This standard specifies the type, size, marking and technical requirements for non-metallic soft gaskets for pressure vessel flanges. This standard applies to non-metallic soft gaskets for NB/T 47021 "Type A Flat Welding Flange", NB/T 47022 "Type B Flat Welding Flange" and NB/T 47023 "Long Neck Butt Welding Flange".