With the improvement in the compressed air technology, efficiency of air compressed air and air distribution has improved. Even with such improvement compressed air leakages cannot be avoided. Unfortunately all compressed air system will have leakages and it cannot be eliminated but off course it can be minimized. Identify and prevent air leakages are important to keep compressed air system efficient. Expert suggest on an average 25% of energy is wasted though leaks and it can be even above 50% if compressed air system is not maintained properly.
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Cost of compressed air leakage
It is important to estimate cost of leak to guage the level of problem and drain of money though compressed air audit. Leakage can be estimated based on the size of leakage and compressed air operating pressure as shown below table.( Source : Bureau of Energy Efficiency)
We may consider, if there is 1 mm of leakage in compressed air system with 5 barg of pressure, air leakage rate shall be 0.22 m3/min. The quantity of leakage multiplied by specific air cost and no of operating house will give us the cost of compressed air leakage.
Annual cost of a leak = leakage rate (m3/min) x kW/m3/min x operating hours x $/kWh
Apart from direct cost involved in compressed air leak. Reduced productivity can be another area where cost can be draining heavily due to unstable pressure in compressed air network. Extra compressor working can also lead to extra maintenance cost together with lower productivity.
Identifying Air leakages:
air leakages are invisible and it may not be realistic to eliminate all leakages but it can be minimized to a lower level. Also as leakages are tend to reoccur proper leakage record should be maintained. If same point is getting repeated leak preventive action needs to be taken.
There are three ways for identifying air leakages
- Listening: As air is not visible air leak cannot be identified though naked eyes. Air leaking out will form hissing sound and large size leaks can be identified though listening hissing sound. This method of leak detection is not useful in case of for smaller leaks or if there is higher noise in surrounding area.
- Soapy water: Soapy water can be used to identify small leaks and it is more reliable than just listening. With the application of soapy water in the leakage area, bubble formation will occur and leak can be identified easily. This method of identification requires complete acess of pipeline and large amount of laborious work is required. Soapy water test may not be feasible for large size installation.
- Ultrasonic leak detection: The most accurate, reliable & scientific method of compressed air leak detection can be though ultrasonic leak detector. With this method of leak detection even pinhole can be detected easily. Ultrasonic leak detector consist of directional microphones, amplifiers, and audio filters. As ultrasonic is high frequency signal, it allows detector to locate leakages very easily. With this method of leak detection background noise has no effect and also access to pipeline is also not required.
Eliminating identified leakages:-
Identify and prevent air leakages for operating compressed air system efficiently. Once the leakage is identified cost of leakage to be estimated with all identified leakages. We may use pareto principle for prioritizing identified leakages. Major leakage plugging will give faster return. Remember leakage elimination is not a onetime activity as it is bound to happen again. Therefore, continual improvement program to be prepared for identifying and eliminating air leakages on regular interval of time. Log for registering leakages needs to be created for identifying repeat leakage area. Preventive action must be planned for all repeat losses.