Like other flanges it has Raised Face (RF) Type and Ring Type Joint (RTJ). Raised Face Weld Neck Flange RTJ Weld Neck Flange Raised face weld neck flange bottom side has a small portion surrounding the bore that protrudes from the face. Gasket seat will be placed in this raised area. Depending on the different pressure ratings, different height of raised face will be adopted. For example, 150# and 300# flange raised face height is 1/6”, above 300# the height will be above 1/4”. The ring-joint type of WN flange has a special made groove, here you can place a metal gasket seat to seal the connects. So this type of SW flange is used in high temperature and high pressure services.