The Selection Principles of Ball Valves
1. Ball valves have the minimal pressure drop and they can form a complete channel with the connecting pipes, which make ball valves suitable for medium conditions sensitive to the pressure drop.
2. Ball valves are the heaviest valves with high prices. When the valves' diameters increase, this feature becomes more and more obvious. Thus, the economical principle should be taken into account when ball valves with large diameters are needed using.
3. Although soft sealed ball valves with small diameters are much cheaper, they will be restricted by the temperature as well as pressure.
4. Trunnion mounted ball valves have closed valve cavities. When they are used under low temperature medium conditions and medium conditions where gasification of media may occur, they should be equipped with relief devices or replaced with globe valves or butterfly valves.
5. Ball valves are ideal choices for cutting off the flow of media as well as meeting working conditions with pigging requirements.
6. Ball valves can be lined.
7. Ball valves can be applied to pressure pulsation medium conditions, high pressure oxygen conditions and medium conditions where cativation of media, erosion as well as corrosion may happen.
8. Ball valves are applicable to the pipelines with multichannel structures. That is, a ball valve can have two or four different flow channels, which can help use fewer valves and save costs.
 
The Selection Principles of Butterfly Valves
1. Compared with gate valves, globe valves, ball valves and plug valves, butterfly valves have the minimal structural size, the lightest weight and relatively low prices. Therefore, it is an effective way to use butterfly vales instead of other shut-off valves to reduce costs of devices in construction.
2. Compared with gate valves, globe valves, ball valves and plug valves, butterfly valves have poor sealing performance, so they are commonly recommended for high temperature conditions (of 200℃ and above 200℃) and high pressure conditions (of Class600 and above Class600).
3. Although soft sealed butterfly valves with small diameters are much cheaper, they will be restricted by the temperature as well as pressure.
4. Butterfly valves have closed valve cavities and can be applied to low temperature medium conditions and medium conditions where gasification of media may occur.
5. Butterfly valves can not be used for cutting off the flow of media in the pipelines with pigging requirements.
6. Butterfly valves can not be lined.
7. Butterfly valves are not applicable to pressure pulsation medium conditions, high pressure oxygen conditions and medium conditions where cavitation of media, erosion, corrosion may happen.
8. Compared with gate valves and ball valves, butterfly valves are not suitable for pipeline systems which have high requirements on the pressure loss because the pressure loss of butterfly valves is huge.