This specification covers electric fusion welded pipe suitable for high-temperature or corrosive service. The pipes are designated into five classes namely Class 1, Class 2, Class 3, Class 4 and Class 5, according to how they are to be welded. The joints shall be full penetration double-welded or single-welded butt joints employing fusion welding processes. The furnished pipe shall undergo heat treatment and a chemical analysis shall be employed for both plate and weld. Each pipe shall be subjected to transverse tension test, transverse guided weld bend test and hydrostatic pressure test.

1.1 This specification covers electric fusion welded pipe suitable for high-temperature or corrosive service as listed in Table 1. (Although no restrictions are placed on the sizes of pipe that may be furnished under this specification, commercial practice is commonly limited to sizes not less than 8 in. [203 mm] nominal diameter.)

1.2 Five classes of pipe are covered as follows:

1.2.1 Class 1—Pipe shall be double welded by processes employing filler metal in all passes and shall be completely radiographed.

1.2.2 Class 2—Pipe shall be double welded by processes employing filler metal in all passes. No radiography is required.

1.2.3 Class 3—Pipe shall be single welded by processes employing filler metal in all passes and shall be completely radiographed.

1.2.4 Class 4—Same as Class 3 except that the weld pass exposed to the inside pipe surface may be made without the addition of filler metal.

1.2.5 Class 5—Pipe shall be double welded by processes employing filler metal in all passes and shall be spot radiographed.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to become familiar with all hazards including those identified in the appropriate Safety Data Sheet (SDS) for this product/material as provided by the manufacturer, to establish appropriate safety, health, and environmental practices, and determine the applicability of regulatory limitations prior to use.

1.5 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.