Why compressed air matters so much in glass and ceramics
Both industries run hot processes that cannot simply be switched off. A glass furnace runs for years between rebuilds, and a roller kiln or tunnel kiln is kept at temperature around the clock. The machines that form, handle, decorate and pack the product around them depend on compressed air for movement, cooling, cleaning and control.
The consequence of poor air is therefore different from a general engineering workshop. Low pressure at a container-glass forming machine changes mechanism timing and gob delivery, which shows up as defective ware within minutes. Wet air in a glaze line causes spitting and surface defects. Loss of instrument air at a furnace or kiln forces valves and dampers to their fail-safe positions and can upset firing. Compressed air in these plants is the fourth utility after power, fuel and water, and it should be engineered with the same discipline.
Where compressed air is used, process by process
The table shows typical users. Pressures are typical plant figures at the point of use; actual values depend on the machine builder and the plant’s own specification. Air-quality classes refer to ISO 8573-1 in the form particles.water.oil (for example Class 1.4.1).
| Process area | Typical users | Typical pressure | Flow pattern | Typical air quality |
|---|---|---|---|---|
| Container glass – IS machine | Mechanism cylinders (invert, takeout, pusher, plunger), counterblow and final blow, valve blocks | Low-pressure blow air and higher-pressure mechanism air, often on separate headers | Large, steady base load with fast cyclic peaks per section | Dry, well filtered; Class 2.4.2 or better for mechanism air |
| Container glass – hot end | Swabbing and lubrication assists, ware transfer, cooling and dead-plate blow-off | Plant air pressure | Intermittent, high instantaneous flow | Filtered and dried |
| Float glass | Instrument air for furnace, bath and lehr controls; cutting and snapping; stacker and handling automation | Instrument header around 5–7 bar (72.5–101.5 psig) | Steady, critical, low variation | Instrument quality, typically Class 1.2.1 to 2.2.2 with desiccant drying |
| Cold end and inspection | Reject kickers, inspection machines, palletisers, shrink-wrap and stretch-wrap units | Plant air | Short, fast pulses | Filtered and dried; oil-free where it contacts finished ware |
| Ceramic tiles – body preparation | Spray dryer controls, pneumatic conveying of powder, silo aeration, bag-filter pulse cleaning | Conveying and filter air often lower than plant air | Continuous with pulsed peaks | Dry air essential for powder handling |
| Ceramic tiles – pressing and glazing | Hydraulic press automation, glaze spray guns and airless assists, digital printer services, line cleaning | Spray air reduced at the gun; machine air at plant pressure | Variable with line speed | Clean, dry, low-oil air for glaze quality |
| Kilns and furnaces – auxiliaries | Burner and combustion-control valves, dampers, roller drive clutches, kiln car pushers, cooling-zone controls | Instrument or plant air | Low flow, very high criticality | Instrument quality |
| Sanitaryware and tableware | Pressure casting, mould release, glaze spraying booths, finishing tools | Plant air, reduced at the point of use | Batch and shift dependent | Dry and filtered |
What does a sound system architecture look like?
Most large glass plants and tile plants are best served by a central compressor house feeding separate headers by duty, rather than one header serving everything at one pressure.
- Separate pressure levels. In container glass, blow air and mechanism air are often generated or regulated separately. Generating everything at the highest pressure and throttling down wastes energy: as a rule of thumb, each extra bar of generation pressure costs about 7% more compressor power.
- A protected instrument-air header. Furnace, kiln and bath controls should sit on their own header with its own desiccant dryer, filters and receiver, and a non-return or priority valve so that a burst hose on the production floor cannot draw the instrument header down.
- Base load and trim. Fixed-speed rotary screw machines carry the steady base load, with one variable-speed machine trimming the peaks. A sequencer keeps the units in a tight pressure band.
- Storage near cyclic users. Local receivers close to IS machines, presses or glaze lines supply short peaks without forcing another compressor to load.
- Ring mains and low pressure drop. Loop distribution with correctly sized pipe keeps pressure even across long buildings; long single-feed lines are a common cause of pressure complaints at the far end of a plant.
- N+1 redundancy. At least one compressor and one dryer more than peak demand, so maintenance or a breakdown does not cut supply.
