Hello Stressers,

I have come across this one requirement from a client.

"Integrally reinforced branch welding fittings that abut the outside surface of the run wall, in sizes NPS 4 (100 mm) and larger, are not permitted under any of the following conditions:

a)The d/D ratio (branch NPS/run NPS) exceeds 0.8
b)The run piping wall thickness is less than standard schedule
c)The run piping wall thickness is less than 0.75 in. (19 mm) where outside diameter exceeds 36 in. (900 mm)"

What's the possible reason behind this requirement? Is this due to high "stress intensification factor or stress concentration factor" at the branch/header junction? or is this due to fabrication reasons where it's hard to fabricate this type of fitting at the given size and thickness range? When we say "integrally reinforced branch welding fittings", I'm thinking "weldolet" is one of them?

Your opinion is greatly appreciated.

Cheers!!!

I'd say a combination of factors:

• It's harder to cut a perfect hole that wraps around so much of the pipe.
• In some sizes, you're removing so much of the pipe that you'd have to make up for with so little space on the attachment that it makes for a "hard spot" on the line, whose stresses won't be quantified with beam theory.
• Preferred vendor doesn't offer such an option.
• No vendor offers such an option.

Thanks Michael for your opinion. Maybe the client has some past experience (similar to what you've mention) for this type of situation so they write about it in their spec.

Cheers,

To some degree, most users of CAESAR have changed the SIF calculation method without enough thought given as to whether or not it's dimensionally possible.

And most pipers have said that because the engineer said it was possible, that it must be so.

And most checkers have said surely they looked at this in the model, and therefore, that it must be so.

And then the end user is left with an in-field retrofit.

After enough of these, they'll make adjustments to their specifications.

You're right Michael. It's not all about theory & calculations. Some practical aspects of the design need to be considered also.

Cheers,