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What is the True Cost of Leaks?

What are compressed air leaks?

Compressed air leaks are demands for air that create no value. They consume flow needed for other productive uses. Leaks are by far the biggest problem in most compressed air systems. Most leaks are generally found close to the usage points.

What are the effects of leaks?

i. Wasted electricity

Leaks release expensive compressed air directly into the atmosphere without producing any useful work. Leaks account for 10-30% of compressed air output.

  • Taking electricity cost of 18kshs/Kwh and assuming a constant operation at 100 psig (6.9bar) for 24 hrs for the year (8760hours).
  • Specific energy consumption of 18 KW/100 cfm(47.2l/s). (lossless system) Note that a real system could be using up over three times more energy to deliver the same amount of air. The table below shows a calculation of leak cost per  year.
Size of leak Air Flow(cfm) Air Flow l/s Leak cost per year(kshs)
1/16” 6.49 2.83 184,201
1/8” 26 12.27 327,974
¼” 104 49.08 2,951,769

 

ii. Higher pressure

Leaks result in low pressure at the usage point and to compensate for leaks most users turn up compressor pressure. This has two effects.

  • Higher pressure increases the flow rate of leaks creating what is known as artificial demand. The rule of thumb (6.9bar system) is for every 0.07 bar reduction in air pressure flow demand reduces by 0.9 to 1%. Reducing pressure in the ¼” leak above by 0.7 bar reduces both the flow and annual leak cost by 10%.
  • Higher pressure the energy consumption of the compressor. The rule of thumb (6.9bar system) is that for every 0.07 bar reduction in pressure the energy input to the compressor reduces by 1 to 2%.

iii. Reduced productivity

excessive leaks causes system pressure to fluctuate which can cause air operated equipment not to operate as intended. Tools take longer to do the required work and in other cases it can lead to product rejects.

iv. Increased service costs

To serve a leaky system the compressor runs longer hours. Longer hours mean more frequent maintenance and reduce equipment life.

Finding, repair and tracking of leaks has never been easier with modern innovations in ultrasonic detection which also estimates the size of leaks. Contact us to develop a leak management program.

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About the Author

Eng. Mathew Waita Mwenga is a Chemical/Mechanical Engineer with over 12 years’ experience in the industrial sector and petroleum industry. He has 6 years working for Atlas Copco Eastern Africa as a service engineer, aftermarket engineer, compressed air energy auditor and Rental manager. He has also spent 3 years working as a drilling solutions engineer in National Oilwell Varco an upstream oil and gas Equipment Company. Mathew is a Chartered engineer of the UK(Ceng) and a registered P.E of Kenya.

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