Compressed air for garment and apparel factories

How compressed air is used in garment manufacturing

A garment factory has many small air users rather than a few big ones. Hundreds of sewing machines, dozens of pressing and finishing machines and a cutting room each take a little air, but together they make a sizeable, steady demand. Because almost every user touches or blows on fabric, air quality matters more than in many heavier industries: a drop of oil or water on white shirting means a reject.

• Sewing automation: pneumatic thread trimmers, presser-foot lifters, back-tack devices, pullers, stackers, folders and automatic pocket setters, buttonhole and button machines.
• Pressing and finishing: form finishers, shirt and trouser presses, collar and cuff presses, and vacuum tables that use air cylinders for head movement and clamping.
• Spot cleaning: cleaning guns that spray solvent or water with compressed air to remove marks.
• Cutting room: clamps on spreading machines, air-flotation cutting tables that lift heavy lays, and some automatic cutters.
• Cleaning and blow-off: removing lint and thread waste from machines and work areas.
• Washing and dyeing (in integrated units): valve actuation and controls on washers and dyeing machines.

Where compressed air is used, process by process

These are typical; sewing and finishing machine makers specify their own pressures and consumption.

Typical system architecture

Medium and large factories normally use a central compressor room feeding the sewing floor, finishing and cutting through a ring main. Small units often use one compressor per section. A good layout is:

1. One or two oil-injected rotary screw compressors, or an oil-free compressor where buyers or product types demand it, with a standby machine for the sewing floor.
2. A wet receiver with an automatic drain.
3. A refrigerated dryer (PDP about +3 °C), followed by a general-purpose filter and a fine coalescing filter for oil aerosol.
4. Activated-carbon filtration on lines to spot-cleaning or other users where oil vapour or smell must be minimised.
5. A ring main with drops taken from the top, so water never runs to a machine.
6. Filter-regulator sets at each machine group, set to the lowest pressure that gives reliable operation.

Choosing between oil-injected with good filtration and oil-free compression is a matter of risk. Oil-injected compressors with properly maintained coalescing and carbon filters give very clean air, but they rely on filter changes being done. Oil-free compressors remove the oil source altogether. See oil-free compressors and what oil-free really means.

Air quality: protecting the fabric

The commonest air-related rejects in garment factories are oil spots, water marks and stains from rusty or dirty air. They usually come from a few avoidable sources:

• Saturated or bypassed filters: coalescing filters must be changed on time; a filter with a high pressure drop is often bypassed by staff.
• Failed drains: water collects in receivers, dryers and filters and slugs through to machines.
• Dryer switched off to save power or because it trips in hot weather.
• Worn separator element on an oil-injected compressor, raising oil carry-over beyond what the filters were sized for.
• Lubricators fitted where not needed: many modern pneumatic components are pre-lubricated; check before adding a lubricator near fabric.
• Old galvanised pipework shedding rust and scale; aluminium or suitable plastic air piping avoids this in new installations.

Regular air-quality checks and filter and drain service are the cheapest insurance against rejects.

Reliability and standby

A garment factory works to tight shipment dates. If the compressor stops, every automatic sewing machine and press stops with it, and hundreds of operators wait. Reliability planning should include:

• N+1 compressors for the sewing floor in larger factories, or a smaller standby machine able to keep the most critical lines running.
• A service plan with filter, separator and oil changes on time, and daily checks of drains and dryer.
• Critical spares on site: filters, separator, oil, drain valves, a temperature sensor and solenoid valve.
• A rental arrangement for long breakdowns or rush orders.
• Protection against power-supply disturbances, with correct restart behaviour after a power cut, since many factories switch between grid and generator.

Energy: small leaks, big bills

With hundreds of machines, fittings and hoses, garment factories often leak a large share of their air without anyone noticing above the noise of the floor. Common savings:

• Leak surveys and repair at machine connections, hoses and worn cylinders; check during lunch or at shift end when machines are idle.
• Lower header pressure: most sewing functions work well at 5–6 bar, and each extra bar costs about 7% more power.
• Isolating valves on each line, closed when the line is not working.
• Replacing open blow-off with nozzles, or vacuum cleaning for lint.
• A variable-speed compressor where demand swings between shifts and sections.
• Recovering compressor heat for washing or pre-heating water in integrated units, where practical.

