Flange couplings – general information

Flange couplings are very extensively used across the industry, most of all to connect sections of pipelines, yet to join them with flexible hoses as well. The flange couplings are usually welded to the pipeline. Typically they are round and made of carbon steel (no coating) or zinc plated, or they are made in stainless steel. The flange coupling is sealed with a seal and screwed together with bolts on the circumference of the flange. The flange has a sealing face which is adjusted to the type of sealing that is to be used. Usually a flat seal is applied.

The flanges used in the industry are manufactured according to the requirements of standards which specify their types, dimensions, types of sealing surface, steel types, acceptable values of pressure at specific temperature.

• The flanges according to European standards, called PN flanges, are manufactured according to EN 1092-1 standard. PN symbol and the number that follows e.g. PN16 indicates the class of flange nominal pressure (class rating) e.g. PN16 means the pressure of 16 bar (at the temperature of +20°C). The flanges: PN10, PN16 (most often), PN25 and PN40 are used with flexible hose assemblies.
• The flanges according to the American standards, called ASA flanges, are manufactured in compliance with ASME (ANSI) B16.5 standard. Their dimensions are different from PN flanges and thus they are not interchangeable. The most popular classes of American flanges: ASA150 (corresponds to PN20) and ASA300 (corresponds to PN50).

To select the connections for the sections of an installation, it is important to know the basic mating dimensions of the flange for the particular nominal diameter DN (diameter of flange face, flange outside diameter, bolt circle diameter, number and diameter of bolt holes). The basic mating dimensions of basic flanges are given in the technical information attachment „Mating dimensions for PN and ASA flanges”.

The flanges are welded to the fixed parts of the installation or as flange fittings of flexible hoses (the flange is welded to the stub – hose tail). The flange fittings come either with a fixed flange or swivel flange (the flange with bolt holes is separate from the sealing face). Generally, if there is the fixed flange at one end of the hose, there should be the swivel flange on the other end, to avoid hose twisting.

Tubes International stocks the following:

• different types of flanges made of carbon steel, AISI304 and AISI316 stainless steel;
• weld-in stubs for flanges;
• complete flange fittings to be assembled to rubber and plastic hoses;
• flange adapters;
• seals and bolts for flange connections.

Tubes International supplies non-standard flange couplings made according to customer specification, made of various materials.

The flange fittings for steel hoses and composite hoses are in the relevant hose groups, hygienic flange fittings (Triclover) are in the group: stainless steel hygienic couplings. High pressure flange fittings (SAE flanges, hydraulic pump flanges) are in HIGH PRESSURE section.

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