Welding the ball valve directly?

I'm trying to accomplish two things. Reduce the number of stainless fittings to buy and keep the ball valve from sticking out from the keg too far.

What if I grind the hex shape off of one end of the valve and have it welded directly into the keg. Can teflon seals handle weld temps?

Isn't the purpose of teflon tape to lubricate the threads such that you can torque the fitting so that the threads do the sealing?

I didn't think that the tape acted as the seal.

Sorry I wasn't clear... Most stainless ball valves use a teflon ring at the ball to body junction. If I have it welded directly to the keg, it could overheat it I guess. There will be no teflon tape here if I do this.

I would say probably not. The entire valve might warp as well.

Right (duh). There has to be a technique for this as I imagine that type of thing would happen alot.

Why not use a nipple instead of a coupler.

The hex part may actually unscrew for a better chance at success (weld this right to the tank and screw the ball body on after) , but you still risk warpage.

What are you planning on doing if/when the ball valve should fail?

Yeah, I already know it's a bad idea. If the seal went bad, I'd have to find an identical valve and change the guts out.

I never liked the idea of putting the nipple right into the wall because it leaves the threads exposed to damage..in the rare chance you had the valve off of course.

Jam a plug on it when the valve is off. To a certain degree you can also fix a nipple with a standard die (or an adjustable die like in threading machines).

I've never had the valve off mine in 2 years and if I did I don't think I'd do anything that could damage the tread.

I've never understood why people us couplers. You need more parts and it increases the size and cost.

Here are a couple ways ways to mount the valve as close to the keg as possible,
Use a male pipe to tubing fitting, threads on outside of keg tube compression inside
Buy a 3 piece valve, grind hex portion with threads flush with flange, cut heads off bolts and weld into modified flange, weld modified flange to keg and reassemble valve.
For the weldless approach use a tubingXMale pipe bulkhead fitting with washers and o ring with pipe threads outside keg.

I like my valve close to the keg too. On mine I just welded a close nipple on the keg. If I were to do what you say I would take the valve apart and weld it on or if thats not possible for some reason I would wrap it in a cold wet rag and weld it on. It can be done. From time to time I have to weld a fixture about 1/2" from plastic inserts and have not melted one yet.
On the other side of the coin having a valve too close to the keg if your not careful can ruin the valve.( Ex:melt the the valve with the burner) But then you carefully grind it off and weld another valve on.