Sanitary and alike tube welders, please read and help!

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Hey y’all, first post here. I posted on Reddit but figured I may get more help here. Sorry if this ends up kind of long. I’m wondering what people who work with sanitary/brewery/etc tubing do for prep/cleaning/tacking/purging/etc?Just curious because at my shop we can’t have any colouring inside our tubing aside from the slightest straw. Most times I have no problem, but sometimes I get colour no matter how well I seal the piece. Even if I do four full pen tacks and 4 lighter ones between. Today is one of those days unfortunately. Is humidity a problem or moisture in the argon? We just use regular argon, no high purity gas. I tested the argon straight out the reg and it sat at 20ppm. Last time I checked in the winter it was around 3ppm so that has me concerned. Our air tools consistently blast moisture out when using them and we have to drain the compressor multiple times daily to give you an idea. Is it possible there’s moisture in the material itself that’s being evaporated during the weld process?Is the anything you guys could suggest? Or even outlining your guys process from prep to finish would be helpful. If you’d like me to add more details about what I do, just let me know.Thanks if you followed through my mess of a post.
Reply:Welcome to the forum,, You are getting oxygen from somewhere,, I worked with guys that welded aircraft engine parts,, with no color allowed,,They welded inside a "Glove box",,It looked like a sandblast cabinet, purged with some gas,, the parts came out beautiful.You are gonna have to track down where the oxygen is getting to the weld zone from, it is getting in,, somehow.
Reply:Yea that’s be nice. My boss would **** if we tried to talk then into purge booths. We use rotators a bunch too so that would be a pain. I’ve think I’ve basically checked everything I can think of that can cause leakage. As I said sometimes there’s no colour and sometimes there’s is, even if it’s an identical setup. Perhaps I’ll just have to put like 8 full pen racks on the tube just to see if it’s just the joint opening up a tad mid weld. But I think about that and how there’s a positive purge pressure so how would it pull oxygen in? So many variables, haha.
Reply:Without more details it is hard to comment. But we purge 8 times volume, then trickle gas in during welding. Also we introduce the argon at the closest end to the weld, and allow some small opening at the other end as to not allow pressure buildup. As we weld the joints we make our way across the pipe to the escape end. The welded joints are already sealed.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Originally Posted by shovelonWithout more details it is hard to comment. But we purge 8 times volume, then trickle gas in during welding. Also we introduce the argon at the closest end to the weld, and allow some small opening at the other end as to not allow pressure buildup. As we weld the joints we make our way across the pipe to the escape end. The welded joints are already sealed.
Reply:Originally Posted by JtrnkzI can provide as much info as you need but basically everything you said is what I do. The only part that has me stumped is purging 8x the volume. Can you go into detail on that for me? I usually just set it to like 15-20cfh to start and then drop it down when I'm going to weld.As of right now I always have a bleed at the highest point(or points if need be), and everything taped off with basic masking tape. Maybe the tape breaths too much, I don't know. I mentioned above that maybe I just need to put more tacks, but sometimes they suck to weld through for some reason.
Reply:You didn’t mention diameter, length of run, or number of joints being fabricated. We use manufacturer foam insert plugs for argon on small tube diameter to 4”. On larger tube we make round cardboard cutouts and use masking or the blue painters tape to attach hose and cardboard. Blue painters tape is wrapped over unweeded joints. Are you sure you are getting enough of a purge ? Here’s basic info that may help,https://www.mcaa.org/ncpwb/wp-conten...-PurgeTips.pdfSent from my iPhone using Tapatalk
Reply:If you think that you have O2 at higher than you can tolerate in the Argon bottles you might be able to buy an in-line filter or trap. I’ve looked at gas traps for water contamination. Switching from gas bottles to liquid argon tanks might help too. The liquid should have less contamination, in theory.  Depending on how much argon you’re using it might be less expensive too. The disadvantage is spiders with gas hoses running all over the place from the centrally located liquid argon tanks. That and the tanks are always. Venting some argon, so they’ll run empty eventually, whether you’re using argon or not.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:You say your setups are identical but they are obviously not, you just haven't found the difference(s)!You might try looking outside of the weld area. Do you have a fan running, an ac/heat register nearby, a garage door nearby?The slightest change in ambient airflow can cause the changes you mention.
Reply:Originally Posted by shovelon8 times volume means that if you can visualize the internal volume of your tube or pipe assembly to cubic feet, then flow 8 times that internal volume. So if you think internal volume might be 1 cubic foot, then flow 8 cubic feet to dilute the air to an insignificant amount. Set your flowmeter to say 24 cubic feet for 20 minutes, then reduce to say 10 cubic feet flow to maintain inert gas and weld away. You could flow faster but you might blow out your purge dams. If you have a 1/4 cubic foot internal volume then flow 24 cfh for 5 minutes then reduce to maintain inert gas flow.Like I said I like to push the air downstream of my first welds. Also I don't purge downhill as the argon is heavier and air likes to rise.
Reply:Originally Posted by BD1You didn’t mention diameter, length of run, or number of joints being fabricated. We use manufacturer foam insert plugs for argon on small tube diameter to 4”. On larger tube we make round cardboard cutouts and use masking or the blue painters tape to attach hose and cardboard. Blue painters tape is wrapped over unweeded joints. Are you sure you are getting enough of a purge ? Here’s basic info that may help,https://www.mcaa.org/ncpwb/wp-conten...-PurgeTips.pdfSent from my iPhone using Tapatalk
Reply:Originally Posted by rexcormackYou say your setups are identical but they are obviously not, you just haven't found the difference(s)!You might try looking outside of the weld area. Do you have a fan running, an ac/heat register nearby, a garage door nearby?The slightest change in ambient airflow can cause the changes you mention.
