcome system pressure loss, or to compensate for transient low-pressure events. It can be seen in Figure 1 that the flow of compressed air increases as higher pressure is applied to a constant sized leak.  The relationship is about 1% more airflow for every one psi in higher pressure. If the air compressor discharge pressure is increased at the same time, the power consumed by the air compressor per unit of compressed air output also goes up by 1% for every 2 psi in pressure increase.

Poor control might limit the savings achieved by leak reduction efforts due to poor system power turndown characteristics. Figure 2 shows the problem: If a compressed air system is operating on Curve No. 1 or Curve No. 2, the power reduction as the airflow reduced is limited to only about 3% for every 10% reduction in leakage airflow. Best practice would be to have a system control characteristic very near Curve No. 4, which is near a 1:1 ratio of power reduction for reduction in airflow.

Challenges Preventing Leakage Repairs

When asked if he had repaired any of the 170 leaks detected in a recent assessment, one client answered this way, “No, not even one…. Problems in scheduling work, overloaded people, and overspent budget money all prevented any action. And the question came up, ‘Does it cost more money to fix it than it is worth?’ This was hard for me to answer.”

A leak detection and repair service provider said this about typical plant repair efforts, “Don’t get me started about leak repairs! We’ve had some spectacular success…because we took responsibility for the leakage survey. We’ve also had some spectacular failures. By far the biggest issue is that there is almost never any money allocated to the end-user maintenance budgets for leakage surveys or repairs. And if assessments are done, the repairs will always be much more costly than the leakage survey, but with no allocated budget there will be few or no repairs done.”

Too often when a leak auditor shows the client their leakage detection equipment the maintenance staff will root in their tool cabinet to find a dusty, top-of-the-line leak detector, purchased years ago, but sitting unused in its storage case. The staff will cite lack of training, instrument complexity, and a shortage of time for reasons why they never use this expensive equipment.

Obviously, getting leakage repaired after the detection effort is done is extremely challenging and sometimes frustrating in today’s economy. But, where many plants fail, others do extremely well in managing their leakage levels. The latter plants are the ones using best practices.

 Four Best Practices Leakage Assessment Steps

In conducting leak assessments four important steps come up when researching the practices of the best performing industrial plants. These are:

  1. Baseline and monitor: The best plants keep track of their leaks with flow meters and are able to identify where they are at and how much they have saved each time they do their leakage assessments.
  2. Proper tools for the job: Top-performing plants have an excellent set of ultrasonic detection tools at their disposal, with available staff trained on the use of the devices. There is a wide range of available leak detectors out on the market, from basic small budget units costing less than $500 to top-of- the-line units costing over $10,000. For compressed air leakage auditing it is usually best to use simplified leak detectors of mid-range cost. Very complex detectors designed for other ultrasonic work are often so complex they defend themselves from use, therefore staff with rarely want to place these into service.
  3. Detect, document and fix: Best-practice plants have a simple set of procedures in place where leaks are detected and tagged with brightly colored identification. The leaks are all documented and recorded in a database with accompanying photographs so the location can be easily found again and the required parts for repair procured. Staff are all trained on the cost of leakage and the use of leakage detection equipment. The database will provide an ongoing record of the trouble locations and the financial savings, which is available for staff and management. In all cases, a successful program requires someone to take responsibility for the follow-up of the leakage repair.
  4. Verification: Excellent leakage reduction programs ensure the results of the leakage repair is captured by some sort of easy to use monitoring system, with real savings calculated. This can go a long way in proving to management the benefits of spending the staff time in repairing the leaks. The monitoring systems can also serve as a catalyst to further efforts. If the plant leakage level is regularly monitored, and a significant change is detected, emergency detection and repair efforts can be initiated.

Addressing Leaks: Best Practices Examples

There are a number of superior compressed air leakage management programs running in plants that can be used as examples to follow for success, some of these have already been written about. 

A past article published in Compressed Air Best Practices Magazine, entitled “Compressed Air Training; It’s a Gold Mine!” showed the benefits in training plant staff about the high cost of compressed air and what to do about it. (The article is available at www.airbestpractices.com/system-assessments/leaks/compressed-air-training-it’s-gold-mine.) In the article Andrew Cooper, the plant site’s award-winning Energy Manager, describes how he trains each and every employee about the efficiency of compressed air and how they can help reduce system waste. His plant maintains a leakage tag board that assists in identifying individual leaks for not only the compressed air, but also other utilities such as steam and water. 

With a large group of trained employees Andrew now has hundreds of partners to help him find and detect costly system waste. Andrew has had many of the key staff attend the Compressed Air Challenge’s (CAC) Fundamentals and Advanced Compressed Air Systems trainings.  Recently CAC has developed a new, one-hour awareness training session called “Compressed Air: It Isn’t Free,” that can be self-administered and delivered by plant staff. This is something all plants should consider delivering to their production line staff.

As another example, a very good compressed air maintenance program is being delivered by Monarch Industries in Winnipeg, Canada. This company is one where plant management holds a keen interest in reducing compressed air costs. They offer some important key points to their success:

To add to this list, a manager said, “And most importantly, I express extreme displeasure when leaks are not dealt with as soon as detected. Most are simple fixes and there is no excuse to ignore them. I expect our total facility leakage at any given time to be no greater than 50 cfm. I occasionally verify this when I am in the building during off hours.” 

As the manager points out, dealing with leaks is likely the most important element of a leak management program. It shows management is very involved in reducing the waste due to leakage, and this attention drives corrective action.

Additional Tips to Maximize Leak Reduction

Additional things that can be done to maximize leakage reduction efforts:

Getting Help: Wide Range of Available Resources Available

You may feel you need some assistance with your leakage problem. Here are some suggested sources:

Protect Well-deserved Profits

In summary we know that compressed air is an expensive utility to waste. Most compressed air systems have a significant number of leaks that reduce system efficiency and increase costs.  High system pressure and poor air compressor efficiency can further increase the electrical bill.

Key to managing system waste is to do regular compressed air leakage assessments. Capturing a baseline, carefully finding and documenting leaks, and ensuring they are quickly repaired is an important part of plant maintenance. Verifying the savings gained through your efforts can inform management their money is well spent.

It is important to have strong management support for your programs and a budget to support leakage reduction efforts. Training and awareness is a very important part of a successful program as well as the partnering with plant personnel. Continuous monitoring of your compressed air system airflow can go a long way in keeping the leakage levels low and alerting staff of any unforeseen problems that might rob you of your well-deserved profits.

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