The sectional stainless steel reception tank at the anaerobic digestion site was leaking food waste into the surrounding bund. This required sealing in order to be compliant with the sites odour permit. The existing polyurethane sealant had debonded from the tank walls, allowing the fluid egress.
Stainless steel is a difficult surface to adhere to and likely the cause of the issue. Either preparation by method of abrasive blasting or the use of specialist primers is required in order to gain adhesion. We proposed the application of a multi layer sealing solution to resolve the issue.
Initially the existing sealant was mechanically removed to allow access to all surfaces to be sealed. The area to be treated and adjacent was cleaned using a steam cleaner and emulsifying degreaser in order to remove fats and greases present from the feedstock. Waste water was pumped out to a location agreed with the client for appropriate disposal.
The presence of chlorides on the surfaces was tested for as it essential to determine that these are within permitted levels prior to abrasive blasting as this will force any present into the profile created. If left in place chlorides and soluble salts will lead to osmotic blistering and premature failure of tank linings/protective coatings.
Once clean the stainless steel and the concrete were prepared by method of abrasive blasting, ensuring that a minimum surface profile of 50 microns was raised on the stainless steel. This was tested and recorded using a surface profile needle gauge as part our standard QA process.
All surfaces were vacuumed clean and a dust tape test conducted to ensure that the surfaces were clean enough for optimum adhesion of the tank lining/coating.
The first layer of the sealing solution was then applied in the form of Remmers Stopaq at the stainless steel/concrete intersection. This permanently elastic sealant swells in contact with moisture, forming a pressure seal. As the first layer applied this acts as a final sealing layer in the event of layers above becoming degraded or damaged.
Dehumidification equipment was installed in order to ensure the correct climatic conditions for coating application which was tested and recorded as standard.
To gain adhesion to the stainless steel all surfaces were primed using Remmers Epoxy FAS100. This primer has excellent adhesion properties to difficult substrates such as glass and stainless steel.
To spread the point of potential movement and form a secondary sealing layer a cove detail was installed at the floor wall intersection using a high strength epoxy mortar using Remmers Epoxy FAS100 as the binder. Cove details allow coatings to move over a greater area, thus multiplying the elongation potential of any subsequent coatings applied.
The next sealing layer involved the application of Remmers VF120 bandage embedded in a Remmers Epoxy WHG crack bridging epoxy resin. Remmers VF120 contains a flexible core within a woven bandage, providing a third sealing layer.
To spread the point of potential movement and form a secondary sealing layer a cove detail was installed at the floor wall intersection using a high strength epoxy mortar using Remmers Epoxy FAS100 as the binder. Cove details allow coatings to move over a greater area, thus multiplying the elongation potential of any subsequent coatings applied.
