ASME B31.1 types of stresses 1

[pegus]

Good day,

I just started researching about how to validate a pipe line using ASME B31.1. But I have a couple of questions regarding how to compare those stresses with the allowable stress.
I see that there are 3 types of stresses: Sustained, displacement and occasional, I am trying to use FEA to compute the stresses on the FEA program (ANSYS), I created an expression on the program so it computes the stress with the ASME equations.
My questions is:
1.-What stress should I compare against the allowable strength? (or maybe it is the combined stress)

If you can recommend a book or a course to understand these concepts better, I will appreciate it.

Thanks in advance,

P.P.

 

[DriveMeNuts]

I think you are referring to loads, not stresses.
Sustained is for non-relenting loads like gravity and pressure.
Displacement is for relenting loads such as thermal expansion. Where if the component is allowed to expand, then it will relent any stresses.
Occasional loads are for earthquakes or occasional pressure tests or process operations.

The definitions and tables at the back of part 5 of ASME VIII Div 2 provide some insight into what you are trying to learn.

 

[KevinNZ]

Pegus

Are you using FEA with bean elements for each pipe run or shell elements to model the surface of the pipe. B31.1 assumes you are calculating the moments in the pipe using beam elements.

There are many commercial pipe stress programmes that work with beam elements and work out the flexibilities and SIFs of fittings and do all the code stress checks. Some you can use some in demo mode for free.

Modelling pipe with shell (or brick) elements requires the rules in part 5 of ASME VIII Div 2. Good luck with thank!