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 pressures not exceeding the weight of the roof plates), but a higher internal pressure is permitted when additional requirements are met (see 1.1.10). This standard applies only to tanks whose entire bottom is uniformly supported and to tanks in nonrefrigerated service that have a maximum operating temperature of 90°C (200°F) (see 1.1.17).

This standard is designed to provide the petroleum industry with tanks of adequate safety and reasonable economy for use in the storage of petroleum, petroleum 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 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.

Note: A bullet (•) at the beginning of a paragraph indicates that there is an expressed decision or action required of the purchaser. The purchaser's responsibility is not limited to these decisions or actions alone. When such decisions and actions are taken, they are to be specified in documents such as requisitions, change orders, data sheets, and drawings.

This standard has requirements given in two alternate systems of units. The requirements are similiar but not identical. These minor differences are due to issues such as numerical rounding and material supply. When applying the requirements of this standard to a given tank, the manufacturer shall either comply with all of the requirements given in SI units or shall comply with all of the requirements given in US Customary units. The selection of which set of requirements (SI or US Customary) shall apply to a given tank shall be by mutual agreement between the manufacturer and purchaser.

The appendices of this standard provide a number of design options requiring decisions by the purchaser, standard requirements, recommendations, and information that supplements the basic standard. An appendix becomes a requirement only when the purchaser specifies an option covered by that appendix. See Table 1-1 for the status of each appendix.

Appendix A provides alternative simplified design requirements for tanks where the stressed components, such as shell plates and reinforcing plates, are limited to a maximum nominal thickness of 12.5 mm (½ in.), including any corrosion allowance, and to the minimum design metal temperatures stated in the appendix.

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

Appendix C provides minimum requirements for pan-type, pontoon-type, and double-deck-type external floating roofs.

Appendix D provides requirements for submission of technical inquiries on this standard.

Appendix E provides minimum requirements for tanks subject to seismic loading. An alternative or supplemental design may be mutually agreed upon by the manufacturer and purchaser.

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

Appendix G provides requirements for an optional aluminum dome roof.

Appendix H provides minimum requirements that apply to an internal floating roof in a tank with a fixed roof at the top of the tank shell.

Appendix I provides acceptable construction details that may be specified by the purchaser for design and construction of tank and foundation systems that provide leak detection and subgrade protection in the event of tank bottom leakage, and provides for tanks supported by grillage.

Appendix J provides requirements covering the complete shop assembly of tanks that do not exceed 6 m (20 ft) in diameter.

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

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

Appendix M provides requirements for tanks specified and designed to operate at temperatures exceeding 90°C (200°F) but not exceeding 260°C (500°F).

Appendix N provides requirements for the use of new or unused plate and pipe materials that are not completely identified as complying with any listed specification for use in accordance with this standard.

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

Appendix P provides minimum recommendations for design of shell openings that conform to Table 3-6 that are subject to external piping loads. An alternative or supplemental design may be agreed upon by the purchaser or manufacturer.

Appendix S provides requirements for stainless steel tanks.

Appendix T summarizes the requirements for inspection by method of examination and the reference sections within the standard. The acceptance standards, examiner qualifications, and procedure requirements are also provided. This appendix is not intended to be used alone to determine the inspection requirements within this standard. The specific requirements listed within each applicable section shall be followed in all cases.

Appendix U provides detailed rules for the use of the ultrasonic examination (UT) method for the examination of tank seams.

LIMITATIONS

The rules of this standard are not applicable beyond the following limits of piping connected internally or externally to the roof, shell, or bottom of tanks constructed according to this standard:

a. The face of the first flange in bolted flanged connections, unless covers or blinds are provided as permitted in this standard.

b. The first sealing surface for proprietary connections or fittings.

c. The first threaded joint on the pipe in a threaded connection to the tank wall.

d. The first circumferential joint in welding-end pipe connections if not welded to a flange.

COMPLIANCE

The manufacturer is responsible for complying with all provisions of this standard. Inspection by the purchaser's inspector (the term inspector as used herein) does not negate the manufacturer's obligation to provide quality control and inspection necessary to ensure such compliance.