In 1980, during a routine tank inspection, the staff at a public utility water treatment plant noticed some fine leaking cracks in the interior of two Fiberglass Reinforced Plastic (FRP) tanks where the bottom meets the side.
The tanks are 8′ in diameter x 9′ deep and contain Hydrofluosilicic Acid (HFS Acid). Plant personnel were advised that the tanks could be repaired but it would not be a long-term solution. The repair would also be less resistant to chemical attack than the rest of the tank.
The conclusion was that the tanks were still structurally sound but they required lining if they were to continue in long-term use. Replacing them was considered but, in addition to the cost of new tanks, the city had to allow for opening a section of the building which housed the tanks to move the new ones in. Kentain’s heavy gauge, flexible PVC, bag-type membrane liners were chosen for the following reasons:
- excellent chemical resistance;
- a closed top, one piece construction;
- flexible and unaffected by the tank flexing;
- the tanks require very little preparation prior to installing the liners;
- leak detection system assures early awareness should a problem occur;
- the tank would provide the extra security of becoming a secondary containment area; and
- liners are virtually maintenance free.
The tanks were prepared including a fiberglass repair inside, then the liners were installed. The job was completed in three days by Kentain’s installation supervisor and one helper supplied by the customer. The entire inside of the tanks, fittings and manway were lined so that the FRP tanks would no longer come in contact with liquid or the vapour.
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In 1994, Kentain replaced the liners in both tanks. Installation was simple, removing the suspension system holding the old liners and installing the new liners. The liners were replaced after fourteen years as a part of a preventive maintenance program. The liners had never leaked and the utility had not spent any money on maintenance.