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Choosing an air compressor for a textile plant
In most textile plants, compressed air is one of the biggest electricity bills after the main machines. Weaving sheds with air-jet looms are the heaviest users. Spinning mills use less per machine but run round the clock, so the hours add up.
The right compressor for a textile plant is usually a screw compressor with a VFD, sized to the real demand rather than the loom catalogue, with a dryer and filters so the air doesn't mark the fabric. Below we explain how to get each of those right.
Where the air goes in a textile plant
- Air-jet looms. The air carries the weft yarn across the shed. This is by far the largest use in a weaving plant, and demand rises with loom speed and fabric width.
- Winding (autoconers). Air is used for splicing yarn ends and for cleaning.
- Spinning and preparation. Cylinders, pneumatic controls, and blowing and cleaning on ring frames and other machines.
- Processing and finishing. Valves, actuators and machines in dyeing, printing and finishing.
- Cleaning guns and general use. Small for each point, but often left open and wasted.
Step 1: work out how much air you really need
Don't add up the nameplate figures of every machine. In a running plant not everything draws air at full rate at the same time. Instead:
- Take the loom maker's air figure for your speed and reed width, multiply by the number of looms that run together, and add your other machines.
- If the plant is already running, measure it. The load/unload hours on your existing compressor controller tell you how hard it is working. An air audit with a flow meter is better still.
- Add about 10–15% for leaks and growth. Textile plants often lose far more than that through leaks. Fixing them is the cheapest air you'll ever get.
A shed with looms of different widths, or running different fabrics, can swing a lot during the day. That swing is what a VFD handles well (see Step 3).
Step 2: choose the right pressure
Most textile machines run on normal plant air, typically 6–7 bar at the machine. The compressor is usually set a little higher, around 7–8 bar, to cover the pressure lost in dryers, filters and piping.
Don't set the compressor higher than it needs to be. Every 1 bar of extra pressure adds roughly 7% to the power bill. If one machine needs higher pressure than the rest, it's usually cheaper to give it its own small compressor or booster than to raise the whole plant.
A pressure drop at the loom usually comes from undersized piping or a blocked filter, not from too small a compressor. Our compressed air piping guide shows how to size the main header.
Step 3: fixed speed, VFD or two-stage?
| Plant | Usual choice | Why |
|---|---|---|
| Small unit, one shift, steady demand | Fixed-speed screw | Lowest purchase price; runs loaded most of the time |
| Weaving shed with demand that swings | VFD screw | Slows down when looms stop or change fabric instead of running unloaded |
| Large plant running round the clock, 30 HP and up | Two-stage VFD screw, or VFD plus fixed-speed base load | Gives the most air per unit of power |
A fixed-speed screw compressor still draws a large share of its full power when it runs unloaded. In a weaving plant where demand rises and falls, a VFD machine can save up to 35% of the energy, depending on how much the demand varies. Our VFD machines have IE4 permanent magnet motors.
For large plants, a two-stage screw compressor gives about 15–20% more air per HP than a single-stage one. See two-stage vs single-stage screw compressors.
A common setup in bigger mills is one fixed-speed machine for the steady base load and one VFD machine to follow the swings.
Step 4: keep the air clean and dry
Wet or oily air causes problems you can see on the fabric: stains, spots, and yarn that sticks or breaks. It also wears out the valves and nozzles on the looms.
The usual chain after a lubricated screw compressor is:
- an air receiver, to settle out water and steady the pressure
- a refrigerated air dryer, to remove moisture
- line filters, to remove particles and oil
- automatic drains on the receiver, dryer and filters
Colt supplies refrigerated and desiccant dryers, filters and receivers to go with the compressor. See our air accessories page.
Step 5: plan for Indian conditions
- Heat. Compressor rooms in textile belts often go above 40 °C in summer. Choose a machine rated for high ambient temperatures (our screw compressors have oversized coolers for up to 48 °C) and ventilate the room.
- Lint and fibre dust. Fly from the plant clogs intake filters and coolers. Put the compressor in a separate room with clean intake air, and clean the cooler regularly.
- Power supply. Voltage dips and frequent stops are hard on motors. A VFD gives a soft start, which also helps.
What it costs to run
Over ten years, electricity is usually by far the biggest cost of owning a compressor, much more than the purchase price. Our running cost guide shows how to work out yours from your running hours and tariff.
Frequently Asked Questions
It depends on the number of looms, their speed and reed width. Start from the loom maker's air figure per loom, multiply by the looms running together, add your other machines, and add 10–15% for leaks and growth. If the plant is running, measure the real demand before buying.
Usually 6–7 bar at the machine, with the compressor set around 7–8 bar to cover losses. Check your loom maker's figure.
Yes, when demand changes during the day, which it usually does in weaving. A VFD can save up to 35% of the energy compared with a fixed-speed machine running loaded and unloaded.
Usually not. A lubricated screw compressor with a good dryer and line filters gives air clean enough for looms and most textile machines. Ask us if a process needs oil-free air.
Screw air compressors from 10 to 350 HP, in fixed-speed and VFD versions, and two-stage VFD machines from 30 to 350 HP.
Get a sizing for your plant
Send us the number and type of your looms or machines, the working pressure, your running hours and your electricity tariff through our contact page. Our engineers will suggest a compressor, dryer and filter setup with the running cost.
For model details, download our brochure or see our screw air compressor and VFD screw compressor pages.