Reduction of energy costs and CO2 emissions through the combination of flow measurement and leakage detection in compressed air
How much energy can be saved?
Around 10% of total industrial electricity consumption is used for compressed air generation in industrialized countries, and in Germany the figure is as high as 14%. Leakages are the main factor for energy losses and most compressed air systems show losses in the range of about 20 % to 40 %, in bad systems even more than 60%. Fixing compressed air leaks is the most effective action for reducing the energy consumption. Compressed air leaks often waste energy 8760 hours (24 h x 365 d) a year and increase compressor run times, which also shortens maintenance intervals. Therefore, it is a must to detect and eliminate leakages frequently. Our LD-Series will give you all the function needed to detect leakages and measure the consequences in terms of energy consumption and wasted money.
1. practical example - a pharmaceutical company
High compressed air leakage rates and incorrectly sized components (compressors and compressed air receivers) reduce the efficiency of your compressed air system and generate unnecessary CO2 emissions and reduce competitiveness.
How much compressed air a production requires over a week and how components need to be sized so that they run as efficiently as possible and are utilized to their capacity, can be measured with a compressed air flow meter.
In the graph shown, you can see the volume flow profile measured behind the compressed air tank of a pharmaceutical company for about 10 days.
The green curve corresponds to the actual measured volume flow profile (moving average) and the red curve corresponds to the volume flow profile after the “simulated” leakage elimination.
As you can see, the entire curve shifts downward.
During the times marked in red, production was at standstill and did not produce any goods – i.e., at that time compressed air escaped solely via leakages and open nozzles.
This value should always be as low as possible and should decrease after leakages have been eliminated.
In the graph shown, the following improvements are based on the following assumptions:
- Specific power: 20,388 kW / 100 cfm
- Electricity price: 25 €Cent / kWh
- Running time: 8000 h/ year
- CO2 emissions electricity mix domestic consumption: 0,925 pound / kWh
| Unit | Measurement before repair | Measurement after repair | Improvements |
| Flow rate [cfm] AVR | 294,28 | 147,14 | 147,14 |
| Flow rate [cfm] stillstand | 185,98 | 38,84 | 147,14 |
| Leckage-Rate [%] | 63,2% | 26,4 % | 36,8 % |
| Savings potential [€ / a] | 75.835 € / a | 15.837 € / a | 59.998 € / a |
| CO2-Emission | 127,25 Tons / a | 26,58 Tons / a | 100,67 Tons / a |
2. practical example - a bakery business
The following graph shows the volume flow profile of a bakery:
- The bakery consists of 2 production halls.
- Hall 1 (older equipment) is shut down temporarily
- In hall 2 production starts at 10:00 am
A VA 500 (thermal flow sensor) was installed behind the compressed air tank to measure the consumption of the two halls.
In the original volume flow profile (light green) you can see the compressor switching on and off. Therefore, the moving average was calculated additionally (dark green).
The following findings can be derived from this:
- Although there was no production before 10:00 am, the compressor delivers a lot of compressed air.
- The “production peaks” are very small compared to the base load
This indicates a very high leakage rate. To confirm the assumption, the ball valves to the machines were closed in the shutdown area in hall 1, so that their leakages are no longer supplied with compressed air.
The volume flow profile shows that the base load can be reduced enormously from closed ball valve to closed ball valve, thus demonstrating the influence of leakage elimination on the compressed air profile.
- Volume flow at the beginning: 88,28 cfm
- Volume flow after closing the ball valves: approx. 23,54 cfm
When the equipment in Hall 1 is operated again, the ball valves must be opened and thus compressed air escapes again via the leakages on and in the machines.
3. recommended procedure for permanent reduction of compressed air leakage rate
Conclusion and recommendation: The process described here should be carried out cyclically in the company in order to keep the leakage rate as low as possible in the long term. The aim of the measures should be to achieve a permanent leakage rate of 5-10%, as experience has shown that a one-off search and rectification does not permanently reduce the leakage rate and new leaks will naturally occur again afterwards.
Practical tip: In order not to miss the optimal time for the leakage audit, the use of a volume flow sensor (e.g. VA 500) in the main line behind the tank is recommended. At least one week (Monday to Sunday) is recommended as the period for the measurement. In addition, the volumetric flow measurement can be used to validate the result of the leakage search and repair, as this must reduce the volumetric flow during standstill.