Please note: The redline edition of this publication is a comparison of the original 12th edition to the original 11th edition, it does not incorporate any future addenda.

Please note: as a requirement of the API committee that develops this publication, some addendums may not be available as standalone files, they are simply incorporated into the base publication.

Please note that the API Monogram Program effective date for the this document's next edition is September 2020. Until then, this edition will still be considered active and not historical.

This standard establishes minimum requirements for material, design, fabrication, erection, and inspection 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.

Russian translation includes Errata 1 and 2, Addenda 1, 2, and 3