Sanitary TIG Welding

admin

Hi all. New here. Can I get any info on sanitary TIG welding. Just started doing this and I really enjoy it. Dont know if I am doing it right or not, but sometimes they look good, sometimes they dont. Wanna know more. Read, i'll read, point me in the right direction. Heck, will even do it. Aint skeered. I'll TIG almost anything. Some weird reason I have a real fascination with this and stainless steel. Dont ask why, dont know, just do. I seen in here somewhere someone was saying something about cup walking and how it is useless and a lazy way and blah blah blah. I can really see where they are right but however, where I am from they wont hire you unless you know it. Two sides to every opinion I suppose. Thanks in advance for any pointers or of the such.
Reply:Pics help so we know what you are doing. There are different levels of "sanitary tig"  . I`ve seen stuff that was supposed to be hygienic in restaurant food prep areas that would make you double take, and probably not feel like going out to eat....Stainless welded with mild steel mig....carbon steel hardware rusting on stainless hoods. Then there is more controlled stuff like food tooling manufacturing where joints are always welded 100% as to prevent inclusions/holes where bacteria can grow or process pipe that requires purge and full pen for the same reasons.
Reply:What is "Sanitary TIG welding" ? As far as I know, all TIG welding requires cleaning of base metal before hand. "SOUTHPAW" A wise person learns from another persons mistakes;A smart person learns from their own mistakes;But, a stupid person.............never learns.
Reply:Well here is my take on it:Take a stainless steel pipe, fit it up, purge it with argon, tig it and presto, you have a mirrored weld on the inside of the pipe. Ive only done this a few times and nailed it a couple, only because the inpector said so. did i do it right? couldnt tell ya but he allowed it. (If you were joking papabear, sorry)As far as pics go, well they wouldnt be happy cause I would have to take it apart and then they really wouldnt be happy cause they cant run then. LOLJust want to know more about it. Took a tig class once, wasted 10 weeks of my life, it was all directed towards aluminium, not stainless pipe like I was told. Not very happy over that. Still completed it though.
Reply:So here is what got me interested, we had a 3" stainless pipe break, actually the coupling broke, I was like heck I can TIG that. Then everyone made a big deal out of sanitary welding, so off to the machine shop I went. The guy there cut the pipe, ask if it had to be that length, I said yes, so he prepped it all with a small gap and prepped for purge. OK so now he had my attention, he threw me a helmet and said learn....(Meen while I was drooling with anticipation) laid 4 tacks and off he went with the root pass. Cup walking none the less. (I was all flushed with adrenaline) Came back and capped it. I popped off the helmet and I was like what the f####. What is the deal with the gas? He was like so it welds on the inside just like the outside. I was like you root welded it, it is. He then butt fitted two pipes together and told me to tig it. I was like cool. So I TIG it. He took it out and said look on the inside. I was like barf, not good. He made another one, set up for purge and told me to do it again, Yeah, so I did it again, he took it out and said look inside. I was BLOWN AWAY and been hooked ever since. Problem is, I dont have a chance to get back to that shop to learn more. AHH man I am a 2 year old in a candy store when it comes down to this. Just not alot of info around and everyone keeps it locked up.
Reply:PapabearWhen I hear sanitary TIG or Hygienic TIG  I believe it is referring to FOOD/MEDICAL grade work.Last edited by BrianNye Welding guy; 12-19-2009 at 01:12 AM.
Reply:Sorry FOOD grade. Like milk lines, waterlines. stainless steel and the such.
Reply:Catchy name by the way, I use to watch bill nye the science guy on T.V. I am assuming that is where you got it? LOL
Reply:Every industry has their own standards for what is considered "a good weld" In production sheet metal for electronics/CNC machines people hardly clean oil or dust off the material before it is welded even with TIG...some places this is tolerable all the time with hardly a quality issue. In Hygienic industries....ie  pharmacutical/medical/food tooling  not only must it all be welded 100%....meaning all welds fused from BOTH sides or all pipes purged with zero oxidation on the inside, every hole covered because you can not have any cracks/crevices/inclusions etc. where bacteria/fungi/viruses can grow and fester and not be properly flushed/sanitized.  Other industries that are "SUPPOSED to be sanitary" are  restaurant  equipment fabrication/repair etc . but because of lack of oversight or understanding there is a lot of sub par work that is done. The difference you are talking about  DJ is just the addition of argon to the inside of the pipe which is required for any food/medical/pharmaceutical operation and in most needs to be full penetration with no oxidation/inclusions or holes.
Reply:Not exactly.....given the name Brian Nye by birth....just acquired the welding guy portion somewhere along the way when coworkers thought they were being funny.
Reply:Wasnt trying to be offensive with your name, sorry if I offended you. Just clicked in my head when I seen your name. But anywho, thanks for definition, I found the search button up above. There is some awsome pics in there.
Reply:No offense taken Dj...sorry if I came off that way...thats why I threw in the smiley too!
