Compressed air is extensively used in industrial settings. Its use is so common that it is often considered the fourth utility, coming after electricity, natural gas and water. Along with its wide application, it’s also an expensive utility compared to the other three. It takes 7-8 HP of electrical power to produce 1 HP of compressed air power. As a result, it’s important to ensure your compressed air system is running at peak performance.
When managing your compressed air system for best performance, both the demand and the supply side of the system need to be optimized. From a demand standpoint, you will often find that air leaks account for the largest demand in your plant. Undoubtedly, it’s important to understand the magnitude of air leaks, their impact and how to detect and fix them. Like most process improvement programs, compressed air leak management is a journey. You cannot fix your leaks all at once and just rest. You need to develop a program to routinely identify and fix leaks and develop a culture that helps you prevent future leaks.
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Compressed Air Is Expensive
Compressed air leaks can be a major source of wasted energy in industrial facilities. Leaks can result in wasting 20% to 30%.In some cases, even up to 50% of an air compressor system’s output is wasted if the plant does not have a proactive leak management program. Conversely, facilities that have a disciplined leak prevention program are able to reduce their leaks to less than 10% of their compressor system’s output.
Assuming leakage of 30% of compressed air, a system with 200 HP of compressor power is wasting 60 HP due to leaks. Using the national average cost of seven cents per kWh, this costs over $31,000 in wasted electrical energy annually.
Losses Beyond Financial Damages
Beyond the electrical financial impact, air leaks have detrimental effects on the tools and components of your plant and result in higher than necessary capital investments. Some of the issues include:
Productivity loss due to inefficient tools: Leaks result in a drop of air pressure at the input to air tools. This can make the tools function less effectively, resulting in lower productivity.
Reduced system equipment life: Leaks result in a higher demand of air from the compressed air system than what’s really needed. This causes the compressor package and the entire system to cycle more frequently, reducing the useful life of the compressed air system. Plants with higher air leakage have to replace their compressed air systems more frequently.
Higher maintenance costs: Since the system is running more, the need for air compressor repairs and maintenance increases along with it.
Higher downtimes: Higher maintenance translates to higher downtime. Essentially, you are reducing your production time and replacing it with maintenance time. As you trade precious production time for maintenance, your production assets now have a poorer utilization and a lower return on investment.
Unnecessary capacity addition: If your compressed air needs are higher than what your leaking system can support, you will end up adding more capacity to compensate for leaks. Also, if leaks cause greater loss of production time, you may have to spend more on additional production equipment to increase your production capacity.
Air Compressor System – Measuring Leakage
An easy way to estimate a plant’s leak load is during a non-production time. Operate the air compressor in a load/no-load or start/stop mode, and record the time it takes to load and unload the compressor. In this case, the compressor will load or unload because of the demand of air driven by leaks in the system. To estimate a plant’s leak load, operate the air compressor in a load/no-load mode during a non-production time. Record the loaded vs. unloaded times, and compare these to the compressor’s capacity.
Air Compressor System – Total Leakage %
Leakage % is the percentage of air compressor capacity that’s being wasted due to air leaks. A plant with a strong leakage prevention program will have a leakage % less than 10%, whereas leakage % can be as high as 50% in a poorly-maintained industrial facility.
Air Compressor System – Identifying, Fixing and Preventing Air Leaks
Air leaks are expensive and cause significant financial and operating losses in a production environment. Identifying where the leaks are is the first step to reducing the total leakage in your plant.
More than anything else, you should establish a program to detect and reduce leaks. One simple approach is to walk the plant during a non-production period and detect leaks which have a noticeable sound.
Not all leaks, however, are noticeable to human ears, and often, entire plants or production lines do not shut down. For these reasons, industry best practice is to use ultrasonic leak detectors. As you identify leaks, put a tag in those locations, and record the leak in your leak logs or maintenance-planning software.
Ultrasonic Leak Detectors
These are sophisticated tools that can accurately detect leaks in a noisy production environment while actual production is taking place. They consist of directional microphones, amplifiers and audio filters, and they can identify the high-frequency hissing sounds produced by air leaks. With advances in technology, these units have become highly compact and portable. An operator generally walks the plant with an ultrasonic leak detector. Headphones or displays connected to the portable detector signal the operator as to the exact location of the leaks.
Plant personnel should perform leak audits on an ongoing basis using ultrasonic leak detectors. Record the location and size of leaks and quantify the cost of leakage. If you don’t have an ultrasonic leak detector, doing a leak audit using a third party can help justify the cost of implementing a leak management and prevention program. It can also help justify investing in an ultrasonic leak detector so you can perform audits with greater accuracy.
Prioritizing Leaks to Fix
Not all leaks are created equal. After you perform air leak audits, you might find numerous leaks of various sizes. A good plan prioritizes which leaks to fix first.
