The leaking pipe was partly entombed in concrete as part of the buildings foundations. Removing the concrete with breakers or powered plant risked damaging both the building above and the pipe itself. More of the pipe was required to be exposed in order to allow proper fitment of the leak sealing clamp.
We proposed the application of our glass flake reinforced tank lining in the form of Corroless EPF.
As per our standard tank lining quality assurance prior to preparation we first tested for soluble salts.
It is best practice to remove these prior to preparation as these can be forced further into the surface profile of the steel. Surprisingly given the tanks usage these were found to be very high. A washing regime was undertaken to reduce these to the specified limit before preparation works commenced.
Failure to remove soluble salts can lead to osmotic blistering as they draw moisture through the tank lining film. This is why these is such an important part of the tank relining process.
Because of the tanks small size and the dust sensitivity of the area we proposed removal of the existing tank lining by method of low dust sponge blasting. A simple enclosure was built to contain the Spongjet.
More information on sponge blasting can be found here
The surface roughness was checked and recorded using a surface profile needle gauge as part of our standard tank relining quality assurance, and the steel prepared to SA2.5 as per ISO8501-1.
All surfaces were vacuumed clean and a dust tape test conducted to ensure all surfaces were suitably clean prior to application of the new tank lining.
During preparation we exposed skip welded seams in the tank structure which could be a point of water egress. This were filled using a ceramic reinforced epoxy filler to ensure a seamless tank lining application.
Prior to application of the tank lining the climatic conditions were tested and recorded to ensure compliance with the tank lining manufacturers recommendations.
As per best tank relining practice separate stripe coats of the new tank lining were applied to all angles, edges and welds. The purpose of a stripe coat in the tank relining process is to apply additional thickness in the areas where paint will pull thin through surface tension and gravity. When visiting corroded tanks you can often tell if this has been omitted as it is in these areas where corrosion will often start due to lower thickness of the tank lining.
Corroless EPF was applied in two coats at a thickness of 200 microns per coat. As per best tank relining practice these were applied in contrasting colours to aid visual identification of which areas had been coated. This also incorporated a second stripe coat of welds, angles and edges.
During the tank relining wet film thickness readings were taken during application.
Once the tank lining was applied dry film thickness readings were taken and recorded, with any areas below the necessary thickness having additional material applied to meet the specification.
Finally the new tank lining was tested for porosity using a DC holiday spark tester to identify any pin holes in the new tank lining. Where found these were marked prior to making good using the same material.
