Sect VIII Appendix 2 and corrosion allowance
Sect VIII Appendix 2 and corrosion allowance
(OP)
Is there any guidance in the code on what dimensions are to be in the corroded condition and what are not inside of these calculations?
It is difficult to predict the most conserative condition since these calculations are complicated enough to 'bury' the appearant effect of corrosion allowance on the stresses. Sure, I could make a few spreadsheets in an effort to quantify this effects on the flange stresses, but I would think there may be code guidance on this matter.
Does anyone know? I've examined the Compress calculations, and I feel there might be an error in there somewheres, so I'd rather see the code citings if any exist. (My professional side commands I see the print!)
It is difficult to predict the most conserative condition since these calculations are complicated enough to 'bury' the appearant effect of corrosion allowance on the stresses. Sure, I could make a few spreadsheets in an effort to quantify this effects on the flange stresses, but I would think there may be code guidance on this matter.
Does anyone know? I've examined the Compress calculations, and I feel there might be an error in there somewheres, so I'd rather see the code citings if any exist. (My professional side commands I see the print!)
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Fitter, happier, more productive





RE: Sect VIII Appendix 2 and corrosion allowance
Hope this helps,
Cheers,
gr2vessels
RE: Sect VIII Appendix 2 and corrosion allowance
look at the print, chapter 4.1.4 Corrosion Allowance in Design Equations.
4.1.4.1 The dimensional symbols used in all design equations and figures throughout this Division represent dimensions in the corroded condition.
please have a look also at 4.1.4.2 and 4.1.4.3
yours truly,
tigny.
RE: Sect VIII Appendix 2 and corrosion allowance
please disregard my first post since it does not answer your question. I'd like to edit or delete if but cannot find the way to do so.
Except for UG-16(e) I don't know of other requirements for corrosion allowance in design formulas in the code, nor especially for Appendix 2. Appendix E has no more information regarding to which dimensions corrosion applies.
As far as corrosion thickness is concerned for flanges with appendix 2
- I apply a value of internal corrosion thickness to flange bore (B) and (g0) and (g1) for all formulas related to hub thickness. (Table 2.6 and 2.7.1 parameters included)
If you have access to Code Interpretation it seems there are a few about corrosion allowance so maybe there is an answer to your questions in them.Except that I don't use internal corrosion thickness for the R dimension (B appears in the calculation of R).
I think external corrosion can be applied to R as well as all other values stated before.
Concerning flange thickness t I apply corrosion thickness on both sides of t (from gasket side to back of flange side). This corresponds to external corrosion.
yours,
tigny
P.S. since you are in flange calculations, may I ask you to have a look at my recent post Hub taper
RE: Sect VIII Appendix 2 and corrosion allowance
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Fitter, happier, more productive
RE: Sect VIII Appendix 2 and corrosion allowance
Thanks for sharing your methods! It appears that Compress is doing nearly the same thing you are with the corrosion allowance.
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Fitter, happier, more productive
RE: Sect VIII Appendix 2 and corrosion allowance
incidentely I opened the TEMA 7th edition; in RCB-1.515 it is stated that corrosion allowance shall be applied only to the inside diameter of flanges where exposed to fluids.
yours,
tigny
RE: Sect VIII Appendix 2 and corrosion allowance
For Appendix 2, it is common to apply CA to the ID dimensions, B, go, g1, but not the thickness. External CA is uncommon, unless the outides surfaces are exposed to the process, such as internal flanges.
Regards,
Mike