ASME VIII Div.1 Mandatory Appendix 1 Thick-Wall Thickness Z factor 5

[Northeastern Tiger]

I have a question for the "Z factor" in ASME VIII Div.1 (2023 version) Mandatory Appendix(MA) 1-2 Cylindrical Shells .

According to MA 1-2 (b) , equation (3).

Z = (P/SE + 1)

While, when I search on website , I found another formula for Z factor.

Z = ( SE + P) / (SE- P)

See link below.

https://www.boardmaninc.com/news.html/2020/01/07/volume-xliv-vol-iii-asme-pressure-vessels/

My question is: why there are two formulas for Z factor?

All the bright minds please help.

 

[XL83NL]

There aren’t two Z-factors. There’s only one. The second one you mentioned is from a website and not from the ASME BPVC Code book, and therefore incorrect. It may be a copy from an old version of an ASME BPVC Code book, or someone made it up, and put it in that website - point is, only the (current) Code book is right.

Huub
- You never get what you expect, you only get what you inspect.

 

[Christine74]

Earlier versions of ASME Section VIII Div. 1 Appendix 1 used "Z = (SE + P)/(SE - P)", but in 2010 the Code began using "Z = (P/SE + 1)". Not quite the same.


-Christine

 

[SnTMan]

You will notice the Boardnman Inc site has differing Z factors applicable to either longitudinal or circumferential stress.

The factor Z = (P/SE + 1) is used as recently as the 2017 Ed of Sec VIII, Div 1 for longitudinal stress only, There is (in that Edition) no Z factor for circumferential stress. I suspect the use of the factor Z = ( SE + P) / (SE- P) was replaced in the past by the (presumably) more accurate Eqn 1-2(a)(1). Probably

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Northeastern Tiger]

Seems like ASME modified the Z factor formula before. Understood. Thanks for your insights Huub, Christine, and Mike.

 

[XL83NL]

You're welcome, TIger. Thanks for coming back (a lot of new members post a question and never bother coming back after they've been given input/advice)

Huub
- You never get what you expect, you only get what you inspect.