Cup Size

Date 11-16-2006 14:40

Weld with the smallest thoriated/ceriated alloyed tungsten diameter possible, with the low amperages, the arc will start easier. You may want to try 0.040" diameter. You may want to try the gas lens collet (short not the standard length) bodies & collets and weld with a longer tungsten stick out. Use whatever length of back cap that doesn't get in the way. If you are welding consistently at low amperages (less than 100 amps) probably the best investment is Weldcrafts WP-9 torch. Welding at low amperages smaller is always better.

By SWP

Date 11-16-2006 14:58

Sounds like good advice to me. I am curious, is some reason why a small orifice cup would be an advantage, other than just fitting in a tight space or giving more visibility? Why not use the largest gas lens/cup to get the best shielding?

By MBlaha

Date 11-16-2006 15:55

I agree with you SWP. The bigger the gas cup, the better coverage. The nice thing about larger cups, is you can stick your tonugsten out farther. Good rule of thumb is 1/2 the diameter of the cup stickout.

Mike

By Molten Metal (**)

Date 11-16-2006 15:55

I dont see where 357 says to use a smaller "cup".Read it again.Gas lenses work great.Is this a water cooled torch or gas cooled?They also make Pyrex/glass cups that work good for improved visability.Usually you have to also get an adapter kit to use them though.

By thedroid420 Date 11-16-2006 19:01

What kind of cup collet combination should I ask for. I think that I would like the standard length better. I think that we are using a #4 cup now. Also whats the usual procedure for cutting and fitting say 3" stainless tube thinwall. I've been using a contaminated chop saw and a file to practice with, but this doesn't seem like it would be the proper way to go for a real sanitary weld.

By 357max

Date 11-16-2006 19:47

How thin is the thin wall piping? For less then 1/16 wall thickness and using the chop saw, square cut the pipe. Then clean up the edges & break the square edge of the face side with a "pencil" grinder. Use a floppy flap wheel designed for stainless steel on an arbor. Clean/polish the surfaces with something like Scotch Brite or SAIT's Abrasive hand pads for stainless steel. Wipe surfaces clean with acetone. Dam and back purge the inside/root side of the pipe; tape up the groove opening. Use a tee cylinder fitting and two flowmeter regulators or better yet use the Smith's HI970-580 Dual flowmeter regulator. Set the purge at 1-3 cfh and the torch shielding gas flow at 10 cfh.
Use a #4 to #6 cup nozzle size with 0.040 diameter thoriated/ceriated tungsten. Use 0.035 filler wire from a 1 pound spool of GMAW wire.
The WP-9 torch is an air/gas cooled torch by the way.

By thedroid420 Date 11-17-2006 15:43

I ordered a .040 gas lens collet standard size and two different cups 1/4" and 5/16" today. I also ordered the same for 1/16" tungsten. I give them both a try tonight and see how it works. Most of the stainlees tubing is 1/16" wall and the welds have to be super because everything is cleaned in place. It can't be pulled down and scrubbed. I was practicing walking the cup on some 2" pipe last night and I did alright, I also finally learned the right way to hold the torch. When walking the cup around the the tubing the weld looked kind of wide. Is this the right technique for thinwall stainless, or is there a better one. I've been using 20 cfm at the cup and 30 for purge. I'll give your suggestions a try tonight.

By eekpod

Date 11-17-2006 20:18

Keep in mind that it sounds like you will be repairing/ welding "Process Piping" which has to meet either USDA or Pharmaceutical requirements. I worked at a pharmaceutical plant inspecting process piping welds made with the automated orbital head welding units and because a drug ran through the piping the welds had to be perfect. This way there wasn't anyplace for bacteria to get trapped in and grow. Check w/ the owners/ management before you weld a real piece, Good Luck

By thedroid420 Date 11-18-2006 04:17

that is what we'll be doing, and the welds do have to be good or alot of product can be ruined by bacterial counts. Every day after the product is run, the lines are washed with a hot caustic/chlorine wash and then an acid sanitizer.

By SWP

Date 11-17-2006 21:41

My experience is with the automated welds that Eekpod has described. I have no idea how a human can get the torch around a tube with the consistency of the machine. I see what you're saying about walking the cup producing a wide weld. The machine welds are straight line, no side to side oscillation, so they are only as wide as needed to get full penetration. Milk may not be as critical as many other processes, but crevices of any kind on the inside bead are surely rejectable.

By Molten Metal (**)

Date 11-17-2006 22:58

Personally,I wouldnt "walk the cup" on 1/16th Stianless.Make sure you hold your filler rod as close to horizontal as possible in relation to the direction of travel.In other words,dont be coming at the joint with your rod at a 30degree angle.Lay it pretty flat and tack it real good.

