A flanged joint
is a connection between a pipe and another piping equipment (example, another length of pipe, a valve, or a pressure vessel). Hundreds, even thousands, of flanged joints are necessary for a piping system to function.
The three main components of a flanged joint are:
two mating flanges (the “main” and the “companion” flange).
a number of stud bolts for flanges (flanges of different diameter, class, and face finish require different numbers and sizes of stud bolts and nuts for proper sealing);
two gaskets, which can be either metallic (spiral wound, ring joint, jacketed and Kammprofile), or non-metallic (non-asbestos gaskets).
A steel pipe can be welded on the flange (this is the case of weld neck, socket weld, slip-on, and lap joint flange) or screwed onto it (threaded flange). Welded connections between pipes and flanges are used for high pressures and temperatures applications, and diameters above 2 inches. Threaded connections are used for small diameter piping systems that are not subject to mechanical forces as expansion, vibration, contraction, oscillation.
A Flange insulation kits can also be used for a flanged connection, to protect the corrosion on flanges, bolts, and gaskets generated by the static currents running through the pipeline (this is called “cathodic protection”).
To prevent dangerous leakages in the pipeline, flanged joints shall be executed by trained personnel only (the standard TSE – TS EN 1591 Part 1-4, “Flanges and their joints” is the reference norm).