Hi,

I want to know which stress is considered for the HYD case, I explain:
in my client spec, the Hydrotest case have to be SUS in stress Type so I have to calculate manually the Hydrotest allowable 0.9 x Yield stress for each model.

To avoid this matter I used the HYD stress type in the case option.

The problem is that I get different results. How it can be? I tried to found in the B31.3 code which type of stress is considered in the Hydrotest case (Slp? or Sb? or may be Slp+Sb) because I know that for SUS case the stress considered is :
SL= Slp+(Fax/Am)+Sb < Sh

Regards

I get the same B31.3 stresses from CAESAR II for both the hydrostatic and sustained load case when my fluid density = 1SG and I have no spring hangers (to lock) and P1=Phydro. My hydro case allowable stress is Sy (not 90%Sy) and my sustained allowable stress is Sc.

Thank you for your answer but I have the same problem for all my calculation models:

Material API 5L Gr B Tc = 50°C / Calculation code B31.3 /Sy = 217.2 Mpa

first Run:

WW+HP with HYD stress Type: Stress Code:43.5 Mpa ALLOWABLE 217.2 Mpa node 98

Second Run:

WW+HP with SUS stress Type: Stress Code 70.7 Mpa allowable 137.9 Mpa node 260.

it's really strange and there is no Spring support!!!

I'm using CAESAR II 5.30.03

Best Regards,

Hi Abdelkader,

yes
1st run uses hydrotest allowable sy=217.2 Mpa based on ASME B 31.3 only as it states for carbon steel Sy can be considered for checking hydrotest allowable,but 0.9 or 90% of sy is applicable only for SS and other non CS pipe materials.

2nd run
uses sustained allowable sh only as defined by you in the load case editor as sus.

if you use hyd in load case then it will show you hydro allowable and if SUS then sustained allowable.
so whats wrong....its correct only

Hi deb,

Thank you for your answer but the problem is not about the allowable stress it's about the calculated stress by CAESAR II (in stress report : Code stress)

I know for sustained cases in B31.3 code, the stress calculated is:

SL= Slp+(Fax/Am)+Sb < Sh

But I don't know the stress formula for the Hydrotest case:

Stress formula ????? < Sy

I'm asking this question because I get different calculated stress results for HYD case when it's calculated as SUS or HYD:

First Run:

WW+HP with HYD stress Type: Stress Code:43.5 Mpa A @ node 98

Second run:

WW+HP with SUS stress Type: Stress Code 70.7 Mpa @ node 260.

You can see the difference 43.5 and 70.7: it's about 1.62 time greater for the SUS type stress while its the same loads (WW,HP) it mean that Caesar is using a different calculation stress formula for the HYD stress type.

Can any one tell me where I can find this formula in B31.3???

Best regards,

You won't find a stress equation for the hydro-test case in B31.3, it's not there. However, this is a "weight" case - primary loads. Therefore CAESAR II uses the Sustained analysis procedure.

As was pointed out above, your model may be different between the HYD and other load cases. Once you designate a load case as HYD, CAESAR II automatically locks springs and expansion joints (sets their stiffness to rigid). Therefore the global stiffness matrix is different, therefore you end up with a different solution.

One other difference is that B31.3 states corrosion should be removed from the SUS and OCC cases, so be default that is all CAESAR II will corrode. That means if you have corrosion in your job, the SUS case will consider corrosion but the HYD case won't. You can force corrosion to be considered in all load cases by changing the "configuration", set the ALL_STRESS_CASES_CORRODED directive to TRUE.

Hi Richards,

Thank you very match everything is correct now it was the corrosion states.
I checked it with all cases corroded option and everything is OK.

Best Rigards