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Welding stainless steel safely for brewing

Started by Ciaran, February 13, 2015, 03:42:56 PM

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Ciaran

February 13, 2015, 03:42:56 PM Last Edit: February 13, 2015, 04:04:36 PM by Ciaran
So might have a possibility of getting some stainless brewing equipment put together.  First thing on the shopping list is a hop spider.   However, knowing nothing about welding, is there anything that the welder needs to be aware of from a food safety point of view before he starts?

My vague list of requirements which might be completely off the mark, are


  • 300 series steel - thinking 302/304 guage steel is best for food safety?
  • 300 Micron steel mesh for the spider wall and floor (have heard this is right size for pellet hops which is mostly why it is required in the first place)
  • It will probably need to have a wide enough diameter for a decent hop utilization while being thin enough to fit in the centre of the immersion chiller during the last 15 minutes of the boil
  • A final worry is about what kind of welds are required and what kind of welding rod would be needed for food safety.

I've read this and understood maybe 30% of it :
http://morebeer.com/brewingtechniques/library/backissues/issue2.6/palmer.html

QuoteSilver brazing rod contains no lead, but some of the alloys contain cadmium, which is worse. Cadmium will cause severe heavy metal poisoning. The American Welding Society alloy designations are listed in Table III. Do not use the alloys containing cadmium. Look for rods that are made for food industry applications. The AWS BAg-5 is recommended for this purpose and is readily available from weld supply shops at about $15.00/oz (1/16-in. diameter, spooled).

Does AWS BAg-5 go by the same name in Europe?

DEMPSEY

Make sure to not have any nooks and crannies as the hop debris is a bitch to get out of those places :).
Dei miscendarum discipulus
Forgive us our Hangovers as we forgive those who hangover against us

Will_D

You will not find 302 as sheet or fittings.

Beware of 303 it has some Sulphor and even Selenium for machoinability.

The grades we use are either 304 or 316 both are food grade its just that 316 is ever so slightly higher spec (and 30% more in the Wonga department)

304 and 316 are WELDED either without a filler (autogenious welds - the metal just collapse together) or you use a filler of the same spec. So you buy (or tell the welder) to use 304 or 316 as appropriate.

The quoted reference:

"Silver brazing rod contains no lead, but some of the alloys contain cadmium, which is worse. Cadmium will cause severe heavy metal poisoning. The American Welding Society alloy designations are listed in Table III. Do not use the alloys containing cadmium. Look for rods that are made for food industry applications. The AWS BAg-5 is recommended for this purpose and is readily available from weld supply shops at about $15.00/oz (1/16-in. diameter, spooled)."

    refers to BRAZING which is a lower temperature process and you REALLY need to know what you are using as a lot of brazing/silver soldering rods contain toxic ingredients.

So find a good SS welder and its Simples!

HH Will
Remember: The Nationals are just round the corner - time to get brewing

Beerbuddha

I use a tig welder and 316 where possible.

The easy part is getting a tig welder, then you need argon gas from BOC.

It will be nearly impossible to to produce quality welds without some sort of 1 on 1 guidance.

Unless you are DIY enthusiast and will use the welder allot its gonna be a waste of cash V paying someone to do the work or just buying the parts ready made online.

There might be alternatives but in a brewery of any standard its Tig for stainless.
IBD Member

biertourist

February 16, 2015, 05:24:09 PM #4 Last Edit: February 16, 2015, 05:42:21 PM by biertourist
The learning and experience curve necessary to go from nothing to sanitary welds is INSANE.


Will is right you want 304 or 316 and really nothing else.  304 is actually just fine, 316 is more expensive AND much, much harder so if you screw it up and need to grind it down you're going to need pneumatic tools and a diamond dust grinding bit and you're going to need to spend forever grinding it back down. -This is the primary reason why I'd steer you towards 304.


TIG weld for sure without a doubt; NOT MIG (I can show you pictures of what MIG welds will look like -it looks like some sort of robotic bird took a liquid stainless steel crap on your vessel and then you stepped in it -that's after grinding the weld down for HOURS with a diamond bit; before that it just looked like robotic bird stainless crap) -you don't want the metal coming out of the head of the welder, you want a separate stick in your other hand ala TIG. -You also need the inert gas that the TIG will put off; you also need to back flush the backside of the weld with inert gas/ appropriate gas blends.

