IMO , stay away from the mig , tig only
When I weld stainless, I only use straight argon, tight gap, and purge
Remember stainless expands 4 times more than carbon steel , expansion in the way of long hangers
Good luck:thumbsup: :thumbsup: :thumbsup: :thumbsup:

Got this on mind, 321 SS bellows w interior sleeve ( directional ) these will compress , stretch , handle vibration and heat so they can be used close to or at collector. Like everything else it has its limitations but I'm not sending this thing to the moon:D

A stainless steel single or multiply bellows designed to accommodate pipe growth due to thermal conditions in engine exhaust piping. Series EFB bellows are also constructed to absorb vibration normally associated with engines and generators. Bellows are series 300 stainless steel and can incorporate internal flow liners where necessary. The light weight bellows is highly flexible and will protect the low pressure exhaust piping. End connections can be standard commercial 150# ANSI drilling, beveled weld ends, or special flange styles such as Caterpillar, Cummins, or Detroit Diesel. Exhaust bellows expansion joints are made to order, according to the pipe motion expected, temperature, velocity, vibration, and end connections.

Not to jump on your thread but ....
That's actually a awesome idea, I was thinkin the same thing.
Well actually I was talkin with a union brother and we came up with it together, we use these in the oil and gas industry coming of headers, usually 18+ " in diameter , these expansion bellows.
But your suggestion , who would supply those, you have a contact with 300 series stainless in a 3 " scenario

Yeah I found some 3" 321 SS With sleeve as mentioned. If interested let me get my hands on them and I'll post up results

Just one source...there are many others.


http://www.stainlessworks.net/produc...ex-joints.html

This one had a good selection too:
http://vibrantperformance.com/catalo...php?cPath=1022

flex joints are readily available just about anywhere but the bellows in mind ( picture below ) are just a bit harder to find locally. since they are normally about $100 a pop I want to get to see it before I buy.

I already have the flex joints in there but those well not stretch or compress as much they're more for vibration. these bellows are more durable and suitable for this application.
http://i1232.photobucket.com/albums/...kv11/photo.jpg

some pictures of the progress
http://i1232.photobucket.com/albums/.../photo2-16.jpg
http://i1232.photobucket.com/albums/.../photo4-15.jpghttp://i1232.photobucket.com/albums/...1/photo5-7.jpg
these are the ones I'm looking to replace since they're right at the collector..

What you have will do the job as they also help with expansion and vibration issues....


Read the description on this "flex" joint and they say that the bellows style creates turbulence.... and I'd agree. Whether it's critical for your application is a different issue.


3" versions.

http://www.treadstoneperformance.com...Coupler+Bellow


Vibrant does NOT carry flex bellows in 3"

These guys supply the BELLOWS style with an internal slip joint for smoothness....



http://www.spdexhaust.com/pdfs/AccPDFs/Bellows.pdf