See leak detection and air-loss management.

Indian context: garment production in Telangana, Andhra Pradesh and India

India’s garment industry is spread across major clusters in Tamil Nadu, Karnataka, Maharashtra, Gujarat, Punjab and the National Capital Region, among others. Telangana and Andhra Pradesh are growing apparel and textile centres, with state-promoted textile and apparel parks and many units in and around Hyderabad, Warangal and other districts. Many factories are export-oriented and work to buyers’ quality and compliance requirements.

Conditions that affect compressed air include:

• High summer temperatures that overload dryers and raise compressor discharge temperature; compressor rooms need good ventilation.
• High humidity in monsoon months, which increases condensate and makes drains and dryers critical.
• Lint and fibre in the air, which chokes intake filters and coolers.
• Frequent switching between grid and diesel generator power in some areas.

Common problems and practical fixes

How much air each garment-unit user consumes

Pressure and air quality decide what kind of system a garment unit needs; consumption decides how big it must be. The figures below are typical average free-air consumption at about 6 bar(g) while the machine is working. They vary with make, cylinder size and operator speed, so use the machine maker’s data where it exists and these ranges where it does not.

As a check on the snap and button press figure: a 63 mm bore cylinder with a 30 mm stroke sweeps π ÷ 4 × 6.3² × 3 = 93.5 cm³. At 6 bar(g) that is 93.5 × (6 + 1.013) ÷ 1.013 = about 0.65 litres of free air per stroke. A double-acting cylinder uses about twice that per out-and-return cycle (slightly less, because of the rod), so 20 cycles a minute use about 26 litres a minute (0.91 cfm), before hose and dead volume are added.

Worked example: demand build-up for a 200-machine unit (illustrative)

A stitching floor of 200 machines with a finishing section and a cutting room, working two shifts. Average demand per user is taken from the table above.

1. Leakage: a typical unrepaired garment floor loses 20% or more of compressor output. Required output = 225 ÷ (1 − 0.20) = 281 cfm.
2. Margin for peaks when automats and presses cycle together, and for growth: 25%. 281 × 1.25 = about 350 cfm (350 ÷ 35.315 = 9.9 m³/min) at 7 bar(g).
3. Selection: for example two machines of about 180 cfm (5.1 m³/min) each, about 30 kW class, with standby as described under reliability above.
4. If leakage is brought down to 10%, required output becomes 225 ÷ 0.90 = 250 cfm, 31 cfm less. At about 0.19 kW per cfm (a typical 7 bar screw), that is about 5.9 kW; over 4,800 hours a year it is 28,500 kWh, about ₹2.4 lakh at an illustrative ₹8.50/kWh.

Very small units, such as a sampling room or a few embroidery machines, may need only a few cfm; a 2–10 hp piston compressor, available for sale or on hire with its air receiver, can suit them, preferably an oil-free type or one with proper filtration. See reciprocating air compressors.

Keeping oil off the fabric: the arithmetic

An oil-injected screw with a healthy separator still passes roughly 2–3 mg of oil per m³ of air. That sounds trivial until it is multiplied out. For the unit above at 250 cfm average, over a 16-hour day:

• Air delivered: 250 ÷ 35.315 × 60 × 16 = about 6,800 m³ a day (assumptions: 250 cfm average, 16 hours, 3 mg/m³ carry-over).
• Oil carried at 3 mg/m³ with no filtration: 6,800 × 3 = about 20 g a day, about 6 kg over 300 working days.
• After a coalescing filter pair holding oil aerosol to about 0.01 mg/m³: 6,800 × 0.01 = about 0.07 g a day, well inside the class 2 oil limit (0.1 mg/m³) of the ISO 8573-1 classes in the table above.

