How to read Alloy steel Grade No in Mandatory Appendix A of ASME B31.1

[YANGzhou01]

I'm reading A213 T91 and A335 P91 in Table A-2 "MANDATORY APPENDIX A", Pg #110 of ASME B31.1-2004. They look to me the same. So, what's the difference between T91 and P91? Also, how to interprete those alphas in A359 FP12, A213 TP304, A217 WC1,A451 CPF8M etc. in Table A-3? I mean what "FP", "TP", "WC", "CPF8M" represent? What's related between "A213" and "T91"?
Thanks a Lot!

 

[metengr]

The designations for the various grades and conditions are explained in the ASME/ASTM Material Specifications.

TP-Type
A- ASTM
SA - ASME
T-tube
P-pipe

I can go on, but you need to research this information on your own.