Steel Flanges for pipes GOST 12820-80

Steel grade determines the purpose and scope of products. For the manufacture of such parts, various steel grades are used: alloyed, low alloyed, cold-resistant, etc. (steel 20, 09G2S, 13KhFA, 12Kh18N10T)

Flange connections are key structural elements and make it easy to connect pipelines from different grades of steel, provides easy dismantling, repair and modernization of various instruments and equipment.
Valves, valves and other locking equipment of large and small diameters are mounted using a flange connection, it is one of the simplest in execution and reliable in operation.

GOST 12820-80, as well as its new edition of GOST 33259-2015, is designed for flat steel welded flanges for pipelines and connecting parts, as well as for connecting flanges of fittings, devices, connecting parts of equipment, nozzles of apparatuses and tanks.

Conditional pressure of parts: Ru from 0.1 to 2.5 MPa (from 1 to 25 kgf / cm2), medium temperature from 203 to 573 K (from - 70 to + 300 ° C).

Notes:

• Surface treatment A with a roughness of Ra £ 100 microns is permitted.
• It is allowed to perform a chamfer angle under the weld (55 ± 3) °.

Steel flanges must be manufactured with sealing surfaces of versions 1, 2, 3 and connecting dimensions in accordance with GOST 12815-80.
There is a tolerance for the manufacture of planes with sealing surfaces of versions 4, 5, 8 and 9.
An example of the designation of a round steel flat welded flange Dy 50 mm on PN 1.0 MPa (10 kgf / cm2) of steel 25, version 1 (with a connecting protrusion):

Connecting flange 1-50-10 Art. 25 GOST 12820-80 (1-type design, 50-conditional diameter, 10-working pressure)

Steel flanges are produced in various ways:

• Stamping (stamped flanges).
• Forging (forged flanges).
• By the method of turning from a steel billet.
• By plasma arc and oxygen cutting.
• Flexible of rolled steel with further welding of the joint.
• Centrifugal electroslag casting (cast flanges).

It is allowed to produce products in other ways and in other sizes individually according to the drawings.

Extreme deviations of the sizes:
dв - according to Н 14 (during manufacturing by stamping - according to accuracy class Т4 GOST 7505-89);
b - for stamped flanges, as well as those manufactured by bending from strip steel with subsequent butt welding and hot straightening - according to accuracy class T4 GOST 7505-89. In this case, reinforcement of the seam is allowed, which is not taken into account when determining the maximum deviation.

Unspecified dimensions and deviations - according to the working drawings approved in the prescribed manner. Pipes of other diameters and grades of steel are allowed.

Allowed for flanges DN 200 mm boring of the inner diameter of the actual outer diameter of the pipe with a gap on the side of not more than 2.5 mm; for DN flanges ‹200 mm, the internal diameter is allowed without a gap with the pipe.

Technical requirements, material of flanges, fasteners and gaskets, as well as marking, packaging, transportation in accordance with GOST 12816-80.