Thermoplastic Welder Qualification Standards for Distribution Systems

By Ted Hutton


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One of the things most overlooked in the installation of thermoplastic weldments in high-purity water systems is the qualification of the welders. It is common to require the metal welders be qualified, and even certified, depending on the criticality of the weldment. However, isnメt the integrity of a facilityメs thermoplastic weldment worth verifying the welderメs ability to perform to the qualification of the American Welding Society (AWS) standard (1) for thermoplastic welders, or the German Welding Society (DVS) guideline (2) for thermoplastic welders? The AWS B2.4 Specification for Welding Procedure and Performance Qualification for thermoplastics is available from AWS. The DVS guidelines are also available in English. The American Society of Mechanical Engineers (ASME) BPE bioprocessing standard (3) contains quality specifications for beadless welding in high-purity water systems. For those involved with any operations that require thermoplastic welding, this article contains needed information to assure quality welds. Most thermoplastic failures are the result of inadequate control of welding parameters, and in the high-purity water handling process what constitutes an acceptable weld is more involved than is standard chemical handling application.

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