This guide covers standard specification for black or galvanized welded or seamless threaded steel couplings for use with steel pipe joints in NPS 1/8 to NPS 20 [DN 6 to DN 500] inclusive. The steel for both welded and seamless couplings shall be made by one or more of the following processes: open-hearth, electric-furnace, or basic-oxygen. Welded couplings NPS 3½ [DN 90] and under may be butt-welded. Welded couplings over NPS 3½ [DN 90] shall be electric-welded. The steel shall conform to the required chemical composition for phosphorus and sulfur.

1.1 This specification covers black or galvanized welded or seamless threaded steel couplings for use with steel pipe in NPS ¹/₈ to NPS 20 [DN 6 to DN 500] inclusive (Note 1). Couplings ordered under this specification are intended for the uses outlined in the pipe specifications referencing this specification.

Note 1: The dimensionless designator NPS (nominal pipe size) and DN [diameter nominal] has been substituted in this standard for such traditional terms as nominal diameter, size, and nominal size.

1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. 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.