what is the difference between rf and ff flange?
RF is raised face flange, which can be used under the pressure of PN1. 6~PN10MPA. FF is flat face flange, which has lower sealability than RF, its pressure is 1.6~2.0MPA (standard: GB9113), and other joint faces like RTJ, FM have higher pressure. The gaskets for RF and FF can be used for each other.