Could a expert person please verify the following?

The maximum operating pressure VS minimum temperature (0C) of carbon steel piping A106 Gr.B of class 300# is 51 Barg. I believe this is the maximum operating pressure of the 300# flanged vlave in a closed position in order to not stuff it. Pipes, fittings and flanged joints can sustain far more pressure than that. If the in line valves remains open, the pressure of the 300# can rise more than allowable pressure for class 300#.

One correction from a previous post is that material group 1.2 applies to A 216 WCC not WCB.

B16.5 still applies to flanged valves.  The updates are not simultaneous and some differences exist.  ASME B16.34 uses  similar material groups with two tables, A-Standard Class and B-Special Class.  Special Class valves include somewhat higher values but exclude flanges.  My copy is B16.34-2004, Valves - Flanged, Threaded and Welding End.  I have not checked to see the material group differences.  I may do that another day.

For A - Standard Class Valves, group 1.1 includes A 216 Grade WCB for 51.1 bar.  Material group 1.2 is 51.7 bar at zero degree C.

API 600 applies to gate valves, common in refinery service.  My offshore experience includes mostly API 6D and API 608 ball valves.  These also comply with ASME B16.34 and B16.5.

At the end of the day, Class 300 valves are limited near 51 bar at zero degree C.  All are gauge pressure.

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