1.1This specification2 covers minimum-wall-thickness, low-alloy steel tubes for pressure containing parts such as economizers or other applications where corrosion resistance is important.

1.2The tubing sizes and thicknesses usually furnished to this specification are ¹/₂to 5 in. [12.7 to 127 mm] in outside diameter and 0.035 to 0.500 in. [0.9 to 12.7 mm] inclusive, in minimum wall thickness. Tubing having other dimensions may be furnished, provided such tubes comply with all other requirements of this specification.

1.3Mechanical property requirements do not apply to tubing smaller than ¹/₄in. [3.2 mm] in inside diameter or 0.015 in. [0.4 mm] in thickness.

1.4This specification covers three grades, two types, and two manufacture finishes:

1.5Optional supplementary requirements S1 and S2 are provided and, when desired, shall be so stated in the order.

1.6The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. The inch-pound units shall apply unless the “M” designation of this specification is specified in the order.

1.7This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.