EN 13445 external pressure calculations

[JackSam]

Hi,
I'm a little confused by the requirements of EN 13445 paragraphs 8.4.2 and 8.4.3. For shells made in non austenitic steel the nominal elastic limit is given by R_p0.2/T but for austenitic steel it's the same value divided by 1.25.
Could anyone help with an explanation as to why the nominal elastic limit for austenitic materials are 80% less than the equivalent non-austenitic material please?
Additionally for duplex/super duplex materials should I consider them as austenitic or non-austenitic?
Thanks in advance

 

[OSIRIS7]

Might it have something to do about the difference in the 0,2% yield strength for CS vs 1% yield strength for SS?

 

[JackSam]

Thanks for the response and apologies for not replying sooner.
I don't think so as EN 13445 paragraphs 8.4.2 and 8.4.3 refer to R_p0.2T for both CS and SS. SS seems to be taking a hit and I don't understand why.

 

[OSIRIS7]

Okay, I presumed it was about allowable stresses for internal pressure, but this is about external.

I can not help you there. The Dutch Rules for Pressure Vessels do not make a distinction.