A flange is a method of connecting pipes, valves, pumps and other equipment to form a piping system. It also provides easy access for cleaning, inspection or modification. Flanges are usually welded or screwed. Flanges are available in round, square, and rectangular shapes. In some cases, flanges are usually in the shape of a ring or a plate to form a rim at the end of a pipe when fastened to the pipe.
The most used flange types are:
MATERIALS FOR FLANGES:
The most common materials used in flanges produced is carbon steel, stainless steel, cast iron, aluminium, brass, bronze, plastic etc.
In addition, flanges, like fittings and pipes, for specific purposes sometimes internally equipped with layers of materials of a completely different quality as the flanges themselves, which are "lined flanges".
The material of a flange, is basically set during the choice of the pipe, in most cases, a flange is of the same material as the pipe.
1. ANSI FLANGES
Size : 1/2" TO 54"
Pressure Rating : 150#, 300#, 600#, 900#, 1500#, 2500#
Carbon Steel : A-105, A-350 LF2, etc.
Alloy Steel : F-5, F-9, F-11, F-22, F-91, ETC.
Stainless Steel : SS 304, SS 304L SS316,
SS 316L, SS 316Ti, SS 321, SS 347, SS 304H, 317L, Etc.
Duplex SS : F-51, F-55
High Strength Steel : A694 Gr 52, 60, 65, 70,
AISI 4130, 4140
Nickel Alloys : Monel 400, Inconel 625, Inconel 825, Alloy 20, etc.
Standards : ASME B 16.5, ASME B 16.47, API 6A
Type : SORF, WNRF, SWRF, BLRF, Threaded etc
Specials : Spacers, Spectacle Blinds, Drip Rings, RTJ, Tongue, Groove, Orifice, etc.
Size : DN 10 to DN 800
Pressure Rating : PN6 to PN64
Material : 1.4404, 1.4307, 1.4571, 1.4541, 1.4462, 1.4306
Standards : EN 1092-1, BS 4504, UN 2278 etc.
Type : SORF, WNRF, BLRF, SWRF, Threaded, etc.
Specials : RTJ, Tongue, Groove, Orifice, etc.
Flange dimensions are determined by the pipe size and the pressure class required for the application. Flanges are standardized according publications from organizations like ASME, MSS, API and others.
Center the gasket on the flange. This is extremely vital where raised faces are involved. Note: standard ANSI ring gaskets, when cut properly, should center themselves with the bolts in place.
Use a torque wrench and well-lubricated fasteners with hardened flat washers to ensure correct initial loading.
Tighten bolts to compress gasket uniformly. This means going from side to side around the joint, in a star-like crossing pattern.
All bolts should be tightened in one-third increments, according to proper bolting patterns. Retorque 12 to 24 hours after start-up, whenever possible.
All applicable safety standards including lockout/tagout procedure should be observed.
Never use liquid or metallic based anti-stick or lubricating compounds on the gaskets. Premature failure could occur as a result.
ASME PCC 1:2000 (R2005) :Guidelines For Pressure Boundary Bolted Flange Joint Assembly