6 steps to achieving external floating roof tank safety

Written by Matthew Pattinson on July 21st, 2014

External floating roofs are fitted atop of large above ground hydrocarbons storage tanks which typically stand in excess of 20m diameter.

With the grace of oil on water, they float on the surface of the stored fluid. Proper maintenance of external floating roofs for storage tanks is indeed important as failure of the roof can lead to a loss of containment, opening the door to the potential of a major accident.

So it is that we’ve put together 6 steps to help you control potential hazards pertaining to the specification, inspection and maintenance of external floating roofs for storage tanks built to BS 2654(1), BS EN 14015(2) and API 650(3).

Step 1: external floating roof tank safety

Operators of tanks with external floating roofs should undertake calculations to demonstrate that for the fault conditions of a flooded centre deck or two adjacent pontoons flooded, the roof will remain buoyant in the tank fluid.

The calculations should be checked for validity when operational changes occur such as a change to tank contents of reduced specific gravity.

Step 2: external floating roof tank safety

Carry out in-service examinations to guard against floating roof failure. Also conduct out-of-service examinations which include a suitable internal and external examination of pontoons for on-going integrity.

Step 3: external floating roof tank safety

Following any repairs or modifications, ensure fresh integrity checks are completed.

Step 4: external floating roof tank safety

Put in place a system of routine operator checks whereby the findings are logged within the maintenance system.

Step 5: external floating roof tank safety

Make sure any build-up of standing water on the roof deck is managed. This is important as heavy rainfall with low roof levels could lead to slow rainwater discharge rates, increasing the risk of failure due to water build-up on the tank roof.

Step 6: external floating roof tank safety

Duty holders, where reasonably practical, should provide a deviation alarm so that a warning is given if there is excessive differential movement of the roof and liquid.

For detailed guidance check out our article on the HSE’s recent safety notice