THE PROBLEM
The steel filter membrane tank was exhibiting corrosion and breakdown of the existing epoxy tank lining which was affecting water quality which had been identified during routine sampling.
We proposed the application of Acothane DW – a solvent free polyurethane which is tested and approved to the highest regulatory standards for UK potable water.
The high build nature of this material offers outstanding corrosion protection and the flexible nature of the material offers good impact resistance – important given the loading and unloading of filter membranes in this application.
Initially all surfaces were thoroughly cleaned by high pressure washing to ensure that all contaminants such as soluble salts were removed prior to preparation.
This is a critical part of the tank lining process as if left in place soluble salts can lead to tank lining failure through osmotic blistering. Failure to remove these before preparation by abrasive blasting can lead to contaminants being forced into the surface profile of the prepared steel.
To ensure the best finish possible the decision was made to apply Acothane DW in three coats to avoid sags and runs.
A full coat in a cream colour was first applied in order to ensure the highest possible surface preparation standard was maintained.
A stripe coat in a contrasting blue colour was then applied to all angles, edges and welds. Stripe coating ensures full tank lining thickness is achieved on edges where tank linings can pull thin through surface tension.
Finally following the application of the final coat a DC holiday spark test was undertaken to check for holidays. By applying a high voltage across the tank linings surface any breaks in the lining can be identified and marked for rectification.
Post application data loggers were installed in order to monitor and record the curing of the completed tank lining to ensure compliance with the instructions for use before returning the tank to service.