#65052 - 12/11/15 04:17 AM
Issue with (MAX) of (EXP) cases?
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Member
Registered: 04/05/07
Posts: 21
Loc: France
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Hi,
On the exemple at the bottom (CAESAR 7.00.01.1600 Build 141003) I perform the following load cases: L1 WW+HP+H HYD L2 W+T1+P1+H OPE L3 W+T2+P1+H OPE L4 W+T3+P1+H OPE L5 W+T4+P1+H OPE L6 W+T5+P1+H OPE L7 W+P1+H SUS L8 L2-L7 EXP L9 L3-L7 EXP L10 L4-L7 EXP L11 L5-L1 L7 EXP L12 L6-L7 EXP L13 L8,L9,L10,L11,L12 EXP
Options: L2-L7(EXP) Keep Disp/Force/Stress Algebraic L3-L7(EXP) Keep Disp/Force/Stress Algebraic L4-L7(EXP) Keep Disp/Force/Stress Algebraic L5-L7(EXP) Keep Disp/Force/Stress Algebraic L6-L7(EXP) Keep Disp/Force/Stress Algebraic L8,L9,L10,L11,L12(EXP) Keep Disp/Force/Stress Max
The allowable of the MAX of EXP cases (L13) is equal to 1.5Sh instead of 1.25SC+0.25Sh as for the others cases (L8 to L12). Did I miss something or is there a issue?
**** RESULTS:
8(EXP) 10 38.74 192.86 13 38.74 192.86 B31.3 9(EXP) 38.74 192.86 38.74 192.86 B31.3 10(EXP) 38.74 192.86 38.74 192.86 B31.3 11(EXP) 38.74 192.86 38.74 192.86 B31.3 12(EXP) 38.74 192.86 38.74 192.86 B31.3 13(EXP) 38.74 122.90 38.74 122.90 B31.3
*********************************************** Input Echo
PIPE DATA ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- From 10 To 15 DX= 3,107.000 mm B31.3 (2012) Cycle Max Switch = ON App.P Sy/St Switch = ON Sc= 138 MPa Sh1= 82 MPa Sh2= 82 MPa Sh3= 82 MPa Sh4= 82 MPa Sh5= 82 MPa Sh6= 138 MPa Sh7= 138 MPa Sh8= 138 MPa Sh9= 138 MPa Sy= 207 MPa Fatigue Curve (1)= 1 Cycles Dia= 863.600 mm. Wall= 52.370 mm. Cor= 1.0000 mm. Wl Factor= 1.000 GENERAL T1= 495 C T2= 495 C T3= 495 C T4= 495 C T5= 495 C P1= 86.7000 bar P2= 69.0000 bar PHyd= 219.0000 bar Mat= (185)A335 P22 E= 212,596 MPa EH1= 174,931 MPa EH2= 174,931 MPa EH3= 174,931 MPa EH4= 174,931 MPa EH5= 174,931 MPa EH6= 212,596 MPa EH7= 212,596 MPa EH8= 212,596 MPa EH9= 212,596 MPa v = .292 Pipe Den=7833.4116211 kg/m3 Insul Thk= 130.000 mm. Insul Den= 135.0000000 kg/m3 Clad Thk= .700 mm. Clad Den=8000.0000000 kg/m3 BEND at "TO" end Radius= 1,295.400 mm. (LONG) Bend Angle= 90.000 Angle/Node @1= 45.00 14 Angle/Node @2= .00 13 RESTRAINTS Node 10 ANC ALLOWABLE STRESSES ----------------------------------------------------------------------------- From 15 To 20 DY= 5,740.000 mm RESTRAINTS Node 20 X
Edited by Rdlm (12/11/15 04:18 AM)
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#65055 - 12/11/15 09:47 AM
Re: Issue with (MAX) of (EXP) cases?
[Re: Rdlm]
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Member
Registered: 12/13/99
Posts: 6226
Loc: Houston, Texas, USA
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If would be helpful to have the job. Can you open a Support Request on Smart Support and attach the file please?
_________________________
Regards, Richard Ay - Consultant
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#65069 - 12/14/15 12:00 AM
Re: Issue with (MAX) of (EXP) cases?
[Re: Rdlm]
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Member
Registered: 06/18/12
Posts: 345
Loc: India
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Richard Ay,
The issue is not related with the Particular system.
I checked in CAESAR-II 5.3.1, 2013R1 and CAESAR-II 7.00 VERSION
MY OBSERVATIONS:
1. CAESAR-II 5.3.1 the allowables of all EXP case(Alg, Scalar, Max etc.,) is same.
2. From CAESAR-II 2013 R1 version up to LATEST 7.00, the allowable value is reduced for load case EXP(MAX)only as mentioned by Rdml
3.This reduction of the allowables happens for the higher temperature only.
Is this related to f (Stress range reduction factor) for EXP case - COMBINATION METHOD "MAX"??
Edited by durga (12/14/15 12:00 AM)
_________________________
Thanks, Durga
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#65080 - 12/14/15 09:56 AM
Re: Issue with (MAX) of (EXP) cases?
[Re: Rdlm]
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Member
Registered: 12/13/99
Posts: 6226
Loc: Houston, Texas, USA
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This really doesn't make sense, so I want to see a job file which illustrates what is said above.
