GOST 12836 FLANGE tells you that the flange is the interconnected part between the shaft and the shaft, which is used for the connection between the pipe ends; it is also used for the flange on the inlet and outlet of the equipment, which is used for the connection between the two types of equipment, such as the reducer flange.

GOST 12836 FLANGE tells you that flanges have holes and bolts that hold the two flanges together. The flanges are sealed with gaskets. GOST 12836 FLANGE tells you that flanges are used in pairs, wire flanges can be used for low-pressure pipelines, welded flanges can be used for pressures above 4 kg, and gaskets are added between the two flanges, and then solid bolts are used. 
GOST 12836 FLANGE tells you that flanges have different thicknesses for different pressures and they use different bolts. GOST 12836 FLANGE tells you that when pumps and valves are connected to pipelines, the parts of this equipment are also made into corresponding flange shapes, also known as flange connections.
The above information is the GOST 12836 FLANGE manufacturer's introduction and analysis of the flange, hope it helps you.