Reply:"Just curious because at my shop we can’t have any colouring inside our tubing aside from the slightest straw. Most times I have no problem, but sometimes I get colour no matter how well I seal the piece. Even if I do four full pen tacks and 4 lighter ones between. Today is one of those days unfortunately."How long do you post purge inside the tubing? Had that problem many years ago. Mostly 1" tube for milk. Would sometimes be shiny then others times coloured or even black. I do a routine now of hang up the torch, take off my helmet, then gloves. Then turn gas off last. Always remember gas last, nothing worse then coming back after lunch to an empty bottle! Seems to give just the right amount of time for the weld to drop below 200 F. A few seconds can make all the difference. Do a test with a couple of welds may explain why sometime you are good and other times not, just by a few seconds difference.
Reply:I alot of good info has been posted, I would add use a high temp tape instead of masking, something like kapton or powdercoat tape, it isn't that expensive.Amazon linkRichardWest coast of Florida
Reply:Originally Posted by LtBaddI alot of good info has been posted, I would add use a high temp tape instead of masking, something like kapton or powdercoat tape, it isn't that expensive.Amazon link
Reply:So this is from today. 2” tube with 8 tacks purged down to 10ppm for much longer then required. This is why I’m thinking humidity is causing a problem because I’ve never had dark areas right next to the weld before. Usually you can read the puddle via swirling etc and this weld puddle was kind of inactive so to speak. I’ll also attach a photo of how basically all my previous welds used to come out, just so people don’t think I’m just incompetent haha.
Reply:I would think of post purge time. The weld itself has no colour, it cooled to below 200 while purge was on. Beside the weld had residue heat when argon shut off. But usually that has a more bluish or gold colour. Or possible argon turbulence while flowing by the weld. Hence the brown colour. How big is you vent letting the purge out? Perhaps too big causing a large low pressure argon flow, smaller would keep the are flooded with slight pressure.  Have had that on the torch end when a slight breeze blows on the argon. There are purge kits that have rubber seals close to each side of the weld so that contained purge area is much smaller.   such as -https://www.intercon1978.com/interpurge-products/complete-purging-units/purge-kits/?matchtype=b&network=g&device=c&keyword=&campaign=  656390289&adgroup=33647354859&gclid=EAIaIQobChMIqe  309Puk8gIVRfTjBx2JzAmLEAAYAiAAEgIRt_D_BwE Have used ones like these for years, doing straight runs up to 150ft in 20ft lengths of pipe. Would take a lot of argon to flood 150ft of 3" pipe. The 1" pipe I do now, purge goes in 20ft from weld and vent cap on far end of pipe have done up to 200ft. Give good pre-purge to flood the pipe with argon, the good post purge until pipe cooled. Post a couple of pictures of the purge setup.Last edited by robocow; 3 Weeks Ago at 06:28 PM.Reason: add picture
Reply:In the first picture, it seems as though your weld is sucked inside the pipe quite a bit. What amps are you running on 2"? If your running hot, that will make your post purge timer a lot longer and your haz will stay hot. So 2" tube,How long?How much purge time?How many amps and approx time to complete weld?How long post purge?How much gas flow pre, during, and post weld?If you have a pencil sized exit hole for 10 cfm, that not good. Also a .035 filler wire hole on 25 cfm also isnt good.Sent from my SM-G960U using Tapatalk
Reply:Originally Posted by robocowI would think of post purge time. The weld itself has no colour, it cooled to below 200 while purge was on...
Reply:Take a piece of pipe and put a not tight but not loose piece of painter's tape on the end. Plug the other end and turn the purge on. Turn in to 5 cfm. Now the tape will bulge out a little as the pressure cant escape. Now tap in the tape with your finger, it should bulge right back out. Now poke a small hole in the end. Say 1/16. Niw keep tapping on the tape. At some point the pressure will almost equalize so either the tape will not bulge out or just slightly bulge out. Your just too small for 5 cfm.Now crank it up to 10 cfm and do it again, putting another hole in the end. I like multiple small holes over 1 big hole as a big hole can rip too wide. Filler wire makes great pokers.Now do it at 15 cfm, 20 cfm. As long as the tape is not bulging out, you have a good purge (assuming it's not too low).If the tape is bulging out, your second weld will end up bulging out for sure.Edit, also remember that if you have a small hole, and 20 joints to weld up, you may need to make a larger hole as you keep welding as the small gaps are being filled.Sent from my SM-G960U using TapatalkLast edited by Country Metals; 3 Weeks Ago at 09:08 PM.
Reply:Originally Posted by Country MetalsIn the first picture, it seems as though...
Reply:Originally Posted by Country MetalsTake a piece of pipe and put a not...
Reply:There is a flow check tool available to check the gas flow rugh5 at the cup. I have one and use it often.  A dial regulator doesn5 always flow what you think. I use a double flow meter and switch between them occasionally just to mak3 sure my rate is what I want.They are about $6 on eBay. I also use it when mig eeldingByronLast edited by bentwings; 2 Weeks Ago at 08:12 PM.