As outlined in QW-200.4, more than one WPS maybe used to complete a single production joint. For the most part combining WPSs is straightforward, if a WPS is qualified for 1/16” to ¾” base metal and weld metal thickness, it can be combined with another WPS is qualified for the same thickness ranges and be used with those ranges.
If you have a WPS that is qualified for 1/16” to ½” and you combine it with a WPS that is qualified from 3/16” to 1”, you would be limited to only using this combination of WPSs for material from 3/16” to ½” thick. This is also specified in interpretation IX-83-80.
The Code does permit a special case as outlined in QW-200.4(b), when one PQR has a test coupon of at least ½” thick, it can be combined with one or more PQRs with base metal thicknesses greater than ½”.
When these requirements are met, you can use for example a GTAW process with base metal thickness range on the WPS of 3/16” to 1” (PQR ½” base metal thickness used), combine it with a SAW WPS with base metal thickness of 3/16” to 8” (PQR 1.5” base metal thickness used). A new WPS can be created with a base metal thickness range of 3/16” to 8” with GTAW being used up to 1” thick and the remainder with SAW.
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