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Extrusion welds

Q&A: GMA Techline | October 1, 2011 | By:

RE: Welds
Are destructs typically conducted on extrusion welds?

Our flexible membrane liner (FML) spec doesn’t specifically address this. It does explicitly list a destruct frequency of every 500 linear feet of seam length.

Does “seam” refer to both extrusion and fusion welds, or just fusion? Should we track both separately (i.e., take a destruct for every 500ft of extrusion and another for every 500ft of fusion) rather than a running combined total, which might make it harder to keep a proper balance?

(Brian | Kentucky)

Reply: Destructive tests are indeed taken on both wedge and extrusion seams. The 500-ft rule generally is applied to the wedge welds and then whenever and wherever the CQA wants them taken on extrusion welds.

Robert M. Koerner, Ph.D., P.E., NAE; E-mail:

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