Modified demolition plan due to contaminated compartments in double-deck floating roof

In September 2019, we were again engaged in the demolition of a double-deck floating roof. Every so often, major maintenance is done on large storage tanks, and in some cases the 500-ton roofs can no longer be repaired. It's up to us to systematically demolish those roofs. You can read how we usually do that in another article about replacing a double-deck floating roof.

This time we were dealing with fouled sections in the roof. This contamination had been caused by a leakage. The flammable product that was in the storage tanks had migrated into these compartments. This required a slightly different approach than normal, which we described in a modified engineering plan.

Removal of contaminated boxes

In the upper deck, we created inspection hatches with air tools to determine where the greatest contamination was. Using this information, we adjusted the rest of the demolition method. We first cleaned the areas where there was the most dirt and adjusted the cutting lines to match the dirt. Where the dirt is, you cannot cut with the burner because of fire hazards.

Additional support under lower deck

Normally before dismantling, we place the lower deck on outriggers so that it does not sag during the work. In this case, the roof was already standing on its own steel legs. However, these legs were not enough to stabilize the roof, because other forces are released during demolition. Therefore, we added additional support and partially relocated the work to ensure that we could demolish in a safe manner.

Extra early shifts

We were not alone in the tank pit. Another contractor, who was responsible for blasting the tank (ed. removing existing paint layer), was performing his work on the same days. Since a lot of dust and blasting grit is released during blasting, it was important that our guys were gone before blasting began at 2 p.m. To still ensure that the double-deck floating roof was dismantled before the deadline, we started demolition around 05:00 in the morning. Thus, we were still able to complete our work within 5 weeks and this project was once again completed efficiently.