WRC Calculation in PV Elite

[roca]

Hi All
I have run a high pressure vessel WRC 107 nozzle calculation using PV Elite / Codecalc software and have received the following error:
Error Messages for WRC107 Analysis 1
WARNING - Design Pressure, 28. , is greater than 3000 psi.

I have also run the same vessel and nozzle using Compress and I receive no error of this kind.

Does WRC 107 give a limit to the maximum internal pressure you can use? I was not aware of this requirement

 

[TGS4]

It would help us if you gave the details of your vessel/nozzle:
- design temperature
- design pressure
- vessel OD
- vessel thk
- nozzle OD
- nozzle thk

 

[JStephen]

I would suggest that if you're designing nozzles based on WRC 107 and/or 297, that you go ahead and get a copy of each. You wouldn't need all the charts, but the write-ups that go with them is fairly informative. If you're using a numerical method based on them, you'd probably assume the results are more accurate than what they are.

As far as I know, both methods are essentially based on standard bending equations in shells, which assume a "thin" shell with linear stress variation through the shell, etc., and it wouldn't be suprising if they weren't applicable to cases where the wall thickness was comparable to the nozzle size or the vessel ID.

 

[Mandeep1]

Roca,

You have entered the design internal pressure as 28 MPa or about 4061 psig. The pressure vessel codes ASME Sec. VIII Div. 1 and Div. 2 do not address all the requirements for vessel designed for 3000 psig internal pressure. You have to refer to Div. 3 code for high pressure vessels.

The software is just giving you a warning/note about the high pressure. But, you should still get the results. WRC bulleting 107 is itself code independent.

I agree with JStephen that understanding the limitations and assumptions of these bulletins is important. These bulletins are not very expensive, you may check

http://www.forengineers.org/wrc/index.html

Mandeep Singh
COADE, Inc.

 

[TGS4]

If what Mandeep says is true, then consider yourself lucky that you were warned. Thin-shell theory may not be applicable.

Perhaps this can serve as a lesson to others that just because your software doesn't "warn" you about something, that you should assume that it's correct and applied appropriately - that's for you as the engineer to determine.

 

[roca]

Thanks all
Mandeep
I have copies of all the bulletins
If the high pressure is just a warning then why does the program not run in PV Elite like it does in Compress?
As a PV engineer I know that IO am outside the Code linits for pressure

 

[Mandeep1]

Roca,

It should run the analysis. Send the input file to support@coade.com and put it to my attention. I will investigate.

Regards,
Mandeep

 

[roca]

Hi Mandeep
I will send you the file
What is the basis for the 3000 psig limit mentioned above?
As far as I am aware (and I may be wrong) ASME Div 2 gives no limit. Div 2 AG-110 "does not specify a limitation on pressure. For very high pressures some additions or deviations to code rules may be necessary"

ASME VIII Div 3 is for vessels in excess of 10000psig.

Thanks

 

[niko2]

In my opinion a finite element analysis should be performed for this nozzle. Depending on the vessels local thickness the radial stress may not be neglible, but this may be true for rest of the vessel in terms of thickkess sizing. I am not sure that WRC 107 takes sirgma r (radial stress into considration) when it can not be ignored!