Let us be straight from the first line, because this is where a lot of buyers get mis-sold: the actual stretch-blow step that forms a PET bottle needs high- pressure compressed air, typically in the region of 40 bar, and that is a compressor job — not a blower job. A regenerative or centrifugal blower cannot and should not be used to inflate the bottle. What a blower does do on a PET line is everything around that step — preform and bottle conveying, air-knife drying, cooling and low-pressure handling. This guide draws the line clearly so you buy the right machine for each stage.
The two pressure worlds of a PET line
A PET blowing line has two completely separate air systems:
| Stage | Pressure | Correct machine |
|---|---|---|
| Stretch-blow forming (inflating the bottle) | ~40 bar (high-pressure compressed air) | Dedicated PET blowing compressor |
| Preform / bottle air conveying | A few hundred mbar | Regenerative / high-pressure blower |
| Air-knife drying after filling/rinsing | A few hundred mbar | Regenerative blower |
| Cooling and low-pressure handling | Low pressure, high volume | Regenerative / centrifugal blower |
The number that matters: 40 bar is roughly a hundred times the pressure any side channel or centrifugal blower produces. Yash blowers top out in the region of 1 bar. So the forming air is never a blower — anyone who tells you a blower can blow a PET bottle is wrong. Where we help is the low-pressure side, and that side is substantial.
Where the blower earns its place
Air conveying of preforms and bottles
PET lines move preforms and finished bottles through air conveyors — tracks where a curtain of air pushes lightweight bottles along by the neck ring. This is a low-pressure, high-volume duty spread over the length of the conveyor. A High Pressure Series or a strong Single Stage Turbine Blower supplies the air-conveyor plenum; the YEBL-1-700P at 10 HP moves around 700 m³/hr for a long conveyor, and the YEBL-HP-DS-87 gives higher pressure where the track needs more push. Sizing follows the same logic as any pneumatic conveying plenum — volume across the track, pressure for the lift.
Air-knife drying after rinse or fill
Rinsed or filled bottles carry surface water that ruins labels and glue. An air knife fed by a regenerative blower strips that water oil-free before labelling. On a food/beverage line this must be oil-free — the same imperative covered in our food processing hygiene post — which is another reason it is a blower and not a compressor tapping. The YEBL-1-400 at 5.0 HP and 330 mbar suits a typical drying knife.
Cooling and low-pressure handling
Mould cooling assists, low-pressure hold-down and general blow-off around the line are all high-volume, low-pressure duties that suit a CX-Series Centrifugal Blower where big volume matters more than pressure — the YBCB-CX-100A moves roughly 1,200–1,450 m³/hr.
How to spec the blower side correctly
- Draw the line first. List every low-pressure air job — conveying, drying, cooling — separately from the forming compressor.
- Conveying: volume across the track, pressure for the push. Longer air-conveyors need more volume; steeper or faster tracks need more pressure.
- Drying: pressure for the water film, volume for the knife length. See the air knife guide.
- Oil-free throughout the beverage zone. Anything whose air can reach the bottle interior or the sealing surface must be oil-free.
- Leave the 40-bar job to the compressor. Do not let a supplier blur the two systems to sell you the wrong machine.
Why the honesty helps you
Some sellers happily quote a "PET blowing blower" and let the buyer assume it forms the bottle. It does not. Being clear about the split means you buy a proper PET compressor for forming and right-sized blowers for conveying, drying and cooling — which is both cheaper and more reliable than trying to make one machine do everything. The full low-pressure duty list is on our PET bottle blowing application page.
Why the forming step needs so much pressure
It helps to understand why stretch-blow forming sits so far out of blower range. To form a PET bottle, a heated preform is stretched by a rod and inflated hard against a cold mould so the plastic takes the mould's shape and detail sharply. That inflation has to happen fast and firm — which needs a large pressure differential, in the region of 40 bar, delivered in a controlled burst. Only a high-pressure reciprocating compressor built for PET does that. A blower produces pressure by spinning air in a channel or impeller; it physically cannot reach tens of bar. So the two systems are not interchangeable at any size.
Many modern PET plants also recover air from the forming exhaust to feed lower- pressure duties — but the source of forming pressure remains the compressor.
| Air job | Pressure order | Machine class |
|---|---|---|
| Stretch-blow forming | ~40 bar | PET blowing compressor |
| Air-conveyor plenum | Hundreds of mbar | Regenerative / HP blower |
| Air-knife drying | Hundreds of mbar | Regenerative blower |
| Cooling / handling | Low, high volume | Regenerative / centrifugal |
A worked example: the air-conveyor side
Take an air conveyor carrying empty bottles by the neck ring from the blow-moulder to the filler. Size it as a plenum:
- Volume. The conveyor bleeds air through slots along its whole length; sum the demand over the run — longer conveyors need more volume.
- Pressure. Set by how much push the bottles need to move at line speed and any rise in the track.
- Model. A YEBL-1-700P (10 HP, ~700 m³/hr) suits a long conveyor; where the track needs more push, the High Pressure Series adds pressure.
Frequently asked questions
A supplier offered me a "bottle blowing blower" — is that the forming machine? No. A blower never forms the bottle. If a quote implies a blower inflates PET, they are describing the low-pressure conveying/drying side, or they are wrong. Ask directly which stage it serves.
Can I run the air knife off my forming compressor? You can tap it, but it is wasteful — you throttle 40-bar air down to a few hundred mbar and pay for all that compression. A dedicated blower is far cheaper and oil-free.
Is oil-free needed on the conveying side? For beverage lines, yes anywhere air can reach the bottle interior or sealing surface — a regenerative blower is oil-free by design.
Installation notes for the blower side
The low-pressure air system around a PET line is straightforward to install well:
- Keep runs short to the air conveyor. Pressure lost in long, undersized pipe is push the bottles never receive — size the header generously so the far end of the conveyor is not starved.
- Oil-free everywhere in the beverage zone. Any air reaching the bottle interior or the sealing surface must be oil-free; a regenerative blower delivers that by design, the same imperative as food processing hygiene.
- Filter and protect the intake. PET halls carry dust and preform debris; a maintained inlet filter keeps the impeller clean.
- Site for cooling and noise. Give the blower clear cooling air and add a silencer if the filling hall is noise-sensitive.
- Plan continuous duty and spares. The line runs long shifts; spec the blower for 24/7 service and keep spares for the conveying and drying machines so a stop does not idle the whole line.
None of the low-pressure duties are exotic — they just need to be sized honestly and kept off the forming compressor.
Get the low-pressure side sized right
Tell us your line speed, air-conveyor length and drying requirement, and we will size the conveying, drying and cooling blowers — and point you to a proper forming compressor for the 40-bar stage. WhatsApp +91 9311693322 or email sales@yashblowers.org for a quote in 24 hours.