Characteristics and Selection Principles of Plug Valves

The plug valve can also be called the 90 degree rotary switch valve which has the best flow performance and the minimum fluid resistance next only to those of the ball valve.

If the plug valves have runners with round holes, they can also meet the pigging requirements. Compared with ball valves and gate valves, plug valves have no closed valve cavities, which makes them suitable for the medium conditions where solidification or crystallization of media left may occur. Compared with butterfly valves, the sealing elements of plug valves are not in the middle of the runners, and thus fluid have small resistance and good flow performance.

One shortcoming of plug valves is that they are not applicable to the pipelines with large diameters because of their heavy weight. Limited by the wear compensation, the seal pressure of the plug valves' internal parts can not be too large, which makes plugs valves usually used for the low temperature and low pressure working conditions, especially for the corrosion resistance medium conditions. In the case of the corrosion resistance medium condition, the full lining structure can be selected. Plug valves with metallic seal structures used for the relatively high temperature and high pressure conditions are usually a little bit expensive.
 
According to the above characteristics of plug valves, the selection of plug valves should be based on the following principles.

1. With small resistance drop, plug valves are suitable for the medium conditions containing media sensitive to the resistance drop.

2. Plug valves have heavy weights as well as high prices, and this feature becomes more and more obvious when sizes of plug valves become larger. Thus, the economical principle should be taken into account when plug valves with large sizes are chosen.

3. For soft sealed plug valves, their operating temperature and pressure are limited by the sealing and lining materials.

4. Without any closed valve cavities, plug valves can be used for low temperature medium conditions, viscous media conditions and medium conditions containing solid particles.

5. When plug valves are with full bore round flow channels, they can also be used to cut off media in pipelines with pigging requirements.

6. Plug valves can be lined, and usually adopt the full lining structure, so they can be applied to medium conditions with strong corrosion.

7. Plug valves can be used for the pressure pulsation medium conditions, high pressure oxygen conditions, and medium conditions where cavitation of media, erosion and corrosion may happen.

8. Plug valves are recommended for the pipelines with multichannel structures. That is, a plug valve can get two or four different flow channels, which can help to use less valves and save the costs.