[baer19d]

I'm new to TIG welding and I wan't to do some stainless welding with back purge. Does it matter what size defuser I use on the end of the hose, i.e .05 or 2 microns ,etc? Also, does it matter what a back purge block is made of? I know stainless and copper are good choices, but could I use aluminum or even an empty can like tuna, beer or soup?

Thank

[Otto Nobedder]

Welcome aboard!

I rarely use a diffuser of any kind; just a 1/4" line from the flow-meter to the purged area. When I do need a diffuser, I use a sintered bronze pipe vent in 1/8" NPT.

I've made custom purge boxes, and I've taped an aluminum foil tent over the back of the weld.

It's all purpose-specific.

We need more information to properly advise you.

Steve S

[exnailpounder]

Remember that argon is heavier than air so anything you are going to purge is akin to filling it with water until it runs out. I don't do much stainless but like Steve said, any diffuser is job specific. I have built a few nut I never use them.

[baer19d]

My current project is to weld some 1/2" couplers to a beer keg that I use for beer brewing. A foil tent taped to the inside will probably work great since the keg is contoured.

[MosquitoMoto]

I received a can of Solar Flux Type B in the post today.

Looking forward to seeing how this works with stainless. Mind you, my job is an exhaust, so having some glassy flux residue left inside is no big deal. I imagine that for a beer keg, back purging with argon would be the only way to go.


Kym

[Coldman]

My can of solar b arrived yesterday. We'll compare notes although I won't get to it till later next week.

[MosquitoMoto]

My can of solar b arrived yesterday. We'll compare notes although I won't get to it till later next week.

Did you score one of the $50 cans from eBay Oz as well? Seller from over in the west, I think. I'll probably also only get to weld with it come the weekend. I need some alcohol to mix with it, wondering what to use and where to get it. They reckon ethanol is best.

EDIT: I wonder if good old metho would do the job?

Kym

[exnailpounder]

My current project is to weld some 1/2" couplers to a beer keg that I use for beer brewing. A foil tent taped to the inside will probably work great since the keg is contoured.

Thats a coincidence. I weld kegs for homebrewers quite a bit. If you are welding on couplers you don't really need to purge. I weld them to the outside of the keg and then drill the hole after wards. You get discoloration inside the keg but no sugaring. Concentrate your heat on the thicker coupler and wash your puddle into the thinner keg material. Kegs are 18ga. so be careful on amps or you will have a mess right quick. Also, weld a little bit and stop, cool the metal with a damp rag to draw out the heat, repeat. If you have the top cut out then it won't hurt to make some sort of dam but I weld them alot without purging and haven't had any problems. Some guys dimple the keg to mount the fitting so they have molten metal exposed to air inside the ke. If you do it that way you do need to purge but I weld them to the outside and save my gas.

[Coldman]

Yes I got the $50 sand groper deal. I'm going to give metho a go for sure to start with. It's mostly ethanol anyway.

[MosquitoMoto]

Yes I got the $50 sand groper deal. I'm going to give metho a go for sure to start with. It's mostly ethanol anyway.

Nice.

If it works as well as the reviews say, I'll be ripping into my exhaust rebuild job pretty soon. My guinea pig job before I do the exhaust will be a little stainless garden trowel I 'accidentally' broke last weekend.


Kym

[Coldman]

Gonna read the msds first to see if there are any nasties in it.

[Rick_H]

From what I understand SF isn't food grade, as the residue can be tricky to get off.

Exnail is correct, however he is an experienced welder so the back purge may give you a little extra protection. I weld triclovers and other fittings in food stuff daily, I usually cut the hole to a perfect size then weld 100%pen, backpurged. I also use a thicker wall tri clover stand off fitting and cut my hole in the tank so it falls half way through the wall, weld the outside then fuse the inside and polish smooth.

[exnailpounder]

From what I understand SF isn't food grade, as the residue can be tricky to get off.

Exnail is correct, however he is an experienced welder so the back purge may give you a little extra protection. I weld triclovers and other fittings in food stuff daily, I usually cut the hole to a perfect size then weld 100%pen, backpurged. I also use a thicker wall tri clover stand off fitting and cut my hole in the tank so it falls half way through the wall, weld the outside then fuse the inside and polish smooth.

Rick, I agree that if the OP has the gas to back purge then, by all means, do it, it surely won't hurt anything. I have a bottle just for purging and depending on what fitting I am welding on, I sometimes will do a sanitary weld but I found out the easy way for couplers is just weld them on the outside and drill the hole after. Heat control is paramount because of the difference in thickness so if the OP is not really experienced , then blowing a hole in the keg is a definite possibility and he should purge.

[Coldman]

Agreed. If sanitary application sf is not suitable. I do a fair few flanged spools for glycol pump connections and also condensate drain pipework. SF has to be ideal for that if it works like promised.
I bought a can to try it out and see. If it works savings in time and purge gas are there.

