Approach Flow System Optimization
The Challenge: Air in Approach Flow System
Air in the approach flow system is more than a minor nuisance - it is a hidden efficiency killer. Entrained and dissolved air can silently reduce sheet quality, machine stability, and chemical efficiency. The challenge is not only removing visible entrained air, but also preventing dissolved air from turning into new entrained air at critical pressure drops. The solution requires more than traditional vacuum tanks - it requires controlled, inline degassing. And success must be measurable. Here is how AFT approaches the challenge, the solution, and its verification.
Entrained air can slow drainage, impair paper formation and tensile strength, introduce variations in basis weight, create pinholes, and reduce the initial wet strength of the sheet on the forming table. On the other hand, removing air before the headbox promotes better machine runnability, fewer sheet breaks, reduced chemical use, and greater cleanliness. It sounds like we have a mission here.
This is not just a quality issue — it’s a system stability issue.
The white water returning from wire section in paper machine’s short circulation can carry several percents of entrained air. Furthermore, white water is saturated with dissolved air, which turns into entrained air when the pressure goes down in your process.
You can see this happening in a soda bottle when you open it, and it also happens when thin stock leaves the headbox. So, how to get rid of air when white water is trundling through your short circulation at rate of one cubic meter per second?
The Solution: Inline Degassing with Centrifugal Acceleration
The solution is AFT’s POMp Degasser, the only inline degasser that uses both centrifugal force and vacuum for degassing. Vacuum releases the dissolved air from the white water and removes the entrained air as well. And as we understand that you are busy making your product, we speed up things with centrifugal force. This also helps us to minimize our footprint at your mill as degassing time gets shorter. Traditional vacuum tanks rely only on retention time. By combining vacuum with centrifugal acceleration, degassing becomes faster and more controlled.
As a result, entrained air content drops below 0.1%, helping with challenges described earlier. In addition, (drums please,) the white water is no longer saturated with dissolved air. This means that entrained air carried by the incoming thick stock has plenty of room to dissolve into the white water in short circulation. As the white water is not fully saturated with dissolved air, the dissolved air is not turned to entrained air when the thin stock is leaving the headbox. You are not just removing air. You are preventing air regeneration.
Verification: Measure What You Improve
How to verify our success in degassing then? First, have a good look at your product and mill statistics, you will see the difference. Second, ask operators how they feel about runnability, they will be delighted. Third, verify the air content around the short circulation with the GasMaster, AFT’s industry-grade diagnostic tool.
GasMaster enables:
- Entrained air measurement
- Dissolved air measurement
- Total air measurement
- Portable verification across short circulation
We can either do the process audit for you, or you can purchase your own GasMaster and make the measurements by yourself.
GasMaster is a portable gas content meter which has now evolved to agile power bank version (EM500R4U). It uses expansion method to measure entrained, dissolved and total air contents with 0.02% resolution for 0-2.4% gas content, 0.04% resolution up to 6% gas content and 0.1% resolution up to 11.5% gas content. Measurements can be made with GasMaster up to 0.8% fiber consistency. For fiber consistency up to 1%, we can offer high fiber consistency gas content measurements as a service.
AFT GasMaster
About the Author
Jukka Heinonen is Product Manager at Aikawa Fiber Technologies (AFT), responsible for the POMp Degasser product family and other POM solutions. With a background in process equipment, wastewater pumps and valve technologies, he joined AFT in 2022 and works on developing approach flow solutions for the pulp and paper industry.
About AFT
AFT is a global supplier specialized in stock preparation, screening, refining and paper machine approach flow systems. With over 100 years of experience, we offer expert solutions that help mills produce more while using less energy, water and chemicals. Our solutions are tailored to the customer’s furnish, their application and the end product being produced to optimize their return on investment. For more information, please visit www.aft-global.com or contact us at
