![]() A quick calamity response is hereby assumed to be possible, to happen and to be effective. The, short-term, adverse environ-mental impact of a liquid filled bunded area or a soaked sub-soil is thus apparently considered acceptable. The risk of a catastrophic floor or shell failure of the tank is considered very small. These secondary containment provisions are to ensure containment of any leaked or spilled liquids. This applies for both mentioned types of tanks. Only in case of a failure of this prime containment function, a bund-wall and a geo-textile-based containment are meant to be in place, as a “second line of defence”. ANALYSES OF FLOORS AND SHELLSįundamentally, a liquid storage tank provides for the first or prime containment of the liquid. The functional relationship of tank roofs with vaporisation avoidance and vapour containment and emissions will be analysed secondly hereinafter. Rain falling into such tank, or water-damp evaporating from the tank is not a problem while there are no operational nor “working at heights” requirements making a roof necessary. Water storage tanks at farms, generally, can be of the “open top” type. To enable operators to walk and work on it, possibly using instrumentation and provisions positioned on the roof to enable such.To prevent liquid or vapours thereof to escape from the tank.To prevent “things” falling out of the sky into the liquid.So, what is the function of the roof of a storage tank? Answer: The roof does not have a (direct)containment function. The liquid containment of tanks will be analysed first. The mentioned tank parts, except for the roof, are in contact with the liquid and have an obvious “containment function”. ![]() Schematic of one external floating roof tank. Usually the mentioned parts of tanks made of metal, mostly steel and are commonly coated primarily to delay corrosion of this steel. There are two types of roofs fixed and (“external”) floating roofs. Such tanks generally comprise a “floor”, a cylinder-shaped side wall or “shell” and a “roof”. Permanently installed, large tanks have been used for over a century to store large volumes of liquids, especially hydrocarbons (fuels) and chemicals. KEY WORDSĬairbag, Floating roof, Best Available Technology, Double Hull, Vaporisation avoidance, Emission-free liquid storage. Resolutions as presented in this paper qualify as “alternative and different” rather than “add-on’s and extra”. Historically technology improvements in liquid storage focused on symptom mitigation rather than on elimination of the cause of a problem. This paper analyses both the “best liquid containment” technology as well as the “best vaporization avoiding” technology. ![]() Although tanks are envisaged to store and contain liquid only, the entire tank construction usually also contain substantial volumes of vapour saturated air. These additions provide a predictable indication of the imminent changes in “Best Available Technologies” for the storage of large volumes of especially dangerous liquids. Both types of tanks have become subject to additional provisions. There are basically two different designs and constructions of tanks, i.e. Technical scientific designer (PhD, MSc, MBA) Paper BAT for liquid storage tanks Rev 0.2 Best Available Technologies for Liquid Storage Tanks
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