REHABILITATING LEAKING FLOATING ROOF PONTOONS

After several decades of service the amount of maintenance required to keep an external floating roof operational increases drastically. Whenn looking at ageing external floating roofs there are multiple points of attention. The most important are the following (in random order):

- coating and conservation
- rolling ladder and ladder track
- tank gauging system
- fire fighting system
- tank seal
- gauge pole and its cover
- leg sleeves and roof support legs

Roof pontoons and their integrity

The buoyancy of an external floating roof is based on pontoons at the perimeter of the roof for single deck type roofs or at the full surface of the roof for double deck roofs. It is quite common for pontoons become leak after long periods in service. Leaking pontoons will result in reduced buoyancy of the floating roof.

In all design codes for external floating roofs there is a provision for roofs still to float despite a certain percentage of failing pontoons. Also the roof must be capable of being afloat with a certain amount of collected rainwater. Leaking pontoons will always be a mayor concern for tank owners, especially when these leaking pontoons are directly adjacent to each other. They can destabilise the roof, and eventually cause the roof to sink partially or completely.

Rehabilitating leaking pontoons on tanks in service

In recent years CTS was asked frequently by many tank owners to ensure the integrity of an external floating roof with leaking pontoons. As an answer to these questions CTS has developed a system where polymer balloons are inserted in the pontoon, and inflated with an inert gas. This will stop further product penetration and ensures the buoyancy of the roof.

While this is not a long term solutionit will help bridging the gap between the moment that the lleak deveops and the scheduled maintenance cycle of the tank involved.

In its regular maintenance interval the pontoon can then be permanently repaired.