GasFree Valve™

Reduced defoamer usage, improved air removal technology

As the pulp mat dries, the drainage channels of a vacuum washer drum fill with air. With a traditional valve, this air is forced down the dropleg, reducing vacuum and increasing air entrainment. The patented GasFree™* Valve segregates this air from the dropleg flow, redirecting it back to the hood or collection system. Mills facing high defoamer consumption can utilize this upgrade to save chemical costs and reduce air entrainment. Additionally, the all-stainless construction makes the GasFree Valve a very durable design.

Our patented opening in the GasFree Valve allows for the separation of the air and filtrate. The air is piped back to the hood (or atmosphere) while the filtrate is piped to the filtrate tank. Additionally, the DrumSafe™* surface is a bolt-on feature which protects the stainless valve body and drum from contact. This upgrade is available for both conical and cylindrical valves.



  • Reduced defoamer usage
  • Increased dropleg vacuum increases effective filtrate tank capacity
  • Increased drainage rate
  • Improved mat formation

MaxVac Valve™

High-capacity valve upgrade

Vacuum washer capacity and washing efficiency can be increased by applying increased vacuum to the critical stages of filtering, washing and drying. Increased vacuum compacts and strengthens the pulp mat and allows initiating the washing stage earlier. By increasing the surface area available for washing, the washing time is substantially increased enabling the use of additional wash water. Further, a thicker pulp layer contains less liquid to be displaced at the washing stage, which improves the washing result.

Higher vacuum in the drying stage provides clear advantages by allowing the cake to be dried to a higher dryness than usual. The high discharge consistency is especially advantageous in brown stock washing followed by bleaching and in all bleaching stages where process conditions change considerably between stages. Improvements to the washer are accomplished economically and quickly by upgrading the valve, increasing the number of shower pipes and increasing the vacuum

MaxVac upgrade chart


  • Increased capacity
  • Improved washing efficiency
  • Easy start-up
  • Air removal from the process
  • Savings in bleaching expenses and chemical recovery
  • Reduced emissions of pollutants
  • Improved adjustability of the washer
  • Applicable for most washer systems

* Trademark of the ANDRITZ GROUP. For information regarding ownership and countries of registration, please visit

  • GasFree™ for Vacuum Washer PDF : 1.2 MB
  • MaxVac™ valve upgrade PDF : 194 KB