There are certain things in the life which gives you sense of fulfillment specially those which are done by yourself. We place a much stronger belief in the data and reports, which are created either by us or some trusted source. But the sense of fulfillment that we get from own findings is extremely satisfying.
One of the activities in the manufacturing plant that can be done by yourself is air leakages detection. These compressed air leakages are generally observed in the compressed air system and industry experts classify the leakages into two categories - planned leakages and unplanned leakages.
The planned leakages by design of the compressed air system e.g. blowing, drying, purging, etc. On the other hand, the unplanned leaks are due to maintenance & operating issues of the plant.
As per study, the compressed air leakages in the plant can lead to approximate 10 - 30% of the compressed air energy and thus result in huge power losses coupled with operating losses.
The air leakages also lead to other issues in the plant like pressure drop, moisture in compressed air application and bad air quality, therefore reducing the overall efficiency of the entire system including performance of the air compressor and compressed air dryer.
So, it is highly recommended that leaks should be quantified and accordingly arrested. This can only be done with proper measuring techniques as if you cannot measure it, you cannot improve it.
The most common practices in industry to reduce the leakages are:
- No load Test for leak quantification
- Leak Identification through ultrasonic leak detector
Out of these two, no load test can be done easily at plant itself without much investment. However, this test requires plant shutdown, so that compressor running during no production can be evaluated for total leaks available across network.
Atlas Copco experts guide you on how you can do “No load test” and quantify leakages and thus can evaluate the possibility of
- Up to 10% energy bill reduction
- Up to 5% reduction in pressure set point
- Up to 25% reduction in unload hours of the compressors
Steps to conduct No Load Test at the plant
Pre-requisites:
- Ensure selected compressor should be properly maintained without any physical abnormality.
- Ensure all your applications are off and there should not be any use of compressed air.
- Ensure test will be conducted at same pressure band at which plant is operated.
Steps to follow:
- This test should be conducted during a shutdown period.
- All the application valves should be closed.
- Run the desired compressor. In case of multiple installation with different power ratings, select any compressor.
- Let the compressor stabilize by loading and unloading.
- Note down the load and unload timings and collect 5 samples for the average.
- Now enter the readings in the below formula.
Leakage (QL) = { T/( T + t )} X QR
where,
- T = Load time (seconds)
- t = Unload time (seconds)
- QR = Rated compressor capacity which is used for leak test
- QL = Leakage calculated
Illustrative Example
Let’s assume there are four compressors in the plant with following flow rating in cfm
- 100 cfm (running compressor)
- 100 cfm (stand-by compressor)
- 75 cfm (running compressor)
- 60 cfm (stand-by compressor)
Now, select 75 cfm compressor for no load test and follow the above mentioned 6 steps to record the load and unload time. Assuming average time calculated after 5 samples as:
- Avg load time : 25 seconds
- Avg unload time: 45 seconds
Enter the data in the above formula; Leakage (QL) = { T/( T + t )} X QR
i.e. Leakage (QL) = {25 /( 25+45)} X 75 = 26 cfm (Potential compressed air leakages)
As a thumb rule, screw compressors consume 1 kW energy to genrate 6 cfm of the compressed air.
So, your 26 cfm = approx 4.3 kW = approx $2012 / Year**
**Assuming 6000 running hours annually and average Energy cost is $0.078 per unit.
You may also convert the potential leakages into leakages percentage as:
- Leakage % = Leakage result/ Total running capacity
So, for our example, leakage % = 26/ 175 = 14.8% of total runnig capacity.
Conclusion
The above example gives you an idea of percentage leakages in your plant as well as a potential energy-saving through leak repair. Our experts recommend the leakage percent should always be less than 5% so that you can run your plant at optimum energy levels. Also, calculating the compressed air system’s life cycle cost can guide you further on how to minimize the financial and operational impacts.
