Dear All,

Please find the Load case definations below.

1. W+P1 SUS
2. W+D1+T1+P1 OPE
3. W+D2+T2+P1 OPE
4. W+D3+T3+P1 OPE
5. D1+T1 EXP
6. D2+T2 EXP
7. D3+T3 EXP
8. L2-L5 SUS
9. L3-L6 SUS
10. L4-L7 SUS
11. L8,L9,L10 SUS
12. L2-L1 EXP
13. L3-L1 EXP
14. L4-L1 EXP
15. L2-L3 EXP

The problem what I observed from this load case is:

I am using Liberal stress ON. so because of addition of (SH-SL) the allowable of EXP stress is increased.

But here SL is code stress calculated for SUS case, For this load cases :: SL is using liftup sustained value means L11 case , not main sustained value means L1. Because of this allowable of EXP stress is reduced.

Why CAESAR-II is taking SL value from liftup sustained case even though I mentioned clearly in the load cases for considering main sustain value

If any changes needed in load cases to overcome this problem, please guide me.

Any comments

Dave-San & Richard-San,

Any help on this topic please..

CAESAR II uses the highest SL from any load case (per node) when conputing any Expansion Alowable. Any other value would be non-conservative.

Thank you Richard-san, For your reply.

Yes CAESAR-II using the max SL.

1. But in this case SL is the Hot sus value. Is it correct way to use Hot sustained SL in EXP stress allowable calculation.

If it is correct then,

2. In most of the projects we did lift up case seperatly by creating a new CAESAR-II file by removing +y restraints and in that case we never check the EXP stresses.

which one is best method?

The default SUS case in CAESAR II is the "as installed" (what I would call the cold sustained) case. Yes you can define additional SUS cases (perhaps due to different pressures or the hot condition). The maximum SL from all SUS cases is used in determining the EXP allowable.

This is justified in the new B31.3 2014 edition.

Thank you Richard-San, For your reply.

In B31.3 2014 Edition, This ststement will be there --

"The maximum SL (Due to different pressures or hot condition) from all sus cases is used in determining the EXP allowable."

Richard –san,

I referred ASME B 31.3 2014 edition,

It states: SL= stress due to sustained loads; in systems where supports may active in some conditions and inactive in others, the maximum value of sustained stress, considering all support conditions shall be used.

CASE 1: T1 = 400 °C A358-304 Material.. Sh=106 Mpa
CASE 2: T2 amb sh= 137mpa

For this cal f(1.25SC+0.25SH)+(SH-SL)

SH from that particular temp and SL is max irrespective of temp.

What I feel is : There is no consistency between SH and SL

For the particular temp Sh we have to consider that particular SL for the calculation.

Please correct me If I am wrong

Your statement "there is no consistency between SH and SL" is correct.

However, the Code says you have to use the maximum SL - you don't have a choice. The intent is that the Primary Stresses must remain below the allowable, regardless of the position of the pipe.

Thank you Richard-san,

As per our Discussion; we have to consider max SL for Exp case- when liberal stress ON (Irespective of our load cases defined).

Then for OCC case why CAESAR-II is adding SL (only due to gravity) to individual OCC load cases.

As per CODE ; For OCC case also CAESAR-II must add the max of SL (irespective of our load cases). But it’s not happening like that.

What is the reason behind that??

Please correct me, If I am wrong.

Any comments..

The SL value used in computing the expansion allowable is the maximum experienced from all positions of the piping system. This is what CAESAR II has always done, and this is what B31.3 2014 (finally) states.

The occasional load cases are user defined - you define the possible combinations of the sustained stresses plus the occasional stresses that can occur.