GOST-12820 is standards for steel plate flat welding flanges formulated by the Russian Standardization Organization. It is applicable to pipe and valve connections.
GOST Flanges are flanges manufactured according to the standards set by the Russian State Standard (GOST), which defines the specifications for flanges used in various industries, particularly in Russia and other former Soviet states.
Lap joint flange shape is similar to slip on flange, it has a curved radius at the bore, which can connect with a stub end fittings and slide over the pipe.