31.3 Formulas

[SteveMcQ]

Hello,
I have been tasked with doing a quick guesstimate/gut feel check of some piping using provided loads. I have a load table for sustained loads and occasional loads and need to evaluate sustained, occasional, and stress range due to expansion. I am encountering some good tips but I am perplexed over the exclusion of a torsion component in most formulas. It appears, on the surface, that torsion is not always accounted for. Is this the case?

 

[BigInch]

Many things are not always accounted for. The design code is a minimum requirement and it is up to the engineer of record to decide what actually needs to be included or excluded at any given time. If torsional stresses are considerable and the engineer of record suspects that they could be a controlling factor in the design, even the code does not require that they be included, he must satisfy himself and supposedly his client, that the torsional stresses are safe to carry without further checking and it doesn't matter what the code says you have to check or not, as long as you can back up the fact that you and your client are satisfied that strtesses are within the code's allowables. If you can do that with a simple "hail Mary", or it requires a couple of runs on Caesar, or a full blown FE analysis, that's what you gotta do.

If it ain't broke, don't fix it. If it's not safe ... make it that way.

 

[stanier]

BigInch is coreect in what he says. ASME B31.3 and other codes are NOT design guides. Codes are no substitute for first principle engineering.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[BigInch]

Left out the IF, "even IF the code does not require that they be included,"

If it ain't broke, don't fix it. If it's not safe ... make it that way.