This is the most commonly used form of connection in valves. According to the shape of the joint surface, it can be divided into the following categories:
1. Smooth type: For valves with low pressure. Processing is more convenient
2. Concave-convex type: high working pressure, medium-hard washer can be used
3. Tenon-groove type: gaskets with large plastic deformation can be used widely in corrosive media, and the sealing effect is better.
4. Trapezoidal groove type: Use elliptical metal ring as gasket for valves with working pressure greater than 64 kg/square centimeter or high temperature valves.
5. Lens: Washers are lens shaped and made of metal. High-pressure valves or high-temperature valves with working pressure greater than 100 kg/m2.
6. O-ring type: This is a relatively new form of flange connection. It is developed with the emergence of various rubber O-rings. It is in the form of sealing effect connection.