Connection surface types for pipe flanges in non-standard equipment

Actually, this question has been discussed in great depth on the forum; you might as well search there for “Further discussion on design concepts: advantages and disadvantages of convex-concave flange sealing surfaces.” I am also quoting answers from others because I think they are more accurate. Comparison of various types of compression surfaces: a) Convex compression surface: Features: simple structure, easy to manufacture, convenient for installation and removal, and suitable for anti-corrosion lining； Usage: The pressing surface can be smooth, suitable for applications with PN of 2.5 MPa or less ； Grooved (2–4 grooves, with a width and depth of 0.8mm X 0.4mm; the grooves are triangular in cross-section), which facilitates deformation of the gasket and prevents non-metallic gaskets from being pushed out, allowing for wider application ； Container flanges can withstand pressures up to 6.4 MPa, while pipe flanges can handle pressures as high as 25–42 MPa; however, as the nominal pressure increases, the corresponding nominal diameter decreases. b. Ribbed compression surface: It facilitates alignment during installation and effectively prevents the gasket from being pushed out; however, its greater width requires a higher bolt pre-tensioning force, as well as larger flange dimensions. Suitable for container flanges and pipe flanges with PN less than or equal to 6.4 MPa. c. Tenon and groove compression surface: It is formed by the combination of the tenon surface and the groove surface; the gasket is placed within the groove and thus does not get pushed out of the compression surface, experiencing less erosion and corrosion from the medium. Due to its narrow sealing surface, it requires less bolt force, making it suitable for applications with higher pressures and stringent sealing requirements, such as those involving flammable, explosive, or highly toxic substances. However, the structure is complex; the gaskets are prone to being squeezed into the grooves and are difficult to remove, making it hard to replace them. It should also be noted that the tenon-flanged parts need to be protected during transportation to prevent deformation from collisions. d. Trapezoidal groove compression surface: The trapezoidal groove compression surface is used in combination with an elliptical ring gasket or an octagonal ring gasket. The conical surface of its groove forms a line-contact seal with the ring gasket, hence it is used in high-pressure applications.