Air Compressors for Glass Manufacturing – Air Compressor Manufacturers

When picking compressors for a glass plant, first thing is figuring out where the compressor room can go. Furnace area ambient temps run 60-70°C, forming area around 50°C, annealing lehr side in the 40s. Many plants have compressor room location locked in during facility design phase, hard to change later, can only work on intake air and cooling solutions.

60-70°C

Furnace Area Temp

~50°C

Forming Area Temp

~40°C

Annealing Lehr Side

Intake temp impact on output volume, different manufacturer tech manuals give different numbers. Some say every 10°C higher drops output 2.5%, some say 3%, some say 3.5%. Take middle ground at 3%, glass plants having intake temps 20-30°C above standard conditions is normal, output volume takes a 10% hit or more. A machine rated for 10 cubic meters actually puts out 8-something, this derating must be factored into selection. Discharge temp follows intake, screw machine compression adds 70-80°C temp rise, intake at 45°C means discharge heading toward 120°C, high temp protection triggers and machine shuts down.

Inside the furnace runs around 1500°C, soda-lime glass and borosilicate glass formulas differ, melting temps can differ by 100-200°C. Furnace temp itself doesn't directly affect compressors, the trouble is radiant heat. Standing six meters from the furnace, actual measured ambient exceeds 60°C. July-August even higher, readings above 70°C have been recorded. Forming shop a bit lower, glass liquid leaving furnace still carries 1000°C+ residual heat, molds maintained at 400-500°C, surrounding area around 50°C. Annealing lehr cools progressively along its length, that side around 40°C, relatively better.

Water-cooled models are basically standard at glass plants.

Air-cooled isn't impossible, but when ambient hits 40-50°C cooling efficiency tanks, small temp differential means heat can't dissipate. If you insist on air-cooled, size up one notch, add fans where possible, set up negative pressure ventilation in the machine room. Max out all the measures and the hottest few days of summer might still be too much. Water-cooled advantage is cooling water temp is controllable, if cooling tower output stays below 32°C there's no cooling pressure.

High Temperature

Glass Furnace Environment

Essential

Cooling Solutions

Location

Compressor Room

Cooling tower sizing is an easy place to trip up.

Towers sized per calculation barely handle normal times, summer high temp season outlet water temp creeps up, 35°C is routine, consecutive hot days 38°C, 40°C happens. How much margin to add depends on local climate. Some plants add a holding pond to the cooling water loop, 10-20 cubic meters of water sitting there as thermal buffer, handles short-term high temp spikes. Cooling water temp needs online monitoring, set alarm values, don't wait until discharge temp alarms to find out cooling water has problems.

Intake air cooling doesn't cost much but works well. Most common approach is drawing air from outside, run a galvanized or stainless pipe, punch through the wall or bring down from the roof, 10-20 meters long. Outside air is 10-20°C lower than shop floor, this temp difference helps stable operation a lot. Pipe opening faces down or install rain cap, add coarse screen to catch leaves and bugs, few thousand bucks handles it, most glass plants use this.

Higher requirements can add a surface cooler, installed before the intake, chilled water or cooling water for temp reduction, press intake below 30°C. Chilled water approach needs a chiller, not small investment. Some plants just run cooling tower water through the surface cooler, saves the chiller, cooling effect is compromised but cost is way lower.

Plants with basements or equipment trenches can draw air from below. Underground temp is 7-8°C lower than surface in summer, costs nothing, uses no power, depends whether your facility has this option.

The oil issue.

Manual says oil change interval 2000 hours, 3000 hours, that's based on normal temp conditions. Glass plant machines running high temp long-term, oil oxidation is way faster. Some machines run 1500 hours, pull an oil sample and test, acid number and viscosity both over spec, continuing use is burying trouble. Some machines at 2000 hours oil condition is still okay, one-size-fits-all doesn't make sense. Recommend doing oil analysis, test acid number and viscosity changes, use data to set oil change timing. Synthetic oil handles high temp better than mineral oil, costs more, but change interval can be extended, failure rate can be pushed down, total accounting may not lose out.

Machines frequently triggering high temp protection, oil ages faster, seals suffer too, small problems drag into big problems. Units with discharge temp running high long-term need special attention on oil condition.

Compressed air uses in glass plants, blow molding takes the lion's share. Initial blow at 2-3 bar shapes the parison, final blow at 5-6 bar or higher blows final shape. IS machines running fast use more air, slow down and use less, fluctuation range is big. If receiver capacity isn't enough, network pressure swings wildly, blow quality can't stabilize. A four-IS-machine bottle plant, blow molding plus mold cooling plus pneumatic controls, totals 30-something cubic meters per minute, specifics depend on product specs and production tempo.

2-3bar

Initial Blow

5-6bar+

Final Blow

30+m³/min

4-IS Plant Total

Mold cooling is continuous load, 3-4 bar, steady flow. Pneumatic elements distributed plant-wide, individual point usage small, adds up to something.

Blow molding air directly contacts glass liquid, particles and oil mist get in, glass surface gets bubbles and defect spots, product is scrapped. Per ISO 8573 standard, particulates Class 2 to Class 3, dew point below +3°C, oil content Class 2. Mold cooling and pneumatics side requirements are much lower, dry is enough.

Select high-temp compressor models, ones with nameplate intake temp limit marked 45°C or 50°C. VFD machines have obvious value for glass plants, blow molding air usage swings big, VFD following load saves power versus fixed speed. Three running one standby is common configuration.

Dryers need to verify allowable inlet temp. Compressor discharge after the aftercooler might still run hot, exceeding dryer design range hurts performance. High inlet temp dryer models cost a bit more, or add another cooling stage between aftercooler and dryer.

Air filters clog fast at glass plants. Glass raw material dust, particles drifting from the furnace, air filter gets coated quickly. Clogged means intake resistance rises, output drops, energy use climbs. Shorten inspection intervals, or install differential pressure gauge to watch, differential exceeds spec then change.

Cooling system needs regular dust removal and descaling. Air-cooled fins accumulate dust and heat exchange efficiency drops straight down, water-cooled piping scales up bad enough to block. Cooling tower fill, water distributors, fans also need regular checks.

Temperature monitoring becomes daily routine. Intake temp, discharge temp, cooling water inlet/outlet temp, machine room ambient temp, watch all these points, record data to see trends. Discharge temp climbing for several consecutive days, most likely cooling efficiency dropping or oil needs changing, catch early and deal with it, don't wait for high temp protection to trip before acting.