threadolet vs half coupling

Thread-O-Lets BAD?

Good and Bad of welding

It Really Really Hurts to have a failure. Makes you more humble... and smarter. How is this possible?!? I can weld as good as the next guy. I have years of experience. There are a million things I have learned in the trenches. Stringer passes are better than one weave pass. Clean everything between passes. Pre Heat, Inter-Pass, and Post Heat temperatures... yes actually are important. But sometimes you are wrong... maybe even the whole industry is wrong.
Here is what I learned:
Just because they hand you a typical fitting and tell you to weld it to a typical looking pipe, doesn't mean your weld will be a success.
Temperature control is a huge issue!! Rapid cooling, weld speed, filler rod size are all important issues.

When welding fittings on Stainless Steel Chill Pipe

Thread-O-Let joint type - 2:1 depth to face ratio
Rapid cooling during a weld
Lots of weld passes / Small Filler Rod
Fast welding speed
Concave weld shape

Half Coupling joint type - .5:1 depth to face ratio
(make sure your fitting is coped to match the pipe)
Less Passes / Bigger Filler Rod
Convex weld shape
Clean between passes
Adequate Fill on Stop crater

Excellent video on the subject
Carbon Steel Crystal Structure

This article really nails it.
(this is the same information given to me by a local SCWI about the subject, confirming my research)

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