Carbonated Drink Filling FAQ: 8 Answers B2B Buyers Need Before Building a CSD Line

Views: 204 Author: Howie SUN Publish Time:
Carbonated filling is a pressure and temperature problem: CO2 stays in the product only while the bottle is held above the saturation pressure for its temperature.

24,000 BPH PET Bottle Carbonated Cola Drink Rinser Filler Capper Machine

Key facts at a glance
Filling systemIsobaric, CO2 counter-pressure
Rated output12,000-36,000 BPH at 0.2-2 L
ContainersPET bottle, glass bottle, aluminum can
CO2 handlingPre-pressurisation and return pipe, no venting
ValvesMechanical, semi-electric or volumetric
Line scopeWater treatment, syrup mixing, carbonation, filler, pack

What actually decides the shortlist?

Four inputs fix the shortlist: the product, the package, the daily demand and the number of formats per week. Everything else, including the brand of the PLC, is a detail that can be settled after those four are written down.

Why does carbonated product need isobaric filling?

A carbonated drink is a saturated solution held in equilibrium by pressure and temperature. If the filler exposes it to atmosphere, CO2 leaves the liquid as foam and the fill level collapses. Isobaric filling pressurises the bottle to the bowl pressure first, fills under counter-pressure, then releases in a controlled ramp.

Valve typeSettingBest for
MechanicalFixed cam profileSingle product, long runs
Semi-electricSignal-timed open and closeRecipe changes within one product family
VolumetricChamber dosePressure or temperature drift during the shift
Isobaric + volumetricChamber dose under counter-pressureHigh CO2 with tight fill accuracy

The Isobaric Filling Machine for CSD and Sparkling Water is the matching unit when this becomes a line project.

How does a can line differ from a PET line for CSD?

A can is filled and seamed, a PET bottle is filled and capped. Cans run faster per unit and are counted in CPH; PET allows larger formats and a lighter package. The filler principle is the same isobaric one, the closing equipment and the line rate are not.

A different bottle format means a different unit; see the CSD & Sparkling Water by Mechanical Filler.

What is overfoaming at the filler and how is it controlled?

Overfoaming is gas leaving the product too fast at the end of fill. The pressure release has to be ramped, not dumped, and the fill height has to leave the right headspace. A snift valve that opens too early turns a good fill into a wet bottle.

The same question is worked through from another angle in Exploring Isobaric Filling: Core Technology for Carbonated Drinks.

How to read the numbers. Capacity is quoted as a reference range from the product specification. A rated BPH is measured at one CO2 level and one temperature; format changes and CIP sit outside it, so size on 0.65-0.85.

Frequently asked questions

Can one filling machine run both still water and CSD?

No. Carbonation needs isobaric valves under counter-pressure; still water runs gravity or volumetric. A combiblock can carry both valve sets, but they are specified separately and are not interchangeable at the push of a button.

Why is my fill level dropping through the shift?

Usually product temperature rising in the bowl or a worn valve seal. Both change the pressure balance, so the fill cuts off earlier. Log bowl temperature and fill weight together for one shift before changing any valve.

What is the difference between 2.5 and 4.0 volumes of CO2?

The higher the volumes, the sharper the mouthfeel and the more pressure the package must hold. Higher carbonation also needs a colder fill and a tighter pressure ramp, so it reduces practical line speed.

Can a CSD line fill glass bottles?

Yes, with a different infeed, spacing and capping set. Glass needs mechanical spacing rather than an air conveyor, and the filler runs at 4,000-20,000 BPH on glass against 12,000-36,000 BPH on PET.

Key takeaways
  1. Semi-electric and volumetric valves buy recipe flexibility; mechanical valves buy simplicity.
  2. Size the CO2 plant on average demand, not on the filler nameplate.
  3. Warm product loses CO2 before the filler can dose it.
  4. A can line and a PET line share the valve principle, not the closing equipment.
About the author
Written by the Sunswell engineering team - led by Howie SUN, Founder & CEO, with 14 years in filling and blow-moulding equipment R&D and turnkey project delivery across 71+ countries.
Last reviewed: 2026-08-28 . Reviewed by Sunswell engineering team
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