I may be taking a welding test for a new job at the end of the week and they do a lot of .065" stainless tube by fusing and backpurging. I want to do a little research on it before I go. I assume the ends are cut square and fitted tight then fused in one smooth pass...is this right?

 

Yeah thats about right. Most sanitary stuff you don't use two things, filler rod, and remote amperage control (foot pedal or finger control). I would practice your scratch starts and finishes, go at about 45-55 amps, usuall run about 30cfh for the back purge, use a #8 cup with a gas lense, because it might be scratch start use a 3/32 tungsten instead of a .040 or a 1/16".

Sanitary fittings like 45's, 90's, t', farrules, etc come square, ready to weld, straight tubing you have to cut to fit.

Find out if they use remote amperage control or not, its a lot harder than you might think to do on thinner material like .065". Depending on application they can be really picky about I.D. color as well. Full penetration is a must and consistancy is key.

Heres an ok I.D. weld for some process piping I did a couple weeks ago.

 

great thanks for the info Dave.

Give me an idea how far you might travel in 5sec if you dont mind.

I would probably tack this in 4 places and then weld in 1/4s, does that sound realistic? I hadn't even though about what machines they might use. Is it usually a portable welder/generator with a tig rig on it, hence the scratch start?

 

A lot of that sort of stuff won't use scratch start....You can trigger the HF with the pedal and not use it for amperage control on certain machines.

 

anyone running a remote to trigger HF and using no remote heat control has it wired in as a trigger on the torch. I took a weld test on one of those once it was a little wierd getting used too. It demanded that I hold the torch a certain way so that I could turn it on and off at the beginning and end of the weld.

Yes I passed and no it was not on process piping.

I think Dave, Engloid and RMF are the only ones I know that used to /do weld sanitary. Maybe SMPS too or whatever his name is.

 

Yea I was using a dynasty 300dx and just used the pedal and was playing around with some of the features. Hand control would work better, hell you could probably build your own button pretty easy.

 

I tack in three places evenly spaced, than depending on wether I am using a positioner or not I try to weld in one solid pass, I usually hold the torch with my left hand than spin the piece with my right hand, it takes some practice to do it in one motion but once you get it down you get much more desireable results. When doing welds without filler and no amperage control its better to try and do it in one motion because when you trail off to stop the arc you can get "fish eyes" or pinholes where the arc stopped.

The welders I use on the job are a maxstar 150, some small thermal arc machine thats basically the same thing, and some other blue welder thats the same thing just about 15 years old, they all run on 115, and get **** kicked everyday. I like how the inverters weld compared to most transformer welders. In the shop we use a 300dx and a sync200 and hopefully another 200dx soon.

On that piece of 2" process piping above there I think it takes me about 20 seconds to go around it somewhere around 45-50 amps. I'll get a more definite answer tomorrow cause I'll b welding more of it I'm sure.

 

i use 53 amps..



my pedastel, purge gas comes up through center hole

 

i really think every one in canada welds sanitary tubing its awesome. I usually tack it in four spots at about 35 amps. setup my purge about 30 cfm and let her rip at 50 amps.

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my pedastel, purge gas comes up through center hole </TD></TR></TABLE>
that thing is awesome. we built the same style thing at work but i havent had a chance to use it. i bet with alittle practice your consistancy is as good as an orbital weld