scope:

General

This standard covers material, design, fabrication, erection, and testing requirements for vertical, cylindrical, aboveground, closed- and open-top, welded steel storage tanks in various sizes and capacities for internal pressures approximating atmospheric pressure (internal pressure not exceeding the weight of the roof plates), except that a higher internal pressure is permitted when the additional requirements of Appendix F are met. This standard covers only tanks whose entire bottom is uniformly supported and only tanks in nonrefrigerated service that have a maximum operating temperature of 200°F (see 1.1.12)

This standard is designed to provide the petroleum industry with tanks of adequate safety and reasonable economy for use in the storage of petroleum and its products and other liquid products commonly handled and stored by the various branches of the industry. This standard does not present or establish a fixed series of allowable tank sizes; instead, it is intended to permit selection by the purchaser of whatever size tank may best meet his needs. This standard is for the convenience of purchasers and manufacturers in ordering, fabricating, and erecting tanks and is not intended to prohibit purchasers and manufacturers from purchasing or fabricating tanks that meet specifications other than those contained in this standard.

Appendix A provides for an alternative (and simplified) tank in which the stressed components, such as shell plates and reinforcing plates, are limited to a maximum of ½ inch nominal thickness, including any corrosion allowance, and to the minimum design metal temperatures stated in the appendix.

Appendix B contains recommendations for the design and construction of foundations under flat-bottom oil storage tanks.

Appendixes C and H present rules for special types of roofs for storage tanks. Appendix C provides requirements for pan-type, pontoon-type, and double-deck-type external floating roofs. Appendix H provides requirements for an internal floating roof in a tank that has a fixed roof at the top of the tank shell.

Appendix D provides a format for the preparation and submission of technical inquiries regarding this standard to the director of the API Refining Department.

Appendix E provides a recommended practice for the design of storage tanks subjected to seismic load when seismic design is specified by the purchaser.

Appendix F covers additional requirements for the design of tanks subject to a small internal pressure.

Appendix J presents requirements covering the complete shop assembly of tanks not more than 20 feet in diameter.

Appendix K provides an example of the application of the variable-design-point method to determine shell-plate thicknesses.

Appendix L provides data sheets to be used by the purchaser in ordering a storage tank and by the manufacturer upon completion of construction.

This standard applies to tanks with a maximum operating temperature of 200°F. When the requirements of Appendix M are fulfilled, a maximum operating temperature of 500°F is permitted.

Appendix N presents conditions for the use of materials that are on hand but are not completely identified by this standard as complying with any listed specification.

Appendix O contains basic recommendations for the design and construction of under-bottom connections for storage tanks.

Appendix P presents recommended basic requirements for the design of storage tank openings that conform to Table 3-8 and will be subjected to external piping loads.