Oil-injected rotary screw compressors with good treatment meet most requirements. Oil-free compressors are worth considering where air touches finished ware or where an oil carry-over incident would be costly; the decision should be based on risk, not habit.
Air treatment for heat and dust
Glass and ceramics plants combine two hostile conditions for compressed air: high ambient temperature near furnaces and kilns, and fine abrasive dust from batch house, body preparation and cutting.
- Clean intake air. Draw compressor intake air from a cool, clean location, ideally ducted from outside the building away from batch house and kiln exhausts. Use suitable pre-filters and check intake filters more frequently than the standard interval in dusty months.
- Aftercooling and separation. Make sure aftercoolers are clean so that discharge temperature into the dryer stays within its rating; a fouled cooler in summer overloads the dryer.
- Drying. Refrigerated dryers giving a typical pressure dew point of about +3 °C suit most plant and machine air. Instrument air, powder conveying and outdoor lines in cold zones are better served by desiccant dryers at a typical −20 °C or −40 °C pressure dew point.
- Filtration. General-purpose and coalescing filters after the dryer, with an activated-carbon stage where oil vapour must be controlled, for example at glaze spray or ware-contact points.
- Condensate. Automatic drains on every separator, receiver and filter, with oily condensate treated in an oil-water separator rather than run to open ground.
Dryer sizing must be corrected for the plant’s real inlet temperature and ambient. A dryer selected for nominal conditions can lose a large share of its capacity in an Indian summer, and the first sign is water at the press or the glaze booth.
Reliability, criticality and standby cover
Rank every user by the consequence of losing air. A useful approach is three tiers:
- Critical: furnace, bath and kiln instrument air, forming machine mechanisms, safety valves. Loss means scrap, firing upset or a safety trip.
- Production: presses, glaze lines, inspection, packing. Loss stops output but is recoverable.
- Discretionary: blow guns, cleaning, housekeeping. These should be the first to be shed.
Plan for the day a compressor is out for overhaul or fails. A temporary electric or diesel compressor connected through a pre-installed tie-in point can keep critical users running. Furnace rebuilds and cold repairs also create short-term demand for site air for tools, cleaning and demolition, which is often best met by rental machines. See our temporary air engineering centre for how a hire package is specified.
Energy: where the savings usually are
Compressed air is often among the largest electrical loads in a glass or tile plant after the furnace or kiln fans and grinding mills. The usual opportunities are:
- Lowering generation pressure to what the highest-pressure critical user actually needs, and boosting locally where a single machine needs more.
- Replacing open blow pipes for cooling and cleaning with engineered nozzles, or with low-pressure blower air where the duty allows.
- Finding and repairing leaks, which are common on hot-end equipment because heat hardens hoses and seals.
- Avoiding unload running by matching compressor control to demand and adding storage.
- Recovering compressor heat for washing, process water pre-heating or space heating where there is a genuine user.
An audit with power and flow logging gives the specific power of the compressor house and shows which of these matter most in a particular plant.
The Indian context
India has container-glass plants serving the beverage, pharmaceutical and food sectors, float glass lines for construction and automotive glazing, and a very large ceramic tile and sanitaryware industry, with the main tile cluster in Gujarat and further plants across the south, including Andhra Pradesh and Telangana. Glass bottle and tableware units, refractory and insulator manufacturers also operate in the region.
Conditions that affect compressed air here are consistent: summer ambient temperatures of 40–45 °C in Telangana and much of Andhra Pradesh, and above 45 °C on open sites, compressor rooms that sit close to hot zones, monsoon humidity that loads dryers, and airborne dust from raw-material handling. Power quality varies by location, so compressor controllers, starters and drives should be protected against voltage dips and harmonics, and restart logic should be checked so that compressors come back in sequence after a supply interruption.
