Pangea (works for NASA) and BC on the Hobart board are big fans of DC and "lab grade" helium for heavy aluminum weldments.

I've used DC/straight Helium quite extensively in the past, but for many years now, I've found I can get my work done with AC and the addition of about 25% helium.

DC welding with Helium definitely has it's place, but when you factor in the cost of the Helium along with the higher flow rates required, your covering gas ends up costing you about 7 times as much as using Argon.

Sometimes you just got no other options though.

Yea. I know what you mean. The process has been used for years in obscure (to the public) circles. I was really thinking about the final weldments/product(s). When you use 60-70CFH of UHP+/labgrade He it costs big time! Maybe it's just me, but I love to feel the filler penetrate like it does running .040 ceriated tungsten at 140 amps on 3/4" Al. Also pushing 300+amps AC is hotter than helle (had to add an e for the forum to allow it) to me.

I am nearly 50 and can't count the bottles of high dollar He, tungsten, and filler rod I smoked up over the years. The final product and selling price was good. Now days I rarely see over 40 amps on a TIG. All I do is weld critical stuff with no tolerance for error. Good to hear your input though.