Pipe flanges connect pipes, valves, pumps and other equipment in a piping
system. Flanges are usually welded or screwed into the systems and then joined
with bolts. The eight types of pipe flanges are available in round, square and
A blind, or blanking, flange is a round
plate with no center hold (but with bolt holes) that closes the ends of piping
Lap Joint Flanges
Piping fitted with lapped pipe or with
lap joint stub ends often use lap joint flanges. Also, systems frequently taken
apart for inspection and cleaning often use lap joint flanges.
Orifice meters that measure the flow rate
of either gases or liquids use orifice flanges.
When a change in diameter is required in
a piping system, reducing flanges are used. A reducing flange has a specified
diameter with a bore of a different, smaller diameter.
Slip-on flanges slide over the end of a
pipe and are then welded into place. These flanges work well for low-pressure
Socket Weld Flange
The socket weld flange is
counter-bored to accept the pipe before being fillet welded. This type of flange
is similar to a slip-on flange. The bore of the pipe and flange are the same,
which provides good flow characteristics.
Threaded flanges, which are threaded in
the bore to match an external thread on the pipe, are attachable to a pipe
Weld Neck Flanges
Weld neck flanges have a long tapered
hub and are often used for high-pressure applications. The pipe and flange bores
match, which reduces turbulence and erosion inside the pipeline.