Thermoplastic pipe gets AWS standard

The American Welding Society (AWS) has published the “Specification for Welding Procedure and Performance Qualification for Thermoplastics” standard (AWS B2.4:2006). The new, first-of-its-kind standard provides requirements for welding thermoplastic pipe and other materials.

Thermoplastic pipe is no longer limited to small diameter sizes used for gas distribution, high purity water, or process systems. “They have spread into larger diameter hot and chilled water piping, for example,” said United Association Special Representative Brian MacDonald in a recent JobScope article (Fall 2005). “They are finding more and more uses for it all the time,” he said.

As the applications have grown so has the need for installation requirements. Up to now bidding documents simply directed the builder to “see manufacturer’s recommended practice.”

Publication of the new standard in February 2006 was preceded by a few years of thorough review and discussion by volunteer peers including UA representatives, chemical and mechanical engineers, an insurance person, and member of the British Welding Institute. McDonald, who chaired the AWS B.2.4 subcommittee, said when the rules change to require qualification of thermoplastic pipe installers, the UA wants to be ready to train and test their members. Some states already call for qualification for pipe used to carry material hazardous to the environment or human body. More will follow.

The standard is for use in new construction as well as retrofit or repair projects. It addresses these welding processes:

• Socket Fusion Welding (SFW)

• Butt Contact Welding (BCW)

• Flow Fusion Welding (FFW)

• Electrofusion Welding (EFW)

• Infrared Welding (IRW)

• Hot Gas Welding (HGW)

• Speed Welding (WZ)

• Fan Welding (WF)

• Extrusion Welding (EXW)

Thermoplastic applications that are bonded to backing materials are not addressed.

The Specification for Welding Procedure and Performance Qualification for Thermoplastics standard can be purchased for download from the AWS Web site at: http://www.awspubs.com/ (Select “plastics” in Publications window.).