[atomicjoe23]

Could anyone provide any general info on sanitary/food grade welding? I'm not exactly sure what I'm looking for. . .I will take anything from tips to requirements.

I am looking at TIG welding 304SS in a brewery application (anything from external repairs to new brewery piping and equipment). . .I completed a two-year ATA in Welding Technology and I have a little experience welding stainless steel (more experience with carbon steel) so I'm not a complete newb, but since I have no industry experience with food-grade welding I don't want to just assume the only things I need to worry about are proper filler metal selection and quality welds. I've been doing general welding (external brewery repair) and decorative (tasting room decorations) for them for a while, but there is an opportunity to expand. . .

Thanks for the help!!!

[Otto Nobedder]

Welcome Joe,

For sanitary piping, you won't usually be using filler metal. You'll be focusing on extremely precise fits that are autogenously welded. You simply butt them up, and fuse them with your TIG torch. There's an arcane art to this, to use the right heat for complete penetration, and not blow it out. Your finished weld will be "slightly" below the pipe's OD, which would be a no-no in any other craft.

This is an overview, from my having worked with sanitary pipers for Hershey Foods, and others. Someone with real experience will chime in within a few days, I'm sure.

Steve S

[Superiorwelding]

atomicjoe23,
Welcome to the forum! I will try to answer on the general food grade.Forgive me if I am saying things you know. I have two customers that bring me repairs and new fabrications. One requirement if all welds are to be smoothed completely with absolutely no holes, undercut or large scratches/sanding marks. One is a major milk manufacture, and they can't take the change on bacteria growing on even the smallest place. I will use the term "mirror polish" for lack of better term. I am not allowed to use any sort of die penetrant to check for leaks, only water or pressure where applicable. Everything I use on my food grade is absolutely dedicated to SS only. I use 316 brushes and all discs or scotch brite does not touch anything else. My grandpa does sanitary piping and he goes so far as to use a dedicated grinder for SS. His thought it he does not want to blow carbon out of the grinder from steel onto his SS. He even has some of his tools custom made out of SS. All his equipment is locked up in a toolbox so no one can cross contaminate it. I have all kinds of tricks and little pieces I use for SS, again dedicated.
I have done some sanitary piping runs that did require filler and we used 316L for that application. Purged with argon and used as little filler as necessary. As far as the autogenously welded joints, will let someone else give pointers on that one. I don't consider myself a expert on that topic.
-Jonathan

[Rick_H]

I work in the food industry and do all the sanitary welding... Lots of good tips posted above. I also have dedicated tool box, dedicated files, clamps, saws, grinders, brushes etc... Typically I am only using 316l no filler unless I am doing a repair that calls for the need.

Cutting and prep is critical, everything needs to be straight and square, back purged with Argon and welded full penetration no inclusions at all. Every welder is different but I use any where from 40-60 amps on .065" wall, 1/16" tungsten, #8 cup with a gas lens. I have been experimenting with pulse over 100pps, 75amps 45% peak, 25% background. Best to grab some scrap tubing and getting some practice, fittings are too expensive to waste. I also mirror polish and pickle my welds....

I'll purge anywhere from 3-10mins depending how long the run is, then when welding you look for a small dot in the middle of the weld pool some call this the devils eye at that point you know your getting full pen. Just takes practice and time to get your travel speed down especially when your not welding on a bench.

[atomicjoe23]

Thanks for all the tips guys. . .I wouldn't have guessed about the autogenous welds. . .what about using consumable butt weld inserts, like a consumable backing ring to make sure you've got a solid root pass???

[Mongol]

I have no experience with consumable inserts, but we didn't use any of them when I worked in semiconductor.

The most important part, as far as I'm concerned, is fit up. Since these are most likely going to be autogenous welds you'll need to make sure the pieces are faced properly and deburred. A good facer with a good blade will do both. Also, when facing, make sure the the chips don't scratch the inside; this can cause bacteria to be trapped, or something like that. And if anything is out of square there's a good chance you'll blow through even at low amperage.

When welding you're going to have to know when you've penetrated all the way through, as keyholing is a no-no. You'll notice the puddle kind of swirl which is basically the puddle resting on the argon. Maintain this throughout the weld and you should be good. It takes some getting used to.

[Bonanza]

Hi there everyone

I'm also looking at this area of welding and are wondering.. is it more common to wiggle the cup while resting it slightly or alternatively weld freehand around the pipe?

How can I pickup the technique easier for uniform looking welds should pulse be used ideally for this?

[sswelder]

hello. i have been welding sanitary pipe in the milk and yogurt industry for 3 + years now.
a couple pointers. 90% of the time we are using .065 wall tubing. 304 and 316 they weld very close to each other. 316 can be tricky at times. any way when setting up to weld start off with the welder set up. i use a miller maxstar 150 stl. works great very light portable and nothing to it. for 2.5 od .065 wall 304 i set my amps at 43 - 45 i use a number 7 cup with a screen (screen is a must) you can use cups from 5 to 10. the # 7 works well for all applications and tight positions. back to the welder. no pulse. hf start. with it set at 43amps. for the regulator you want a 2 stage for best results and constancy. other reg will work but can be difficult setting purge if doing many pipes because when you set your purge then turn the torch on the purge will drop and the the weld will sink ( No NO ) i set my purge by feel on my lips. if i had to guess it would be around 9 on the ball float in the regulator ( barely on ) for the torch i set it at 15. if set to high it can also push the puddle to sink dont want that. ( practice will get this perfect) ok to sum this up welder set at 43 to weld 2.5 od .065 argon is set to purge and set on torch. give it time to purge. and start you purge LOW. ( physically) position your purge plug lower then the weeper. its heavier than air. so you want the argon to push the air out. if done opposite will cause a pocket and the weld will be burnt on the inside. ( coli flower look ) when your ready to weld i start at the bottom and weld to the top then pull off in the same motion as im welding not to just pull straight up. this can cause a pin hole. (leak ) wire brush the start and finish of the weld very fast. then start immediately as the pipe will warp or even break a tack on the side not welded yet. start at the bottom again. but when you start you weld back over the welded part by a 1/4 in ward. then start. when you come to the top where your first weld ended you want to pass over it by at least 1/2 (this is were the wire brush helps keeps it clean and a beautiful pull off) then start moving gradually faster and move the tungsten to the edge off the weld. this will make a perfect pull off and 99 % of the time eliminate any possible leaks or misses on the inside. the pull of should be at least 1 inch long. until the weld it to a point then pull off to break the arc. now your done. once this is done a few times and you get the feel for the torch and you see how the puddle moves you can start to pay more attention the puddle it self. i do a 1 2 count move forward pre heat, back 1 2count ( penetrate) forward pre heat, back Penetrate 1 2 ......... when i move back to get penitration i look for the puddle to spin but most important off all is you will see a light grey in color halo ( half moon shape ) in front of you puddle when you see this its penetrating. i have noticed a spinning puddle but little to no pen and when the halo is at the very edge of the puddle 99.9 % is penetrated. it might take a few welds to see it but it will show up around the half way point to your second count. on each pass ( roll of dimes) walking the cup was mentioned this is a good technique to learn but in my experience its great for bench welding. once on a latter or hanging up side down on pipes bent in ways i never thought i could bend walking isnt the way to go. other may argue this so i say figure out what fits you then go with it. a comfortable position is a good weld.

[Bonanza]

Hi sswelder

Thanks for some great info and great pics!!