Hello everyone,

I have the following load cases:

L1: W+D1+T1+P1 OPE ( THE HOT OPERATION LOAD SET )
L2: W+D2+T2+P1 OPE ( THE COLD OPERATION LOAD SET )
L3: W+P1 SUS ( SUSTAIN LOAD )
L4: L1-L3 EXP ( EXPANSION IN HOT OPERATION )
L5: L2-L3 EXP ( EXPANSION IN COLD OPERATION )
L6: L1-L2 EXP (DISPLACEMENT STRESS RANGE FOR EXPANSION STRESS CALCULATION)

So, I have some doubts.

B31.3 says that I have to calculate the "displacement stress range" to ensure that the stresses are not above the acceptable 0.8 SA.

- First: The Case 6 represent correctly the case for the displacement stress range?
- Second: If so, how caesar calculate this? I have to put something in case 6 to CAESAR understand that in this case the stresses cannot exceed permissible 0.8 SA?

Thank you very much my friends.

Regards,

Saulo Cunha

PS:

ASME B31.3

Severe Cyclic Conditions: conditions applying to specific piping components or joints in which SE computed in accordance with para. 319.4.4 exceeds 0.8SA (as defined in para. 302.3.5), and the equivalent number of cycles (N in para. 302.3.5) exceeds 7000; or other conditions
that the designer determines will produce an equivalent
effect.

I'd just build it like a regular expansion case. The Code does not limit the stress to 0.8SA here. The Code says that if the stress is greater than 0.80SA (and other conditions), then the system is subject to severe cyclic conditions. In which case, additional design requirements (non-analysis) must be followed (e.g. materials, welds, etc.).

Review the stress ratio and if it exceeds 80%, then you have a severe system.

There you are, you got the same answer from this and the Eng-Tips forum.

Great Dave....Thank you very much...I understood now. I just thought that there was some place that I could put a value or click in something to ensure that the stresses were not above the acceptable 0.8 SA. We need just to see the radio in stress summary, if it exceeds 80% we have a severe system, didn't we?. But It depends of another things like the equivalent number of cycles (N in para. 302.3.5) exceeds 7000.

Just one more thing:

My load cases, is it alright ?

I have the following conditions:

T1 = -198 ºC ( Design temperature (cryogenic) )

T2 = 55 ºC (During shutdown, the pipe system could encounter temperatures as high as 130F in summer (caused by solar radiation) )

P1 = 20 barg

Is it important to do these three expansion case ( CASE 4, 5 and 6) ?

Thank you very much for all my friends.

OB: Dave I remember when you went to Rio de Janeiro in february 2011. You gave us a course when I worked at Chemtech, did you remember that course? hehehe

So, I'm pleasure to talk to you again.

Have a nice week.

Regards,

Saulo Cunha

Yes, adding Load Case 6 is a good idea here.

Well, yes, I do recall that class, a little. Still doing the same...

Regards

Dave, using Load Case 6 I could not meet 0.8SA. It's almost 99%. I'm using A312 TP304, so can I use stress range factor 1,2 or not ? When I can use stress range factor 1,2 ?

Thank you very much again .

Regards,

Saulo Cunha