Performing a leak survey
August 10th 2009

The success of a leak survey requires three major elements: knowledge planning, and follow-through.Without a thorough understanding of where leaks are occurring and whether they have been satisfactorily repaired, large amounts of money is wasted

Knowledge requires an understanding of the compressed air system on a wide scale, including all the subsystems and components. What are the sizes, types, and ages of the compressors? Have they been properly maintained? What about traps and drains? Are pressure gauges working, and if so, do they indicate adequate pressure for the various areas of use? What are the assigned pressures for these areas? Can some compressed air applications be replaced by other methods? For example, instead of using compressed air for cooling, drying, or cleanup, low pressure blowers or fans may suffice.

Most compressed air systems require not only clean, but dry air. Wherever moisture is separated out of the compressed air stream, some form of drain must be provided to remove the water. A manual drain may be used in small systems, but plant air systems generally incorporate automatic drain traps. Drains should be located in the lowest portions of system piping, which makes them difficult to reach. Just because they are hard to get at does not diminish their potential for leakage.

Using ultrasound instrument to test air leaks can save money and time spent by technicians trying to determine the cause, source, and size of a leak. When a drain trap sticks in the closed position it causes the condensed water to accumulate within the system. Thus, the air will contain water that can impede proper operation and cause long-term effects, such as rust, dirt, and corrosion. This makes it important to repair or replace drain traps that are stuck closed.

If a drain valve fails in the open position, energy is wasted by allowing the compressed air to escape to atmosphere without having done any work. Because most drain traps are piped into discharge manifolds and then to waste drains, it is not generally visually apparent that they might have failed in the open position. Therefore, it is essential that regular ultrasonic tests be performed on drain traps.

Valves, solenoids, and other components can plug or stick in the open position. Also, the gaskets between banks of valves begin to leak when water has not been drained from the compressed air system. Oil carryover from compressors can degrade O-rings and gaskets, causing them to leak. If portions of the air system piping are routed outdoors, and temperatures can drop below freezing, the air lines and the equipment to which it leads can freeze. Once frozen, the portions that freeze can crack and be permanently damaged. The air system is like a food chain, in that a shortcoming in one component in the system can affect others.

Like a wallet with a hole in it Leaks translate into cash. Allowing leaks to exist without a leak identification and repair program will add a hidden cost to the products your company produces which can negatively impact the ability of the company to compete and affect profitability. These leaks can be compared to having small pinholes in your automobile gas tank. After a while, you’ll notice how they’ve created a hole in your wallet. The sooner leaks are eliminated, the more money you’ll save. Can a compressed air audit be cost effective for small plants? The answer is yes. Leak detection is important in any size plant, but in smaller plants, financial survival and competitiveness are that much more important. For larger plants, the impact may be exponentially more costly.

When performing an audit in a large plant, it is not unusual to find $5000 or more per day of loss through leakage. Once you get a handle on your leaks, you may be capable of shutting down the operation of an extra compressor.

Everyone can pitch in

When leaks become large enough, they become audible without the need for ultrasonic scanning. Heighten the awareness of all individuals in each department. Ask them to report leaks that may be audible. If you do not already own ultrasonic leak detection, consider purchase of equipment and train one or more individuals in each department to perform their own leak audit. These leak auditors should be recognised as ‘energy conservation champions.’ As energy continues to become more expensive, we must take steps to conserve. Our very manufacturing existence might depend on it.

Knowledge can also include the understanding of your ultrasound instrument, how it works, and the techniques of inspection. If you are not sure about the technology or how to use the instrument, training courses can help make you and other inspectors in your facility more competent and effective in your inspections.

Planning incorporates elements such as a map of the compressed gas system and its various components. If none exists, shoot digital photographs of each section using wide-angle and close-up views and labeling them. Planning also includes scheduling of the survey. Break up the survey so that it can be performed without negatively affecting other maintenance responsibilities of the personnel assigned to be the leak team.

ID for action

Another component to planning includes a leak identification method. Once a leak has been located, it should be tagged. A tag number can be used, along with a photograph of the leak in the report. The identification process is extremely important. The leak rate can be assigned to the leak in a report that can than be used to demonstrate the cost savings and potential environmental impact of the leak. In addition, the leak identification process can be used to be sure a leak is repaired. It is very costly not to repair an identified leak.

Follow-through is another important factor. If a leak is not repaired, all the effort and cost of the survey will be wasted. Therefore, use a follow-up method to ensure that all identified leaks have been repaired. In addition, when a leak has been reported as fixed, the repair should be checked. Sometimes the repair might cause another leak to occur or the wrong component may have been ‘repaired.’ Follow-through includes a review of the survey, cost analysis, and, when possible, environmental impact analysis. A report can then be generated to demonstrate the effectiveness of the survey and the related cost savings benefits.

Follow-through should also include leak management. Even though a survey has been completed, many leaks may still exist. The problem is that the shear volume of these leaks can seem overwhelming to a maintenance department that is already working hard at meeting the daily maintenance requirements they are normally assigned.

Establishing a system that will allow for the leaks to be repaired is important. One method is to prioritise the leak repair so that the most costly leaks are repaired first. Progressively smaller leaks are then repaired over time. Once the last of these has been repaired — which may be several months after the audit — it might be wise to plan another audit. This helps hold leakage at bay and also helps you gain a greater return on your investment of equipment used in the audit. Record keeping is another important element to the follow-through part of a survey. Some companies provide software that can help, such as freeware offered by UE Systems. It combines data management and comprehensive compressed gas survey analysis. Users can review annualised and monthly data that include leak cost and greenhouse gas savings.

Conclusion

Compressed air can be costly in more than the obvious. The cost of producing or purchasing the gas is one factor. Safety, the environment, and equipment degradation caused by leaks and equipment inefficiencies can all add up in many ways that can impact a company’s ability to compete and maintain profitability. A planned, comprehensive leak survey program can provide savings that can improve plantwide productivity and profitability.

Bruce Gorelick, vice president, Enercheck Systems, Charlotte, N.C., wrote this article, and Alan Bandes, vice president, UE Systems, Elmsford, N.Y., assisted with statistics. For more information, visit www.enerchecksystems.com and www.uesystems.com.

More articles from Air User News Desk: