B31._ Values of Y for Non-metals and Cast Iron

[Ben4piping]

Which is correct in B31.1 -2010:

(1) Table 104.1.2(A) Values of Y, general note (a) which states: "For cast iron and non-ferrous materials, Y = 0."

or

(2) Table A-_ (material tables) general notes which have Y = 0.4 (except for some nickel alloys)

I realize Y = 0 is most conservative.

Thanks, Ben Nottingham

 

[Korichnevijgigant]

I believe the Y coefficient is referring to the material's ductility.

I would trust the earlier table.

What exactly are you trying to find out?

 

[Ben4piping]

Hello Korichnevijqiqant,

Thanks for your reply. I was wondering if there are errors in the Code. The Y table is more conservative, then I probably should use it and not the general notes. Still, it would be good not to confuse others with calculations we make.

Best regards, Ben

 

[Korichnevijgigant]

I have found a few errors in the Code, things get changed in revisions and new editions, but some things are overlooked.

I looked around Table A-1 and I'm not seeing where that coefficient is listed.

 

[Ben4piping]

B31.1 -2010 has Y = 0.4 in general notes for non-metals and cast iron. Thanks to Steve Perry who pointed me to this in another post.

Ben

 

[Korichnevijgigant]

Oh okay, that is the problem, I misread your post and looked at B31.3

 

[StevenHPerry]

See "A Wall Thickness Formula for High-Pressure High-Temperature Piping" by Burrows, Michel, and Rankin (ASME paper 52-A-151).

The "y" factor is a transition between two different equations (modified Lame & "Creep-Common III")for calculating stress in thin walled pressure vessels as you venture into the creep zone. The paper indicates that before "y" was developed in the early 50s, the modified Lame equation (i.e. y=0.4) was equation for all piping temperatures.

That the code committee hasn't published a definitive y-value for the material you're using tells me that you could be going where relatively few have gone before. It might be worth retaining an expert in the material you're dealing with or reconsidering your material selection.

- Steve Perry

http://www.linkedin.com/in/stevenhperry

This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[Ben4piping]

Thanks Steve,
I appreciate your time and for offering your expert advice. I have most of the information to proceed with revisions to certain spreadsheets. It is my goal to eventually include all material data for B31.1 and B31.3, plus weight data and data from some manufacturers of special materials. Of course, numerous cautions for use must be included.

Ben