1.1 This specification covers aluminum and aluminum-alloy extruded round tubes either in coils or straight lengths, for general purpose applications such as refrigeration service, gas lines, oil lines, and instrument lines, in the alloys (Note 0) and tempers shown in [], in outside diameters of 0.250 through 0.750 in. [6.00 through 20.00 mm]. For diameters over 0.500 through 0.750 in. [over 12.50 through 20.00 mm], the diameter and wall-thickness tolerances and eddy-current test parameters, if required, shall be agreed upon by the producer and the purchaser. Only tubes in aluminum 1200-H111 and 1235-H111 are sized after extrusion to minimize ovalness.

1.2 Alloy and temper designations are in accordance with ANSI H35.1[H35.1M]. The equivalent Unified Numbering System alloy designations are those of preceded by A9 (for example, A91050 for aluminum 1050) in accordance with Practice E 527. Note 2For extruded tubes see Specification B 221, and for drawn tubes for general-purpose applications see Specification B 483.

Throughout this specification the term alloy in the general sense includes aluminum as well as aluminum alloy.

For inch-pound orders specify B 491; for metric orders specify B 491M. Do not mix units.

1.3 For acceptance criteria for inclusion of new aluminum and aluminum alloys in this specification, see .

1.4 The values stated in either inch-pound or SI units are to be regarded separately as standards. The SI units are shown either in brackets or in separate tables. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from two systems will result in nonconformance with the specification.