Finding and Fixing Compressed Air Leaks at Industrial Plants


Compressed air is vital to the operation of industrial plants and facilities. Still, it is one of the most expensive utilities, and a company can lose up to 10,000 dollars because of a quarter-inch-sized leak. Luckily, a quarter-inch leak rarely occurs.

Fixing small leaks will not dramatically improve a system’s pressure. However, repairing the leak will stabilize production if the leak is large and the system’s air supply is short.

APenergy focuses on production, not the volume of compressed air a plant uses, as not many companies even track their plant’s compressed air usage data. Compressed air is one of those systems that everybody has but rarely views as essential or critical – that is, until pressure is low or water gets in the lines.

Companies need to implement a formal compressed air leak control program, as companies without a program experience a leak load upwards of 30 percent. And in some extreme cases, the leak load can be as high as 50 percent.

For example, let’s say we have a plant with a blended or energy cost rate of seven cents a kWh (kilowatt-hour). And it operates three shifts per day, seven days a week, with a single-stage, lubricant-cooled rotary screw compressor. The plant will spend nearly 100 dollars per CFM (cubic feet per minute) to produce 100 PSIG (pounds per square inch, gauge) of compressed air.

In a 1,000 CFM total system, with a leak load of about 30 percent, the cost would be 30,000 dollars a year in electric energy costs to produce the compressed air to feed the leak. That’s not including other expenses such as maintenance, repair, cooling water, etc.

Resolving the energy cost waste due to compressed air leaks should be the goal of operational management, considering how many products a company has to sell to make up for the loss of 30,000 dollars annually.

Compressed Air Leak Control Program

Too often, compressed air leak programs fall by the wayside. Some personnel falsely believe that the program over-promises and lacks delivery. Companies have implemented similar programs since the 1990s to combat inefficient energy transfers.

The early programs reduced inefficiencies with relatively low investment and good payback. The design of the most straightforward program was to fix quarter-inch leaks for an annual savings of 10,000 dollars. The results of the low-cost, high-return program were underwhelming.

Some early leak specialists would find more leaks than the air supply and promise unrealistic six-figure savings. Management universally became dubious of similar programs after their negative experience, even though other successful programs scored well.

Since the ‘90s, compressed air leak programs have dramatically improved, but there are always bad apples in every field. That’s why it’s essential to work with a trusted leak management company like APenergy (

A great leak control program must include identification, tracking, repair, measurement, and verification. It will also have maintenance measures to ensure efficiency and cost-effectiveness. The APenergy team has hundreds of years of collective experience in compressed air auditing and energy analysis and a proven successful leak management program with a solid return on investment.

Estimating Leakage Amount

Years ago, an experienced professional would size the amount of compressed air leakage with an educated estimate. Before and after repairs, the professional would check the total leak accuracy with flow meter readings, bleed-down tests, etc.

Today, there is a more accurate guideline:

  • A tight system should average around 2.5 CFM.
  • A typical system should average around 3 CFM.
  • A high-leak system should average about 5 CFM.

APenergy performs compressed air system reviews and assessments. Our team observes and measures real compressed air leaks in real-time. While we believe there is no substitute for experience when sizing a leak, modern equipment offers significant new capabilities, which elevates our program’s effectiveness to the highest standards in the industry.

An APenergy team member can determine the average compressor times to load and unload by running the compressor with all the air-powered equipment turned off. Additionally, the team member can calculate the percentage of the total leak load by monitoring the compressor’s cycles created by pressure drops due to the leaks.

Another method of calculating compressed air leakage includes using a pressure gauge downstream to determine the total volume from air receivers, mains, and piping from startup to full operating pressure. A measurement of the compressor’s time to drop to a low pressure must also be taken for the formula.

A leak load of 10 percent is acceptable, whereas 30 percent is problematic and requires immediate attention. The system should undergo a quarterly test to discover if a leak has occurred and, if so, that it is taken care of promptly. A good leak management company should know their relative system impact and give statistics in post-survey reporting.

Ultrasonic Leak Detection

With ultrasonic leak detection advances, searching for leaks has never been easier than today. Ultrasonic leak locating equipment has microprocessor software that significantly improves the accuracy of measuring compressed air leaks 10 CFM and lower. It’s also more portable, versatile, fast, and easy to use.

Additionally, ultrasonic leak detection is not as affected by interference from surrounding noise, and it can test while equipment is online. However, it does have a sensitivity threshold and will not detect lower-level leaks, and if there is competing ultrasound background noise, low-level leaks will get lost in the mix.

The good news is that an APenergy inspector can employ shielding techniques to prevent ultrasound background noise issues. Overall, the pros of ultrasonic leak detection far outweigh the minor cons.

The underlying calculation and assumptions converting decibels recorded to CFM leakage is still an industry gray area. APenergy ( is a proud voice to suggest this is not a fool-proof system. But it provides a standard benchmark with a reasonable accuracy range with repeatable results.

Monitored Compressor Operation

When the plant is not in production, the inspector can measure the total leak volume with a monitored compressor operation. The inspector starts by running the air compressor enough to hold a steady system pressure, then observes and records the percentage of load the compressor is running.

The percentage of time loaded versus the total time is the percent of full-load flow. For example, if the compressor loads for 700 seconds out of 1,000 seconds of operation, it would be 70 percent loaded. If the entire load-rated flow is 1,000 CFM, the flow to feed the leaks and the left on air is 700 CFM.

Bleed-Down Test

During a bleed-down test, the inspector will pump the system up to full-load pressure, then shut the compressor off. The inspector will bleed the system to half the full-load pressure PSIG and record the time. The recorded information is then used in a formula to estimate the total volume of wasted air from leaks. These tests can be insightful for zone isolation and the whole facility during shutdown periods.

A leak repair log is a great measure to record leaks and tag for repairs. The log should include columns for repair time, date, cost, and who performed the work. The information helps determine the value of the leak project.

A good leak control program should provide the information to management so that management does not have to do the work and instead can focus on evaluating the program’s success. APenergy believes that one should always show their work – a validation principle that every performance contracting company should use.

Fixing the leaks

Leaks usually occur at joints and connections. Sometimes it’s an easy fix, such as tightening a loose connection. Other times, it’s more costly, requiring the replacement of faulty equipment.

The cause of most leaks is usually thread sealant that has gone bad or improperly applied. Properly installing high-quality parts with the correct use of thread sealant will solve leakage issues.

Any equipment not in use should have an isolation valve installed to separate them from the system, as they can likely be leak culprits. Once the leaks have been fixed and isolation valves installed, the system should undergo another evaluation.

Valuing the Leak Control Program

After identifying the leaks and repairing them, the next step is evaluating the effectiveness of the leak control program on the electric bill.

The leak project identifies the cost of producing the total air leakage by volume and is site situational. APenergy performs many air assessments with performance contraction, our model projects operational alignment for post-projects.

Internal software then generates recoverable annual electric energy, which is site-specific and proven accurate. Eliminating the majority of compressed air leaks and sustaining low leak levels is a continuous effort, and for achievable success to occur, all personnel must embrace the program.

Contact APenergy Today

APenergy has a deep understanding of leak detection and control. We pride ourselves on the most cost-effective solution for our clients who need trusted experts that can minimize internal facility staff hours.

Our expert team is ready to help companies start saving energy and money today. If interested in our leak detection and control program, contact the APenergy team, the leading energy efficiency consultants, at 740-862-4112 or message us at (