Piping Class

The classes are combined temperature pressure ratings (ASME B16.34)

Flange B16.5 (table 2 gives the pressure temperature ratings for class 150 to 2500 depending on the material 1.1 to 3.16)

Piping class B31.3 (process piping guide),

Next portion is the WOG rating (Water, Oil gas rating) this is different from the class and belongs to cold fluid ratings that the valve can handle. Note that the ANSI/ASME ratings are more of flange oriented.

Then is API 602. The class 800 does not figure in ASME but does in API.

API 602 Section 4 :
"Class 800 is not a listed class designation, but is an intermediate class number widely used for socketwelding and threaded end compact valves." (Section API 602)

4.1.2 Interpolated ratings
Pressure/temperature ratings for Class 800 shall be determined by the equation:

P8 = 1/3 P6 + 2/3 P9
where P8 is the pressure at the specified temperature, expressed in bar3, for Class 800 rounded to the nearest (10 kpa);
P6 is the listed pressure, at the specified temperature, for Class 600, expressed in bar;
P9 is the listed pressure, at the specified temperature, for Class 9004, expressed in bar.

Thanks very much guest....

For a simple answer for flanges check this link:

http://www.scsenergy.com/scsdataflgrating.htm