by Bruce Gorelick, Enercheck Systems
and Alan Bandes, UE Systems, Inc.

Most of the companies I perform audits for do their best to conserve energy.  Most energy engineers realize the high cost of energy drain due to how much extra horsepower air compressors waste while trying to maintain pre-set air pressures.  Likewise, they realize how costly leaks in their Nitrogen, Carbon Dioxide, and Freon systems can be.    The focus of this article will be not only how leaks can negatively impact the system as a whole, but also how leaks can affect the environment and quite possibly the well being of the personnel that have to work around them.

Air Leaks: Negative Impacts on Process Control
Air leaks can impact processes negatively.  Control and pressure reducing valves are relied upon to control the manufacturing process.  Precise control is critical to the product we produce and to the indoor environments we seek to maintain.  Air operated for heating and ventilating system needs to accurately control the heating and/or cooling process.  For example, in biotech facilities compressed air may control environments where maintenance of humidity and temperatures are an utmost priority.  If the degree of humidity in a controlled bio-genetic research facility goes awry, it can ruin months or years of research.  Loose connections or splits in the tubing can adversely impact proper control.  Obviously a ruptured diaphragm in a control valve cannot be properly controlled by a computer.  Therefore, it should be apparent that facilities need to perform compressed air /gas leak audits on a regular basis, or make arrangements with a competent and professional firm to have audits periodically performed.

In a compressed air and gas system there are many critical components that require validation of proper operational capabilities.  Non-critical system components likewise need to be scanned and tested for leakage. They include, but are not limited to: relief valves, solenoid valves, flange gaskets, thread connections, filter/lubricator/regulators, weld, thread and quick connection devices.  At any given time they may not only be wasting energy but sacrificing proper process control.

Compressed air systems depend on supplying clean dry air to their equipment and components.  Separators, receiver vessels, compressors and other components in a compressed air system depend on drain traps to automatically discharge the condensed water from the system.  When a drain trap fails in the closed position it causes a back-up of condensate.  The air fed to system will contain water that can be detrimental to the equipment.  Rust, dirt and corrosion are additional consequences of not replacing these failed drain traps in a timely fashion.  Ignorance of plugged drain traps also contribute to other portions of the system becoming adversely affected.  If a drain valve fails in the open position large quantities of energy are wasted.  Since, 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 these drain traps.

Valves, solenoids and other sensitive equipment can plug or stick in an open position and eventually fail.  Many times the gaskets between banks of solenoids begin to leak when water has not been drained from the compressed air system.  Sometimes oil in compressed air systems can cause o-ring or gasket failures.   If part of the system is outdoors and is subject to low temperatures, the air lines and the equipment to which it leads can freeze.  Once frozen the portions that freeze can crack and be permanently damaged.   A proper air leak audit should identify the components that are causing energy loss.  As you can see the air/gas system is like a food chain, in that any one portion of the system that has failed will impact the others.

Gas Leaks: Costly and Dangerous
Other gases are quite a bit more expensive than compressed air.  The rule of thumb for contrasting a compressed air leak vs. a nitrogen leak, for example, is that typically, nitrogen is ten times more expensive than air.  So who wants to live with even tiny nitrogen leaks?  The cost of living with many nitrogen leaks will without doubt take a big bite out of your profits.  If the leaking gas is volatile, such as natural gas, identifying and repairing the leak becomes an urgent priority.  In one plant I found 22 natural gas leaks in one section of piping near the ceiling.  The gas line was feeding an oven that had ignition points every ten feet along the length of the equipment.  The potential safety hazard of these leaks far outweighs the actual cost.  Should an explosion have occurred, aside from the physical harm it could cause workers in the immediate area, it would have shut down the plant for quite some time.   In a parts manufacturing plant I found a huge argon leak.  The feed line had a hairline split that was carrying the gas to a welder.

Inert gases such as argon, helium, and nitrogen are non-toxic and do not burn or explode. However, they can cause injury or death at high concentrations by displacing oxygen in the air. Should oxygen levels fall too low, individuals in the area or entering the area can lose consciousness or die from asphyxiation.

It is crucial that leaks be found and corrected before a small problem becomes a severe problem.   In my business there is old truism: "everything leaks, it is just a matter of when."

