THE PROBLEM – Polyurea Water Tank Lining Repair
A leaking tank was presenting a serious environmental hazard posing a high risk of leaking untreated storm water and sludge entering the soil.
THE SOLUTION – Polyurea Water Tank Lining Repair
We proposed the refurbishment of the tank with a seamless, spray applied Polyurea lining to resolve the problem for the foreseeable future. Following the draining of the tank we prepared the tank by method of abrasive blasting (Swedish Standard SA2.5) to both remove the failed existing coating and raise a surface profile to provide an excellent mechanical anchor for the subsequent tank lining.
Unfortunately a previous attempt to resolve the leaking tank by stripe coating and affixing steel plates with mastic could not be removed efficiently by abrasive blasting. Therefore the steel panels were removed using vibration damped breaker and fortunately through our continued investment in plant and equipment we had a 40,000 PSI ultra high pressure water jetting unit at our disposal to effortlessly remove this stubborn coating. This also ensured that any remaining chloride salts where removed prior to coating application, which if left in place would result in premature failure of the tank lining.
Initially all nuts, bolts, welds, seams and joints received a heavy stripe coat of Chemco RS500P surface tolerant epoxy primer by method of brush and roller to ensure full film build. The tank was subsequently primed throughout using the same material applied by method of airless spray. A quartz aggregate was broadcast into the uncured epoxy primer to provide and excellent mechanical anchor for the subsequent polyurea tank lining.
All of the tank’s many bolts were isolated using a rubber profile secured using Ralithane polyurethane adhesive. This technique isolates difficult details that if sprayed using rapid cure products could result in the formation of caves and pin holes. The main drain point of the tank was similarly isolated using an epoxy mortar, creating a significantly less complex shape to spray. Finally a chase was cut around the entire perimeter of the tank floor to provide a suitable finish point for the polyurea tank lining.
The tank was lined throughout using SPI PTU 300, a high performance chemical resistant elastomer applied using heated plural component spray equipment. All angles and edges received a heavy stripe coat prior to a membrane thickness in excess of 2mm throughout. Because Polyurea coating can elongate over 300% and remain fully flexible when cured the installed tank lining will be able to resist the rapid filling of the tank which can occur in storm conditions.
The Tank Lining Was Tested
The tank lining was tested for defects using a DC holiday spark tester and where found touched in using the same material.
Finally the previously cut chase was infilled using Ralithane polyurethane mastic to prevent against creep under the tank lining.
This case study highlights again the benefits of Polyurea to refurbish and repair water tanks. Polyurea can also used for bund lining, sump lining and asbestos encapsulation by a number of sprayed roofing solutions.