Optimising compressed air systems: demand side before supply side

Compressed air optimisation should always begin on the demand side. Leaks, unnecessary venting, excessive operating pressures or inefficiently operated consumers increase the actual demand for compressed air. If compressed air generation is initially designed or optimised to meet this increased demand, the supply side is tailored to existing losses.

In the case of new or replacement investments, this can lead to the selection of oversized compressors. In existing systems, the subsequent elimination of leaks or other reductions in consumption can result in unfavourable operating conditions, such as high idle periods, inefficient part-load operation, excessive minimum delivery rates or an unnecessarily wide pressure band.

The technical sequence should therefore be as follows:

• Measure and optimise the demand side
• Validate savings
• Adapt the supply side to actual demand

‘Demand side’ means: understanding consumers’ actual needs. Key metrics include flow, consumption, base load, load profiles, the proportion of leakage and pressure levels at the consumer's point of use. A weekly measurement shows whether consumption remains high during downtime or production breaks. This is often precisely where the greatest potential for savings lies.

Weekly measurement: base load, production consumption and losses during downtime become apparent.

When prioritising, it is not the number of leaks alone that counts, but the volume flow of the loss and the resulting costs. Large, dominant leaks should be documented and repaired first. The area is then measured again, as smaller leaks that were previously masked may become visible.

Prioritisation: The largest leaks often account for the largest proportion of losses. Therefore, identify, prioritise and rectify the most significant leaks first.

The camera shows where a loss is occurring. Whether the measure has improved operations can only be determined through monitoring. Consumption, base load, pressure level and specific output should be compared before and after the measure. Base load and peak load must be considered separately so that savings are not misjudged due to fluctuations in production.

Continuous improvement process: consumption measurement, analysis, leak detection, documentation, reporting, repair and re-evaluation.

Once the demand-side factors have been taken into account, the generation side can be reliably assessed. Key performance indicators include compressor power, air delivery, system pressure, pressure losses, running and idle times, and specific power. The pressure band, compressor control, load distribution and pressure losses can then be optimised in line with actual demand.

If compressors are designed to cope with an increased demand caused by leaks, losses are factored into production on a permanent basis. Following a subsequent repair of the leak, the system may operate in unfavourable partial-load ranges. This results in increased idle times, excessively high minimum supply volumes, inefficient load/idle cycles and a pressure band that does not match actual demand.

Monitoring ensures that the improvement achieved is not merely estimated, but actually measured. Flow, pressure and performance data show whether repairs are effective, whether new leaks are developing and whether production should be adjusted following demand-side optimisation. Compressed air purity remains a separate but related issue for quality-critical applications such as food, pharmaceuticals and semiconductors.