November 14, 2017
What exactly are external floating roof storage tanks? To a novice, the term conjures up an image of a lightweight tank, one that floats like a ship's metal hull. In point of fact, these tanks don't float. Rather, it's the floating roof above and inside the tank that's buoyed by a stored fluid. Typically speaking, an EFRST will contain a petroleum product.
That's a good question. Furthermore, that question will direct us towards the reason for installing a floating roof. Picture a drum-shaped tank. Inside that metal-panelled container, there's crude oil, a processed condensate, or a petroleum product of some kind. The roof seems to exist solely to stop the elements from diluting or contaminating the fossil fuel derivatives, right? Well, couldn't a regular tank do the same thing? Couldn't a fixed roof safely protect the oily medium from rain or blown debris? A simple covering obviously isn't the answer. There's a more elaborate purpose in mind here, one that's designed to stop a void forming above the fluid line.
The open cylinder contains a fluid that creates a vapour component. If the tank had a fixed ceiling, then the vapour space would generate VOCs (Volatile Organic Compounds), and those compounds would enter the atmosphere in this gaseous state. External floating roof storage tanks manage the vapour space. Actually, they entirely eliminate that void by floating right on top of the fluid surface. However, as with any truly advanced engineering asset, there's more to this containment equipment than an open-topped cylinder and a circular sheet of floating metal. For starters, a dedicated rim seal is required. Otherwise, the vapours can still seep past the roof panel.
They're installed in biofuel facilities and petroleum storage sites, places that store stabilized liquids. Waxy crude oil reservoirs are commonly stockpiled inside these tanks, so how does this vapour space feature operate? Well, pontoons and pans keep the roof buoyant. Curved and sloped variants remove accumulated water, so expect a series of drains installed somewhere in the vicinity of the floating roof. Other than these essential features, a reliable rim seal must be installed between the roof and the storage unit.
Fuel gauges and drains, guide poles and access ports, the design of an external floating storage tank (EFST) is relatively uncomplicated, although the existing design features must be reliable. That design concludes with the geometry of the roof, including the flotation pontoons, the curving ribs, and the rim seal type.
Fusion - Weld Engineering Pty Ltd
ABN 98 068 987619
1865 Frankston Flinders Road,
Hastings, VIC 3915
Ph: (03) 5909 8218
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