to purge or not on 6-g pipe test/tig root

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i have not seen any photos of purging done while testing on the above, is it optional? is it only for a stainless root? thanks
Reply:Not necessary unless it's called out on the WPS you're testing in accordance with.  You'll rarely see it done, because a) carbon steel test coupons cover most of the base material P numbers that are seen on the typical job site and do not require a back purge, and b) when qualifying with stainless filler per ASME IX, you may do so on a carbon steel coupon.  The idea is to keep the cost of everything as low as possible, including test coupons and gas.  Most of your D1.1 work is covered by the plate tests, and they typically use backing strips.
Reply:on carbon steel there is no need for purging.  ALMOST every other metal does need a purge.
Reply:I disagree.  We will weld up to 2 1/4 chrome with no purge on a routine bases.  This covers all P1, P3, P4, and P5A materials.
Reply:P8 (stainless steel) will require a purge or back shielding.JasonLincoln Idealarc 250 stick/tigThermal Dynamics Cutmaster 52Miller Bobcat 250Torchmate CNC tableThermal Arc Hefty 2Ironworkers Local 720
Reply:Originally Posted by SupeI disagree.  We will weld up to 2 1/4 chrome with no purge on a routine bases.  This covers all P1, P3, P4, and P5A materials.