THE PROBLEM
The new Braithwaite sectional tank required a lining suitable for immersion in 60 Degree Centigrade demineralised water.
The tank externals also required a suitable protective coating.
Braithwaite Tank Lining and Protective Coating, Swansea
THE SOLUTION
We proposed the lining of the tank with a solvent free polyurethane tank lining that offered both the chemical resistance as well as flexibility that is desirable when applying tank linings to sectional storage tanks.
For the externals we proposed the application of Rustoleum Noxyde Plus, which as well as providing excellent corrosion protection offers 200% elongation.
The tank panels had been installed blasted and with a holding primer applied. The polyurethane tank lining proposed must be applied directly to steel, meaning that the first stage of the tank lining process was to remove this holding primer.
This was undertaken by method of low dust sponge blasting using Sponge Jet equipment and media, preparing the steel to SA2.5 as per ISO8501-1.
This is of critical importance, particularly in a tank storing demineralised water as if soluble salts are left in place they will draw moisture through the tank lining film leading to osmotic blistering and premature tank lining failure.
All surfaces were vacuumed clean and the effectiveness of these operations confirmed by the conducting of dust tape assessments.
If a layer of dust is left on the steels surface, this will disrupt the bond of the tank lining.
The blast standard was maintained by the introduction of dehumidification equipment, which was left in place throughout the tank lining application to ensure the correct climatic conditions for polyurethane tank linings were present.
These were tested and recorded as part of our tank lining quality assurance.
All angles and edges received a heavy stripe coat of solvent free polyurethane tank lining material applied by brush.
This is essential to ensure full tank lining film build in areas where coatings pull thin through surface tension.
The polyurethane tank lining was then applied by method of plural component spray unit to a nominal thickness of 1500 microns.
Wet film thickness readings were taken during application and then confirmed by the taking of dry film thickness readings following cure of the tank lining.
To ensure a pin hole free tank lining all surfaces coated were checked using a DC Holiday Spark tester. In an immersion environment a single pin hole is a point of tank lining failure.
Any pin holes identified were abraded and made good by applying the same material by brush.
Once the internals were completed the tank externals were prepared by method of high pressure washing.
Rustoleum Noxyde Plus was applied in two coats of contrasting colour by method of airless spray at a practical coverage rate of 0.5Kg/m2 per coat.
Dry film thickness readings were taken after each coat to ensure that the correct thicknesses had been achieved.
Rustoleum Noxyde Plus is an excellent protective coating material for this application due to its excellent edge retentive properties, a huge bonus given the large quantity of bolts and edges.
