Valve end connection structure and size is very important to the normal installation and use of the valve, if improper selection, easy to cause size or connection structure mismatch during the installation process, resulting in the valve can not be installed. Therefore, when selecting the valve, special attention should be paid to the correct and appropriate selection of the valve end connection structure to ensure the smooth installation and use of the valve.
The main connection type of the valve: threaded connection, flange connection, welding connection.

1.Threaded connection type
Threaded connection is a detachable connection, mostly using threaded connection in the case of unfavorable welding or need to be disassembled , for > DN50 threaded connection can be used for fluids without danger, but its connection is not easy to control, and it is difficult to apply enough torque to tighten the connection joint without damaging the member, so the threaded connection is mostly used in the pipeline ≤ DN50 without dangerous fluids,Such as threaded end ceramic lined ball valve,.etc.

2.Flange connection type
For pipes > DN50, flange is the most commonly used connection method, and Flanged end valves are very convenient to install and remove, and can be applied to a wide range of nominal sizes and pressures. The flange connected with the valve can be divided into flat welding flange, butt welding flange, socket welding flange, integral flange, etc.; According to the sealing surface form, it can be divided into full plane flange, raised face flange,female and male flange, tongue and groove face flange and ring connection flange. The choice of various flange construction forms and sealing surface forms depends on different operating conditions.Such as flange end ceramic swing disc gate valve,flange end ceramic double disc gate valve,flange end ceramic lined ball valve,.etc.
 
3.Welding connection type
The butt weld end connection structure is suitable for various pressures and temperatures, and is more reliable than the flange connection when used under harsher conditions. However, welded valves are difficult to disassemble and reinstall, so they are mainly used in situations where they usually operate reliably for a long time, or where conditions are harsh and the temperature is high. Such as thermal power stations, nuclear energy engineering, ethylene engineering on the pipeline.Such as butt welding end butterfly valve,welding end globe valve,.etc.