Here’s an example: A chemical plant performed a compressed air leak audit at their facility. Leaks, approximately equal to different opening sizes, were found as following: 100 leaks of 1/32″ at 90 psig (pounds per square inch gage), 50 leaks of 1/16″ at 90 psig, and 10 leaks of 1/4″ at 100 psig. Assuming 7,000 annual operating hours, an average electric rate of $0.05/kWh, and compressed air generation requirement of approximately 18 kW/100 cfm, the following cost savings were calculated:
Cost savings from eliminating 1/32″ leaks = $5,765
Cost savings from eliminating 1/16″ leaks = $11,337
Cost savings from eliminating 1/4″ leaks = $39,967
Total cost savings from eliminating these leaks = $57,069
As you can see, the savings from elimination of just 10 leaks of 1/4″ make up for almost 70% of the overall savings. In this case, these 1/4” leaks should be the first ones that should be addressed.
Common Sources of Air Leaks
Air leaks can happen throughout your plant — from the source of compressed air to the distribution pipes and right up to where air is being used. Some areas and components are more prone to leaks than others. The most common areas of air leaks are:
Air hoses and air hose connections or couplings
Open condensate traps
Worn disconnects, or disconnects missing O-rings
Filters, lubricators and regulators, if improperly installed
Leaking or botched drains
Control and shut-off valves
Worn out seals or gaskets
Old or poorly maintained pneumatic tools
Idle or unused machine or production equipment with air input
Failed or inferior quality thread sealants, or incorrectly applied thread sealants
Inappropriate use of air, i.e. as a blower for cleaning instead of using other cleaning tools
Using air to cool electric control panels and cabinets
Using compressed air to cool cabinets such as control or electric panels
Air hose connections, couplings, control and shut-off valves, worn out seals and gaskets are some of the common sources of leaks. At times, you can stop a leak by simply tightening the point of connection, or following the right procedures for parts installation or assembly. In some cases, though, repairing a leak is more complex and expensive. Higher-quality parts are expensive, and MRO departments often choose lower cost parts over quality. However, time after time, it’s been proven that investment in higher-quality fittings, tubes, hoses, valves or couplings pay off in the long run in the form of reduced leaks and downtime.
Old or poorly maintained pneumatic tools and idle machines or production equipment with air input can also cause compressed air leaks. Replace old pneumatic tools with new ones if they can deliver higher uptime and result in lower maintenance and reduced leaks.
One way to reduce leaks that often gets ignored is by lowering the demand air pressure of the compressed air system. If there is less pressure differential across the point of leakage, the amount of air leaking will be low, which reduces the amount of compressed air wasted. Make sure to continue to optimize the system header pressure as you address leaks in your plant.
Minimizing Misuse of Compressed Air
Along with repairing the obvious leaks, reducing the inefficient use of compressed air is just as important. Compressed air is versatile and has many uses. As a result, production and maintenance operators often resort to compressed air as a shortcut for solving a problem quickly instead of eliminating root causes of issues.
Examples of misuse or suboptimal use of compressed air include:
Use of open blow-offs to cool or transfer products
Use of compressed air to cool or clean a work area
Use of compressed air to cool electrical and control panels
Compressed air leaking when connected to temporarily idle production equipment
These issues can be addressed in the following ways:
Use engineered nozzles.
Instead of using open blow-offs to cool or transfer products, install engineered nozzles that are designed to perform the same task while requiring less compressed air.
Use coolers designed to cool electrical and control panels.
Compressed air can cool electrical panels and control panels and cabinets, but it’s not the most cost-effective method for cooling. Understand the root cause of excessive heat generation in these panels, and if necessary, install cooling units designed for panels or cabinets. These units consume less energy and will help take the load off your air compressor system.
Connect cutoff valves before unused equipment.
Depending on the production schedules, certain lines and equipment may not be scheduled to run. When you shut down equipment for scheduled downtime, make sure you valve-off the compressed air line that is supplying air to the production equipment.
Air Compressor System Leak Maintenance Program
Beyond leak identification and managing repairs effectively, a robust air leak prevention program should include employee training and development of a leak maintenance schedule.
Involving employees is key to proactively identifying new leaks and staying on top of repairs. Educate your employees on the cost of air leaks so they share the same concern as you when it comes to identifying and fixing those leaks. Some facilities incorporate One Point Lessons around identifying and reporting leaks as part of their start of shift activities.
As with any management program, you have to communicate often to engage your team members. You should also consider incentivizing employees to identify and report leaks. This is a great way to get more people involved and to help sustain the improvements you are making. Rewards can be in the form of recognition, prizes or monetary awards.
Develop a Maintenance Schedule
Once you’ve identified the leaks and production areas where compressed air is misused, the next step is to address them. You should label the leaks with proper tagging, record the leaks in your logs or maintenance information system and prioritize repairs.
Next, develop a maintenance schedule which will help you identify and repair leaks on an ongoing basis. Some plants schedule leak repairs in line with their air compressor service schedule. Say, you have a quarterly scheduled maintenance for your air compressor. Visit the points of past leaks and identify and repair new leaks at the same time. New leaks, and new misuses of compressed air will continue, and it’s important to identify and address them on a consistent basis.