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Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

(OP)
Code ASME VIII Div 1
WE have to attach a new nozzle for revamping a vessel.
Shell an nozzle are 515 Gr 70/516 Gr70 repectively.
We have to get the WAWP for this process column, limited by the 42"inlet nozzle.
We are using FEA analysis instead of WRC 368  (WRC 107 was discarded as there is no data for this diameters ratio) . We decided to work in the program  with  Von misses stress.

Maximun stress is in the intersection of the vertical  axis at 12 and 6 hours.

Questions:
1)Are we in the correct way of analysis with this type of  comparison between von misses and Allowable stresses?
2) WE are using  1.5* Sa (maximun allowable metal stress code value) as allowable stresses  for all the nozzle-shell area
Can we consider  3*Sa as allowable stress for this case?
 

RE: Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

lganga (Mechanical)

do yu have a drawing or skitch?

RE: Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

(OP)
LSHILL
Dear sir
I can send a word document with stress levesl and excel graphics of stress along the wall and the nozzle.
Later I will send and autocad drawing

Thanks
Luis
Let me know if you coul open it. maybe RTF format can open. Any way I can send in a better way tomorrow
Regards
Luis

RE: Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

ASME uses 2 theories of failure criterion.  
The maximum-principal-stress theory: where the maximum principal stress reaches the tensile yield strength.
The maximum-shear-stress theory (also referred to as Tresca theory): where the maximum shear stress reaches the shear yield strength.  (there are 4 other theories (of which von Mises theory or the maximum-distortion-energy theory) is discussed in Roark's Formulas for Stress and Strain Chapter 3)

ASME VIII-1 uses: maximum-principal-stress theory
ASME VIII-2 uses: maximum-shear-stress theory

The use of von Mises theory in you analysis in my opinion would satisfy the ASME Code requirements as von Mises is a closer prediction than the theories used in the Code as those theories are easier to apply and are more conservative.

All your stresses need to broken down and categorized according to ASME (i.e. Primary, Secondary and Peak)

Then the maximum stress and combined stresses need to be within the allowable. i.e.:
Pm < Sm
PL < Sm
PL + Pb < 1.5Sm
PL + Pb + Q < 3Sm

 

RE: Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

lganga (Mechanical)
Do you have?:
RE: "ASME Section VIII – Division 2 Example Problems Manual", ASME PTB-3-2010

 

RE: Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

(OP)
LSHILL
I dont have it,  I can afford to buy it now.
Can you you give an abstract what it is about.
The problem is that WRC368 (i have PVELITE2011) does not give accertanty of the relation.
I have great discrepance between repad or not.
I wa not able not able to repad more than 8 "(bottom limits it) but 368 only consider 16". with out pad no condition passes (shell and nozzle). Wit 16" repad it passes .Von misses doesnot pass 1.5 Sa not even 0.9Sy

I will appreciate your comments
Thanks
Luis

RE: Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

lganga (Mechanical) Luis  

1) Can you you give an abstract what it is about:

http://files.asme.org/Events/BCW/27409.pdf

ASME PTB-3-2010: ASME B&PV Code, Section VIII, Division 2 contains mandatory requirements, specific prohibitions, and non-mandatory guidance for the design, materials, fabrication, examination, inspection, testing, and certification of pressure vessels and their associated pressure relief devices. This document is provided to illustrate the design calculations used in the ASME B&PV Code, Section VIII, Division 2.

ASME PTB-1-2009. ASME Section VIII Division 2 Criteria and Commentary

This document provides a complete description of the ASME B&PV Code, Section VIII, Division 2, including technical background, an overview of the many new features, and where significant differences now exist between the new and old Section VIII, Division 2.  Valuable background information is provided to assist users in using the Code, ensuring that the technology introduced into the Code is properly documented. It covers the 2007 Edition of Section VIII, Division 2, including the 2008 and 2009 Addenda.  Some of the changes planned for the 2010 Edition of the Code are also included.  This document will be updated as required to keep pace with future developments in Section VIII, Division 2

RE: SME VIII-1, the conical output has been embellished
Example problems from ASME PTB-3-2010 ( VIII-2 ) are now included
http://www.coade.com/UPLOADS/dwnld/PVElite/Build.txt

2)I have great discrepance between repad or not.
Look at pate 4-40 full insert Nozzle --no repad.

Please add additonal information

Stephen

  

RE: Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

LSThill,
        Superb "cut and paste" job again!!!

RE: Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

(OP)
Stephen
after your email, I have downloaded yesterday night the SP1 from COADE site , I could not find the examples yet.
I am very interested in studying those examples.
I have never worked with Div 2 before.
I appreciate your advise
Regards
Luis  

RE: Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

lganga (Mechanical)

Read & study Annex B1-B4 of API 579-1/ASME FFS-1. Page 601- Page 696?

As stated:
FFS engineers who perform Level 3 assessments will also find the
course beneficial since Part 5 of Div 2 is harmonized with Annex B1-B4 of API 579-1/ASME FFS-1


 

RE: Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

lganga (Mechanical)
1) Question: I am very interested in studying those examples.


Subject: ASME FFS-1
see ASME FITNESS FOR SERVICES API 579-1/ASME-FFS-1 2007; API 579-2/ASME-FFS-2 2009 Importance: High

http://dl.ebmcdn.net/asme/flash/CS/ASME-FFS_6-09_v3.swf

example 1 slide: 25, 26, 27, 28,
31, 32, 33, 34, 35, 36

 

RE: Local stresses in a 103öcylindrical shell with a radial 42ö nozzle

(OP)
The vessel we are revamping is a 10 years old,  it is lined inside with rubber,composite laminate and 2 or three brick layers.
The inlet nozzle is a 24",it is a process gas inlet,tihs gas is quenched in the vessel.This inlet nozzle has a 20" titanium sleeve,and so the distance between rubber and the titanium nozzle (2" in between) was not enough insulation and too hot for the rubber lining and failure appeared after one year of service,producing corrosin on the vessel.

We did a heat transfer calculation and distnace calculated between the nozzle and the titanium sleeve has to be  10"(rubber+laminate+3brick layers). That is the reason for this 42" nozzle. We also changed another 3 but the 42" is the critical one that limits the MAWP

I did this job last year in an spare vessel ,25 years old in 285 GrC and we limited the  MAWP to 6 bars.
What we need now for this vertical vessel (515Gr70)  is 10 bar MAWP due to a process change.
I have to decide this in the next two weeks (we did not buy the flanges yet and one of it is going to be an studding nozzle)

Sorry for this long answer,but this will give you and idea of my hurry to solve it.
thanks a lot for your help
Luis

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