1.Gate valve refers to a valve that moves the closing element (gate) vertically along the axis of the channel. It is mainly used to cut off the medium in the pipeline, that is, fully open or fully closed. Generally, gate valves cannot be used to regulate flow. It can be suitable for low temperature and high pressure as well as high temperature and high pressure, and can be made of different materials according to the valve. But gate valves are generally not used in pipelines that transport media such as mud.
Advantages:
① Low fluid resistance;
② The required torque for opening and closing is relatively small;
③ It can be used on ring network pipelines where the medium flows in two directions, which means that the flow direction of the medium is not restricted;
④ When fully open, the sealing surface is less susceptible to erosion by the working medium than the shut-off valve;
⑤ The body structure is relatively simple and the manufacturing process is good;
⑥ The structural length is relatively short.
Disadvantages:
① The external dimensions and opening height are relatively large, and the required installation space is also large;
② During the opening and closing process, the sealing surface is subject to relative friction and significant wear, which can even cause scratches at high temperatures;
③ Generally, gate valves have two sealing surfaces, which adds some difficulties to processing, grinding, and maintenance;
④ Long opening and closing time.

2.Butterfly valve is a type of valve that uses a disc type opening and closing element to rotate back and forth about 90 ° to open, close, and regulate the fluid channel.
Advantages:
① Simple structure, small size, light weight, and low consumables, suitable for use in large-diameter valves;
② Quick opening and closing, low flow resistance;
③ Can be used for media with suspended solid particles, and can also be used for powdered and granular media based on the strength of the sealing surface. Suitable for bi-directional opening and closing and adjustment of ventilation and dust removal pipelines, widely used in gas pipelines and waterways in metallurgical, light industry, power, petrochemical systems, etc.
Disadvantages:
① The range of flow regulation is not large. When it reaches 30%, the flow will increase by over 95%;
② Due to the limitations of the structure and sealing materials of butterfly valves, they are not suitable for use in high-temperature and high-pressure pipeline systems. The general working temperature is below 300 ℃ and below PN40;
③ The sealing performance is relatively poor compared to ball valves and globe valves, so it is used in places where the sealing requirements are not very high.

3.Ball valves evolved from plug valves, and their opening and closing components are a sphere that rotates 90 ° around the axis of the valve stem to achieve the purpose of opening and closing. Ball valves are mainly used in pipelines to cut off, distribute, and change the direction of medium flow. Ball valves designed with V-shaped openings also have good flow regulation functions.
Advantages:
① Has the lowest flow resistance (actually 0);
② Because it does not get stuck during operation (in the absence of lubricants), it can be reliably applied to corrosive media and low boiling liquids;
③ Can achieve complete sealing within a large range of pressure and temperature;
④ To achieve rapid opening and closing, the opening and closing time of certain structures is only 0.05-0.1s to ensure that they can be used in the automation system of the test bench. When quickly opening and closing the valve, there is no impact during operation;
⑤ The spherical closure component can automatically locate at the boundary position;
⑥ The working medium is reliably sealed on both sides;
⑦ When fully open and fully 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 erosion of the sealing surface;
⑧ Compact in structure and light in weight, it can be considered the most reasonable valve structure for low-temperature medium systems;
⑨ The valve body is symmetrical, especially the welded valve body structure, which can withstand the stress from the pipeline well;
⑩ The closing component can withstand the high pressure difference when closed The ball valve with a fully welded valve body can be directly buried underground, ensuring that the valve components are not corroded. The maximum service life can reach 30 years, making it the most ideal valve for oil and natural gas pipelines.
Disadvantages:
① Because the main seat sealing ring material for ball valves is polytetrafluoroethylene, which is inert to almost all chemicals, and has comprehensive characteristics such as low friction coefficient, stable performance, not easy to age, wide temperature range, and excellent sealing performance. However, the physical properties of polytetrafluoroethylene, including its high coefficient of expansion, sensitivity to cold flow, and poor thermal conductivity, require the design of valve seat seals to revolve around these characteristics. So, when the sealing material becomes hard, the reliability of the seal is compromised. Moreover, the temperature resistance level of polytetrafluoroethylene is relatively low and can only be used at temperatures below 180 ℃. Beyond this temperature, the sealing material will age. When considering long-term use, it is generally only not used at 120 ℃.
② Its regulating performance is relatively inferior to that of globe valves, especially pneumatic valves (or electric valves).

4.Globe valve: refers to a valve in which the closing element (disc) moves along the centerline of the valve seat. According to the movement of the valve disc, the change in the valve seat opening is directly proportional to the valve disc stroke. Due to the relatively short opening or closing stroke of the valve stem and the highly reliable cut-off function, as well as the proportional relationship between the change of the valve seat opening and the stroke of the valve disc, this type of valve is very suitable for regulating flow. Therefore, this type of valve is very suitable for cutting or regulating as well as throttling purposes.
Advantages:
① During the opening and closing process, the friction between the valve disc and the valve body sealing surface is smaller than that of the gate valve, so it is wear-resistant.
② The opening height is generally only 1/4 of the valve seat channel, so it is much smaller than a gate valve;
③ Usually, there is only one sealing surface on the valve body and disc, so the manufacturing process is relatively good and easy to maintain;
④ Due to the fact that its filler is generally a mixture of asbestos and graphite, it has a higher temperature resistance level. Generally, steam valves use globe valves.
Disadvantages:
① Due to the change in the flow direction of the medium through the valve, the minimum flow resistance of the globe valve is also higher than that of most other types of valves;
② Due to the long stroke, the opening speed is slower than that of the ball valve.

5.Plug valve: refers to a rotary valve with a plunger shaped closure, which opens or closes by rotating 90 ° to connect or separate the channel port on the valve plug from the channel port on the valve body. The shape of the valve plug can be cylindrical or conical. Its principle is basically similar to that of ball valves. Ball valves are developed based on plug valves and are mainly used for oilfield development, as well as in petrochemical industry.
Advantages:
① Used for frequent operation, quick and lightweight opening and closing.
② Low fluid resistance.
③ Simple, relatively small in size, lightweight, and easy to maintain.
④ Good sealing performance.
⑤ Due to the limitation of 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 excessive torque and insufficient flexibility.
② Due to the influence of body weight, the caliber size is limited.
③ In practical use, if large-sized valves are used, a reverse plug structure must be used, which can easily affect the sealing effect.