The GOST 12836 FLANGE tells you that flanges are the parts that connect pipes to each other, at the ends of pipes. There are holes on the flanges, and bolts make the two flanges tightly connected. The flanges are sealed with gaskets.

The GOST 12836 FLANGE tells you that a flange is a disc-shaped part, most common in plumbing engineering, where flanges are used in pairs. In pipeline engineering, flanges are mainly used for the connection of pipelines.
The GOST 12836 FLANGE tells you that at the end where two pipes need to be connected, install a flange plate on each side. Wire flanges can be used for low-pressure pipes, and welded flanges can be used for pressures above 4 kg. 
The GOST 12836 FLANGE tells you that add a gasket between the two flanges and fasten them with bolts, different pressure flanges have different thicknesses and use different bolts.
The above information is the GOST 12836 FLANGE manufacturer's introduction and analysis of the product introduction of Flange, hope it helps you.