API STD 650 is a standard that establishes minimum requirements for
material, design, fabrication, erection, and testing for vertical,
cylindrical, aboveground, closed- and open-top, welded storage tanks in
various sizes and capacities for internal pressures approximating
atmospheric pressure (internal pressures not exceeding the weight of the
roof plates), but a higher internal pressure is permitted when additional
requirements are met . This Standard applies only to tanks whose entire
bottom is uniformly supported and to tanks in non-refrigerated service that
have a maximum design temperature of 93°C (200°F) or less.
This Standard is designed to provide industry with tanks of adequate safety and reasonable economy for use in the storage of petroleum, petroleum products, and other liquid products. This Standard does not present or establish a fixed series of allowable tank sizes; instead, it is intended to permit the Purchaser to select whatever size tank may best meet his needs. This Standard is intended to help Purchasers and Manufacturers in ordering, fabricating, and erecting tanks; it is not intended to prohibit Purchasers and Manufacturers from purchasing or fabricating tanks that meet specifications other than those contained in this Standard.