I've done a bunch of searching around and found a few different ways to do this but I wanted to get some opinions before I start welding. I'm still pretty new to TIG, so I wanted some advice. I've fitted all the joints to be as tight as possible and beveled all of them. Other then one or two with maybe 1/32" gap, they are all tight and could probably hold water with just the tack welds.

I've taped over all the joints with 1" wide powder coating tape to hold in the argon. I had planned on doing a root pass with no filler with the backpurge and then doing a cap pass without the purge. Is this two pass method the best option and how hard will it be to keep from heating through the root pass? Or would a single pass work better with less argon required too?

Torch/welder setup is a gas lense with #8 nozzle. 1/16" Lantenated tungsten, pure argon. Any suggestions on how much current for each pass? I'm using a Thermal Arc 185, if it matters much?

Also, when you start the back purge, how long do you ned to wait while it purges before you start welding? Sorry for the crappy picture, but here is the manifold so far. I was planning on running the purge line to the inlet of one runner and then putting a hole in the inlet of the other runner to make a path for argon flow.

Thanks for any help
Mike

 

The 2 pass method is way better than a single pass, even though a 3 pass would be the best but 2 would be adequate. I suggest you have something to hold the runner where they are b/c i'm sure things will not line up the way they were prior to welding.

 

there is some tape specifically designed for this. I believe it melts and leaves no residue. its orange in color.

I do three passes. First one you'll probably be at 130 amps...maybe a bit more. I would run a 3/32 tungsten for teh 1st pass. Make SURE you get full penetration.

I would wait long enough to be sure you filled the tubes and its flowing out. Turn the flow up...lick your finger and see if you can feel the gas coming out the joint. turn it back down and weld. be sure to leave a LITTLE flow once you start welding.

2nd pass i use a 1/16 tungsten and fill it but I stay within the first weld width.

3rd pass I use a 3/32 and turn the pulser on. run a weird duty cycle setup wtih a long post purge and wait after about every 8 pulses for teh material to cool. I make this weld just slightly wider than the 1st.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .R T E r n i e &raquo;</TD></TR><TR><TD CLASS="quote">there is some tape specifically designed for this. I believe it melts and leaves no residue. its orange in color.

I do three passes. First one you'll probably be at 130 amps...maybe a bit more. I would run a 3/32 tungsten for teh 1st pass. Make SURE you get full penetration.

I would wait long enough to be sure you filled the tubes and its flowing out. Turn the flow up...lick your finger and see if you can feel the gas coming out the joint. turn it back down and weld. be sure to leave a LITTLE flow once you start welding.

2nd pass i use a 1/16 tungsten and fill it but I stay within the first weld width.

3rd pass I use a 3/32 and turn the pulser on. run a weird duty cycle setup wtih a long post purge and wait after about every 8 pulses for teh material to cool. I make this weld just slightly wider than the 1st.</TD></TR></TABLE>
You're talking about sch40 right? I think 130 would be a bit too hot for sch10

 

depends on how fast you move... and how close your joints are.

I move very fast and his joints are VERY tight. I only use sch 10. backpurging requires a lot more amperage than typical welding.

 

I honestly can't imagine doing 3 passes on either sch10 or 40.

I'm personally, more of a huge bevel, and 1 pass kinda guy. Less time, less gas, less heat, yet still a full thick weld. nothing on you RT, or your methods, but 3 passes seems just seems a little extreme to me.

About the purge...I've found that taping the joints isn't really neccesary if the joints are tacked up flushly (common sense). If there is a slight gap, you might as well tape it. Set the purge flow to equal your torch flow (20-30 works fine). Then turn on the gas a couple seconds before you start the arc. It isn't going to take much more than that to purge the pipe. Also...make sure the end of the runner has a hole so the gas can "flow" through it.