1.1 This specification 2 covers steel pipe: electric-fusion-welded with filler metal added, fabricated from pressure-vessel quality plate of any of several analyses and strength levels and suitable for high-pressure service at moderate temperatures. Heat treatment may or may not be required to attain the desired properties or to comply with applicable code requirements. Supplementary requirements are provided for use when additional testing or examination is desired. 1.2 The specification nominally covers pipe 16 in. [400 mm] in outside diameter or larger with wall thicknesses up to 3 in. [75 mm], inclusive. Pipe having other dimensions may be furnished provided it complies with all other requirements of this specification. 1.3 Several grades and classes of pipe are provided. 1.3.1 Grade designates the type of plate used. 1.3.2 Class designates the type of heat treatment performed during manufacture of the pipe, whether the weld is radiographically examined, and whether the pipe has been pressure tested as listed in 1.3.3 . 1.3.3 Class designations are as follows (Note 1): Class Heat Treatment on Pipe Radiography, see Section Pressure Test, see Section 10 none none none 11 none 9 none 12 none 9 8.3 13 none none 8.3 20 stress relieved, see 5.3.1 none none 21 stress relieved, see 5.3.1 9 none 22 stress relieved, see 5.3.1 9 8.3 23 stress relieved, see 5.3.1 none 8.3 30 normalized, see 5.3.2 none none 31 normalized, see 5.3.2 9 none 32 normalized, see 5.3.2 9 8.3 33 normalized, see 5.3.2 none 8.3 40 normalized and tempered, see 5.3.3 none none 41 normalized and tempered, see 5.3.3 9 none 42 normalized and tempered, see 5.3.3 9 8.3 43 normalized and tempered, see 5.3.3 none 8.3 50 quenched and tempered, see 5.3.4 none none 51 quenched and tempered, see 5.3.4 9 none 52 quenched and tempered, see 5.3.4 9 8.3 53 quenched and tempered, see 5.3.4 none 8.3 Note 1 - Selection of materials should be made with attention to temperature of service. For such guidance, Specification A20/A20M may be consulted. 1.4 The 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.