Industrial Fire Familiarization: Floating Roof Tanks
HMN-Floating roof tanks are common forms of storage at many industrial sites, especially those processing or storing petroleum based products. Familiarizing yourself with their anatomy will give you the upper hand on any emergency involving one of these tanks.
These tanks are built as a hollow shell, with a movable, floating roof on top of the product stored. This allows a product to be stored with very little or no vapor space on top. The lack of a vapor space provides an extra safety factor, as well as prevents unwanted evaporation of product.
The roof floats on top of the product on its “pontoons”, raising and lowering with the level inside. Any rain or other liquid accumulation on the roof is drained through the tank via hose or other connections and drained to the ground below. The seals, around the edges of the roof, act like gaskets to prevent any other unwanted evaporation or environmental concern. Also be aware, a fixed roof can sometimes be placed over the floating roof containing the moving lid.
Common materials stored in floating roof tanks can range from heavy crude oils, diesel fuel, to lighter gasoline products. Under most circumstances, capacity will be measure in barrels (Bbls), where one barrel, equals 42 gallons. These tanks can be fed by pipeline, truck, rail, you name it. Identifying and isolating feed sources can save large amounts of headache in the end.
Emergencies and Safety Features
Tank fires can put a strain on water and foam resources available to responders. Many safety features over the years have helped make emergencies easier to mitigate. External foam connections can provide a remote site for a response team to inject foam to the topside of the tank, minimizing crew exposure. Foam travels through piping and into the foam chambers perched atop the tank.
The angled spout at the end points the aerated foam towards the roof and allows it to cover the seals.
Alternatively, foam can be injected below the liquid level and allowed to bubble up through via subsurface injections points.
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