There are several species of general pneumatic valve equipment

connection pneumatic valve, pneumatic valve, pneumatic valve welding connection flange connection.
it is known that the pneumatic valve is a fluid conveying system in the control unit, a cut-off, regulation, guide, to prevent the reverse flow, voltage regulator, shunt or overflow relief, and other functions, is widely used metal machinery and equipment, can be used to control air, water, steam, all kinds of corrosive medium, mud, oil, liquid metal and radioactive medium such as various types of fluid flow. Used for fluid flow control system of pneumatic valve, pneumatic valve from the simplest deadline to extremely complex control system used in all kinds of pneumatic valves, its breed and specification is various, classification of the common connection way of pneumatic valve has the following kinds.
( ） Threaded connections pneumatic valve
this connection will be pneumatic valve is usually end processed into thread taper pipe or straight pipe, can make its connection to the taper pipe nipple or road. Because of this connection may appear larger leakage channel, so it can be used sealants, sealing adhesive tape or filler to plug the channel. If the pneumatic valve body material can be welded, but expansion coefficient difference is very big, or change range of working temperature range is larger, threaded connection department must be honey sealing. Threaded connection of the pneumatic valve is nominal given. it mainly in mm below the pneumatic valve. If size size is too big, installation and connection department seal is very difficult.
in order to easy to install and remove the threaded connection of pneumatic valves, the appropriate placement of the piping system on the available pipe joint. Nominal diameter in mm below the pneumatic valve pipe fittings, pipe socket for use as a pipe socket threads will connect the two parts together.
（ ） Pneumatic valve flange connection
flange connection of the pneumatic valve, its installation and removal are more convenient. But heavy than the threaded connection of pneumatic valves, the appropriate price is also high. So it is suitable for all kinds of sizes and pressure pipe connection. However, when the temperature exceeds degrees, due to the bolts, gasket and flange slacken, also obviously reduce the load on the bolt, to force a lot of flange connection leaks may be produced.
( ） Pneumatic valve welding connection
this connection is suitable for all kinds of pressure and temperature, under the condition of the load moment when using, more reliable than the flange connection. But the pneumatic valve welding connection disassembly and difficult to install, so its use is limited to usually can run reliably for a long time, or use the conditions of Dutch engraved, high temperature occasion. Such as coal-fired power stations, nuclear power engineering, ethylene project on the pipeline.
nominal diameter in mm below the welding pneumatic valve usually has a flat side pipe welding socket to undertake. Because the socket welding forming gap between the pin and pipeline, thus has the potential to crack corrosion by some media, at the same time, the vibration of the pipeline can make the connection part fatigue, so the application of the socket welding by certain restrictions.
in the nominal diameter is bigger, use condition load, high temperature occasion, groove used to determinate the pneumatic valve body welding, at the same time, the butt joint with the original requirements, the welders must choose very skillful to complete the job.