Five valve advantages and disadvantages analysis, you may not know all!

There are many types of valves, each of which has its own advantages and disadvantages. The following table lists the advantages and disadvantages of five valves, including gate valve, butterfly valve, ball valve, globe valve and plug valve. I hope it can help you.

Gate valve

Gate valve refers to the valve whose closing part (gate) moves along the vertical direction of the channel axis. It is mainly used to cut off the medium in the pipeline, that is, fully open or fully closed. In general, gate valve can not be used to regulate flow. It can be used for low temperature and high pressure as well as high temperature and high pressure, and can be made according to different materials of the valve. But the gate valve is not generally used to transport mud and other media in the pipeline.

advantage:

① The fluid resistance is small;

② The torque required for opening and closing is small;

③ It can be used in the loop network pipeline where the medium flows in two directions, that is to say, the flow direction of the medium is not limited;

④ When the valve is fully opened, the erosion of the sealing surface by the working medium is smaller than that of the stop valve;

⑤ The structure is simple and the manufacturing process is good;

⑥ The length of the structure is short.

Disadvantages:

① The overall dimension and opening height are large, and the installation space is also large;

② In the process of opening and closing, the sealing surface is relatively friction, and the friction loss is large, and even it is easy to cause scratch at high temperature;

③ Generally, gate valves have two sealing surfaces, which add some difficulties to machining, grinding and maintenance;

④ The opening and closing time is long.

butterfly valve

Butterfly valve is a kind of valve which uses disc type opening and closing parts to turn back and forth about 90 ° to open, close and regulate the fluid channel.

advantage:

① The utility model has the advantages of simple structure, small volume, light weight and less consumables, and is especially used in large-diameter valves;

② Quick opening and closing, low flow resistance;

③ It can be used for medium with suspended solid particles, and can also be used for powdery and granular medium according to the strength of sealing surface. It is widely used in gas pipeline and water channel of metallurgy, light industry, electric power and petrochemical system.

Disadvantages:

① The range of flow regulation is not large. When the valve is opened to 30%, the flow will be more than 95%;

② Due to the limitation of butterfly valve structure and sealing material, it is not suitable for high temperature and high pressure pipeline system. The general working temperature is below 300 ℃ and PN40;

③ Compared with ball valve and globe valve, the sealing performance is poor, so it is used in places where the sealing requirements are not very high.

globe valve

The ball valve is evolved from the plug valve. Its opening and closing part is a ball. The ball rotates 90 ° around the axis of the stem to achieve the purpose of opening and closing. The ball valve is mainly used to cut off, distribute and change the flow direction of medium in the pipeline. The ball valve with V-shaped opening also has good flow regulation function.

advantage:

① It has the lowest flow resistance (0 actually);

② It can be reliably used in corrosive medium and low boiling point liquid because it will not get stuck in operation (without lubricant);

③ In a large range of pressure and temperature, it can achieve complete sealing;

④ It can realize fast opening and closing, and the opening and closing time of some structures is only 0.05 ~ 0.1s, so as to ensure that it can be used in the automation system of the test bed. When the valve is opened and closed quickly, the operation has no impact;

⑤ The spherical closing part can be positioned on the boundary automatically;

⑥ The working medium is sealed reliably on both sides;

⑦ When the valve is fully opened or closed, the sealing surfaces of the ball and valve seat are isolated from the medium, so the medium passing through the valve at high speed will not cause the erosion of the sealing surface;

⑧ Because of its compact structure and light weight, it can be considered as the most reasonable valve structure for low temperature medium system;

⑨ The valve body is symmetrical, especially the welded valve body structure, which can well withstand the stress from the pipeline;

⑩ The closing part can withstand the high pressure difference when closing. (11) the ball valve with all welded valve body can be directly buried underground, so that the valve internals will not be corroded, and the maximum service life can reach 30 years. It is the most ideal valve for oil and gas pipelines.

Disadvantages:

① Because the main sealing ring material of ball valve seat is polytetrafluoroethylene, it is inert to almost all chemical substances, and has the comprehensive characteristics of small friction coefficient, stable performance, not easy to aging, wide range of temperature application and excellent sealing performance. However, the physical characteristics of PTFE, including high expansion coefficient, sensitivity to cold flow and poor thermal conductivity, require the design of valve seat seal must focus on these characteristics. Therefore, when the sealing material becomes hard, the reliability of the seal is damaged. Moreover, the temperature resistance grade of PTFE is low, so it can only be used under the condition of less than 180 ℃. Beyond this temperature, the sealing material will age. In consideration of long-term use, it is generally not used at 120 ℃.

② Its regulating performance is worse than that of stop valve, especially pneumatic valve (or electric valve).

Globe valve

Stop valve: it refers to the valve whose closing part (disc) moves along the center line of the valve seat. According to the movement of the disc, the change of the valve seat opening is proportional to the disc stroke. Because the opening or closing stroke of the valve stem is relatively short, and it has a very reliable cut-off function, and because the change of the valve seat opening is directly proportional to the stroke of the valve disc, it is very suitable for regulating the flow. Therefore, this type of valve is very suitable for cutting off or regulating and throttling.

advantage:

① In the process of opening and closing, the friction between the valve disc and the sealing surface of the valve body is smaller than that of the gate valve, so it is wear-resistant.

② Generally, the opening height is only 1 / 4 of the seat channel, so it is much smaller than the gate valve;

③ Generally, there is only one sealing surface on the valve body and disc, so the manufacturing technology is better and easy to maintain;

④ As the filler is generally a mixture of asbestos and graphite, the temperature resistance grade is higher. General steam valves are globe valves.

Disadvantages:

① Because the flow direction of the medium through the valve changes, the minimum flow resistance of the stop valve is also higher than that of most other types of valves;

② Due to the long stroke, the opening speed is slower than the ball valve.

Plug valve

Plug valve: it refers to the rotary valve whose closing part is in the shape of plunger. Through 90 ° rotation, the passage port on the plug is communicated with or separated from the passage port on the valve body to realize opening or closing. The shape of the valve plug can be cylindrical or conical. Its principle is similar to that of ball valve. Ball valve is developed on the basis of plug valve. It is mainly used in oilfield exploitation and petrochemical industry.

advantage:

1. It is used for frequent operation, quick and light.

2. The fluid resistance is small.

3. Simple, relatively small size, light weight, easy to maintain.

4. Good sealing performance.

5. Limited by the installation direction, the flow direction of the medium can be arbitrary.

6. No vibration, low noise.

Disadvantages:

1. The cover is too large, resulting in too much torque and inflexibility.

2. The caliber is limited due to body weight.

3. In actual use, if large-size valves are used, the inverted cock structure must be used, which is easy to affect the sealing effect.