An insulating glass line uses around 300 to 600 l/min of compressed air at about 6 bar, as a rough guide, for its cylinders, press and conveyors. Added to the rest of the workshop, it often takes demand towards 2 m³/min, which corresponds to a 15 kW 4-in-1 screw compressor such as the K 150 (2.2 m³/min at 8 bar). The air must be dry and filtered: a trace of water or oil on a face to be assembled ends up sealed between the panes.
For every air need in glass processing, see our page on the compressor for glass processing and glazing.
Where does the air go on a double glazing line?
An insulating glass line strings together several stations, and almost every one has its cylinders:
- the washer, whose valves and sometimes blow-off nozzles are pneumatic;
- the conveyors, with their stops, retractable rollers and air transfer cushions;
- the assembly station, where the spacer is applied and the second pane brought into position;
- the press, which clamps the two panes together with a controlled force;
- miscellaneous automation: doors, turning grippers, handling suction cups.
Consumption depends on the size of the line, the number of cylinders and the cycle rate. The line's manual gives a value in l/min or Nm³/h: that is the figure that counts. Our flow and pressure converter turns Nm³/h and CFM into l/min.
How do you estimate cylinder consumption?
If the manual only gives a list of cylinders, you can do the calculation yourself. On each out-and-back stroke, a cylinder uses the volume of its chamber multiplied by the absolute pressure.
Example for a cylinder of 63 mm bore and 200 mm stroke, at 6 bar:
- Area: 3.14 × 3.15 cm × 3.15 cm ≈ 31.2 cm².
- Volume of one stroke: 31.2 cm² × 20 cm ≈ 624 cm³, or 0.62 l.
- Out and back (ignoring the rod): 1.25 l.
- At 6 bar, you need 7 times that volume in free air: about 8.7 l per cycle.
- At 60 cycles an hour, or one a minute: about 9 l/min.
A single cylinder therefore uses little air. It is the number of cylinders, the large bores on the press and the cycle rate that push the total up. Our article on pneumatic cylinder air consumption explains the method in detail.
The full step-by-step calculation
Take a workshop making double glazing units, with cutting and edging upstream (indicative values):
| Station | Value used |
|---|---|
| Insulating glass line (washer, conveyors, press) | 400 l/min |
| Cutting table | 250 l/min |
| Two edging machines | 300 l/min |
| Vacuum lifters, counted at 50% | 120 l/min |
| Two blow guns, counted at 50% | 150 l/min |
| Base total | 1,220 l/min |
Margins used by the configurator: 1,220 × 1.25 = 1,525 l/min with the safety margin, then 1,525 × 1.2 = 1,830 l/min with the expansion margin.
The K 150 delivers 2,200 l/min at 8 bar. It covers this demand with a comfortable margin, and its refrigerated dryer and filtration are built in. If the line stands alone, with no cutting or edging on the same network, a K 110 (1.7 m³/min) is generally enough. If you are planning a second line or a sandblaster, the S 220 PM gives 3.6 m³/min at 8 bar.
Why does the press need a stable pressure?
The press clamps the assembly with a force that depends directly on the air pressure in its cylinders. If the pressure drops just as the press closes, because the cutting table is breaking at the same moment, the clamping varies from one unit to the next. Most lines have their own regulator and a safety pressure switch, but the network still has to stay above the required value.
Three precautions:
- A buffer receiver near the line. It supplies the press's peak without pulling down the rest of the network. The air receiver size calculator gives the volume; allow about one litre for every 3 l/min of demand.
- Properly sized pipework. A pipe that is too narrow makes the pressure drop at the end of the line, even with a large compressor.
- A variable speed compressor. The S and K series follow demand and hold a steady set pressure, without a swing of several bar between cut-in and cut-out.
What air quality for insulating glass?
This is the tricky part. On a double glazing line, the air drives cylinders, but it also blows onto the glass in the washer and passes through the suction cups that touch the faces. Those faces will then be bonded to the spacer and sealed in for years.
- Water. Damp air leaves rings as it dries and can make water bead at the end of a nozzle. A refrigerated dryer is the minimum; it is built into the K series.
- Oil. Our compressors are oil-lubricated: the outlet filtration captures carried-over oil. For air that touches the glass, add fine filters and an activated carbon stage at the station. A thin film of oil on the assembly face can impair the adhesion of the seal.
- Particles. Glass dust and rust from an old network settle on the face to be bonded. A network in a non-corroding material and filtration at the station stop them.
The air class to aim for under ISO 8573-1 is set with our technicians and the line manufacturer. Our guide to ISO 8573-1 air quality explains how to read these classes.
The traps to avoid
- Connecting the line at the end of an old network. Water collected at the low points heads back into the washer at the first big demand.
- Forgetting the drains. An automatic condensate drain on the receiver and at every low point.
- Letting the filters saturate. A clogged fine filter pulls down the press pressure and no longer protects anything. Change the elements at the interval the manufacturer gives.
- Stretching compressor servicing. First service at 500 hours, then every 1,500 hours. A worn air/oil separator lets more oil through to the filters.
To size your installation, enter your line and your other machines in the configurator, then send us the line's manual with a quote request.
For your trade: Compressor for glass processing, glaziers and double glazing.