Common flange sealing surfaces and their codes

1.Flat face (FF)
Introduction: The flat face sealing surface is a relatively simple form of sealing surface. It is a smooth flat plane without protruding or grooved structures. It is relatively easy to process and has a low cost.
Application scenarios: This type of sealing surface is generally applicable to occasions with low pressure, non-toxic media, and where the medium is neither flammable nor explosive. For example, in the connection of some small water pipes, when the requirement for sealing is not extremely high, it can be used. In low-pressure circulating water systems, when the temperature and pressure are relatively stable and the medium is harmless, the flat flange can play its simple and practical role well.

2.Raised face (RF)
Introduction: The raised face sealing surface has a protruding platform. When connected, the raised face contacts the raised face of another flange through a gasket to achieve sealing. The height of the raised face is generally small, and its sealing performance is improved compared to the flat face sealing surface.
Application scenarios: The raised face flange is one of the most widely used forms of flange sealing surfaces. It can be used for connecting pipelines with various media under medium and low pressures in industries such as chemical and petroleum. For example, in the general chemical material conveying pipelines, as long as the pressure is not particularly high, the raised face flange combined with a suitable gasket can meet the sealing requirements.

3.Male and female face (MFM)
Introduction: The male and female face sealing surface consists of a concave face and a convex face as a mating structure. During installation, the convex face flange is inserted into the concave face flange, and the gasket is placed inside the concave face, which can effectively prevent the gasket from being extruded and has good sealing performance.
Application scenarios: It is suitable for occasions with relatively high pressure, such as in some medium and high-pressure steam pipelines or high-pressure chemical pipeline systems. Due to its reliable sealing performance and good effect in preventing medium leakage, it is used in situations where high sealing requirements are imposed.

4.Tongue and groove face (TG)
Introduction: The tongue and groove face sealing surface is a more complex structure, consisting of a tongue face and a groove face. During installation, the tongue face is inserted into the groove face, and the gasket is placed inside the groove. This structure has a better fixing effect on the gasket and excellent sealing performance.
Application scenarios: It is often used in occasions where the medium is flammable, explosive, toxic, and in high-pressure situations. For example, in the pipeline systems for transporting toxic, harmful, highly flammable and explosive media (such as hydrogen, hydrogen sulfide, etc.) in the petrochemical industry, the tongue and groove face flange can maximize the sealing and safety of the system.