Strange 3G Test

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I was given an open root tig cert test the other day. It was 3/8 thick stainless plate test with a 1/8 gap.The strange thing is, I was required to weld out the backside as well! Never heard of this...Guys at work say to weld the back side up first, then flip it over and do the "root".I tried this method. When I ground my welds down for the bandsaw, I had a straight line going all the way down the backside! Right down the middle.I welded the backside, then flipped it over and cleaned the burn through with a die grinder before putting in the "root" pass. Did I dig too deep? Is this what caused the line?When I cut my coupons, I had zero defects on the inside and zero defects on the face. However that root is bound to split open when they bend.If I fail and retry, would it be a good idea to do the front root first, then the back? Or try again the way I did?
Reply:Did the back weld on about 100 amps FYI. Worked my way up to around 140 on the cap. Will post pics when I get on my computer
Reply:I would weld the whole front side first, the grind the crap outta the back until it's clean. Then burn the back side in hot.That's a bad test procedure. Did you have a purge on the back? If not, you should have a copper bar or ceramic backing to weld up against. Or get somebody to hold a purge can over where you're welding the root in.
Reply:They should have stated the welding procedure before you started considering it's an odd test.
Reply:Originally Posted by TimmyTIGI would weld the whole front side first, the grind the crap outta the back until it's clean. Then burn the back side in hot.That's a bad test procedure. Did you have a purge on the back? If not, you should have a copper bar or ceramic backing to weld up against. Or get somebody to hold a purge can over where you're welding the root in.
Reply:If you can't see where you're going, try a lighter shade lens.
Reply:I would tack it up. Tack run off pieces to it so you have a nice place to start and stop.  Weld out the entire front side, then flip it over and back grind the root out until it's clean.  Weld back up. Done.
Reply:That's not a strange test. The TSSA has a structural test with stick here using carbon steel and no backing strip. Weld your root side first, then grind/gouge the back side till clean, then weld the back side. Piece of cake.JasonLincoln Idealarc 250 stick/tigThermal Dynamics Cutmaster 52Miller Bobcat 250Torchmate CNC tableThermal Arc Hefty 2Ironworkers Local 720
Reply:Like snoeproe said, done lots of plate stick tests where the root was not important because everything was background/gouged.  Not understanding this tig test though.   Was there a regular no land bevel, double bevel, or was it straight edge 3/8" plate with a 1/8" gap?  If the later, I can see welding the back side first, comfortably penetrating about 1/8".  Then grind (open up) a bevel on the front, making sure any sugaring and lack of fusion is ground out.  Then fill the front.  Question is...would this procedure remove the need for back purging?  Don't really know if a weld will bend properly after sugaring has been ground out.
Reply:Weld from the front. Grind down the center of the weld(back of the joint) with a hard disk so you have a line to follow. Grind around the line until you are in clean steel. Fill groove.Airco Ac/Dc 300 HeliwelderMillerMatic 200 (stolen)Miller Maxstar 150STLMiller AEAD200LE (welding and generating power) Hobart MIG