ASME B31.3 Allowable Stress values

[jorgefherrero]

In ASME Code 31.3 for Pressure Piping there are some steels for which I do not know the allowable stress value. I mean 904L, and Superduplex S32750 or S32760, all in seamless pipes, I have not found anything about them in Appendix A of B31.3 tables. Which value does apply?

Moreover, I have found an apparent mismatch for A312 TP316L seamless pipe. Table 1 in Appendix A of B31.3 gives a set of values for allowable stress against temperature. Looking in ASME BPV Section II, Part D, Table 1A (Stress Tables for ferrous materials) for the same steel specification it gives lower stress values for temperature over 200ºF. Should they not be the same values?

 

[NozzleTwister]

jorgefherrero,

The Superduplex S32750 and S32760 are both listed in my ASME B31.3, ver 2004 and 2006 under ASTM A790 and grades above. I didn't check for other ASTM standards.

I can't hlep you with the 904L though having never heard of it.

Also, you are correct, the stress values in ASME B31.3 don't match ASME BPV for the lower temperatures.

Stress values do change from edition to edition so make sure you are always using the latest edition or the one that is the Code of Record for you Project.

NozzleTwister
Houston, Texas

 

[jorgefherrero]

OK, I am using ASME B31.3 1980 edition, I will have to update it. Thanks a lot

 

[NozzleTwister]

Jorge,

When you get an updated copy, be sure to keep your old one for reference. It still applies to work done when it was valid.

Since 1980, allowable stresses have changed several times in Appendix A. Most of the changes have occurred for alloys (Chrome alloys for sure) and Stainless Steel. Most of the chrome alloy changes are in the higher temperature ranges. Stainless seems to be all over. With better data and history of performance the codes are updated where required to reflect this new information.

I believe it's been since 1980 that the modulus of elasticity has been changed in B31.3 for carbon steel, possibly other materials as well.

Also, if you are using B16.5 for flange ratings, there have been changes there as well.

Good luck,


NozzleTwister
Houston, Texas

 

[metengr]

Use ASME Section II, Part D, Table 1B. There is a stress line for SB-673 Grade UNS N08904 (904L) annealed pipe.