Here at Rasmussen, we are all about preventative maintenance. Preventative maintenance practices are at the foundation of financial responsibility for any company. The less reactive repairs that a company has to pay for, the less money is going toward avoidable expenses. Preventative maintenance puts your company ahead of problems and solves issues before they have the opportunity to derail production.

Compressed air is a widely used utility in plants and facilities, but it is also likely the most expensive one. Approximately 19% of the total power used in a compressed air system, even on a well maintained one, is converted into clean, compressed air flow. The other 81% is lost as heat. Because of this, compressed air is often more expensive than other electricity, natural gas and water when it comes to running a facility. Compressed air systems are invaluable assets to facilities in numerous industries, but air leaks could be leaving you dry when it comes to energy efficiency.

A single ¼-inch leak in an air line can cost a facility from $2,500 to more than $8,000 per year. Click To Tweet

Compressed Air Leaks Are Dangerous

Compressed air leaks can be financially crippling under the wrong circumstances. The most terrifying aspect of a compressed air leak is just how long they can go undetected, especially if your air compressor and compressed air distribution components are not routinely inspected for proper operation. According to the Compressed Air & Gas Institute, depending on pressure requirements and energy costs, a single ¼-inch leak in a compressed air line can cost a facility from $2,500 to more than $8,000 per year. For just one leak, your company could be losing $2,500+ and not even know it.

That one leak may not be noticeable at the bottom line. However, it can upset the functionality of the whole system when accompanied by other leaks. The added wear on the air compressor from producing that extra air can compromise equipment reliability, add operating hours to your machines and increase lifecycle costs.

Persistent air leaks also decrease the longevity of your air compressors. These inefficiencies will only add up and put stress on the productivity of the facility, the uptime of the air compressors, air dryers and other compressed air system components. The first step is to be aware of this threat. The second is to address the issue.

PSIG leakage table

Did you know? When 100 leaks are found and sized, a tight system should average around 3 cfm each. A typical system should average around 4 cfm each and a high leak system should average around 5 cfm each. Numbers above or below these levels should have a clear explanation! (Source)

How to Identify a Compressed Air Leak

A simple walkthrough with a pair of good ears may detect some major leaks. Additionally, you might notice a change in equipment productivity. However, by the time either of these issues are detected this way, the problem has already become very costly. Specialized equipment and a skilled technician are required for reliable compressed air leak identification, especially in loud environments or where distribution piping is out of easy reach. Ultrasonic leak detection devices are the best tool to recognize compressed air leaks, which is exactly why we turn to them in our preventative maintenance strategies. Their regular use, according to a maintenance plan, can help maintain consistent and high functionality of a compressed air system. Regular leak audits reduce wasted energy expenses, unnecessary wear on air compressors and help prevent air compressor downtime.

Since air leaks are almost impossible to see, other methods must be used to locate them. The best way to detect leaks is to use an ultrasonic acoustic detector, which can recognize the high frequency hissing sounds associated with air leaks.

At $0.05 per KWh:

  • A $100/year leak can not be felt or heard
  • A $400/year leak can be felt, but not heard
  • A $700/year leak can be felt and heart

If you are unsure how much money is being spent on your compressed air system, use this equation given from Compressed Air & Gas Institute:

Cost ($/year) = motor bhp x .746 x hours of operation (per year) x electric rate ($/kwh) / motor efficiency

Preventative maintenance helps solve problems before they have the opportunity to derail any projects: Click To Tweet

Quantifying the Leakage Rate

Identifying and quantifying the leak load is important when considering the entire effect of leaks on your system. Use a bleed down test to quickly and easily quantify the leakage rate of a whole system. Leakage can be estimated in systems with other control strategies if there is a pressure gauge downstream of the receiver. This method requires an estimate of total system volume, including any downstream secondary air receivers, air mains and piping (V, in cubic feet). The system is then started and brought to the normal operating pressure (P1) and the compressor is turned off.

Measurements should then be taken for the time (T) it takes for the system to drop to a lower pressure (P2) which should be a point equal to about one-half of the operating pressure.

Leakage can be calculated as follows:

leakage rates table

Leakage (cfm free air) = [V x (P1-P2)/(Tx14.7)] x 1.25

  • Where: V is in cubic feet
  • P1 and P2 are in psg
  • T is in minutes

The 1.25 multiplier corrects leakage to normal system pressure, allowing for reduced leakage with falling system pressure to 50% of the initial reading. Again, leakage of greater than 10% indicates that the system can likely be significantly improved. These tests should be carried out once a month as part of a regular leak detection and repair program.

Source: “Fundamentals of Compressed Air Systems” The Compressed Air Challenge

Minimize Compressed Air Leaks

Leaks are a significant source of wasted energy. 20-30% of the compressor’s output is often wasted. A typical plant that has not been well maintained will likely have a leak rate equal to 20% of total compressed air production capacity or more. On the other hand, proactive leak detection and air compressor repair can reduce leaks to less than 10% of output.

Leaks are worse with higher pressure, so reducing system pressure not only saves you money by requiring less energy to compress the air, but it also reduces leakage rates. Plant header pressures should be as low as possible to support the process because it minimizes compressor energy use and leakage.

Compressed air leaks can also contribute to problems with system operations, including:

  • Fluctuating system pressure, which can cause air tools and other air-operated equipment to function less efficiently, possibly affecting production.
  • Excess compressor capacity, resulting in higher than necessary costs.
  • Decreased service life and increased maintenance of supply equipment (including the compressor package) due to unnecessary cycling and increased run time.

The most common areas where leaks occur are couplings, hoses, tubes, fittings, pipe joints, quick disconnects, FRLs (filter, regulator, lubricator), condensate traps, valves, flanges, packing, thread sealant and point-of-use devices.

Leakage rates identified in cubic feet per minute (cfm) are also proportional to the square of the orifice diameter. This means that if you double the leak orifice size, you will quadruple the leak flow rate.  See table below:

In addition to being a source of wasted energy, leaks can also contribute to other operating losses. Leaks:

  • cause a drop in system pressure, which can make air tools function less efficiently, adversely affecting production;
  • shorten the life of almost all supply system equipment (including the compressor package itself) by forcing the equipment to cycle more frequently;
  • cause increased running time, which can also lead to additional maintenance requirements and increased unscheduled downtime; and
  • can lead to adding unnecessary compressor capacity.

Next Steps

If you suspect a compressed air leak, we are here to help. There are many facets of air compressors and compressed air systems that require attentive professional care. Proper maintenance staff is absolutely capable of fixing leaks, but you receive more than just fixed leaks when working with Rasmussen Mechanical Services. Our team can help develop the most efficient plan to utilize your compressed air system, prepare for air compressor repair and maintenance and then some. We can assess your system to ensure your air compressors, dryers, storage, regulators, distribution and point of use equipment is right for your application. Keep up with these cost-saving maintenance tips and start saving. Contact us today if you want to save even more!

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