NFPA 69 Fy Stress Ratio

[nuche1973]

Greetings to all,
I am a structural I.E.(recent, I graduated 18 months ago). The company I work for designs the support frames for a small pressure vessel company out of Kansas, and when asked we design or check the vessel itself. (Oddly enough, the structural department takes on this task. Hence the reason for my posting in this forum. I know long story) My question is this: Noted in NFPA 69 is an equation that gives the limits for the maximum allowable working pressure, Pmawp. Within this equation is the stress ratio of yield stress to allowable stress for the material of construction, denoted as Fy (eqn 13.2). The NFPA refers the ASME Boiler and Pressure Vessel Code. I have the 2001 ASME VII divsion 1 and I cannot find this ratio nor the Fy designation. Where is this ratio located in the code?

 

[Wecos]

Not sure about the Fy being specifically listed, but material properties for yield strength (Sy) and allowable strength (Sa) are given in Section II of the Code for a range of operating temperatures.

 

[nuche1973]

Wecos, thanks, for the information. I've done several tanks but none with deflagration requirements. New project, new parameters...good thing there's Eng-tips.

 

[chicopee]

I don't have NFPA69, however, many books that deal with PV's,tanks and concrete related items refer to Fy as the steel yield stress.