Reply:I used to make the Apollo meter for Smith meter. It was all stainless steel tube. Lot of fun to build. Then they went and discontinued it.  It was used in the food industry for packaging granular medium, like cereal, sugar, etc. Measured everything ultrasonically.
Reply:Oops, I thought you meant "sanitary" as in sanitary lines on shipboard Attached Images"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by farmersammOops, I thought you meant "sanitary" as in sanitary lines on shipboard
Reply:Originally Posted by dj722000Well here is my take on it:Take a stainless steel pipe, fit it up, purge it with argon, tig it and presto, you have a mirrored weld on the inside of the pipe. Ive only done this a few times and nailed it a couple, only because the inpector said so. did i do it right? couldnt tell ya but he allowed it. (If you were joking papabear, sorry)As far as pics go, well they wouldnt be happy cause I would have to take it apart and then they really wouldnt be happy cause they cant run then. LOLJust want to know more about it. Took a tig class once, wasted 10 weeks of my life, it was all directed towards aluminium, not stainless pipe like I was told. Not very happy over that. Still completed it though.
Reply:I think I found my problem yesterday. I think my problem is speed. I noticed that while I was welding, I am getting a little to fast and not allowing it to burn in deep enough. I had to go back and look at the bead I was laying, it started to stand up a little and that is where I wasnt mirroring the weld on the inside, once I slowed back down then it started again on the inside. Tiresome learning this on your own.
Reply:Yes....just be patient....when the pipe is purged the inside is protected so make sure you give it time to burn through evenly.
Reply:dj,With stainless steel pipe, if -both- sides of the weld joint are not protected from the air when the joint is welded then the stainless steel oxidizes when it is hot and/or molten.  Another phrase for that is "sugaring", because the inside of a stainless pipe that was welded without inside purge gas looks kind of like crumbly sugar.  The purge gas inside the pipe is to keep air away from the weld from the inside of the pipe, then the shield gas from the torch keeps the air away from the outside.  Want to do some reading?  www.esabna.com and go to the Education section.  Then the Knowledge Center and the ESAB University sections.  Read away.  Also you can read up at www.lincolnelectric.com  Dig through for the documents about stainless steel.  c64000.pdf especially Good stuff.  The best laid schemes ... Gang oft agley ...
Reply:Go slow, and point the tungsten almost strait in. It feels weird going slow because the puddle looks good on the surface, and you just want to move on.  I was always worried I was going to blow a hole in the tube, or burn the metal. The puddle almost looked like it was going to drop into the tube. Hasn't happened yet. And even though the puddle looked like it was sagging into the tube, when ever I checked the inside of the weld, it was always slightly concave.
Reply:A double skined tube for chocolate ( a 25mm x 1.5mm elbow/tube inside a 70mmx 1.5mm elbow/tube), the small pipe is used for chocolate, and the other is for hot water to keep it molten. (completed by using the walking the cup method)   Sorry about the foto quality, camaras are strictly banned in the factory, so I had to snap it with my phone when nobody was looking.Last edited by Baila La Pinza; 12-23-2009 at 04:00 PM.
Reply:Originally Posted by Baila La PinzaA double skined tube for chocolate ( a 25mm x 1.5mm elbow/tube inside a 70mmx 1.5mm elbow/tube), the small pipe is used for chocolate, and the other is for hot water to keep it molten. (completed by using the walking the cup method)   Sorry about the foto quality, camaras are strictly banned in the factory, so I had to snap it with my phone when nobody was looking.
Reply:Originally Posted by Baila La PinzaSorry about the foto quality, camaras are strictly banned in the factory, so I had to snap it with my phone when nobody was looking.
Reply:Interesting thread.  I happen to have to weld fittings to beer brewing vessels.Would that (link) be a good back-purging apparatus for the purpose?  I only have a few to make at the moment.In that post, I'm saying I intent to make an aluminum thin foil seal but I also plan to burn the can lining before using it.  Otherwise, fume could contaminate the "back side" of the weld...USINUM - CNC routing workshopPaco's area - blogspot---Lincoln MIGpack180 (GMAW - FCAW)Miller Syncrowave 250
Reply:used to do some precision work for automated pharmaceutical machines. Some of them had clean room specs some of them had sanitation requirements.As it has been boiled down, "sanitary" tig is a loose term  but mostly it means theres certain minimums for radius and hole size so that there's not crevices for nasties to grow into.  In most ALL code welding stainless steel has to be back purged although you can get away with it in 17.1 if you use another form of backing."sugaring" the nasty black stuff that happens on the backside of an upurged weld is oxide formation. This is unacceptable because it also destroys all the anti corrosion characteristics of stainless steel, and can affect welded strength.Now the people who hate on cup walking are the people who can't do it, or didn't learn. The technique is advocated by professionals and while I don't force my welders to do it. I do force them to learn and pass a cert with it. The way I was touch was with a piece of sidewalk chalk which is nearly identical to about a size 10 cup Larger cup sizes make it a little easier.  all your doing is trying to make an evenly sized zig zag up a piece of chalk board.  If you can do that you can cup walk. you roll the cup in a zig zag pattern on your weld joint.mind you it's kinda of hard to explain without demonstrating.  Personally I only cupwalk when my arm needs a break, I can't see what I'm welding or some other weird situations. for a straight bead in a simple position I'll free hand.TRY to explain.I don't see how "cup walking" relates to "sanitary" or "food grade" TIG. Am I correct in assuming that you are pivoting the torch handle/gas cup back and forth (left side forward, right side forward, etc...) as you work the torch along, laying your weld?This wouldn't work on a butt joint, only on a T (or inside corner) joint, correct?Back purging is still a necessity if that is the case, so what's the big advantage or deal? More consistent arc length and travel speed, and therefore bead?Last edited by Marcel Bauer; 01-22-2010 at 02:57 AM.[B]Forever learning[B].
