As part of the upgrades to the waste water treatment works a new outlet had been installed into the distribution chamber to feed new treatment equipment. During commissioning it was identified that the chamber leaked and therefore the new equipment could not be made live in line with the program.
We surveyed the works on a Wednesday and our client requested that the works be completed Friday and Saturday, with return to service possible from Monday.
Also give the age of the structure and possible seepage from the adjoining tank, we suspected that dampness might be an issue.
Taking all of the above into account we proposed the application of PPG Raven Lining 405.
This ultra high build 100% solids epoxy coating is used as a corrosion protection and structural enhancement lining system, with extensive case histories in waste water applications.
The material has the following characteristics;
Applied typically at between 3 – 5mm, once applied this tank lining has a design life of 50 years. Once applied the lining can be returned to service in as little as 6 hours.
Initially the chamber was cleaned by method of high pressure water jetting to remove organic contaminants from in and around the chamber – around so as to remove the contamination risk during the application process.
Once access to the chamber had been achieved it was apparent that previous repairs had been attempted. There was also visible cracking in the chamber corner where the leak was occurring and in the concrete kicker detail.
All visible cracks were expressed using a diamond blade.
All surfaces to be coated were then prepare by method of diamond grinding to remove the dense face of the bricks and surface laitance from the concrete.
Fortunately with the proposed tank lining system this was not an issue.
The climatic conditions were tested and recorded to ensure conformance with the manufacturers recommendations – with the only restriction for this material being the surface temperature being above 5 Degrees Centigrade, which again offers excellent versatility.
Previously expressed cracks were sealed with a swellable sealant, which in the event of movement of the structure that lead to cracking of the lining will expand in order to maintain fluid tightness.
All corners and cracks received a heavy stripe coat of Raven 405 applied by margin trowel.
Into this a scrim tape was embedded in order to apply additional strength in these areas.
All surfaces were then coated using Raven 405 applied by trowel to a nominal 5mm thickness. This was terminated in previously cut chases as per the manufacturers recommendations.
The coating was lapped on to the previously prepared pipes.
Finally the lining was checked for porosity using a DC holiday spark tester. Any pin holes found were marked with chalk prior to touching in using the same material applied by brush.
