THE PROBLEM
The process vessels were exhibiting corrosion and breakdown of the existing coatings. This was presenting a product contamination risk and also risking degradation of our clients valuable assets.
Process Vessel Refurbishment, West Yorkshire
We were asked to provide a protective coating solution that would resolve both of these issues. This application presented particular challenges given that the vessels operated between minus 15 degrees centigrade and plus 60 degrees centigrade in repeated cycles.
The works also needed to be conducted with minimum dust production during the works given the factory environment.
THE SOLUTION
During our site survey we identified that the existing coatings were poorly adhered and would require their complete removal.
Prior to works commencing our client provided scaffold access with excellent encapsulation in order to fully contain the works and later allow the climatic control of the work area to both prevent flash rusting of the prepared steel and ensure the correct climatic conditions for protective coating application.
The first stage of the process vessel refurbishment was to wash all surfaces to be coated in order to ensure that any chloride residues from chemicals used within the factory were removed.
The effectiveness of these cleaning operations was confirmed by conducting chlor tests.
The blast standard was maintained by introducing dehumidification and heating equipment in order to reduce the relative humidity as low as possible.
Following preparation all surfaces were vacuumed clean and the effectiveness of cleaning operations confirmed by conducting dust tape assessments to ensure optimum adhesion of the new protective coatings.
Prior to and during protective coating application the climatic conditions were tested and recorded to ensure conformance with the manufacturers recommendations.
A full coat of Acothane DW was applied in order to ensure that the protective coatings were applied to the best possible preparation standard.
When applying protective coatings to vessels which experience significant temperature fluctuations a very high standard of surface preparation is required due to the additional stains that the temperature changes place on the adhesive bond of the applied protective coatings.
Stripe coating is essential to ensure a full film build in areas where coatings pull thin through surface tension, ensuring maximum protection.
Wet film thickness readings were taken throughout the protective coating application process, with a target thickness of 400 microns per coat
Following the application of the second coat of Acothane DW a DC Holiday test was undertaken to check for pin holes in the applied coatings. Once the vessels would again be returned to service any maintenance would be extremely challenging and ensuring a pin holes free finish was critical.
Any pin holes found were marked and touched in by brush prior to the application of the third and final coat.
Dry fil thickness readings were taken and recorded ensuring that the minimum thickness of 800 microns had been achieved.
Acothane DW was proposed for several reasons, including is solvent free nature and approvals for drinking water which made it suitable for the production environment. Acothane DW has been used extensively for corrosion protection within the gas distribution network for over 30 years and as per ISO 12944 at the thickness applied would give a very high durability.
