The design temperature should be used only for the pressure thickness calculation. For the thermal stress analysis the operating temperature (or the maximum operating) should be used. Which ever is the temperature that the system will experience for most of the time of its service life cycles.
In CAESAR input spreadsheet the actual temperature should be entered not the relative one with respect to the ambient. The ambient temperature is defined in the settings, which by default is set to 21 deg C. If the connected equipment for which the thermal displacement is to be computed is modeled, then that thermal displacement is computed from the ambient to the temperature input in the spreadsheet. However if input is made as a displacement then the calculated figure from the ambient to temperature is to be entered.
The total thermal expansion values given in Appendix C-1 is taken from 70 deg F. For the below 70 deg F values are negative. Therefore the algebraic difference will give the sum of the 2 values for ambient temperatures below 70 deg F.
Sajit
-----Original Message-----
From: balakrishnan [mailto:balakrishnan@ksrc.com.kw]
Sent: Tuesday, December 16, 2003 11:34 AM
To: PipingDesign@yahoogroups.com
Subject: [Man.Distr]Re: [PipingDesign] Re: Stress calculation
Friends,
I wish to get your valuable opinion on the following.
I am using CAESAR II for Stress analysis.
In CAESAR II , Temperature Input is required on the Spreadsheet .
As per my perception this is OPERATING Temperature
and
NOT DESIGN Temperature.
Further, I need some help in interpreting the Code requirements of Temperature Input in CAESAR II.
ASME B31.3 Clause 319.3.1 says:
"Thermal expansion Data
(a) Values of stress Range.
Values of thermal displacements to be used
in determining Total displacement Strains
for computing the Stress Range shall be determined from
Appendix C
as the ALGEBRAIC DIFFERENCE between the Value at Maximum Metal Temperature
and that at the Minimum Metal Temperature
for the thermal Cycle under analysis.
(b) Values for Reactions
Values of Thermal displacements to be used in determining
the Total displacement Strains
for computation of Reactions on Supports and Connected Equipment shall be
determined as the ALGEBRAIC DIFFERENCE between the Value at Maximum (or
Minimum ) Temperature
for the thermal Cycle under analysis and the Value at the Temperature
expected during installation."
From the above 2 sections (a) and (b),
it seems that we should Input the Algebraic Diffrence between
the Maximum Operating Temperature
and
the Temperature (Ambient) during Installation
for CAESAR II Analysis.
Regards,
Balakrishnan
> I also can help you with CAESAR II calculations.
> How can you send me the isometrics?
>
> Dragos
>
>
>
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[Non-text portions of this message have been removed] Received on Tue Dec 16 07:33:00 2003
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