A pipe flange connects fittings, valves, pipes, and other piping components using gaskets and bolted connections. The type of flange used and its application determine whether it is installed via screwing, lapping, or welding. Factors that must be considered include operating temperature, type of fluid being conveyed, pressure rating, and flange size. When properly specified, pipe flanges provide a secure connection but are easy to disassemble through various access points.
Here, we’ll discuss flanges in further detail, covering their advantages, pressure ratings, and common applications.
Benefits of Flanges
There are certain applications—such as large OD, high-pressure piping systems—where flanges must be used. However, flanges may also offer benefits over traditional hydraulic fittings in other applications, such as severe service applications on mobile construction machinery. In these cases, pipe flanges provide the following benefits:
- Connects pipes and ports more easily
- Easy to assemble in tight spaces with limited clearance
- Can be installed in hard-to-reach places, eliminating adapters in the hose line or tube
- Simpler maintenance in rigid lines like metal tubes or pipes
- Absorbs shock and pressure surges that would otherwise damage a traditional large hydraulic fitting
- Firmer connections, to reduce the risk of components loosening during severe service
Flange Pressure Ratings
All flange specifications are broken down by size and pressure classification. The ANSI B 16.5 has 7 pressure ratings. They are 150#, 300#, 400#, 600#, 900#, 1500#, and 2500# pressure ratings. The ASME B 16.47 Series A and B flanges are supplied in 150#, 300#, 400#, 600#, and 900# pound range. Please note that in the 400#, 600#, and 900# ratings, sizes 38” through 60”, Series B are the same dimensions as Series A.
The industry standards are made to the following pressure ratings: Class 75, Class 125 Light Weight, Class 150/125, Class 175, Class 250, Class 300, and Class 350.
The AWWA classes for the water works industries are Class B at 86 psi and Class D at 175 psi up to 12” nominal pipe size. For 14” and above, it is 150 psi. Class E flanges are rated at 275 psi. Class F is rated 300 psi.
