Floating-Roof Tanks: Design and Operation in the Petroleum Industry

Abstract

The floating-roof tank has been the most widely used method of storage of volatile petroleum products since the first demonstration b Chicago Bridge & Iron Company (CB&I) in 1923. There have been many changes and design improvements to that first pan-style-floating roof. A floating roof is a complex structure. It must be designed to remain buoyant even when exposed to combined loads from varying process, weather and product conditions. There is a continued demand for improved floating-roof tanks to store a wide range of petroleum and petrochemical products in compliance with state and federal environmental regulations. Floating roofs are used in open top tanks (EFRT), inside tanks with fixed roofs (IFRT), or in tanks that are totally closed where no product evaporative losses are permitted for release to the atmosphere. This very special type of installation is referred to as a zero emission storage tank (ZEST). Products that might have been stored in basic fixed roof tanks must now utilize a floating roof to limit evaporative emissions to the atmosphere. High vapor pressure condensate service and blended heavy crude oils also present new design challenges to the floating roof tank industry. This paper will review the most prominent styles of floating roofs from 1923 to the present. Design and operating limits for current da floating-roof structures are presented. New trends in environmental regulations and the potential impact on the design and operation of floating-roof tanks will be presented. Current maintenance practices and the effect on Life Cycle Cost Management of the storage syste are also reviewed.