As part of our clients inspection regime of pressure vessels the mild steel saturation tank had been condemned due to corrosion and break down of the existing lining. To allow a thorough inspection the testing agency requested that all coatings were removed and suitable drinking water approved tank lining applied. This vessel is owned and operated by a water authority, meaning the new tank lining had to have Regulation 31 approval.
We proposed the removal of the existing lining by method of abrasive blasting and application of Acothane DW Regulation 31 approved tank lining.
Another contractor when undertaking similar works on site had incurred significant additional cleaning costs as result of dust egressing their tank when undertaking abrasive blasting works. To mitigate against this we allowed for the installation of a 6,000CFM dust extraction unit.
Removing the existing lining
When removing the existing tank linings which had been applied over each other by abrasive blasting the steel was prepared to SA2.5 as per ISO8501-1. The blast profile was checked using a surface profile needle gauge as per our standard quality assurance to ensure a minimum surface profile of 75 micrometers was achieved as per the tank lining manufacturers recommendations.
The blast standard was maintained using dehumidification equipment following completion of the abrasive blasting.
Ensuring a clean surface
Following abrasive blasting all surfaces were vacuum cleaned to ensure a clean surface for the new water tank lining to adhere to. The cleanliness of the surface was checked using a Dust tape test.
Once prepared and satisfied with the cleanliness a heavy stripe coat of Acothane DW was applied to all angles and edges as per good tank lining practice. This is essential to ensure full film build on angles and edges where tank lining pull thin through gravity and surface tension.
A second stipe coat and full coat were applied in contrasting colours as per good lining practice. The total thickness of new lining was 1000 micrometers.
To ensure a defect and pin hole free water tank lining a spark test was conducted as per our standard quality assurance. Any pin holes found were marked, prior to touching in using the same material applied by brush.