What is a flange rating?

Answer 1

*Any flange having different MOC bears the rating with respect to international standards like ANSI B16.5.
*It is a designed pressure that a flange can withstand.

*For example a flange is having the following specification:
25NBX150#,FORGED CARBON STEEL as per ANSI B16.5

is having 150 psi flange rating.
It can withstand 150 psig pressure safely.

(Noting that in most cases the pressure-temperature charts of a given spec will allow for normal operating pressure to far exceed the class rating at ambient temperature. For example a 150# flange in A105 Carbon Steel will rate for 285PSI at -20 to 100 Degree F. For more information see www.texasflange.com The original intent was to class the parts to safely hold the given pressure at relatively high temperature. Since often times the operating temperatures are much lower the flanges can usually be used well above their given rate. When in doubt take your design criteria to a company that deals in it and ask for the specifics.)

*Pipe flanges that are made to standards called out by ASME/ANSI B16.5 or ASME/ANSI B16.47 are typically made from forged materials and have machined surfaces. They are typically in "Pressure Classes" such as 150#, 300#, 600#, 900# 1500#; however, ASME B16.47 still recognizes the 75# or "Class 75" flange for certain low pressure and low temperature applications. These "Pressure Classes" have both pressure and temperature ratings for specific materials. The flange faces are made to standardized dimensions and are typically "flat face" "raised face" "tongue and grove" or "ring joint" styles, although other obscure styles may be permitted. Flange designs are available as "welding neck" "slip-on" "lap joint" "socket weld" "threaded" and also "blind flange". The gasket type and bolt type are generally specified by the standard(s); however, sometimes the standards refer to the ASME Boiler and Pressure Vessel Code (B&PVC) for details ( see ASME Code Section VIII Division 1 - Appendix 2 ). These flanges are recognized by ASME Pipe Codes such as ASME B31.1 Power Piping, and ASME B31.3 Process Piping. Materials for flanges are usually under ASME designation: SA-105 , SA-266 or SA-182.

*Please visit following link and download the software, you will get both pressure v/s temperature rating of flange: