1. Smooth type: used for valves with low pressure. Processing is more convenient
2. Concave-convex type: The working pressure is high and medium-hard washers can be used.
3. Tongue-and-groove type: Gaskets with larger plastic deformation can be used, which are widely used in corrosive media and have better sealing effects.
4. Trapezoidal groove type: Use oval metal ring as gasket, used for valves with working pressure Greater than or equal to 64 kg/cm2, or high temperature valves.
5. Lens type: The gasket is in the shape of a lens and is made of metal. Used for high-pressure valves with working pressure Greater than or equal to 100 kg/cm2, or high-temperature valves.
6. O-ring type: This is a newer flange connection form. It was developed with the emergence of various rubber O-rings. It has a sealing effect in the connection form.






1. Direct sealing: The internal and external threads directly act as seals. In order to ensure that the joints do not leak, they are often filled with lead oil, linen and polytetrafluoroethylene raw material tapes. Among them, polytetrafluoroethylene raw material tapes are increasingly used; this material has good corrosion resistance and extremely good sealing effect. It is excellent and easy to use and store. When disassembling, it can be completely removed because it is a non-sticky film, which is much superior to lead oil and linen.
2. Indirect sealing: The force of thread tightening is transmitted to the gasket between the two planes, allowing the gasket to act as a seal.