The sealing of gas transmission equipment is mostly contact sealing, including static sealing and dynamic sealing. The sealing between the joints without relative movement or relative static is called static sealing, such as the sealing between the joint faces of various containers, valves and pipeline flanges, the sealing between the joint faces of valve seats, valve bodies and casings of various machines, etc., while the sealing between the joint faces with relative movement is called static sealing is called dynamic sealing, such as the sealing between the valve stem and stuffing box, the rotating shaft of pump, compressor, etc., or the reciprocating rod and the body, etc.
For gas transmission equipment in gas plant, its static seal mainly includes connection gasket seal, O-ring seal, threaded connection seal and the sealing with pressure used in non-stop transmission operation. Among them, gasket seal is the most common. Gasket seal can be divided into non-metallic gasket seal, semi-metallic gasket seal and metallic gasket seal according to different structural materials. According to the working pressure, the static seal can be divided into medium and low pressure seal and high pressure seal. For example, the non-metallic gasket or semi-metallic gasket is usually used for the static seal of medium and low pressure vessels, equipment or pipelines, while the metal gasket is generally used for the static seal of high pressure vessels or equipment.
Gasket sealing is the most important static sealing form of detachable connections in gas transmission equipment, such as pressure vessel, process equipment, power machine and connecting pipeline. Their working conditions are very complex, which is the main means to prevent the transmission medium from leaking out through these joints, and also the most important and difficult task faced by each station. Gasket seal is generally composed of connectors, gaskets and fasteners (such as bolts, nuts, etc.), so when determining the tightness of a joint, the whole connection structure must be considered as a system. As mentioned above, gasket is used to produce initial assembly seal and maintain working seal on the sealing surface of two connections. Theoretically, if the sealing surface is completely smooth, parallel and rigid enough.