SA-264 Maximum Allowable Working Stress 1

[commandotom]

Seems like I've been chasing my tail through the code or may be it's just that I can't quite see the forest for the trees. I'd like to be able to determine the Maxmum Allowable Stress for the following.
SA-264; 20% SA-240 316 on SA 285 backing, Specified Tensile strength; 55K. Nominal thickness 0.375", Temp. 600. Ultimately I'll be using the stress to calculate the min. thickness for the heads and shell.
I've been through UCL-11 and UCL-23(c) seems like I get close but just can't quite get to where I need to be. New to this site. Sure hope someone can set me on the right course. Many Thanks in advance.

 

[doct9960]

Maximum Allowable Stress Values are in ASME Section II, Part D. For SA-285-C at 600°F, it is 15300 psi.

 

[chicopee]

ASME/NB codes one Power Boilers section I, heating boilers section IV and unfired pressure vessels section VII should all have tables at the back of these sections for the values you seek.

 

[commandotom]

UCL-11; states that "clad material used in contstruction which the design calculations includes cladding shall conform to one of the following specifications"...SA-264 is referenced in,"UCL-11(a)" the UCL-23; Maximum Allowable Strss Values, UCL-23(c); "Base Material with Corrosion Resistant Integral or Weld Metal Overlay Cladding with Credit for Cladding Thickness, "When the base material with corrosion resistant integral cladding conforms to one of the following specifications listed in UCL-11(a)...see above....continues....The design calculatons may be based on a thickness equal to the nominal thickness of the material plus Sc/Sb times the nominal thickness of the cladding after any allowance provided for the corrosion has been deducted".
From the Form U-1; SA-264...20% Type 316 on SA-285 Backing (T.S.=55k) Nominal thickness .375"
therefore the SA-285 is a Grade "C",S=15300 @ 600F and for SA-240 316, S=12,600 @ 600F.
From UCL-23(c), t(nominal thicknes base) + (Sc/Sb x t(nominal thickness cladding)
0.300" + [(12600/15300)x 0.075"] = 0.362"
Comments????
Thanks

 

[SnTMan]

commandotom, yeah, as a practical matter the contribution to strength of cladding is generally ignored and the base metal only is considered. It'll make your life simpler.

Regards,

Mike

 

[jtseng123]

Many times, cladding is considered as corrosion barrier, so most people don't include it in the strength calculation. We simply input it as corrosion allowance in the calculation.
You can include it in the strength calc as the combined thickness you show, as long as clad will not wear out in 20 years.
If you are not sure, just treat it as corrosion allowance, make your life easier as SnTMan says.