- Flanges steel welded end-to-end (vorotnikovy), GOST 12821-80.
Flanges of various Du
For flanges, as well as for other details of pipelines, the Russian state standard specification 28338-89 standard established a parametrical row from 49 values of diameter of the conditional pass (Du, Du, DN, the nominal internal diameter of the pipeline) measured in mm. Du of a flange — one of its main characteristics, but it is not the exact basic size of a flange.
Flanges of Du 15, 20, 25, 50, 80, 100, 200 are most often made of high-quality metal rolling by method of hot stamping. Flanges with conditional pass of average value are made from steel cast ring preparations. Flanges of big Du (500, 600, 800, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2800, 3000, 3400, 4000 mm) can be made of shod preparations.
Flanges of various Ru
Other key parameter of flanges is conditional pressure (Ru, PN, kgf/cm ², MPa) as the largest admissible excessive working pressure at a temperature of 20 °C. The state standard specification 26349-84 standard defined a parametrical row from 26 sizes from 0,1 to 800 kgfs/cm ².