ABOVE-GROUND storage tank evaporation loss and emissions stem from many causes, said Gary Tesch, HMT Inc, Houston, Texas. Terminal managers should be wary of problems with seals, welds, vents, manways, hatches, drains, bolted deck seams, deck-support legs, and gauge and guide poles, and vertical ladders. Preventing emissions not only protects the environment, but it saves money.
To measure the amount of loss and emissions, managers can consult a manual provided by the American Petroleum Institute committee on petroleum measurement (http://api-ep.api.org/filelibrary/ACF94D.pdf).
Typically, there are four types of storage tanks in use: fixed roof, external floating roof, internal floating roof, and covered floating roof. Floating roofs are used to reduce evaporation, comply with federal, state, and local regulations, reduce odor, and provide cost savings, he said.