Most of that oil settles in the piping and is released in slugs when flow changes, which is why stains appear at random rather than continuously. A practical filter chain is a general-purpose coalescing filter (about 1 micron) followed by a high-efficiency coalescing filter (about 0.01 micron), after the dryer, with an activated carbon filter where odour or vapour matters. Where air touches the fabric, such as spot-cleaning guns and press heads, a point-of-use high-efficiency filter is cheap protection against contamination picked up in old pipework. Oil-free compression removes the oil source, but still needs particle filtration and a dryer.

What blow guns, thread suckers and single leaks cost

Blow-off and leaks are often the largest single use of air on a sewing floor, and the easiest to cut. Figures use about 0.19 kW per cfm and an illustrative tariff of ₹8.50/kWh.

• Open 3 mm blow gun at 6 bar(g): about 17 cfm, or about 3.2 kW of compressor power while open. Ten guns open an hour a day each for 300 days: 3.2 × 10 × 300 = about 9,700 kWh, about ₹82,000 a year. Engineered nozzles and a regulator set to 2–3 bar(g) typically halve this.
• A 1.5 mm leak at 6 bar(g): about 4.2 cfm, about 0.8 kW, pressurised 4,800 hours a year: 0.8 × 4,800 = about 3,800 kWh, about ₹32,500 a year, from one leak.
• Venturi thread suckers left on through breaks and lunch: 1–4 cfm each. Fifty left on for an extra two hours a day draw 50–200 cfm for those two hours, up to the full output of a 30 kW-class compressor; fit a valve that opens only while the machine runs.

Isolate each line with a valve at the end of the shift and listen. The leaks heard in a quiet unit at 6 bar(g) are the ones that cost money every hour the compressor runs.

Power cuts, DG changeover and restart

Garment units in industrial estates often switch between grid and DG supply several times a day. The air system needs to survive this without damage or wet air.

• Phase sequence: after any DG or panel wiring work, confirm rotation before loading. A screw compressor run in reverse can damage the airend quickly; the controller’s phase-sequence protection should be working, not bypassed.
• Staggered restart: do not let two compressor motors start together on a DG. Set restart delays of 30–60 seconds apart, and start the dryer first.
• DG capacity: as a first check, allow about 2.5–3 kVA of DG capacity per kW of a star-delta started compressor motor, and about 1.25–1.5 kVA per kW for a VSD machine, on top of the other load already connected. For example (illustrative), a 30 kW star-delta compressor needs about 75–90 kVA of headroom for its start. Confirm with the DG maker’s motor-starting data and the permitted voltage dip.
• Dryer on the same supply: if the compressor restarts on DG but the dryer does not, the floor receives saturated air and water marks appear after pressing.
• Repeated short interruptions can trigger the controller’s too-many-starts inhibit; low DG voltage raises motor current and causes overload trips.

How Reddy Compressors helps

Reddy Compressors is an independent multi-brand compressed-air specialist at Tarnaka, Secunderabad, serving industry since 2002. We sell, rent and service compressors from ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other makers. For garment and apparel factories we:

• Supply new oil-injected and oil-free rotary screw compressors, refrigerated dryers, coalescing and carbon filters and receivers, plus used or refurbished machines.
• Rent compressors from 50–2,000 cfm and 2–30 bar for breakdowns, expansions or rush orders.
• Service and repair compressors and dryers through our team of more than 20 service engineers and technicians, with AMC options.
• Identify and supply spare parts from the nameplate, serial number or old part, confirming fit before quoting.
• Carry out leak surveys, pressure checks and air-quality checks.

Our service teams cover all of Telangana and Andhra Pradesh, and we supply equipment and spares across India.

Our track record. We have supplied compressors to leading companies in garments and apparel across Telangana, Andhra Pradesh and beyond – new and used machines, long-term rental, and breakdown cover when a factory’s own compressor fails – backed by our own service team.

What to send us

• Make, model and nameplate photo of each compressor and dryer.
• Number of sewing machines with pneumatic functions, presses and other air users.
• Working pressure set now, and any air-quality rejects you are seeing.
• Factory location, power supply and whether a generator is used.
• Whether you need a new system, service, AMC or rental cover.

Frequently asked questions

Do garment factories need oil-free compressors?