You will use different techniques depending upon what type of join / union you're making between the two pieces of metal, you need to prep the metal well, you want to probably build a dam behind the weld to hold the inert gas on the backside otherwise you'll spend a fortune on gas -if you don't do this the weld will "sugar" and have ugly dark pitting on the backside.  You then want to cleanup the weld after welding it with specialty chemicals or acids.

You need to dial-in the amperage for the particular application and thickness of the 2 pieces of stainless that you're welding together; if you don't go hot enough the weld won't penetrate to the backside and you have a real problem from a sanitation perspective (I can post a pic of what this looks like as I have this problem in my HLT) and if you go too hot you'll get too much metal and overheat the surrounding metal and warp it (I can show you pictures of this from my previous boil kettle; MASSIVE overheating and warping). -In some applications you want a heat sink to suck up the extra heat so that you don't warp the metal.



Even just the theoretical knowledge required to make a good looking properly sanitary weld in crazy, but you also need EXPERIENCE and some hours working with the welder and the type of welds that you'll do with the thickness of stainless that you're going to use to dial-in the welder and gas settings.  -You're looking for a "stack of dimes" looking weld and there's a particular technique to getting it that way but all the other things above have to already be perfect before technique even starts to matter.


It's stupid ridiculously complicated, BUT if you think you will ever open a professional brewery, it's a skill that will pay huge dividends if you can get enough practice to get good.  I'd recommend taking a class on stainless welding to start out and then getting lots of expensive practice at home on scrap pieces of stainless.  There's some great YouTube videos on techniques to practice and learn and there's some welding schools that show the techniques that they test on, too.  -Welding a 90 degree angle on a piece of say 2" - 3" stainless tubing above your head, seems to be a test that really weeds people out.

If you're looking for good work done on your homebrewery, I'd say to just hire it out; if you're looking to learn welding and be able to use the skills for a few decades, then go for it.

-You'll want an auto-dimming welding shield too otherwise I have no idea how you'd ever hope to know where you are on the piece.  -They're FAR, FAR cheaper than in year's past as long as you get one with a very small window.  There's a local shop that has small window auto dimming shields for $99 USD as their big Christmas special every year.  You'll also need to make sure the tungsten tip that sticks out the end of the tig welder "head" is the right length and that it's sharpened to a round find point -use a bench grinder and don't forget the safety goggles.  The welders with lots of experience just dial in the right amperage by listening for a sound that they say sounds like frying streaky bacon -there's no way to know what that actually means without experience, though.  You'll also want a good pair of welding gloves and you'll need something to hold the pieces that you're welding together that doesn't get in the way of welding. (The startup costs get pretty crazy once you factor in everything you actually need.)


(Silver solder is nice as you can just torch it back to a liquid state and get rid of it if you screw it up, but it's not going to stand up to as much physical force and requires a lot of surface area in contact between the two surfaces.)  -I'd say silver soldering is easily doable by the home enthusiast and lots of people have been proving this true.  Quality sanitary stainless welding -you're just not going to go from zero to sanitary weld the first time probably no matter how much you read and practice.

-Around here it's $45 - $60 per weld for a proper stainless weld.  I found a guy that charged $30 and it was like a small child did the weld; it was beyond awful; I have pictures I can link to if you want.

Having said all that, I'd still like to get one of the Chinese "3-in-1" TIG, MIG, plasma cutter welders to be able to play around with.  Plasma cutters make making your own stainless false bottoms STUPID fast and easy -we made mind that way and it was like a knife through butter. It literally took 100 seconds then maybe another 2 minutes on a bench grinder getting the edges nice and smooth.

Adam

Ciaran

Great replies guys.  Won't be doing the welding myself, it's a professional welder who will be doing it and should have all the best equipment for the job.  Just wasn't 100% sure of what would be best for food safety so thought I'd ask.  Sounds like 304/316 is the way to go with inert gas TIG welds.  Will post up some pics if it comes to fruition.  Thanks again!