Compressed air is widely used in many factories. If not properly managed, this is a common industrial facility that is highly prone to leakages, and can lead to significant energy losses.

During our energy audit at a paper factory, a particular "no-cost energy saving measure" that caught our attention was the energy and cost saving potential that could be achieved from eliminating compressed air leakages. In this factory, compressed air is used for instrumentation, pneumatic workshop tools, cleaning, and process transport. Out of four, four screw type single stage air-cooled compressor units, two are in normal operation and the remaining two are for back up. The figure below shows the layout-cum-schematic drawing of the compressors and their ancillary equipment.

No Load Test

Taking advantage of an appropriate shut down period, the MIEEIP audit team took the opportunity to conduct a "no-load test" on the compressed air system in order to determine the leakage losses. During the test, the supply valves at the consumption points were closed to avoid air from escaping through the points of use.

The time intervals between "cut-out" and "cut-in" by the compressors to feed into the compressed air system were measured to determine the leakage rates. The table below shows the readings taken during the test.

Analysis of the results revealed that the total system leakage was high at 64% of the air delivered, where 13.5% of the air leakage was found to be at the main distribution loops.

Using an ultra-sonic leakage detector, the audit team, together with the factory's maintenance staff, carried out a joint inspection for air leakages and repaired the leakages as they were detected.

Energy Saving Results

The resulting potential annual energy and cost savings are outlined in the following table.

To sustain the savings achieved, the factory needs to include the leakage test as part of the factory's preventive maintenance programme.

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