Common problems and how to fix them
| Symptom | Likely causes | What to check or change |
|---|---|---|
| Ware defects that follow pressure swings | Shared header with cleaning loads, undersized receiver, poor sequencing | Log pressure at the machine, separate or prioritise mechanism air, add local storage |
| Water in glaze spray or press lines | Dryer overloaded by high inlet temperature, failed drains, no dryer bypass control | Measure pressure dew point, clean coolers, check drains, resize dryer for summer |
| Compressor high-temperature trips in summer | Hot compressor room, recirculating hot air, blocked coolers from dust | Duct hot air out, bring cool air in, clean coolers, review room layout |
| Short filter life and airend wear | Dusty intake air | Relocate intake, add pre-filtration, shorten inspection interval |
| Instrument valves sticking at the kiln or furnace | Moisture or oil carry-over into instrument air | Dedicated desiccant dryer and filtration, regular dew-point checks |
| Rising power bill with no rise in output | Leaks, high set pressure, open blowing, unload running | Air audit, leak survey, pressure reduction, control review |
How Reddy Compressors helps
Reddy Compressors is an independent multi-brand compressed-air specialist based at Tarnaka, Secunderabad, serving industry since 2002. We sell, rent and service compressors from ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and others; we are not an authorised dealer of any brand, which lets us recommend what suits the plant. We have tie-ups with all major and reputed brands.
- Sales: new rotary screw and oil-free compressors, dryers, filters and receivers sized for the plant’s real ambient and duty, and used or refurbished machines where that suits the budget.
- Rentals: electric and diesel compressors from 50 to 2,000 cfm and 2 to 30 bar from our own fleet, for breakdown cover, overhauls and furnace or kiln shutdowns.
- Service and AMC: over 20 service engineers and technicians covering Telangana and Andhra Pradesh, with preventive maintenance, breakdown repair and overhaul for multi-brand compressor houses.
- Spares: parts identified from the machine nameplate, serial number or the old part, with fit confirmed before we quote, supplied across India.
- Audits: pressure, dew-point, leak and power logging to show where air and energy are being lost.
Our track record. We have supplied compressors to leading companies in glass and ceramics 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
- Type of plant (container, float, tile, sanitaryware, tableware) and location
- Compressor make, model, nameplate photo and running hours for each unit
- Required pressures and any separate headers (blow, mechanism, instrument)
- Dryer and filter types, and any water, oil or pressure complaints
- Electricity bill or compressor running data, if an audit is of interest
- Dates of any planned shutdown or furnace or kiln repair needing temporary air
Frequently asked questions
How much compressed air does a glass bottle plant need?
It depends on the number of IS machine sections, gob weights, whether blow and mechanism air are generated separately, and how much air goes to cooling and cleaning. The reliable way is to log flow and pressure on the existing system, then add planned machines. Sizing from the nameplate of the forming machine alone usually overstates or understates demand. We can measure the existing plant and size from the data.
Which dryer is best for ceramic tile plants?
Refrigerated dryers with a typical pressure dew point of about +3 °C suit most press, glazing and machine air, provided they are sized for the real summer inlet temperature. Powder conveying, instrument air and lines exposed to cooler outdoor sections are better on a desiccant dryer at around −40 °C pressure dew point. Many tile plants use both, with the desiccant dryer on a dedicated header.
Do glass and ceramics plants need oil-free compressors?
Not always. Oil-injected screw compressors with coalescing and carbon filtration meet most needs. Oil-free compressors make sense where air contacts finished ware or food and pharmaceutical containers, or where the cost of an oil incident is high. We assess the air-quality class each user actually needs before recommending either technology, and we supply and service both types.
Why do my compressors trip on high temperature in summer?
The usual causes are a hot compressor room close to furnaces or kilns, hot discharge air recirculating to the intake, and coolers blocked by fine dust. Normal oil-injected screw discharge temperature is about 75–95 °C; trips occur when cooling cannot reject heat. Ducting hot air out, admitting cool air low down and cleaning coolers regularly usually resolves it.
Can we rent a compressor during a furnace rebuild or kiln shutdown?
Yes. Rebuilds and shutdowns need temporary air for tools, cleaning and demolition, and sometimes for keeping critical controls alive while the main compressor house is worked on. We hire electric and diesel compressors from our own fleet with hoses and, where required, dryers. Give us the dates, location, pressure and the tools to be used so we can propose a package.
How can a tile or glass plant cut compressed air power cost?
Start by measuring. Common savings come from lowering generation pressure, separating low-pressure blow duties, repairing leaks, stopping open-pipe cooling and cleaning, and improving compressor sequencing so machines are not running unloaded. An audit with power and flow logging shows the plant’s specific power and ranks the actions by payback, so money goes where it gives the most return.
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Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 17 October 2026. How our engineering content is reviewed.