Stainless Sanitary welds

[Photopilot]

I have a guy that owes me and will be doing some welding for me. I am looking to make a few keggle like products. My guy knows how to weld, does it for a living, but is not too familiar with sanitary methods. I have been doing some reading on it, but hoping to get some advice from people who know the specifics of keggle making. In particular how do you create a purge dam?

 

[Rbeckett]

Essentially what you are doing with a sanitary weld is trapping the argon on both sides of the weld and preventing sugaring and martensite formation. This allow the chromium to migrate through the entire weld and maintain the stainless character of the base metals. Sanitary is the name given to preserving the quality of the base metal after welding. You should also passivate the wekd with the proper pickling agent to ensure that the metal will not rust of flake. PM me if you need more info.

Wheelchair Bob

 

[SpikeBrewing]

Has your friend TIG welded thin stainless steel before? Reason I ask is I've seen and heard too many times about a "friend" or "shop" that can weld but then end up butchering the keg or kettle.

If you and he are confident in his skills then you'll need to make a cup on the back side with an inlet for Argon. We have a pneumatic setup but a simple aluminum foil cup and some tape will work. If his welder has a pulse setting use that. It'll keep the heat low and reduce/eliminate warping.

As for passivization, it's over rated for our application. If you keep the heat low you won't affect the area enough to cause any loss in anti-corrosion properties.

 

[kickflip_mj]

I prefer to fusion weld (no filler) when doing sanitary. Its really tricky and takes a lot of practice. I either weld from the inside (I suck at butting up a fitting), or pull the fitting out and weld it that way.

 

[Photopilot]

I kind of have the details figured as to why, it's the how, I was not sure of. He has welded kegs for others but did not do it sanitary style.

I was thinking of buying a 2" nipple and cap forming it to the side of the keg propping into place, puttying the gaps. But if aluminum works, how about forming an aluminum can (should be a bit easier to work with) taping it into place then using a tire inflation needle to fill with argon before welding externally?

 

[kickflip_mj]

their are two ways..

One you get a seperate argon tank with regulator

two- Get a y splitter to back gas.

Use a soda can and tape it into place with HVAC tape , put a small hole on one side and the hose going in in another hole, turn the psi low and start welding at the opposite end.

 

[SpikeBrewing]

^^^ pretty much that

 

[mattd2]

...then using a tire inflation needle to fill with argon before welding externally?

Just to reinforce it - you want to be continuosly purging the cup with argon, not just filling it once and thats it.

 

[dmfa200]

Just to reinforce it - you want to be continuosly purging the cup with argon, not just filling it once and thats it.

Yes.

You should also take some steel wool roll it into a small ball and tape it to the end of your purge hose. This will diffuse the Argon as it comes out of the hose. If you don't the Argon will flow straight out of the hose and create turbulence inside the purge box, can, or whatever you use.
Since you will be removing a small volume of Oxygen, the purge gas only needs to be set at 10 to 20 on the flow meter.

You will also want to stick some steel wool in the end of the fitting you are welding in. That will allow the Argon to vent out yet still maintain shielding of the weld.

Wait for a few minutes too, once you start the flow of back gas. Give the Argon time to push out the Oxygen. The longer the better.

Make sure you tape(masking tape works very well) to seal the cup and where the hose enters the cup very well. Don't leave any cracks for the Argon to seep out, or create a vacuum sucking in more Oxygen.

If you have any other questions feel free to ask, I've welding for 23 years.
I've done xray quality welding in chemical plants on all types of metals especially stainless for close to 15. I also weld for some of the local breweries.

 

[dmfa200]

As for passivization, it's over rated for our application. If you keep the heat low you won't affect the area enough to cause any loss in anti-corrosion properties.

Spike is right.

If you know that you are using uncontaminated tools and consumables while fabricating stainless steel, passivating is not necessary.

Don't drink the cool-aid.

