Why converting plants are demanding air users
A converting plant does not have one big air user. It has dozens or hundreds of small pneumatic devices on presses, corrugators, die-cutters, folder-gluers, laminators, slitters and packaging machines, each switching in fractions of a second. Individually they use little air; together, and in step with line speed and job changes, they create a fast-changing demand that a poorly controlled compressor house struggles to follow.
Print and pack quality is sensitive to air quality too. Oil or water in air that blows onto a printed web, carton or film shows up as marks, poor glue bonds or contamination of food and pharmaceutical packaging. Pressure dips cause mis-feeds, jams and register errors.
Where compressed air is used, line by line
Pressures are typical; follow the machine builder’s specification. Air quality refers to ISO 8573-1 classes (particles:water:oil).
| Line or machine | Typical users | Typical pressure | Flow pattern | Typical air quality |
|---|---|---|---|---|
| Offset sheet-fed and web presses | Plate clamps, blanket washers, impression on/off, feeder and delivery air, web guides, splicers | About 6 bar (87 psig) at the machine | Steady base with peaks at make-ready | Dry, filtered; low oil near the sheet |
| Flexo and gravure presses | Doctor-blade loading, sleeve air mandrels, ink pumps, web tension and guiding | Machine pressure; sleeve mandrels need clean dry air | Continuous with job-change peaks | Dry and oil-free in effect for sleeves and web contact |
| Corrugator | Splicers, glue unit, cut-off and stacker actuators, preheater wraps, steam-trap valves | Plant air | Steady and continuous | Dry, filtered |
| Box making – printer slotters, die-cutters, folder-gluers | Feeders, kickers, glue guns, counter-ejectors, trim blow-off | Plant air; glue guns regulated | Fast pulses, high instantaneous flow | Dry, filtered |
| Carton converting | Pick-and-place vacuum, window patching, folding and gluing, carton erectors | Plant air; ejector vacuum from compressed air | High-cycle, high total consumption | Dry and oil-free where cartons contact food or medicines |
| Flexible packaging – lamination, slitting, bag making | Air shafts, slitter knife positioning, winders, sealing jaws, film blow-off | Air shafts at moderate pressure | Intermittent at reel changes | Dry and low oil |
| Form-fill-seal and end-of-line | Jaw actuation, product blow-off, case erectors, sealers, palletisers, stretch wrappers | Plant air | Cyclic, follows line speed | Typically Class 1.4.1 or better where product is exposed |
| Waste handling | Trim extraction support, baling presses, dust collector pulsing | Plant or pulse air | Pulsed | Dry |
Sequenced demand: how to design the system
Most converting plants run several machines whose peaks may or may not coincide. The design aim is stable pressure at every machine whichever combination is running.
- Measure the demand profile. Log flow and pressure for at least a full production week, including job changes and the busiest shift. Demand built up from machine catalogues is usually wrong.
- Base load and variable-speed trim. Fixed-speed rotary screw compressors carry the base, with a variable-speed machine following the fast changes. A master controller keeps the band tight and avoids several units running part-loaded.
- Storage close to fast users. Receivers near corrugators, folder-gluers and carton lines supply short, sharp peaks that compressors cannot follow.
- Ring main and drops. Loop pipework with drops taken from the top of the main, sized for low pressure drop, keeps far-end machines stable.
- Machine-level regulation. Set each machine to the pressure it needs instead of raising the whole plant to suit one demanding user.
Vacuum and blow-off: the hidden air users
Vacuum ejectors are convenient: they are compact, cheap and need only a compressed-air line. But they consume compressed air for as long as they are switched on, and a carton line with many ejectors can use more air than the rest of the plant. Where vacuum is needed continuously, a central or machine-mounted vacuum pump or a side-channel blower is often far cheaper to run. Ejectors with air-saving valves that switch off once a seal is made are a good middle path.
Blow-off is the other big user. Open pipes and drilled tubes for clearing trim, drying, or cooling waste large volumes. Engineered nozzles, timed blowing linked to the machine cycle, or low-pressure blower air for steady-duty drying usually cut consumption significantly without affecting the process.
Air treatment for print and pack quality
- Draw intake air from a cool, clean area away from paper dust and solvent vapour.
- Use a refrigerated dryer with a typical pressure dew point of about +3 °C for general machine air, sized for summer inlet temperatures.
- Fit general-purpose and coalescing filters after the dryer, with an activated-carbon stage where solvent or oil odour matters, such as food and pharmaceutical packaging.
- Consider oil-free compressors where air directly contacts food or medicine packaging and the risk assessment demands it.
- Use desiccant drying for any line running through air-conditioned or cooler print halls where condensation could form.
- Maintain automatic drains and treat condensate before disposal.
Reliability and standby
A press or corrugator stop is costly because of make-ready time and waste on restart. Plan compressed air so it is never the cause:
- Install one compressor more than peak demand needs, as standby (N+1), and a dryer bypass or second dryer so treatment never forces a shutdown.
- Monitor header pressure and alarm on low pressure before machines fault.
- Agree a rental option for breakdowns and overhauls, ideally with a tie-in point already fitted.
- Follow a preventive maintenance plan based on running hours, with filters, separators and drains on the same schedule.
Energy: the biggest opportunities
- Lower plant pressure to the real need: each extra bar of pressure costs about 7% more compressor power.