[exnailpounder]

Agreed. If sanitary application sf is not suitable. I do a fair few flanged spools for glycol pump connections and also condensate drain pipework. SF has to be ideal for that if it works like promised.
I bought a can to try it out and see. If it works savings in time and purge gas are there.

There are some vids on Youtube about SF and from what I have heard it really works. Mr.Tig did a vid about it. I ould think for your application, it would be good to go. Let us know. I haven't found a need for it yet but ya never know.

[Coldman]

Msds says contains silica and silica dioxide, chemicals known to cause cancer in California. Thank the Lord I live in oz.

[exnailpounder]

Msds says contains silica and silica dioxide, chemicals known to cause cancer in California. Thank the Lord I live in oz.

Everything causes cancer in California! The worlds largest degenerate looney bin. I remember years back they said components of gasoline caused cancer so they had special covers for their gas nozzles to prevent anything from splashing back on the user. I cant imagine how much gas I have swallowed over the years siphoning. I never noticed any ill effects, I was told my right testicle SHOULD weigh 40 pounds at my age!

[Coldman]

Hey I remember those nozzles. I remember having a laugh at the time.

[baer19d]

My current project is to weld some 1/2" couplers to a beer keg that I use for beer brewing. A foil tent taped to the inside will probably work great since the keg is contoured.

Thats a coincidence. I weld kegs for homebrewers quite a bit. If you are welding on couplers you don't really need to purge. I weld them to the outside of the keg and then drill the hole after wards. You get discoloration inside the keg but no sugaring. Concentrate your heat on the thicker coupler and wash your puddle into the thinner keg material. Kegs are 18ga. so be careful on amps or you will have a mess right quick. Also, weld a little bit and stop, cool the metal with a damp rag to draw out the heat, repeat. If you have the top cut out then it won't hurt to make some sort of dam but I weld them alot without purging and haven't had any problems. Some guys dimple the keg to mount the fitting so they have molten metal exposed to air inside the ke. If you do it that way you do need to purge but I weld them to the outside and save my gas.

I welded it today. Overall I'm very satisfied with the results. I did back purge by taping aluminum foil on the inside and it turned out nice, way better than all the other fittings that I had welded on before I had a TIG machine. I'm having a hard time envisioning your technique. Are you not getting full penetration on the keg and that's why there's no sugaring?

[exnailpounder]

Baer, I am getting good penetration, not FULL penetration that is why there is no sugaring inside the keg. With the mrthod I use, if I fully penetrated, I would be blowing thru the wall of the keg. The easiest way to explain it is that when you weld two pieces of any metal together, say a filet, you don't penetrate all the way through the metal to the other side. Your goal is good penetration for a strong weld and that translates to heat/amp control. When I weld a fitting onto a keg wall, I am penetrating the keg wall but not all the way thru. There IS discoloration and maybe a bit of sagging but since the material was not thoroughly penetrated, there was no molten metal exposed to oxygen. Now iy you drilled a hole and/or dimpled the keg to the size of the fitting and welded it that way, you WOULD have molten metal on the backside of the wall, exposed to air and sugaring. On keg with the top cut out I will go inside the keg with a grinder and a fine flap and "polish" away the discoloration. I do work for some people who do ...ahem..."other" things with kegs and the top doesn't get cut out so no access to polish the keg wall but I inspect the wall with a mirror and I have never had sugaring.

[exnailpounder]

Here is an example. On top of the keg is a 2" fill port that was dimpled. A hole was drilled into the keg and it was a sanitary weld. The ring around the spear fitting was surface welded but I did purge it just to be sure as it was 1/4" thick being welded to 18ga. The fittings on the keg wall were surface mounted and not purged. I don't know if that explains it very well but I will say that if you can purge, then you should , it won't hurt anything, I just hate wasting good argon on something I know doesn't require it.

[Superiorwelding]

A question that comes to my mind is do you really need to back purge this weld? Meaning can you just use copper or brass and back it up and save some gas? Do you have a pic of what you are welding? Of course, I love making back purges and trailing shields so I will take any excuse I can to make them.
-Jonathan

[ldbtx]

Hey I remember those nozzles. I remember having a laugh at the time.

Word going around California at the time was that the guy who owned the company that invented and made the vapor recovery nozzles was kin to Jerry "Moonbeam" Brown, the then (and current) governor of CA.

[ex framie]

Yes I got the $50 sand groper deal. I'm going to give metho a go for sure to start with. It's mostly ethanol anyway.

Nice.

If it works as well as the reviews say, I'll be ripping into my exhaust rebuild job pretty soon. My guinea pig job before I do the exhaust will be a little stainless garden trowel I 'accidentally' broke last weekend.


Kym

Well between you 2 buggers and Mr tig, guess where I spent my last $50?
Got his last can as well.
I also have a stainless exhaust to play with, it was rattling at idle from the rear muffler on the 4x4, now its stopped rattling and now whistles loudly at 1500 rpm.
I was wondering how I was going to purge a muffler full of diesel soot, now I wont have to try.

[Coldman]