ANSI B16.5 -2013 is the official standard for ANSI Class Pipe Flanges and Flanged Fittings, applied specifically to those made from cast or forged materials, as well as blind flanges and some reducing flanges crafted in cast, forged, or plate. It covers evaluations and standards for the following characteristics, noted in both metric and U.S. units of measure:
Pressure-temperature ratings, materials, tolerances, dimensions, marking, testing, methods of designating openings.
ANSI standard flange dimensions are designated as 150, 300, 400, 600, 900, 1500, and 2500, in sizes NPS 1/2 through NPS 24.
ANSI Class Flange Types
Regardless of size or specification, flanges are fundamentally designed to close, cover, connect, or support pipe systems. The six common types of ANSI Class Flanges, including:
Slip-on, in both ring and hub style, to fit over a pipe
Weld neck, machined to match a pipe’s inside diameter and attached via welding
Blind, for sealing the end or opening of a piping system or vessel
Lap joint, to pair with stub end fittings for applications demanding dismantling
Threaded, to fit pipes with external threads without the need for welding
Socket-weld, to provide ideal inside flow with the use of a socket fit and top weld
Material Grades and Performance
The most common material grade for ANSI Class Flanges is forged or cast, unless otherwise specified.