The sealing face of flange has the whole plane FF, protruding surface RF, convex surface M, concave surface F, mortise surface T, groove surface G and ring joint surface RJ. General concave and convex surface MF, mortise and groove surface TG are used in pairs.

The surface flange sealing cover has the advantages of simple structure, convenient processing, and convenient for anti-corrosion lining. Due to the large contact area between the sealing cover and the gasket, the gasket is easy to extrude the sealing cover if the pretension is improper. It is not easy to compress, and has poor sealing performance. It is suitable for occasions with low pressure. It is generally used under the pressure of PN less than 2.5mpa.

The sealing face of the flange is flat, which has a large contact area with the gasket. After pretightening, the gasket is easy to extend or move to both sides.

Attapulgite flange sealing face matching two flange joint surface one is concave surface and one is convex surface. It is easy to adjust when installed and can effectively prevent the gasket from being extruded by the sealing cover.

The sealing face of mortise flange is made of a mortise face and a groove face, so the sealing face is narrower. As the gasket is blocked by the groove face, the gasket will not be extruded and compressed, and less erosion and corrosion by the medium. Suitable for pressure range from 1.6 to 10Mpa, the gaskets used are type A, the basic type, in the winding gasket. When installed, it is easy to adjust, the gasket is under uniform force, and the seal is reliable. It is suitable for use of inflammable, explosive and poisonous medium. Only because the gasket is narrow, it is difficult to replace. Mortise and groove flange and concave flange need to be used together.

The groove of the ring joint face is a trapezoidal groove, which needs an octagon gasket to seal. The two face flanges are identical. The sealing face is a ring groove structure, suitable for pressure range of 2.5-16.0 Mpa. The gasket used is a metal ring pad, which can be divided into octagonal metal ring pad and oval metal ring pad according to the structure. The flanges of the ring joint face do not need to be used in pairs, only different gaskets are used. The flanges of the ring joint face are also called ring groove face flanges in the petrochemical department, and the sealing cover is trapezoid groove face. These two flanges are superior to the concave and convex surface flanges, and are suitable for high temperature and high pressure conditions.