Line Components and Technologies
Compressors and cooling: the hidden half of the line budget
Compressed air and cooling are not visible in the filling line specification, but they determine the electricity bill and the shop's ability to work in summer heat.
Two air circuits
PET blowing needs high-pressure air at 25-40 bar — a separate piston compressor with multi-stage compression and cooling. It is usually the most energy-consuming unit on the site.
Line pneumatics, blowing and air transport work on low-pressure air 6-8 bar from a screw compressor. These circuits cannot be combined: feeding pneumatics from the high-pressure compressor is inefficient and expensive.
Both circuits need drying and filtration. Air contacting the product or the inside of the bottle must meet residual oil and dew point requirements.
Approximate air demand
| Consumer | Pressure | Comment |
|---|---|---|
| PET blowing | 25-40 bar | Main energy consumer on the site |
| Line pneumatics | 6-8 bar | Drives, rejectors, blow-off |
| Air bottle transport | 0.2-0.5 bar | Separate blower, not compressor |
| Nitrogen for inerting | 6-8 bar | Nitrogen generator from compressed air |
Where money is lost
- Leaks
- In an unmaintained pneumatic network up to a third of compressor capacity is lost. Ultrasonic leak detection pays off immediately.
- No heat recovery
- Compressor heat can be directed to wash water heating and shop heating.
- No variable frequency drive
- A compressor with regulated output saves a noticeable share of energy under variable load.
- Wrong receiver
- Too small a receiver makes the compressor start frequently, shortening its life.
- Saving on drying
- Moisture in the line means corrosion, blowing defects and pneumatic failures.
FAQ
Can one compressor serve all needs?
No. 40 bar for pneumatics is excessive and economically meaningless. The standard scheme is two independent circuits.
How to calculate compressor power for blowing?
From the number of blowing machine cavities, bottle volume and cycle time. The calculation is done together with machine selection, because a 20% reserve here is not a luxury but a norm.
Is a backup compressor needed?
For continuous production — yes, at least partial redundancy. A compressor stop stops the whole site, not just one unit.
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