By ccjersey (*)

Date 11-18-2006 03:20

I've seen a bit of milk plant SS pipe welding done. When the professionals I have seen can do it, they tack it and then rotate the pipe in a roller stand while welding it. That seems to be the easiest way to achieve the best weld by hand. The joints that cannot be rotated would be a greater challenge. Also no filler is used. Otherwise sounds just like what was described above as far as torches, tungstens, purge and flow rates. They used a borescope to check both old and new welds. At some point there would always be a weld that couldn't be reached to check it, so I suppose you just have to rely on the welding procedure and skill of the welder.

The most recent large scale fabrication I know about was done with the automated orbital welding machines.

I would pay close attention and ask lots of questions whenever the hired welders come in. I think it is a great idea to learn the skill.

By thedroid420 Date 11-18-2006 04:20

It would be nice to have an orbital machine, but we don't install enough line to justify the cost though. Most of out work is repair, and welding new flanges on attachments. We occaisionally have new equipment that goes in also.

By medicinehawk (**)

Date 11-20-2006 01:24

Generally you do not need to add filller wire. Speaking of the biotech industry where alot of orbital welding is done, and piping systems which are fabricated are turned over to the FDA for approval.........they are pretty strict when it comes to welding and parts which are used. They like to trace the heat numbers off the fittings & tubing which is used and they do not like high sulfer contents or other impuritues. Most clients will not accept hand welded joints unless there is absolutely no other means to get the dimension or configuration they want. They will accept hand welds when the need arises and while it is not easy to get machine (orbital) quality......it is certainly doable.
I.D. purge is extremely important and it is necessary to have all the tools at hand to do the job right. Purge caps designed for the size (s) you will use with fittings installed on the ends to change from one diameter to another are also preferred. Even the argon has to be extremely pure and if you plan on doing a real lot of it........get an oxygen meter.
Now as far as food grade welding goes.........they are not as strict having worked building a brewery before. There is no boroscoping of welds and hardley any visual inspection either to my surprize. Weld maps are not required and they like to use 304 stainless as opposed to 316L stainless. I don't know about the dairy industry but I'll let you know as I am supposed to go to a yogurt factory soon to weld some .065 wall tubing.
As far as technique is concerned, walking the cup is the way to go, but "free-hand" welds can be truely sound if you use a spin-table or have done enough of it. Those power sources with all the "bells & Whistles" are the thing to have if you know what all those gadgets are for. Having used an orbital machine is useful dialing in that stuff.
They use tools which cut & face the tubing to be welded in such a way that all you need is a file to clean up the burrs. Take care not to get shavings in the product lines is always good advice.

By thedroid420 Date 11-20-2006 23:37

Last night I made a few nice welds walking the cup. It's tricky on the 2", and I've found that I need to slow down a little in order to get good penetration. I'm using a lincoln squarewave 175 pro with 1/16" tungsten standard length collet and a #4 cup. For walking the cup I'm leaving about about an 1/8" sticking out of the cup. I'm trying to keep the weave under 1/4" wide. I can do the weld in two passes. I do the top half flip it and do the bottom. I was wondering about overlapping the start and stop. Is this a no no. Also im using about 15cfm on the torch and 10cfm purge. 35 amps or so. Does this sound about right?

By medicinehawk (**)

Date 11-21-2006 10:40

Seems abit cold to me. I use 50-60 amps and if you have a rheostat then u shouldn't have any problems. Also, stick out is not enough IMO. Try 3/8" to 1/2". We use 1/4" poly tube with swagelok unions afixed on plastic caps to purge with so there is no way to get air in the lines, set the I.D. around 20cfh and the torch around 35-40 with a gas lense and a # 7 cup. Usually, the outside is copper to gold in color and the inside will be silver.

By Aldridge6670 (*)

Date 01-04-2007 13:21

Remember if it's a gold weld it's a perfect weld purge yes stainless contaminated easy. I've done food grade 316 and 304 if you can get on the inside fuze it together and you don't need to purge
I used 1/16 tungsten and a #6 cup with argon at about 40 -45 walking the cup is nice if you get the feel for it slow is good I run a little cold about 50 or so. starting and stopping doesn't matter because practice this if the weld looks uneven in spots you can always go back over it to fix the look of it always run uphill and only 10 % down all of my teaching as been out in the field no schooling will teach you stuff like that. the key is to not touch that tungsten to that pipe if so it won't pass ex-ray and keep that tungsten sharp sharper the better .040 isn't a bad idea either I prefer 1/16 on 1 inch pipe up to a 8 inch pipe. tungsten other than aluminum is personal preferance aluminum takes bigger tungstens and cups because of the heat. If no cracks and and it's a butt joint tack it in 4 side in a x pattern then fuze it together first then at 316L filler metal. some spoke of using 316L mig wire never heard that before not saying it can't be done. It's Process Piping which means to me perfection. the pyrex cups are nice extremly expensive and brake easy.