Application of harmonized EN standards in th creep regime (Drexl)

[XL83NL]

Im haveing a bit of struggle with the application of EN standards for pressure equipment (specifically EN 13445, EN 13480 and EN 1092) in the creep regime.
I'd like to check this with engineers here familiar with these EN-standards (Drexl?), hopefully some can enlighten me .

1) Where do EN-standards (like EN 131480) show where the creep regime begins for a certain material? Apart from EN 1092-1, annex G, I wasn't able to find other such info.

2) Both 13445 and 13480 (part 2 "Materials", Ch. 4.2.2) address requirements for T > 20 C;

A material shall only be used for pressure parts within the range of temperatures for which the material properties required by EN 13445-3 (or: EN 13480-3) are defined in the technical specification for the material. If the technical delivery condition does not contain the specific material values required for the allowable temperature TS the values required in EN 13445-3:2009 for the design shall be determined by linear interpolation between the two adjacent values

Most EN product-standards, e.g. EN 10216-5 for seamless pipe, EN 1092-1 for flanges, end up listing stress values at 600 C. Beyond that, acc. EN 13445-3/13480-3 Ch. 4.2.2, you're not allowed to go further.
This doesn't seem to stop most of our supplier to supply us with quotes for equipment with design temperatures way beyond what's listed in these EN-standards (T = 750 C). There must be some escape. For En 13445 this might be 13480-3 Clause 19, but I'm not sure on this as I don't know where the EN standards defines the onset of the creep regime for a certain material (EN 13445-3 para 3.8 and 5.1 don't supply such info).

Can someone enlighten where I'm wrong in terms of understanding EN-standards, or which part I didnt get?

Regards,
Hubert
_____________________________________

http://nl.linkedin.com/in/hubertvelten

 

[Drexl]

1) They don't. The design stress is limited by the time dependent stress if it is lower than the time independent stress. You can draw up the two as a function of temperature in excel for a specific material and see where they cross. EN 13480-3 ch 5 first sentence.

2) If the suppliers use standard EN materials outside their range I suspect that they must have a PMA for the range intended. I haven't ever seen this but don't work with that temperature range either. If you ask the supplier regarding this, please share how they have done it.

 

[XL83NL]

Hi Drexl, thanks for your valuable input. Guess I might not be that far offtrack with my thoughts after all.

1) rather strange that the code doesnt provide data on the onset of the creep regime, as at several other parts in the code it seems that it requires the designer to have this data at hand, since it may govern certain design aspects.
Ive made up such a graph for dual certified 800H/HT (1.4958/1.45959), since in the meantime ive found stress values (creep rupture strength) for T > 600 C in the annex of EN 10216-5, see my other topic in the piping section. When Im back at work ill upload the graph, it shows a strange peak around the point where no yield stresses are known (at 550 C and beyond), and only creep rupture. Obviously there's a flaw there due to lack of data.
Ill see if an interpretation to the code committee may provide more insight.

2) Im currently at this track, so ill keep u updated on any news the supplier returns.

I would appreciate it if u could connect to me on linkedin.

 

[XL83NL]

Drexl, find attached the chart/graph mentioned in my previous post

 

[OSIRIS7]

For what it is worth: I second Drexl's statements.