Walking the Cup on Socket Welds

Walking the cup on socket welds is something not taught in most welding schools.


Its usually something you learn on your own in the field.

At least that's the way it was for me.

I didnt even get much training on pipe in school much less socket welds.

I would have loved it if someone made a video for me showing me these tips back then.

So I hope this video helps you.

Gapping the socket weld

I didn't show it in this video, but socket welds need at least a 1/16" gap so that there is room for weld shrinkage.

If the pipe is bottomed out and jammed into the socket and welded, there is no room for the pipe to move as the weld shrinks and that creates too much stress in the finished weld and it will often crack or fail in service.

An easy way to gap the socket weld is just to tilt it back for the first tack weld.

you can also make a sharpie mark or scribe line to  make sure you have a small gap in the finished weld. 

reference ASME codes B31.1 (power piping) or B31.3 (process piping) for gap specifications for socket welds.

root pass settings and technique

I used a 3/32"  er309 rod at 140 amps for the root pass to ensure fusion into the root of the joint.

Sometimes a 1/8" filler rod on the root chills the puddle too much and causes some lack of fusion.

After the root pass, I jumped up to a 1/8" er309 filler rod ...still at 140 amps.

Cup size for Socket welds

you could definitely make this weld with a single cup size but I find that having several choices works better.

A #6 for the root works well.

After the root, it works better if the cup is large enough not to scrub on the deposited weld.  For this weld a #6 seemed to work fine for both root pass and second pass.

For the third and cover pass, I jumped up to a #8 cup.

I used 140 amps for all 3 passes.

Since I was welding stainless steel to carbon steel, and using a stainless er309 filler rod, slightly less amperage was needed than what would be used for carbon steel to carbon steel using er70s2 filler metal.

Gas lens kits

If you would like to learn more about the gas lens kits used on this socket weld video, go to weldmonger.com and check out our kits tailor made to fit your torch.

we have kits made for 17,18, and 26 300 series torches

as well as kits made for 9,20, and 200 series torches

Enjoy this page? Please pay it forward. Here's how...

Would you prefer to share this page with others by linking to it?

  1. Click on the HTML link code below.
  2. Copy and paste it, adding a note of your own, into your blog, a Web page, forums, a blog comment, your Facebook account, or anywhere that someone would find this page valuable.