ASME SECT VIII DIV2, FATIGUE ANALYSIS 3

[rris9]

ASME SECT VIII DIV2 FATIGUE ANALYSIS

AS PER ARTICLE 4, THE STRESS GENERATED AT THE JUNCTION OF NOZZLE TO SHELL/HEADS OF LOCAL MEMBRANE CATEGORY. (TABLE 4-120.1)

MY PROBLEM IS THAT THE DAMAGE FACTOR ACHIEVED IS MORE THAN 1.FOR THIS JOINT.
AS PER ARTICLE 5 AND IN TURN I HAVE TO INCREASE THE THICKNESS OF ENTIRE SHELL/HEADS TO MEET THE ARTICLE 5 REQUIREMENTS. (DAMAGE FACTOR LESS THAN ONE).

IS IT ALLOWED TO INCREASE THE THICKNESS OF SHELL/HEADS SURROUNDING THE NOZZLE PROVIDING INSERT PLATE?
HOW DO YOU DESIGN THE SIZE OF THE INSERT PLATE?

 

[JoeTank]

Local effects normally dissapate to minimal levels after about one to two times the square root of Rt.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[rris9]

Dear SteveBraune
thanks for the response.
I request you to giv the code paragraph refernce.
thanks and good luck
rris9

 

[LSThill]

team member's

please review API 579.

 

[rris9]

ISTHILL
I WISH TO UNDERSTAND WITH RESPECT TO ASME SECT VIII DIV 2
THANKS
rris9

 

[TGS4]

rrsi9 - First things first - turn off the all caps!

"Is is allowed to increase the thickness of shell/heads surrounding the nozzle providing insert plate?" Yes.

"How do you design the size of the insert plate?" However you want.

Division 2 is a Design by Analysis code, particularly when it comes to Appendix 4. Therefore, you am pretty much free to do whatever you want (so long as it doesn't violate any other 'rule' is Division 2) as long as you can back up the design with analysis.

Question for you - how have you determined that your cumulative usage factor is greater than 1.0? (Really - how are you performing your stress calculations?)

 

[rris9]

TGS4
Let us think engineering,not language.
Thanks for the response and continue.

I have used AD 560, alternate rules to design nozzles attachment.

since the stress intensity derived from the table AD 560.7, is high and in turn damage factor is also high beyond 1.
The same applied in article 5 for fatigue evaluation.

I want your help to know as pe which para of div 2, I can provide insert plate to overcome the damagefactor >1

rris9

 

[TGS4]

rris9, I'm only going to repeat my answer once, so pay attention...

"I want your help to know as pe which para of div 2, I can provide insert plate to overcome the damagefactor >1" - YES.

As far as your calculation methodology, let me offer you some advice - read ALL of AD-560.7. Pay particular attention to the part where it says "In the evaluation of stresses in or adjacent to vessel openings and connections, it is often necessary to consider the effects of stresses due to external loadings or thermal stresses. In such cases, the total stress at a given point may be determined by superposition. ... If the stresses are otherwise determined by more accurate analytical techniques...."

If you have nozzle loads on your nozzles (and really, who doesn't), then you will need to do more than AD-560 - might I recommend Appendix 4.

Just out of curiosity, how many cycles is your vessel seeing? Are they pressure or thermal cycles (or both)? How many Appendix 5 fatigue analyses have you done?