WRC 107 bulletin, Design factor

[bellzinc]

In WRC 107, we have to choose a design factor between 1 to 3.
What is the signification of that factor and how we choose
this factor.
Thanks in advance

 

[Heyner]

Hey, friends,

I want to use the opportunity to ask:

Where may I find the complete text of WRC107 & 297 bulletins for download?

Would some of you share this info?

I'm a newbie...

Thanks...

What about bellzinc's question?

 

[TomBarsh]

bellzinc,

A "design factor" is often applied to the shell material basic allowable tensile stress to determine the allowable stress for local membrane and bending stresses arising in the shell from the external loads acting on the nozzle or other attachment. Strictly speaking, this is outside of the WRC-107 bulletin and is more a matter of using some Design Code to determine what allowable stresses should be applied to the calculated stress.

The design code that you are using will define the corresponding allowable stress. For example, ASME Section VIII Division 1 paragraph UG-23(c) defines allowable local primary membrane stress to be 1.5*S (S is basic tensile allowable at design temperature) so the design factor here is 1.5. However, this Code does not define a corresponding allowable stress for combined local membrane plus bending (PL+Pb). Most USA designers will then take recourse (or refuge) in ASME Section VIII Division 2 where the PL+Pb stress may be 1.5*S or, if Q loads are a component of the stress, then 3.0*S (see Division 2, Figure 4-130.1, also reproduced in a number of other references). Q stresses are "self-equilibrating stresses to satisfy continuity of the structure" and can be caused by *mechanical loads* or *thermal loads*.

Other Design Codes (BS-5500, API, piping codes, etc) may specify different design factors.

 

[jte]

Heyner-

You can purchase the documents from

http://www.forengineers.org/store.p...ck&PHPSESSID=6da9ac6aa359ed859eee3d940e5b0abd

jt