Hi FEA specialist, I'm trying to o 2

[harith07]

Hi to all FEA specialists,
I'm trying to obtain SIF values for custom-fab Y-laterals (for a flare line), to be inserted in an AutoPipe model.
Was advised that the easiest way is to use Nozzle Pro as we have licensed access to it.

Results of SIF came out to be:

Source, Inplane, Outplane,
FEA, 1.73, 3.24
B31.3, 2.74, 3.43
B31.1, 3.47, 3.47
WRC 329, 2.24, 2.34

Question: Which set of SIF values should I use?

Thanks

 

[1503-44]

Being a flare line, is it not a B31.3 design? If so, you use B31.3 values.

Reality used to affect the way we thought. Now we somehow believe that what we think affects reality.

 

[TGS4]

I would have used the FEA values. That's sort of the point of performing the NozzlePro analysis.

 

[1503-44]

FEA-in looks low compared to B values and designer may not even know which code he's using.
Designer is responsible for determining SIF values. Designer is not me.

Reality used to affect the way we thought. Now we somehow believe that what we think affects reality.

 

[LittleInch]

Try the B31.3 version and see what happens.

If you're just over allowable then you have room to manouvre due to the FEA model giving you a lower figure.

If you're miles away then maybe a re-design.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

Exactly. I think it would be better to say you have a fully compliant B31.3 SIF component, And nothing wrong with using the higher values, especially if its not going into mass production.

Reality used to affect the way we thought. Now we somehow believe that what we think affects reality.

 

[TGS4]

Be careful of the D/t ratio. The B31.3 values may be outside the applicability limits. I have seen this often in large diameter flare lines.

 

[hacksaw]

The B31 SIV will be conservative in a particular range of services, your FEA is based on how you've modeled the weld attachments and corrosion issues FEA does not include.

Even if you have perfect fabrication, erring on the safe side is a good idea.