How Nitrogen Dosers Maintain CO2 Levels in Aluminum Cans

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A can line is rated in cans per hour because the seamer sets the pace, and the seam, not the filler, is where the rating is usually lost. Nitrogen dosers play a pivotal role in this process by helping to minimize CO2 loss during filling, sealing, and storage.
Key facts at a glance
Filling methodIsobaric for beer and CSD, volumetric for juice and tea
Output rangeUp to 25,000 CPH
Can sizesStandard 250, 330 and 500 ml
SeamingRoller seamer integrated with the filler
OptionsHot fill for juice and tea, nitrogen dosing
Key controlFill level, seam tightness, dissolved oxygen

Why is can filling measured in CPH and not BPH?

A can line is counted in cans per hour because the container is the unit the seamer closes. CPH and BPH cannot be converted without the fill volume, and the downstream packer is sized in cases per hour. Comparing a 24,000 CPH can line with a 24,000 BPH bottle line compares two different plants.

How is oxygen controlled on a can line?

Dissolved oxygen enters at three points: deaeration of the product, the filler bowl atmosphere, and the gap between fill and seam. Nitrogen dosing and a steam or CO2 tunnel at the seamer reduce the last one. For beer and juice, the dissolved oxygen in the finished can is the number to test, not the setting on the doser.

Nitrogen dosers play a vital role in this process, ensuring consistent CO2 levels that enhance the flavor and quality of the beverages.

ProductFilling principleCritical measurement
BeerIsobaric, coldDissolved oxygen and seam tightness
CSD and sodaIsobaric, coldCO2 retention and fill height
Juice and teaVolumetric or hot fillFill temperature and seam integrity
Energy drinksIsobaric or volumetricDissolved oxygen and closure

For the same duty in another bottle format, the Aluminum Can Filling Machine for Beer, Carbonated Soft Drink is specified separately.

What changes between a beer can and a juice can?

Beer and CSD run isobaric, cold, under counter-pressure. Juice and tea often run hot fill or a volumetric fill with a downstream pasteuriser. The can is the same format; the filler, the valve set and the temperature control are not, so one can line rarely covers both without a second specification.

Sizing for this duty runs through the Aluminum Can Filling Machine for Hotfill Juice and Tea, where the valve count is set out.

What does a hot-fill can line need that a cold line does not?

A heated product path, a fill temperature control loop and a cooling tunnel after seaming. The can itself tolerates the heat; the lining and the product do not always. The temperature window belongs to the product specification.

The same question is worked through from another angle in How Aluminum Can Fillers Maintain Beverage Quality.

How to read the numbers. Where a BPH appears below it is the specification range, not a measured rate. Can lines lose more to seamer stops and conveyor accumulation than to filler speed. Plan on a factor of 0.65-0.85.

Frequently asked questions

How many cans per minute is 18,000 CPH?

300 cans per minute. Divide CPH by 60. The seamer, the filler and the packer all have to carry that number, so the line rating is the lowest of the three.

What is dissolved oxygen and why does it matter?

It is the oxygen left in the product after filling. It drives oxidation, off-flavour and haze. Beer and juice have tight limits, and the measurement belongs in the acceptance protocol, taken from the finished can.

How often is a seam checked?

At a fixed interval during production, by tear-down and measurement, plus a check after every seamer adjustment. The interval is set by the plant quality plan; the point is that it is measured, not inspected by eye.

Does a 250 ml can run faster than a 500 ml can?

Yes, at the same filler, because the fill volume per cycle is smaller. The seamer and the packer still have to carry the higher can rate, which is why the line rating is set on cans per hour, not litres.

Key takeaways
  1. CPH and BPH are different units; never compare them directly.
  2. The seamer, not the filler, is where a can line loses its rating.
  3. Dissolved oxygen in the finished can is the number that decides shelf life.
  4. Seam quality needs a tear-down station at any volume.
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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