problem due to have more than one sustain load case

Hi

I am using CAESARII VER.5 , ,I have observed that when we define two sustain load cases ( one is used for hydrotest),stress ratio in load case L7 which is expansion load case and should be independent from load case L4, will be affected by L4, it means that when P2=1.5 P1 (hydrotest pressure) the maximum stress ration in L7 will be changed .

CAESARII VER.5 will use the maximum stress ration from both sustain load cases.

1- W+P1+T1
2- W+P1+T2
3- W+P1
4- W+P2 ( WILL BE USED FOR HYDROTEST)
5- L1-L3
6- L2-L3
7- L1-L2

Please let me know what is the problem , since I have checked the same case by VER.4.5 but there was no problem.

regards

There is no problem. If you have muliple SUStained cases, c2 takes the highest SL value for use in determining the EXPansion allowable. Any other behavior would be reckless.

Don't call case 4 SUS, use HYD instead.

Dear Richard

Thanks for reply , but I want to know why Caesar uses the highest SL, from sustain caeses in calculating expansion stresses?

In case of Hydrotest SL will be more due to higer longitudinal pressure stress and wate wieght ( more bending moment ) , is that correct??

Which method shall be used to check hydrotest , Sustain load case or Hydrotest , ( B31.3)??? since I used to define a sustain load case ( 1.5 P1) and ZERO corrosion allowance.

Please advise me .

Regards

SL is not used in computing the expansion stress, it is used in computing the expansion allowable: Sa = f(1.25Sh + 1.25Sc - SL). The higher SL, the lower your Sa value.

You should define your hydrotest case as HYD. c2 will assume the pipe is filled with water (hence the use of "WW" in the load case), springs are locked (rigid), non-corroded, and in the case of B31.3 an allowable of 0.9Sy.

Richard

What if Liberal stress check is off , then there will be no SL to be deducted ?

Thanks for your attention .

Shk

Yes, that is correct. However, the EXPansion allowable will then be computed as: Sa = f(1.25Sc + 0.25Sh). This equation always produces a lower allowable than the one sited above (unless of course Sl > Sh, which means your SUStained case failed).

HYD load case assumes one more - no insulation.

Yes that is true - sort of. Version 4.50 did include the hydrotest weight - and people complained. So in Version 5.00 c2 ignores the insulation weight for the HYD case - and different people complained. So, in Version 5.10 there will be a configuration switch so it will be up to you as to how insulation is handled in the hydrotest case.

but there is no Sy in material data base.my caesarii is ver4.5.
in B31.1,the allowable is 0.9Sy.as per 102.3.3.
in B31.3,the allowable is Sy,as per 345.2.1.

Appendix 1

• Hydrostatic Test
Case1 (HYD) = WW+HP+F1
• Operating plus PSV Relief Load
Case2 (OPE) = W1+D1+T1+P1+F1+F2
Case3 (OPE) = W1+D2+T2+P1+F1+F2
• Sustained Case
Case4 (SUS) = W+P1+F1
• Sustained plus Wind
Case5 (OCC) = W+P1+F1+WIN1
Case6 (OCC) = W+P1+F1+ WIN2
• Operating plus Wind
Case7 (OPE) = W1+D1+T1+P1+F1+WIN1
Case8 (OPE) = W1+D1+T1+P1+F1+WIN2
• Thermal Case
Case9 (EXP) = Case2 – Case4
Case10 (EXP) = Case3 – Case4

Appendix 2

• Hydrostatic Test
Case1 (HYD) = WW+HP
• Operating Case
Case2 (OPE) = W1+D1+T1+P1+F1
Case3 (OPE) = W1+T2+P1+F1
• Sustained Case
Case4 (SUS) = W+P1
• Sustained plus Wind
Case5 (OCC) = W+P1+WIN1
Case6 (OCC) = W+P1+ WIN2
• Operating plus Wind
Case7 (OPE) = W1+D1+T1+P1+F1+WIN1
Case8 (OPE) = W1+D1+T1+P1+F1+WIN2
• Thermal Case
Case9 (EXP) = Case2 – Case4
Case10 (EXP) = Case3 – Case4

from the above two case the load F1 uses in both cases but the second case do not include the F1 in the Hydrostatic Test,Sustained Case.why?..i want some idea about those two case(only based on the load F1)..normally the load is to be consider in Hydrostatic Test and Sustained Case(if may wrong).please give the solution..

You can't answer this question unless you know what "F1" and "F2" represent. For example, if "F1" is some sort of thrust load you're incoprorating, then it probably shouldn't be considered in the hydrotest case.

Look the value up and type it in.

"The higher SL, the lower your Sa value"
"Yes, that is correct. However, the EXPansion allowable will then be computed as: Sa = f(1.25Sc + 0.25Sh). This equation always produces a lower allowable than the one sited above (unless of course Sl > Sh, which means your SUStained case failed)".

Mr,Richard you said that CAESAR II is use the higher SL value so the Sa value will be lower in expansion case, so why CAESAR II use the Sa= f(1.25Sc + 0.25Sh) - SL as a default ?? Isn't it will be a higher value of Sa compare to Sa= f(1.25Sc + 0.25Sh) when liberal stress value check is off ?? please correct me if i'm wrong.

Regards

Dylan

If you turn off the "liberal allowable", it doesn't matter what SL is, it won't be considered.

Yes "Sa = f(1.25Sh + 1.25Sc - SL)" produces a higher value than "Sa= f(1.25Sc + 0.25Sh)". So we default to the "liberal allowable" because the Codes allow it and your system has a better chance of passing the EXP case. However, if you setup more than one SUS case, we use the highest "SL" value. Anything else would be "reckless".

A simple clarification...

Liberal Allowable is a CAESAR II term, not a Code term.

Relatively speaking, this equation is liberal compared to the other but it's a good Code equation. By all rights, we should call the other equation Conservative but we don't. For many years the "conservative" allowable limit was generally used for two reasons 1) it's simpler and 2) it can be used to check system flexibility before supports are located.