Leaks are Like a Wallet with a Hole in it
Leaks translate into cold 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. Many times I liken these leaks 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 time to stop them is now.  Energy is not going to get less expensive.

If you are employee in plant where leaks are not addressed, safety and your environment can be an unintended consequence.  There are many potentially explosive gases such as hydrogen and natural gas that can leak.  In addition, there are gas leaks that can also impact the environment, such as the "greenhouse gases".  Did you know that something as apparently innocuous as compressed air leaks can have environmental consequences?

Is an Air/Gas Leak Audit Cost Effective Even in a Smaller Plant?
Yes.  Leak detection is important in any size plant.  In a smaller plant your financial survival and competiveness are that much more important.  For larger plants, the impact may be exponentially more costly.

When I perform an audit in a large plant, I typically find between five and ten thousand or more dollars per day of loss through leakage.  Once you get a handle on your leaks, it not unusual to be capable of shutting down the operation of an extra compressor.

How often should a leak audit be performed?  Most of my customers want the audit done semi-annually or at least once a year.

Enlist the help of Department Employees
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 air/gas leak auditors should be recognized as "energy conservation champions".  As energy continues to become extraordinarily expense we must take steps to conserve.  Our very manufacturing existence might depend on it.  It is that important.

Experience and Proper Equipment Matters
I was taught that in some cases you can get by with less.  However, to do the best job, sometimes you need the best.  An investment in good equipment makes your job easier and you ultimately save time.  As they say time is money.  In the end you will thank yourself for using a reliable instrument.

As a professional, I keep my equipment  properly calibrated and take all steps to maintain the instrumentation.

Performing a leak survey
The success of a leak survey requires three major elements: knowledge, planning, and follow-through.  The knowledge component includes an understanding of the compressed air system, including all the subsystems and components.  What are the sizes, types and ages of the compressors?  Have they been properly maintained?  What about your traps and drains?  Are your pressure gauges working and if so is there adequate pressure for the various areas of use?  What are the assigned pressures for these areas? Are there compressed air applications that can be replaced by alternative, less energy intensive methods?  For example, instead of using compressed air for cooling, drying or cleanup, try using low=pressure blowers or fans.

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

Planning incorporates a number of facets such as a map of the compressed gas system and its various components.  If none exists, try taking digital photographs of each section using long range and close-up views and labeling them.  Planning also includes scheduling of the survey.  Don't try to do it all at once.  Break it up so that the survey can be performed without negatively affecting other maintenance responsibilities of the personnel assigned the leak team.

Before the survey begins, have the inspectors walk through the various sections to review their route.  The walk-through can help in a number of ways: it can help identify potential safety issues, note any changes needed to the planned route, identify obvious leaks, and help understand what equipment to bring along such as flashlights, keys, or specialized leak inspection attachments.

Another component to planning includes a leak tag/identification method.  Once a leak has been located, it should be tagged.  The tag number can be used, along with a photograph of the leak in your 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 to leave an identified leak un-repaired.  Money is wasted due to the cost of the personnel used to locate the leak.  In addition the cost of the leak will increase for every second it continues without repair.

Follow through is another important factor.  If a leak is not repaired, as mentioned, all the effort and cost of the survey will be wasted.  Therefore it is important to use a "follow-up" method to assure all identified leaks are repaired.  In addition when a leak has been reported as fixed, the repair should be checked.  Sometimes the repair might cause another leak to manifest or the wrong component is "repaired".  Follow-through includes 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 includes "leak management".  Whenever a survey is complete there are often many identified leaks.  The problem is 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.  It is important to work a system that will allow for the leaks to be repaired.  One method is to prioritize the leak repair so that the most costly leaks or leaks that can affect production are repaired first, the next most important later, and so on.  

Record keeping is another important element to the follow through part of a survey.  Some companies provide software that can help.  One such program is "freeware" offered by UE Systems, Inc.  It is a two-stage software that combines data management and comprehensive compressed gas survey analysis.  Users can review annualized and monthly data that includes leak cost and greenhouse gas savings.

Conclusion
Compressed gases 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 on a company's ability to compete and maintain profitability.  A planned, comprehensive leak survey program can provide savings that can improve plant-wide productivity and profitability.