Liners with double roll lock seams vs. butt welds

Where have you seen liners with butt welds?

Ah, OK I am with you now. I will leave it to the metal guys here but it seems to me the welded seams have gotta be better. I know I am not too crazy about the "roll lock" on the two sections of black pipe on one of my stoves. I wish I had welded pipe for it. It just can't be as strong or airtight as welded it seems to me.

Heat-Fab is sort of the ultimate. I visited their factory (have to go back and get pics), but they have single welders that cost a million bucks! Electron beam and laser stuff - of course, they don't make flex.

My uninformed opinion on flex is that certain brands and processes have a longer history and therefore more moxie in my book. Ventinox being one of them - a patent and process used in Europe for a long time and then brought over here - the first of the flex liners - and .007, which is 40% thicker than .005.

Homesaver has been doing it also for a long time and had their problems early - and then fixed many of them! They are probably the biggest supplier of this stuff in the USA, and therefore they HAVE to get it right since tens of millions are at stake.

Someone asked earlier about liners in the field - chimney sweeps have reported replacing thin flex liners in oil and coal installations after 6-10 years.

When it comes to very heavy wall flex, I suspect they may not be much better because all that really matters is how thick the weakest link is - in other words, the middle of the seam or corrugations. Perhaps metal can enlighten us on my theory.....he's a metal engineer.

Yes, I would say that a properly welded seam beats the roll lock.

That Rhino pipe looks good - I suspect it is not made by Olympia since I don't think they have that kind of machinery or plant. It might een be European made!