scope:

This standard covers the design and construction of large, welded, low-pressure carbon steel above ground storage tanks (including flat-bottom tanks) that have a single vertical axis of revolution. This standard does not cover design procedures for tanks that have walls shaped in such a way that the walls cannot be generated in their entirety by the rotation of a suitable contour around a single vertical axis of revolution.

The tanks described in this standard are designed for metal temperatures not greater than 250°F and with pressures in their gas or vapor spaces not more than 15 pounds per square inch gauge.

The basic rules in this standard provide for installations in areas where the lowest recorded one-day mean atmospheric temperature is - 50°F. Appendix R covers low-pressure storage tanks for refrigerated products at temperatures from + 4O°F to - 6O°F. Appendix Q covers low-1-1 pressure storage tanks for liquefied hydrocarbon gases at temperatures not lower than - 270°F.

The rules in this standard are applicable to tanks that are intended to (a) hold or store liquids with gases or vapors above their surface or (b) hold or store gases or vapors alone. These rules do not apply to lift-type gas holders.

Although the rules in this standard do not cover horizontal tanks, they are not intended to preclude the application of appropriate portions to the design and construction of horizontal tanks designed in accordance with good engineering practice. The details for horizontal tanks not covered by these rules shall be equally as safe as the design and construction details provided for the tank shapes that are expressly covered in this standard.

Appendix A provides definitions of certain tenns used in this standard for design and construction.

Appendix B covers the use of plate and pipe materials that are not completely identified with any of the specifications listed in this standard.

Appendix C provides information on subgrade and foundation loading conditions and foundation construction practices.

Appendix D provides information about imposed loads and stresses from external supports attached to a tank wall.

Appendix E provides considerations for the design of internal and external structural supports.

Appendix F illustrates through examples how the rules in this standard are applied to various design problems.

Appendix G provides considerations for service conditions that affect the selection of a corrosion allowance; concerns for hydrogen-induced cracking effects are specifically noted.

Appendix H covers preheat and post-heat stressrelief practices for improved notch toughness.

Appendix I covers a suggested practice for peening weldments to reduce internal stresses.

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

Appendix K provides considerations for determining the capacity of tank venting devices.

Appendix L covers requirements for the design of storage tanks subject to seismic load.

Appendix M covers the extent of information to be provided in the Manufacturer's Report and presents a suggested format for a tank certification form.

Appendix N covers installation practices for pressure- and vacuum-relieving devices.

Appendix 0 provides considerations for the safe operation and maintenance of an installed tank, with attention given to marking, access, site drainage, fireproofing, water draw-off piping, and cathodic protection of tank bottoms.

Appendix P has been left blank to allow for material to be appended to this standard in the future.

Appendix Q covers specific requirements for the materials, design, and fabrication of tanks  be used for the storage of liquefied ethane, ethylene, and methane.

Appendix R covers specific requirements for the materials, design, and fabrication of tanks to be used for the storage of refrigerated products.