Sequencing and controlling multiple compressors
Compressor sequencing coordinates a plant's air compressors so the right combination runs to meet demand without several machines part-loading inefficiently. A central controller starts, stops and speed-controls the compressors as a system, matching supply to demand and cutting the energy wasted by unloaded running.
What it is
Plants with more than one compressor often run them on independent local controls, leaving several part-loaded and one trimming. Sequencing puts a master controller in charge of the whole set, deciding which machines run, which is the trim (variable-speed) unit, and keeping pressure in a tight band rather than a wide, wasteful range.
Why it is done
A compressor running unloaded still draws substantial power, so several part-loaded machines waste energy. Coordinated control loads each machine fully where possible and uses one variable-speed unit to trim, narrowing the pressure band and cutting both energy and the artificial demand that high pressure creates.
How it is done
Air demand profile and each compressor's part-load behaviour are characterised. A sequencing controller is configured with the machines ranked, a single variable-speed unit chosen as the trim, and a narrow target pressure band set. The system is tuned so base-load machines run fully loaded and the trim unit follows demand, then verified against the previous uncoordinated energy use.
- Profile air demand
- Map part-load behaviour
- Set base & trim units
- Configure controller
- Narrow pressure band
- Verify energy cut
What to watch for
Letting two variable-speed machines fight each other, or setting the pressure band too wide, erodes the benefit. Sequencing without first fixing leaks just coordinates a wasteful demand more tidily.
Related practices
Running a compressed-air leak survey programme
Retrofitting waste-heat recovery
Retrofitting variable-speed drives
Related topics
Compressed Air Efficiency: Leaks, Pressure and Cost · Compressed Air System · Specific Energy Consumption (SEC)
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