THE PROBLEM
The glass fused to steel bolted tank was exhibiting severe perforations despite only being 11 years old. This was allowing effluent to leak into the surrounding environment presenting an environmental hazard.
Glass Fused to Steel Tank Reline, Lincolnshire
THE SOLUTION
We proposed the application of our proven polyurea tank relining system specifically developed for glass fused to steel bolted tanks.
Initially all sealant and previous plates were removed in order to fully expose all surfaces to be coated in order to allow proper preparation.
The tank internals were then cleaned by method of high pressure washing using potable water to ensure that all contaminants were removed prior to abrasive blasting.
This was confirmed by conducting salt tests.
Removable of chlorides when relining tanks is essential as if left in place they can draw moisture through the tank lining film, leading to osmotic blistering and premature failure of the tank lining.
All surfaces to be coated were prepared by method of abrasive blasting to raise a surface profile and ensure that any ingrained contamination and oxidation was removed. Any exposed steel was prepared to SA2.5 as per Iso 8501-1.
All spent blast abrasive was removed and the tank internals vacuumed clean. The effectiveness of this cleaning was confirmed by conduction of dust tape tests, essential when relining tanks to prevent the new tank lining being applied to a layer of dust, which would be detrimental to the tank linings adhesion.
Before priming as part of our standard tank relining quality assurance the climatic conditions were tested and recorded. Dehumidification and heating had previously been installed to minimise flash rusting.
We were not concerned if some flash rusting did occur as the tank was primed using Corrolast DSP – our surface tolerant epoxy primer specifically developed for relining glass fused to steel tanks.
This was applied by method of brush and roller and the thickness checked using wet film thickness combs during application as part of our tank relining quality assurance.
Whilst still wet the primer was dressed with quartz aggregate to provide excellent adhesion for the subsequent polyurea tank lining.
Panel seams were sealed using a polyurethane jointing compound and perforations in the tank structure bridged using galvanized steel plates boned in place using thixotropic epoxy adhesive.
SPI Corrolastic HT was then applied throughout the tank to a nominal thickness of 2mm. This polyurea tank lining has an expected service life in excess of 20 years.
Because this material is highly elastomeric it is ideal for tanks constructed in this manner. More information on this can be found here.
Finally as part of standard tank relining quality assurance dry film thickness readings were taken and recorded for handover upon project completion.
The tank lining was checked for porosity using a DC holiday spark tester. Any pin holes found were marked and made good using the same polyurea material. In aggressive waste water environments such as this a single pin hole in a tank lining is a point of failure, through which attack and corrosion of the tank structure can recommence.