This specification covers external helical, integral finned, seamless or welded low-carbon steel tubes for use in tubular heat exchangers, surface condensers, evaporators, superheaters, and similar heat-transfer apparatus in unfinned end diameters. The tube, prior to finning operation or unfinned portions of the finned tube, shall conform to the requirements for tensile properties prescribed in the governing plain-tube specification. Each tube after finning shall be subjected to a pressure test which shall permit easy visual leakage detection.

1.1 This specification describes seamless or welded low-carbon steel tubes on which the external or internal surface, or both, have been modified by a cold forming process to produce an integral increased surface area for improved heat transfer. The tubes are used in tubular heat exchangers, surface condensers, evaporators, superheaters, and similar heat-transfer apparatus in outside diameters up to 2 in. [50 mm], inclusive.

1.2 Units—This specification is expressed in both inch-pound units and in SI units; however, unless the purchase order or contract specifies the applicable M specification designation (SI units), the inch-pound units shall apply. The values stated in either inch-pound units or SI 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.

1.3 This 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.