ASME 31.8 ch VIII temperature derating factor

I am trying to understand how Caesar implements the ASME 31.8 ch VIII code. When I enter different temperatures, the different temperature derating factors don't seem to be taken into account in the computation of the allowable hoop stress but the SH value is modified taking the temperature derating factor into account.

My load case is : L1=W+P1+T1+F1

Does someone knows what might be happening?
Thanks

For B31.8 VIII, the allowable stress for the hoop consideration is F1*Sy, where F1 comes from the table in Chapter VIII.

I am still unclear of the answer Mr. Ay per below:

A) ASME B31.8-2010 (June 1 2010) page 104 equation (1):
Sh <= F1*S*T.... T = temparature per Table 841.1.8-1

B) C2Quick guide(November 2010) page 4-7:
S hoop < F1 * Sy * T
T = temp. derating factor per Table 841.116A (I am unable to see table 841.116A since it must be from before 2010 B31.8)

C) C2Quick guide (November 2010) page 3-2 gives dates for ANSI B31.8 & Chapter VIII as(2007) November 30, 2007.

It appears above in C) and in the program results output that caesar may not follow the equations in A) and B) if they were different in 2007 B31.8

It also appears that B) matches A) but caesar does not.

Please help.

When you work under B31.8 code, the template shows (proposes) T (derating factor) value corresponding to the temperature declared, instead to show the "classical" SH fields as when you consider other piping codes.
You enter also Fac- construction design factor- in that template, SMSY, etc.

When you work under B31.8 Ch VIII, the template maintain "SH" fields, but shows (proposes) there SMSY*T, I cannot explain why this was the choice. [I understand this is the yield stress at operating temperature, I do not understand why is not the same approach for both B31.8 and B31.8 ch VIII templates]
Buy anyway Caesar docs get the clarification: under B31.8 Chapter VIII Code Stresses explanations, please see the Note: The product of S and T (i.e. the yield stress at operating temperature) is required in SH of the CAESAR II Input."
You enter also Fac-Hoop stress design factor, etc.

Important is the result. Have you checked the correctness of the final result of Sh limit?

Best regards.

I would help you only understanding the question.
And the question is......?

As reference, I extracted the following from docs.

Best regards.



ASME B31.8-2007

Chapter VIII Offshore Gas Transmission
A842 STRENGTH CONSIDERATIONS
A842.2 Strength Considerations During Operations
A842.22 Design Against Yielding
A842.221 Hoop Stress

[page 97]
Sh ≤ F1ST
S = specified minimum yield strength, psi
Sh = hoop stress, psi
T = temperature derating factor from Table 841.116A
F1 = hoop stress design factor from Table A842.22


[page 33]
Table 841.116A Temperature Derating Factor, T, for Steel Pipe
Temperature, °F.........Temperature Derating Factor, T
250 or less............1.000
300.....................0.967
350.....................0.933
400.....................0.900
450.....................0.867

[page 98]
Table A842.22 Design Factors for Offshore
Pipelines, Platform Piping, and Pipeline Risers
........................F1...
........................Hoop Stress...
Location
Pipeline.................0.72...
Platform piping.......0.50...
and risers


==============================================================


ASME B31.8-2010
Chapter VIII
Offshore Gas Transmission
A842 STRENGTH CONSIDERATIONS
A842.2 Strength Considerations During Operations
A842.2.2 Design Against Yielding.
(a) Hoop Stress


[page 104]
Sh ≤ F1ST
F1 = hoop stress design factor from Table A842.2.2-1
S = specified minimum yield strength, psi (MPa)
Sh = hoop stress, psi (MPa)
T = temperature derating factor from Table 841.1.8-1

[page 104]
Table A842.2.2-1 Design Factors for Offshore
Pipelines, Platform Piping, and Pipeline Risers
........................F1...
........................Hoop Stress...
Location
Pipeline.................0.72...
Platform piping.......0.50...
and risers


[page 40]
Table 841.1.8-1 Temperature Derating Factor, T, for Steel Pipe
................................Temperature Derating
Temperature, °F (°C)............Factor, T
250 (121) or less..............1.000
300 (149).......................0.967
350 (177).......................0.933
400 (204).......................0.900
450 (232).......................0.867



=============================================================
Quick Reference Guide

B31.8 Chapter VIII

Hoop Stress: Sh ≤ F1 S T (OPE, SUS, OCC)
[...]

Where:
S = Specified Minimum Yield Strength
F1= Hoop Stress Design Factor (0.50 or 0.72, see Table A842.22 of the B31.8 Code)
T= Temperature Derating Factor (see Table 841.116A of the B31.8 Code)

Note: The product of S and T (i.e. the yield stress at operating temperature) is required in SH of the CAESAR II Input.

I suggest as following.

For B31.8 VIII, the allowable stress for the hoop consideration is F1*(Sy*T), where F1 and T come from the tables in Code.
The product of Sy and T (i.e. the yield stress at operating temperature) is required in "SH" of the CAESAR II Input. F1 factor is required in "Fac" of the CAESAR II Input.

Best regards.

I entered in the SH field the product of Sy and T as explained in the guide but Caesar II doesn't take it into account in his allowable hoop stress. It keeps taking Sy and not SH. That is what I don't understand

Just to understand...would you give some numerical data?
Which are the values you entered in:
SH field
Sy field
Fac field
Temperature field

And the "allowable stress" that Caesar reports?

Sy= 60045
SH=0.967*60045=58106
Temperature=301

allowable stress outputed by Caesar=30022.5

I assume F1=0.5
I cannot confirm "your" allowable stress.

Maybe is a problem of soft version.
In my case, it seems that soft correctly implemented also a condition related to 90%SMYS...but I cannot speculate what is happening in your version, maybe is correct and somehow you forced the input.

I'm sure Intergraph can help you after knowing more details.

Best regards.

B31.8 VIII has three Code equations and three allowables, whereas the output report only has room for one Code stress and one allowable. So c2 determines the ratio from all three pairs, and puts the governing (highest ratio) values of Code stress and allowable in the report. The allowable shown in the report could correspond to the hoop stress, the longitudinal stress, or the combined (equivalent) stress.

If you can't figure this out, open a Support Request (SR) on eCustomer, specify the exact version of c2 you're using and attach your job file (.c2).