Which valve to choose for pipe gate and globe valves
Many users or installation construction units often do not know whether to select gate valve or #globe valve#as main switch or pipeline bypass switch when installing valves to pipelines.
Different types of valves actually work differently; even if they are of the same type, different valve structures can lead to different performance and application ranges.For example, gate valve and globe valve, which one should we choose?Then distinguish between the advantages and disadvantages of gate and globe valves.
Points of knowledge about gate valves
Gate valves are widely used in petrochemical industry, steam pipeline, water system engineering and other industries. According to the internal structure of gate valves, we can divide them into: 1. Wedge type single gate valves 2. Elastic gate valves 3. Double gate valves 4. Parallel gate valves.
Of course, we can also divide gate valves into open-stem gate valves and dark-stem gate valves according to the opening of gate valves and the position relationship between stem and valve body.
The advantages of gate valves over globe valves are:
1. Gate valves are generally not used as medium flow regulating valves and are generally used as normally open and normally closed valves.
2. The sealing performance of gate valve is also better than that of globe valve.
3. Under the same conditions, the fluid resistance of gate valve is small.
4. The open degree of the gate valve can be identified from the lifting height of the valve stem.
5. Compared with globe valve, the diameter of gate valve can be larger, for example, gate valve can be made into large diameter valve larger than DN500;
6. Gate valves have a wide range of applications. In addition to conventional applications in steam, oil and other media, gate valves can also be used in media containing granular solids and high viscosity. Gate valves are suitable for use as protective valves, vent valves and valves for low vacuum systems.
7. Gate valve is not restricted by the flow direction of medium. Gate valve is a double-flow valve.
Gate valves also have their disadvantages:
1. Gate valve processing is more complicated than globe valve.
2. It is inconvenient to repair after the sealing surface of the gate valve is worn out.
3. The shape size of gate valve is larger and the opening and closing time of gate valve is longer.
4. At higher temperature, the sealing performance of wedge type single gate valve is not as good as that of elastic gate valve or double gate valve. Wedge type single gate valve is suitable for coking medium at high temperature.
5. Elastic gate valve has good sealing property in high temperature medium and is not easy to jam after being heated. It is suitable for medium such as steam, high temperature oil, oil and gas, and also for parts with frequent switches, but it is not suitable for medium which is easy to coke.
Points of knowledge about globe valves
Globe valves are mainly used as the medium for cutting off pipelines for switching valves. Because of the high torque required for opening and closing the globe valves, the diameter of the globe valves is usually DN < 200mm; the opening height of the globe valves is small and the closing time is shorter than that of the gate valves.
Cast steel globe valve
The performance characteristics of globe valves are as follows:
1. Compared with gate valve, globe valve has better regulation performance, but the stem of globe valve does not rise or fall from the handwheel, which makes it difficult to identify the valve opening, thus making it difficult to identify the size of valve adjustment.
2. The fluid resistance of globe valve is also greater than that of gate valve, ball valve and cock valve.
3. The sealing surface of globe valve is smaller than that of gate valve.
4. The sealing property of the globe valve is worse than that of the gate valve; if the medium containing impurities such as particles is encountered, the sealing surface of the globe valve will be easily damaged when the globe valve is closed;
5. The cost of globe valve is cheaper than that of gate valve.
6. Globe valves are generally suitable for steam; they are not suitable for medium with high viscosity, particle, coking and precipitation, and for valve of evacuation system and low vacuum system.
How to select gate valve and globe valve?
From the overview of the knowledge points in the appeal, we know that gate valves are suitable for use as valves with larger pipe diameters, while globe valves generally have diameters less than DN200mm;
Globe valve requires high cleanliness of medium in pipeline. If impurities are contained in the medium, the sealing surface of the globe valve will be easily damaged, resulting in poor sealing performance and loose closure of the globe valve.
Gate valves are suitable for coking, granular, sediment-prone, viscous media, which has no advantage over globe valves.
Gate valves, especially flat gate valves, are selected for many valves of oil pipelines in oil fields and oil depots.
In water system, open-rod or dark-rod soft-seal gate valves are generally selected.
