THE PROBLEM
The six new anaerobic digesters required a protective tank lining to guard the concrete against attack from the aggressive environment found within anaerobic digesters. The tank linings were also required to form a gas tight seal in order to contain the biogas produced.
SOLUTION
We proposed the application of our hybrid tank lining system that we have applied in numerous pre cast anaerobic digesters.
Initially the tanks had to be weather sealed by the sealing of the pre cast concrete panel joints on the roof using a polyurethane jointing compound. All joints were high pressure washed, prior to installation of backer rod, priming and the application of a polyurethane jointing compound.
Once water tight the tank internals were prepared by method of high pressure water jetting to remove mould release, contaminants and surface laitance to ensure good adhesion of the new tank linings.
All standing water was pumped out and climatic control introduced to dry the tanks out and ensure the correct climatic conditions for tank lining application as tested and recorded as part of our standard quality assurance.
The moisture content of the concrete was tested to ensure compliance below 6% as required.
All joints in the soffit and 1 metre down the walls were primed 100mm out from the centre of the centre of the joints using Remmers Epoxy MT100 highly damp tolerant epoxy primer.
The soffit joints were then bridged using a foil tape and the roof/wall intersection and vertical joints sealed using a polyurethane jointing compound.
To form a gas tights seal SPI Corrolastic HT was applied to a thickness of 2mm over all prepared areas. This extremely high quality and high tensile polyurea is effectively used as a liquid applied bandage system. Because this polyurea material can elongate nearly 400% it makes it a particularly suitable tank lining material to used when lining pre cast tanks for gas tightness.
Remmers Epoxy Universal tank lining was then applied in multiple coats of contrasting colour by method of airless spray as per best tank lining practice. Remmers Epoxy Universal is specifically designed for lining Anaerobic digestion related tanks and can crack bridge to 0.2mm, the design crack width of the pre cast panels.
To ensure a defect free finish the completed tank linings were spark tested for pin holing as part of our standard quality assurance. In aggressive environments such as anaerobic digesters a single pin hole is a point of failure in the tank lining.
All six anaerobic digesters were completed within or ahead of programme.
