1 flange connection
Flange connection is the most frequently used form of connection between valves and piping or equipment. It refers to the connection between the three parts of flange, gasket and bolt as a detachable connection of a group of combined sealing structures. Pipeline flange refers to the flange used for piping in pipeline equipment, and used in equipment refers to the import and export flange of equipment. Flange connection is easy to use and can withstand great pressure. Flange connection can be applied to all kinds of valves with nominal size and pressure, but there are certain restrictions on the use temperature. In high temperature conditions, the bolts of flange connection are easy to creep and cause leakage. Generally speaking, flange connection is recommended to be used at <350 C.
According to the shape of the joint surface, it can be divided into the following types:
Smooth: for valves with low pressure. Processing is more convenient.
Concave convex type: high working pressure, medium hard washers can be used.
Mortise-groove type: the gasket with large plastic deformation can be used widely in corrosive medium, and the sealing effect is better.
Trapezoidal groove: Use oval metal ring as gasket for valves or high temperature valves with working pressure greater than 60 kg/square centimeter
Lens type: gasket is lens shape, made of metal. High pressure valve or high temperature valve for working pressure greater than 100 kg / square centimeter
O ring type: newer flange connection type, the sealing effect is more reliable than general plain washer.
2 pairs of clip connections
Directly connect the valve and two pipes together by bolts.
3 welding connection
Welding connection refers to the valve body with welding groove, through welding and pipeline system connected to a form of connection.
GB/T 12224, API600, ASME B 16.34 and other standards have made provisions for welding groove.
Valve and pipe welding connection is divided into butt welding (BW) and socket welding (SW), socket welding end should comply with the requirements of JB / T 1751. Butt weld connection (BW) can be applied to various sizes, pressures and high temperature conditions, socket weld connection (SW) is generally applicable to <DN50 valve.
4 threaded connection
This is a simple connection method, commonly used in small valves. There are two situations.
Direct sealing: internal and external threads play a direct role in sealing. In order to ensure that the joint does not leak, it is often filled with lead oil and linen, of which raw material belt is widely used. This material has excellent corrosion resistance, excellent sealing effect, easy use and storage, can be removed completely when disassemble, because it is a non-sticky film, much superior to lead oil, linen.
Indirect sealing: the force of thread tightening is passed to the washers in the two plane, so that the washers are sealed.