I'd like to explain more why you want to keep the "heat low". No disrespect Spike.
What Spike means is to use only enough amperage to get proper fusion.
A rule of thumb is to use 1 amp per thousands(.001) of metal thickness.
For example, a kegs wall is about .050" thick so set your machine to 50 amps.
My experience with welding on kegs says that 50 amps is a little too many. One amp per thousand is just a general starting point.

By keeping the heat low you minimize the size of the "heat affected zone" (this is the region where stainless steels grain structure is vulnerable)and the length of time the HAZ has to change it's crystalline structure.
"Carbide precipitation" is the term.

 

[hugenjapan]

I weld brewing systems for a living. Just make a purge cup out of stainless and put a splitter on your argon tank so you can have two flowmeters. Turn your welding torch's flowmeter to 20 and your purge cup to 15. If you tape your purge cup on then also tape the other side of the fitting but make sure you have a small vent hole. If you don't have a vent hole your fitting will fill up with argon and when you weld it it will blow out. I wouldn't suggest putting steel wool in your purge because of cross contamination. You should also use filler if you start getting undercut in your weld otherwise you'll be fine just fusing it. After you weld it I would suggest using a pickling paste to take off the colour of the weld. I can't remember what we use at work (that's a labourers job. Lol)

 

[SpikeBrewing]

I agree that steel wool can cause cross contamination and really won't help the weld. Pickling paste is expensive and pretty nasty stuff. For the cost involved in removing the color it's probably not worth it. We're looking at picking up one of these, Electrochemical Weld Cleaner, to clean up our welds. More than likely $4k is out of your budget to clean a couple welds

 

[orangehero]

I've seen DIY ones using a carbon fiber brush.

http://www.ferromit.com/Electro polishing.html

 

[hugenjapan]

I would use pickling paste on every weld just cause you never know what you could have got in that weld.. It kind if just ensures the weld is clean or at least cleaner

 

[SpikeBrewing]

If you have access to it, sure. But I wouldn't lead someone to think they need to spend $100 on some pickling paste for a few welds on a brew kettle. Just my .02

 

[mattd2]

If you have access to it, sure. But I wouldn't lead someone to think they need to spend $100 on some pickling paste for a few welds on a brew kettle. Just my .02

Yep, if it is just colour you are worried about just lanish it out. If you have put too much heat into it then reach for the pcikling paste.

 

[hugenjapan]

I guess so. We use pickling paste on everything at work but I guess that's cause we have to. Www.specific.net

 

[dmfa200]

I weld brewing systems for a living. Just make a purge cup out of stainless and put a splitter on your argon tank so you can have two flowmeters. Turn your welding torch's flowmeter to 20 and your purge cup to 15. If you tape your purge cup on then also tape the other side of the fitting but make sure you have a small vent hole. If you don't have a vent hole your fitting will fill up with argon and when you weld it it will blow out. I wouldn't suggest putting steel wool in your purge because of cross contamination. You should also use filler if you start getting undercut in your weld otherwise you'll be fine just fusing it. After you weld it I would suggest using a pickling paste to take off the colour of the weld. I can't remember what we use at work (that's a labourers job. Lol)

The reason I say to use steel wool is because tape gets so hot that the glue breaks down and leaves glue residue on the fitting. It's a pain in the ass to remove.

Do you realize what pickling paste costs? Not to mention that it can cause severe burns, and blindness. You have to take every safety precaution while using pickling paste.



Just found this product

http://www.ebay.com/itm/WALTER-54-A...ectrolyte-100ml-Tube-/130858065805#vi-content

It claims to be a safer alternative, but I have never used it so can't offer any criticisms.

We use

http://www.avestafinishing.com/products/pickling-paste/paste-101.aspx

where I work. I think it's about $80 for a half gallon.

Oh yeah, they do make stainless steel wool. I guess I should have been more specific.

 

[fork]

Passivation can be done cheaply and easily with citric acid which you can get for a couple dollars at a home brew shop.