Not always. A well-maintained oil-injected screw compressor with a refrigerated dryer, coalescing filters and carbon filtration where needed can give very clean air. The risk is that filters are not changed on time. Oil-free compressors remove the oil source altogether, which some buyers prefer for white or delicate fabrics. The choice depends on product, buyer requirements, budget and maintenance discipline.

Why am I getting oil spots on garments from pneumatic machines?

The usual causes are saturated or bypassed coalescing filters, a worn separator element on the compressor, failed drains passing oily condensate, or lubricators fitted near fabric. Start by checking filter pressure drop and change dates, then the separator and drains. Removing unnecessary lubricators and adding fine and carbon filtration near sensitive machines usually stops the problem.

What air pressure do pneumatic sewing machines need?

Most pneumatic sewing functions, such as thread trimmers, foot lifters and stackers, work at about 5–6 bar (72.5–87 psig), regulated at the machine group. Always check the machine maker’s specification. Running the whole header much higher than needed wastes power, since each extra bar costs about 7% more compressor energy, and does not make machines work better.

How big a compressor does a garment factory need?

Count the air users: sewing machines with pneumatic functions, automatic machines, presses, finishers, spot-cleaning guns and cutting-room equipment. Use each maker’s consumption figure, apply a realistic use factor, then add an allowance for leaks and growth. Send us your machine list and we will calculate the flow and suggest a compressor and dryer arrangement, with standby where needed.

Is a dryer really needed for a garment factory air system?

Yes. Without a dryer, water condenses in the pipes and reaches machines, causing water marks, rust stains and sticking valves. A refrigerated dryer with a pressure dew point of about +3 °C suits most garment work, followed by suitable filters. Keep the dryer well ventilated in summer and check its drains daily.

Can you service compressors at garment units in Telangana and Andhra Pradesh?

Yes. Our service teams cover the whole of Telangana and Andhra Pradesh, and we supply compressors, rentals and spares across India. We are an independent multi-brand specialist, not an authorised dealer, so we work on ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other makes, with parts identified from the nameplate before quoting. We have tie-ups with all major and reputed brands.

Do vacuum ironing tables in a garment unit run on compressed air?

Usually not. Vacuum ironing and finishing tables normally have their own electric suction blower, and the steam comes from a boiler or steam generator, so neither load belongs on the compressor. Compressed air is used only where the table or press has pneumatic heads, clamps or valves, typically a few cfm. Some tables can be fitted with a venturi vacuum ejector, but it consumes compressed air continuously and costs several times more energy than a blower for the same suction. If ejectors are already fitted, switch them off between garments or change to a blower.

Why do thread suckers use so much compressed air in a garment unit?

Most thread suckers work on the venturi principle: a jet of compressed air creates suction that pulls thread chain away from the needle. The jet runs continuously while the valve is open, consuming about 1–4 cfm each, whether or not the machine is sewing. Across a floor of overlock machines this can exceed the air used by all the sewing cylinders. Fit a valve that opens only while the machine runs, and switch suckers off during breaks.

What size generator is needed to run a garment unit compressor?

As a first check, allow about 2.5–3 kVA of DG capacity per kW of a star-delta started compressor motor, on top of the other load already connected, and about 1.25–1.5 kVA per kW for a VSD compressor, which starts softly. Confirm with the DG maker’s motor-starting data and allowed voltage dip. Stagger compressor restarts by 30–60 seconds, keep the dryer on the DG supply, and check phase rotation after any changeover wiring work.

Which filters stop oil stains from compressed air in a garment unit?

After the dryer, use a general-purpose coalescing filter (about 1 micron) followed by a high-efficiency coalescing filter (about 0.01 micron), which together hold oil aerosol to about 0.01 mg/m³. Oil vapour passes coalescing filters, so add an activated carbon filter where odour or vapour matters, and a point-of-use high-efficiency filter at spot-cleaning guns and press heads. Change elements on differential pressure or schedule and keep the drains working; a saturated element passes oil in slugs.

Related pages

• Industrial applications engineering centre
• Textile industry compressed air
• Cotton ginning and pressing
• Oil-free air compressors
• Refrigerated air dryers
• Compressor annual maintenance contracts