Profile: Freture Techno Pvt Ltd specializes in providing valves, actuators, joints, and accessories. A slip on flange is a form of flat welding flange. Flat welding is only used to join the outer layer of a sandwich, not the inside layer. In general, a flat welding flange, such as an ASME B16.5 Class 600 Slip-On Flange, could be utilized in both medium and low pressure pipelines. These pipe lines with tapped Slip-On Flanges have a nominal pressure of less than 2.5 Mpa. Flat welding flanges have four different sealing surfaces. They are flat face. RF or raised face, FM/M, and TG, also known as the tongued and groove face.