Good afternoon to all.

I have a project going through my shop that is driving my welders and me crazy. We are TIG welding 11 ga(.115) type 304 SS water tanks and can't get nice flat ripple/distortion free weld seams on the side walls. The tanks are 60" in diameter, have a dished head on the bottom, 48" deep and open on the top. The weld around the dished head comes out nice, no problem. The 48" seam weld is where we are having the problem. It's a butt weld and we have tried weld preps, chill plates, weld one side and then the other, various amperages, various filler diameters,tungsten diameters gas flows, back gassing etc,etc,etc and the 48" seam is rippled and in some cases has peaked outward or inward. Bottom line is we don't know how to get this right. Any help would be greatly appreciated.