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Case study: Pickling, passivation and flushing for hydraulic pipelines


A very large Aluminium producer has made a significant investment with a global EPC.

All the hydraulic pipelines for the rolling mill, especially for the new ones, needed cleaning such as Pickling, Passivation, Flushing to reach the cleanliness requirements and to avoid any malfunction or damage of the sensitive equipment.

Klarwin as a Total Fluid Management specialist is the expert company that is able to provide all this processes end to end.


More than 3.000 m of pipelines starting from DN10 and up to DN 200, had to reach minimum NAS 3 or ISO 4406 – 14/12/10 cleanliness class for flushing liquid.

The time frame to finish was 1 month for the cleaning process and included the pipe connections, the by-passes, and hundreds of adaptations.

Previous work made by a competitor on a similar project had no results, but we were able to deliver the targeted results on time.


Pickling and Passivation relies on chemical concentration and chemical reaction related to the type of pipes and contaminants.

The Flushing process is the most important step since beside reaching a Reynolds value > 5000, it needs a very efficient filtration, and also on-site and laboratory analyses that can confirm the cleanliness results.

Based on different pipe diameters, we employed multiple filtration units from Klarwin mobile equipment fleet, with different flow rates starting from 20 l/min and 20 bar going till 2000 l/min.

Filtration process included high performance hydraulic filter elements starting from 25 µm and going to 3 µm with an   efficiency of 99,95% (beta 2000).

Results have been confirmed using Klarwin mobile particle counter equipment and validated by our Laboratory that is RENAR certified to ISO 17025.



  • Safe Start-Up of the machinery.
  • Downtime reduced to minimum.
  • Good operation and performance for sensitive equipment.
  • Reduced maintenance costs.
  • Reduced the risk of surface degradation due to mechanical wear and corrosion.