Five Types of Flange Facings and Their Characteristics

Flat Face
The flat face flange facing is mainly used for wide flanges and piping systems with low pressures. The flat face flange facing and the contact surface of the corresponding gasket are distributed on both the inner side and outer side of the flange bolt's center. The gaskets are usually made of non-metallic soft materials such as asbestos rubber and the pretightening specific pressures of the gaskets are often low.
         
Raised Face
The raised face flange facing is mainly used for narrow flanges, that is, the contact surface of the gasket is located within the circumference of the flange bolt hole, which also means that the outer diameter of the raised face flange facing's corresponding gasket is exactly the same as that of the flange connecting bolt's inscribed circle and that the position of the gasket can be fixed at the center of the flange facing with the help of the bolt when installed. This type of flange facing is most widely used on flanges.

Gaskets which are applicable to the flanges with raised face flange facing include a variety of non-metallic flat films, wrapped gaskets, metal gaskets, wound gaskets (including wound gaskets with outer rings or inner rings).
 
Female and Male Face
The female and male face of flange facing is characterized by the fact that the gasket is embedded in the groove of the female face to reduce the possibility of the gasket being impacted by the pressure and to facilitate centering during assembly. Compared with the raised face flange facing, this type of flange facing can often be used when there are some stringent sealing requirements on the flange facing. Its drawback is that a flange has two types of flange facing and the process of the female and male face is more complex than that of the raised face flange facing, which also makes the female and male face not used as widely as the raised face on flanges. If compared with the tongue and groove face flange facing, it also has the disadvantage that it can not protect the gasket from being squeezed into the pipeline.

Gaskets which are applicable to the flanges with female and male face flange facing include a variety of non-metallic flat films, wrapped gaskets, basic type or wound gaskets with outer rings or inner rings.
 
Tongue and Groove Face
This kind of flange facing has the similar advantage of the female and male flange facing and is superior to the female and male flange facing to some degree. The gasket of the tongue and groove face is located in the annular groove and is restricted by the metal walls on both sides to avoid its deforming and being squeezed into the pipeline under the effects of the pressure. Without directly contacting with the fluid media in the pipe, the gasket will be less eroded or corroded by the fluid media, which makes the flanges with tongue and groove face flange facing applicable to occasions with high pressure, flammable, explosive, toxic media and with other sealing requirements. This type of flange facing is good for centering, but it is difficult to be processed. When the gasket is replaced, it is easy to damage the flange facing, and the flange must be separated in the axial direction during installation and removal. Therefore, the possibility of separating the flange in the axial direction must be taken into account when the pipeline is designed.

Gaskets which are applicable to the flanges with tongue and groove face flange facing include a variety of metal gaskets, non-metallic flat films and basic type of wound gaskets.
 
Ring Joint Face
Flanges with ring joint face flange facing also belong to the narrow flange, which have a o-shaped trapezoidal groove on the raised face as the flange facing. Flanges with ring joint face flange facing is similar to the flanges with tongue and groove face flange facing in that the flange must be separated in the axial direction during installation and removal, so the possibility of separating the flange in the axial direction must be taken into account when the pipeline is designed.  

This type of flange facing is dedicated to working in with the solid metal gaskets which are made of metal materials and are processed into the shape of octagonal or oval, to obtain the sealing connection. As the metal ring gasket has the inherent characteristics of various metals, thus the ring joint face flange facing has good sealing performance and does not have very strict requirements on the installation, which are suitable for conditions with high temperature and pressure. However, there are high requirements on the processing accuracy of the ring joint face flange facing.