THE PROBLEM
The anaerobic digestion site that we had previously undertaking tank lining works for over 7 years previously was expanding, adding an additional anaerobic digester to the site. This new concrete tank required a protective tank lining in the gas space to protect the concrete from attack from H2S and biogenic sulphuric acid.
The external panel joints also required sealing to prevent water ingress into the tank.
SOLUTION
All surfaces to be treated were first prepared by method of high pressure water jetting to remove surface laitance, contaminants and mould release.
The external panel joints were primed using Sika 3N sealant primer, followed by the installation of backing rod and Sikaflex polyurethane jointing compound.
Once the waste wash water had been pumped out, dehumidification was installed to dry the tank and reduce the moisture content in the concrete below 6% – checked using a Tramex moisture gauge to ensure adhesion of the new tank lining
The use of the dehumidification equipment also ensured the correct climatic conditions with regard to relative humidity and dew point for coating application, both of which are essential for ensuring the tank lining adheres, cures and performs as expected.
All joint areas to be treated internally were primed using Remmers Epoxy MT100 damp tolerant epoxy primer, prior to sealing vertical joints using a polyurethane jointing compound and horizontal joints using a foil bond breaker tape.
To make the tank gas tight SPI Corrolastic HT pure polyurea was applied to these previously primed areas to a thickness of 2mm.
Once gas tight Remmers Epoxy universal was applied to all surfaces requiring protection. This flexible crack bridging tank lining has extensive case histories in the anaerobic digestion market and we have used this material to great success in over 50 anaerobic digestion related tanks.
As part of our standard quality assurance the new tank lining was checked for pin holes and porosity using a DC holiday spark tester. In an aggressive atmosphere such as that found in an anaerobic digester a single pin hole is a point of failure, where break down of the substrate will occur.
The team working on this project did exceptionally well, completing the works a week ahead of schedule whilst maintaining the high standards we expect. The client was greatly appreciative of this as it allowed them to accelerate the commissioning of their new tank.
The works were offered with our standard 10 year warranty.
