Air Leakage Study

Leaks are a significant source of wasted energy in a compressed air system, often wasting as much as 20-30% of the compressor’s output.

 

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.

 

Although leaks can occur in any part of the system, the most common problem areas are:

 

Couplings, hoses, tubes, fittings, pipe joints, quick disconnects, FRLs (filter, regulator, and lubricator), condensate traps, valves, flanges, pickings, thread sealants, and point of use devices. Leakage rates are a function of the supply pressure in an uncontrolled system and increase with higher system pressures. Leakage rates are also proportional to the square of the orifice diameter.

 

 

Leak Detection

 

The best way to detect leaks is to use an ultrasonic acoustic detector, which can recognize high frequency hissing sounds associated with air leaks. These portable units are very easy to use. Costs and sensitivities vary, so test before you buy. A simpler method is to apply soapy water with a paintbrush to suspect areas. Although reliable, this method can be time consuming and messy.

 

Compressed Air

Motors

Steam

 

Suggested Actions

 

• Fixing leaks once is not enough. Incorporate a leak prevention program into your facility’s operations. It should include identification and tagging, tracking, repair, verification, and employee involvement. Set a reasonable target for cost- effective leak reduction—5-10% of total system flow is typical for industrial facilities.

 

• Once leaks are repaired, re-evaluate your compressed air system supply. Work with a compressed air systems specialist to adjust compressor controls. Also look at alternatives to some compressed air uses. If a compressor can be turned off, benefits include cost savings and a system backup.

 

References

Improving Compressed Air System Performance: A Sourcebook for the Industry, Motor Challenge and Compressed Air Challenge,

April 1998.

 

Leakage rates

A  (cfm) for different supply pressures and approximately equivalent orifice sizes

b  Pressure Orifice Diameter (inches)

 

(psig)      1/64         1/32         1/16         1/8           ¼             3/8

70             0.3          1.2           4.8           19.2         76.7         173

80            0.33         1.3          5.4           21.4         85.7         193

90            0.37         1.5           5.9           23.8         94.8        213

100          0.41         1.6           6.5           26.0         104           234

125          0.49         2.0           7.9           31.6         126           284

 

A For well-rounded orifices, multiply the values by 0.97, and for sharp-edged orifices, multiply the values by 0.61.

B Used with permission from Fundamentals of Compressed Air Systems Training offered by the Compressed Air Challenge™.

 

Minimize Compressed Air Leaks

 

Leaks are a significant source of wasted energy in a compressed air system, often wasting as much as 20-30% of the compressor’s output. 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.

Although leaks can occur in any part of the system, the most common problem areas are:

couplings, hoses, tubes, fittings, pipe joints, quick disconnects, FRLs (filter, regulator, and lubricator), condensate traps, valves, flanges, packings, thread sealants, and point of use devices. Leakage rates are a function of the supply pressure in an uncontrolled system and increase with higher system pressures. Leakage rates are also proportional to the square of the orifice diameter. (See table below.

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