Regarding the WRC 107 module of Caesar Ver. 4.5, it is observed that :
1)The allowable stress intensities of vessel material correspond to the allowable stress values (i.e. the specified default Caesar values are UTS/3.5 instead of UTS/3).
2)The WRC 107 check does not ask for nozzle material allowables (in case found lower than vessel shell material allowables) which could be used as allowables for nozzle to shell junction calculated stresses.
3)Further, I would kindly request to have your feedback as to whether the WRC 107 run associated with Caesar Ver 4.5 would generate similar results when compared with those associated with vessel design packages like Codecalc & PVElite for a particular set of inputs.

Would appreciate your advice & clarification on the above.
Thanking you.

Sachin,

Regarding point (1), I have not yet looked into it, but if you are correctly pointing out, it is a matter of concern.

Regading point (2), WRC 107 does not address the stresses at the nozzle, that issue is take care of in WRC 297.

Regards

Anindya Bhattacharya

Sachin,

The material database that is available in CAESAR II is from ASME Section II part D. I think the latest CAESAR II build is using allowable for Div. 1. In this case the basic factor of safety (FOS) is UTS/3.5. As you may know that in Addenda-99 ASME lowered the basic FOS from 4 to 3.5 on UTS. Is there any particular material that you have a question on?

What build of CAESAR II are you using? Make sure it is the latest one.

The WRC 107 calculation engine that is in CAESAR II 4.5 is same as that in CodeCalc and PVElite.

Dear Mandeep,

I am aware of the fact that as per Sec VIII Div I & Sec II Part D, the allowable stress is UTS/3.5

What I am drawing attention through my query is that if Caesar talks of allowable stress "intensities" then these default values ought to be from Sec VIII Div II & should be as per Sec II Part D Tables 2A & 2B (i.e. UTS/3).

Dear Sachin,

There are two points of view here,

I see your point that if we are computing the stress intensities then we should compare them to Div. 2 allowables, which is the allowable limit for the stress intensity.

Typically, engineers for the sake of being conservative have used the Div. 1 allowables, as they were lower. But, after ASME increased the Div. 1 allowables in A-99, the Div. 1 allowables can be higher than the corresponding Div. 2 values for some elevated temperatures.

But, some engineers also believe that if the vessel is a Div. 1 vessel then use the Div. 1 allowables and if it’s a Div. 2 vessel then use Div. 2 allowables. As, there are many other requirements to satisfy for a Div. 2 vessel.

So, one can take sides on this issue. In CAESAR II, the Div. 1 material database is connected to the input. But, if you want to use Div. II allowables then you can type those in by hand.

So, it is up to the engineer.

Dear Mandeep,

There is a contradiction between the way Div. I material database is connected to the input and the help menu associated with the WRC-107 module. If a user selects the material from drop down menu the allowable stress values are being taken as per Div. I automatically but if a user wishes to input the allowables manually and uses the help menu he is being asked to " input the stress intensities as per Div. II ".
Even the language in the help menu suggests that CAESAR is also using Div. II stress intensities. Unless a user checks the allowables manually with the code he won't know that actually Div. I allowables are being used.
In my opinion the user shall be told specifically in the help menu as to what kind of allowables are being used by CAESAR and for the manual input it should be left to individual user whether to use Div. I allowables or DIV. II stress intensities.

Regards,

Rajesh,

I do not agree with your statement" it should be left to individual user whether to use Div.1 allowables or Div. II stress Intensities "i.e. to decide between table 1 & table 2 of sec II Part D.

We are following the stress categorization and summation as per Sec VIII DIV 2 APPENDIX 4 requirements, which clearly defines and calls for use of stress intensities rather than stress.So the user is not free to decide, code requirements will dictate.

Regards

Anindya Bhattacharya

Anindya,
When I wrote " it should be left to user.." I was replying to Mandeep's statement that " few engineers input the values as per the vessel governing code i.e. Div 1 or 2". In that context I replied that if it was an acceptable practice then the user shall not be asked ( as per the Help Menu ) to input the stress intensities as per Div. 2 only.
Now, if general opinion( let's hear from others )or code requirement is to use Div. 2 stress intensities only then CAESAR data base should be revised accordingly.

Regards.