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#73850 - 10/01/19 09:48 AM allowable stress range
pooria1978 Offline
Member

Registered: 02/25/08
Posts: 240
Loc: Netherlands
Hi

I see a difference in the calculation of the allowable limit for (EXP) case between when it is the subtract of 2 (OPE) case and when it is a subtract of a (OPE) and (SUS).
can anyone explain?

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#73852 - 10/01/19 10:21 AM Re: allowable stress range [Re: pooria1978]
anubis512 Offline
Member

Registered: 08/24/18
Posts: 80
Loc: USA
I believe you're saying you see a difference between the Expansion results when its a difference between two OPE cases and an OPE/SUS case?

OPE 1 = Max Temp
OPE 2 = Min Temp
SUS = As-Installed
EXP 1 = OPE 1 - OPE 2 (Max dT)
EXP 2 = OPE 1 - SUS (Max T - Sustained)

If you're doing an Expansion case between two OPE cases, it's typically maximum temperature - minimum temperature conditions. This would be like a steam line shutting down during winter or something like that.

The normal Expansion case between an OPE and SUS case is typically the minimum or maximum temperature - as installed (sustained) condition.

By default Caesar II assumes an installed temperature of 70F. So yes, the results between these two expansion cases will potentially be very different.

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#73855 - 10/02/19 06:10 AM Re: allowable stress range [Re: anubis512]
pooria1978 Offline
Member

Registered: 02/25/08
Posts: 240
Loc: Netherlands
Hi Anubis512

thanks for your reply, I think you perhaps did not read my question carefully; I wonder why the "allowable limits" of those two cases are different.
my system works in 100/-46 C with a material which has Sh of 207 MPa at both aforementioned temperatures so, when I calculate the Sa as per 302.3.5 of B31.3:

Sa= f(1.25x207+0.25x207) (f=1) so Sa=310 MPa

this limit should be considered for all cases including upper temp. to lower temp. range case and (Ope-Sus) case but, CII gives me a different value.

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#73863 - 10/02/19 10:54 AM Re: allowable stress range [Re: pooria1978]
Richard Ay Offline
Member

Registered: 12/13/99
Posts: 5990
Loc: Houston, Texas, USA
No not exactly. Take a look at the definition of Sc and Sh in the Code. Sc is the allowable at the minimum metal temperature expected during the cycle under analysis.
Sh is the allowable at the maximum metal temperature expected during the cycle under analysis.

As explained above, the Sa can be different for different temperature ranges.
_________________________
Regards,
Richard Ay
Hexagon PPM (CAS)
[img]https://hexagonppm.com/-/media/images/hexagon/global/logos/Hexagon%20PPM%20Logo [/img]

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#73864 - 10/03/19 01:16 AM Re: allowable stress range [Re: Richard Ay]
pooria1978 Offline
Member

Registered: 02/25/08
Posts: 240
Loc: Netherlands
Thanks Richard for the reply,

the Sh's (or Sc if you will) are the same from -75C to 120C in the material database for the material I am using so, I do not think if CII goes from 4C to max. Temp. or goes from -46 to max. temp. Sc will differ.


Edited by pooria1978 (10/03/19 02:27 AM)

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#73890 - 10/07/19 12:59 AM Re: allowable stress range [Re: pooria1978]
pooria1978 Offline
Member

Registered: 02/25/08
Posts: 240
Loc: Netherlands
up

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#73904 - 10/09/19 07:36 AM Re: allowable stress range [Re: pooria1978]
Richard Ay Offline
Member

Registered: 12/13/99
Posts: 5990
Loc: Houston, Texas, USA
Please open a Support Request and send in the job so we can look at it.
_________________________
Regards,
Richard Ay
Hexagon PPM (CAS)
[img]https://hexagonppm.com/-/media/images/hexagon/global/logos/Hexagon%20PPM%20Logo [/img]

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