Reply:Originally Posted by Marcel BauerTRY to explain.I don't see how "cup walking" relates to "sanitary" or "food grade" TIG. Am I correct in assuming that you are pivoting the torch handle/gas cup back and forth (left side forward, right side forward, etc...) as you work the torch along, laying your weld?This wouldn't work on a butt joint, only on a T (or inside corner) joint, correct?Back purging is still a necessity if that is the case, so what's the big advantage or deal? More consistent arc length and travel speed, and therefore bead?
Reply:Howdy folks, I was reading through your web site, and noticed this topic. Since I have been doing sanitary welding in the food industry for .... Probably 25+ years I thought I'd join and toss in my 2 cents.I see alot of good advise here on the subject. In my welding stash of goodies for purging. I have what are known as "gas dams" or "Gas cups", might go by other names too. Basically 2 heat resistant rubber cups about 3" apart and sized for the pipe you are welding. One has a 1/8" port on the end to attach purging line to, other cup is solid. Both cups face the same direction which allows purging gas to vent one direction(otherwise without venting you will blow out your weld)(been there done that) the shielding gas besides removing oxygen from the backside of the weld acts as a supporting medium for the weld when internal pressure is right. Too little support and your weld will sag into the pipe, too much and it will raise on the surface. Extremely too much and it will blow out. Idealy you want enough support for the weld to remain flat, or ever so slightly raise the weld. this can be polished to the point that the weld dissappears. The gas cups are nice, but not a necessity. Your best friend is masking tape. Tape one end of your pipe closed, insert your purge line in the other end and seal it off. Now go back to the first sealed end and poke a small hole in the tape for a vent. I usually hit it either with my 1/16" tungsten in the torch or a piece of filler wire. Turn on the purging gas, take a couple minute break or longer depending on the size and length of the pipe. If you are not sure if it's purged long enough, hold a match near the purge vent hole. If it keeps burning, purge longer. OK... with the purge/support gas still on, turn on the gas to your torch. At this point everyone is going to ask"How much flow to each line?" OK... roughly 3 to 5cfh on the inner purge line then add another 8 to 10cfh or so to the torch. A lot of variables here. On 1/16" wall SS tubing I usually run around 35 amps, and use a back step freehand method  rotating the pipe with my free hand. If you see the weld sagging, bump up the internal gas, or make a smaller vent hole, if the weld puddle is lifting, backoff the flow or enlarge the hole. My methodology may not be presise, but with a little practice you will come up with some excellent welds.Like I said a lot of variables like torch size cup size, pipe size, amperage yada yada... It's going to take a little experimenting , another thing I'll toss out here is grinding your tungsten. I usually use a 1/16" 2% thoriated ground to a fine tapered point. When grinding that tungsten, use a dedicated grinder just for your tungsten (don't want to contaminate it) and grind the taper lengthwise, DON'T grind around the tungsten or your arc will wander on you. Some folks use a walking cup technique talked about on other threads. I've tried it, could not master it. Guess you can't teach an old dog new tricks. My hat is off to those who can do it, makes a fine weld. Well, that's the quick and dirty best of luck to you, and Practice, practice, practice..... It'll come ta yaOOPS, forgot to mention.... You want a tight fit up of your joint, and you won't need any filler wire.Last edited by chiptosser; 01-27-2010 at 11:30 AM.
Reply:Read through this thread and was just thinking that the work being performed sounds almost exactly like that done when guys build stainless headers.  Always purge out the inside of the header pipes with argon and tig to full penetration.  Make sure there isn't any oxidization on the inside, etc...Sounds like the "sanitary" welding may be a bit more specific since it's more focused on the quality of the interior weld line (being perfectly or near perfectly smooth) in order to avoid any pockets which could house bacterium, viruses, fungi, etc...You might try checking out some of the guys who do custom stainless headers though as it does sound to me like the process your referencing is pretty close to the same.--Wintermute"No man's knowledge here can go beyond his experience." - John Lockewww.improvised-engineering.comManufacturer Agnostic:Blood----------Sweat---------Tears----|------------------|----------------|----Lincoln Red, Miller Blue, Esab Yellow