What are the selection principles for ball and butterfly valves?

Because the valve is widely used, so it plays a great role. For example, in power plants, valves can control the operation of boilers and steam turbines; in petroleum and chemical production, valves also play a role in controlling the normal operation of all production equipment and processes. The same is true in other sectors. Nevertheless, valves are often overlooked in comparison with other products.

List of content for this article：

1.The Selection Principles of Ball Valves

2.Compared with others

The Selection Principles of Ball Valves

There are many types of valves, the view is not entirely uniform, some points according to the use (e.g., chemical, oil, power station, etc.), some points according to the medium (such as water vapor, air valve, etc.), according to the material points (such as cast iron, cast steel, forged steel, stainless steel, ceramics, UPVC, etc.), according to the connection points (such as internal thread, flange valve, etc.) to the clamp, according to the temperature points (e.g., cryogenic valves, high temperature valve, etc.). Most of our current habits are classified by stress and structure. Namely: according to nominal pressure: ≤ 1.6mpa is low-pressure valve, pressure 2.5, 4.0, 6.4mpa is medium pressure valve, ≥10MPa is high-pressure valve, and over 100MPa is ultra-high-pressure valve

1. Ball valve 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 seated ball valve with small diameters are much cheaper, they will be restricted by the temperature as well as pressure.
4. Trunnion mounted ball valve 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. 

Compared with others

1. Compared with gate valve, globe valve, ball valve and plug valve, butterfly valve 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.

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