_________________________
Regards, Richard Ay - Consultant
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#65094 - 12/15/15 09:30 AM
Re: Issue with (MAX) of (EXP) cases?
[Re: Rdlm]
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Member
Registered: 12/14/99
Posts: 2382
Loc: Houston, TX, USA
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Your MAX combination will display the highest stress in the group but these individual stresses in the group may have differing allowable limits. I do not see the value in using the MAX combination to compare with a single allowable limit.
It appears that, to be conservative, CAESAR II uses the smallest values of Sc & Sh to set the "limit" for this combination so Sc=Sh=82 MPa and 1.25 Sc + 0.25 Sh = 1.5(82).
_________________________
Dave Diehl
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#65103 - 12/15/15 10:24 PM
Re: Issue with (MAX) of (EXP) cases?
[Re: Rdlm]
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Member
Registered: 06/18/12
Posts: 345
Loc: India
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Dave Diehl,
Thanks for your reply.
Its surprising that in Combination MAX; CAESAR-II uses Sc = Sh;
If CAESAR-II takes (min of Sh) and (Min of Sc) from the group is practical, same as CAESAR-II 5.3.1 does.
In older version CAESAR-II 5.3.1 it doesnt take Sc=Sh. What is the reason for changing this COMBINATION MAX allowable in CAESAR-II 6.0?
on what basis from CAEASR-II version 6.00 considers like this?
_________________________
Thanks, Durga
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#65105 - 12/15/15 11:41 PM
Re: Issue with (MAX) of (EXP) cases?
[Re: Dave Diehl]
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Member
Registered: 12/18/09
Posts: 13
Loc: Republic of Korea
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Edited by yongwon (12/15/15 11:56 PM)
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#65114 - 12/16/15 09:12 AM
Re: Issue with (MAX) of (EXP) cases?
[Re: Rdlm]
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Member
Registered: 12/14/99
Posts: 2382
Loc: Houston, TX, USA
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I use the MAX combination method for structural response such as restraint loads and pipe position - these have no specific, load case specific, limits. So I do not have experience using this for stress in any version of CAESAR II.
_________________________
Dave Diehl
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#65315 - 01/14/16 09:54 AM
Re: Issue with (MAX) of (EXP) cases?
[Re: Rdlm]
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Member
Registered: 04/05/07
Posts: 21
Loc: France
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I got many (EXP) cases and I just want which one gaves the maximum stress. I don't understand the answer of Smartsupport which says: "Customer should use a combination method of Algebraic for determination of expansion stresses. However, having said that, when you have a range between two temperatures (not between a temperature and ambient) then CAESAR II uses the highest Sh as Sc and the lower Sh as the Sh value in the equation. As Sc =Sh 1.25 Sc + 0.25 Sh = 1.25Sh+0.25Sh = 1.5 Sh. This is more conservative approach."
1) I indeed use ALG for individual stress. I just want the MAX of theses individual EXP stresses. 2) Where do I speak about RANGE? I want the MAX. 3) It is not my trouble but where the ASME B31.3 says to use Sc = Sh? Why the range is between two positive temperature, I will never install my pipes at 495°C... (SAFETY FIRST, no?) 4) I don't want something conservative but something correct
Edited by Rdlm (01/14/16 09:56 AM)
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#65318 - 01/15/16 09:21 AM
Re: Issue with (MAX) of (EXP) cases?
[Re: Rdlm]
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Member
Registered: 12/13/99
Posts: 6226
Loc: Houston, Texas, USA
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According to B31.3 Paragraph 302.3.5 the definitions of Sc and Sh are:
Sc = basic allowable stress at minimum metal temperature expected during the displacement cycle under analysis.
Sh = basic allowable stress6 at maximum metal temperature expected during the displacement cycle under analysis.
A "displacement cycle" is a "range". For any two temperatures (including ambient), Sh is the allowable from the hottest of the two temperatures and Sc is the allowable from the coldest of the two temperatures.
The Code doesn't say that Sc = Sh, rather the Code wants the highest and lowest allowable stresses in the range being considered. If you happen to setup a load case where T1 and T2 are the same, then it just happens that Sc = Sh.
Consider the following temperatures:
T1 = 200 T2 = 400 T3 = -50
Then:
EXP1 could be: T1 - ambient, (Sh from T1, Sc from ambient) EXP2 could be: T2 - ambient, (Sh from T2, Sc from ambient) EXP3 could be: T3 - ambient, (Sh from ambient, Sc from T3) EXP4 could be: T2 - T1, (Sh from T2, Sc from T1) EXP5 could be: T1 - T3, (Sh from T1, Sc from T3) EXP6 could be: T2 - T3, (Sh from T2, Sc from T3)
This is the intent of the Code. This is not conservative, but rather it is complete.
_________________________
Regards, Richard Ay - Consultant
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#65320 - 01/18/16 06:23 AM
Re: Issue with (MAX) of (EXP) cases?
[Re: Rdlm]
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Member
Registered: 04/05/07
Posts: 21
Loc: France
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Thank you Richard,
With your explanation I understand how to solve my trouble: If I add an (EXP) case with T=amb, I got the result I want.
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