- Replace continuously running ejectors with vacuum pumps or air-saving ejectors.
- Replace open blow-off with nozzles, timers or blower air.
- Find and fix leaks, especially at quick couplings, air shafts and worn cylinder seals.
- Switch air off to idle machines with solenoid isolation valves.
- Check that compressors are not running unloaded for long periods out of hours.
The Indian context
India’s packaging industry is large and growing with food, FMCG, pharmaceutical and e-commerce demand. Hyderabad and its surrounding industrial areas host commercial printers, label and carton converters, flexible packaging plants and corrugated box makers serving the pharmaceutical and food sectors, with more units across Telangana and Andhra Pradesh. Many are small and medium plants that grew machine by machine, often with a compressor added for each new line.
Typical problems follow from that history: several unsequenced compressors, no central dryer, small pipework and high summer ambient temperatures of 40–45 °C that overload dryers. Paper dust blocks compressor coolers, and power dips can trip compressors or drives. Rationalising the compressor house is often one of the best-value investments such a plant can make.
Common problems and fixes
| Problem | Typical cause | Fix |
|---|---|---|
| Mis-feeds and jams at peak production | Pressure drop when several lines peak, small pipework | Demand logging, local receivers, ring main, sequencing |
| Marks or spots on prints or film | Water or oil in blow-off air | Dryer sizing, coalescing and carbon filters, drain checks |
| Weak vacuum on carton or label pick-up | Low supply pressure to ejectors, clogged silencers | Stable supply, ejector maintenance, consider vacuum pump |
| Air shafts not gripping cores | Leaking bladders, low inflation pressure | Shaft maintenance, correct pressure, leak repair |
| Compressor overheating in summer | Hot room, paper dust on coolers | Ventilation, regular cooler cleaning, intake filtration |
| High power bill | Leaks, ejectors, open blow-off, high pressure | Air audit and targeted fixes |
How Reddy Compressors helps
Reddy Compressors, based at Tarnaka, Secunderabad, and serving industry since 2002, is an independent multi-brand compressed-air specialist. We sell, rent and service ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other brands; we are not an authorised dealer of any of them. We have tie-ups with all major and reputed brands.
- Sales: rotary screw compressors including variable-speed units, oil-free machines where packaging contact requires them, dryers, filters and receivers; used and refurbished options too.
- Rentals: electric and diesel compressors, 50–2,000 cfm and 2–30 bar, from our own fleet for breakdown cover, overhauls and peak seasons.
- Service and AMC: a team of over 20 service engineers and technicians covering Telangana and Andhra Pradesh.
- Spares: identified from the nameplate or old part, confirmed for fit before quoting, supplied across India.
- Audits: demand profiling, leak surveys and power logging to right-size and sequence the compressor house.
Our track record. We have supplied compressors to leading companies in printing, packaging and paper converting across Telangana, Andhra Pradesh and beyond – new and used machines, long-term rental, and breakdown cover when a plant’s own compressor fails – backed by our own service team.
What to send us
- List of presses, corrugator and converting or packaging machines
- Compressor and dryer makes, models, nameplate photos and running hours
- Working pressure and any machines that need more
- Problems seen: pressure dips, water, oil marks, high power
- Whether any packaging is for food or pharmaceutical products
Frequently asked questions
What size compressor do I need for a corrugated box plant?
It depends on the corrugator, the number of printer-slotters, die-cutters and folder-gluers, and how many run together. Adding catalogue figures usually oversizes or undersizes the plant. The better method is to log flow and pressure over a full production week and size the compressors, receivers and dryer from that profile, with one unit in standby. We can carry out that measurement for existing plants.
Do packaging plants need oil-free compressed air?
Where air directly contacts food or pharmaceutical packaging, many converters choose oil-free compressors or high-grade coalescing and carbon filtration after an oil-injected compressor, depending on their customers’ requirements and risk assessment. For general machine air, a well-maintained oil-injected screw compressor with a dryer and filters is normally adequate. We supply and service both.
Why is my printing press getting water in the air lines?
Usually the dryer is undersized for summer inlet temperatures, bypassed, or its drains have failed, so condensate passes into the lines. Missing drains at low points and drops taken from the bottom of the main make it worse. Check the dryer’s pressure dew point, clean coolers, test drains and take drops from the top of the main.
Are vacuum ejectors expensive to run?
They can be. An ejector consumes compressed air the whole time it is on, and producing compressed air is energy-intensive. On high-cycle carton or label lines with many ejectors, the total can be a large share of plant demand. Air-saving ejectors that cut off once a seal is made, or a vacuum pump for continuous duties, usually reduce running cost considerably.
How can a printing or packaging plant reduce compressed air costs?
Measure first, then lower plant pressure to the real need, repair leaks, replace open blow-off with nozzles or blowers, address vacuum ejectors, isolate idle machines and sequence compressors so they do not run unloaded. A short audit with power and flow logging ranks these actions by payback so the plant knows where to start.
Can you supply a rental compressor if our main compressor breaks down?
Yes. We hire electric and diesel compressors from our own fleet, sized from 50 to 2,000 cfm, to keep presses and converting lines running while the main machine is repaired. Send us the required flow and pressure, your location and the connection size, and we will propose a suitable unit with hoses. We also repair the failed machine, whatever its brand.
Related pages
Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 7 November 2026. How our engineering content is reviewed.