1. Gate valve: Gate valve refers to the valve whose closing member (gate) moves along the vertical direction of the channel axis. It is mainly used to cut off the medium on the pipeline, that is, fully open or fully closed. General gate valves cannot be used to regulate flow. It can be applied to low temperature and high pressure as well as high temperature and high pressure, and it can be used according to different materials of the valve. However, gate valves are generally not used in pipelines that transport media such as mud.

advantage :
1. Small fluid resistance;
2. The torque required for opening and closing is small;
3. It can be used on the ring network pipeline where the medium flows in two directions, that is to say, the flow direction of the medium is not restricted;
4. When fully open, the sealing surface is less eroded by the working medium than the globe valve;
5. The shape and structure are relatively simple and the manufacturing process is good;
6. The structure length is relatively short.

shortcoming:
1. The overall size and opening height are large, and the required installation space is also large;
2. In the process of opening and closing, the sealing surface is relatively rubbed, and the friction is relatively large, and it is easy to cause abrasion even at high temperature;
3. Generally, gate valves have two sealing surfaces, which add some difficulties to processing, grinding and maintenance;
4. The opening and closing time is long.

2. Butterfly valve: Butterfly valve is a kind of valve that uses disc type opening and closing parts to turn back and forth about 90° to open, close and adjust the fluid passage.

advantage :
1. Simple structure, small size, light weight, less consumables, not used in large-diameter valves;
2. Rapid opening and closing, small flow resistance;
3. It can be used for media with suspended solid particles, and it can also be used for powdery and granular media according to the strength of the sealing surface. It is suitable for two-way opening and closing and adjustment of ventilation and dust removal pipelines, and is widely used in gas pipelines and waterways in metallurgy, light industry, electric power, petrochemical systems, etc.

shortcoming:
1. The flow adjustment range is not large. When the opening reaches 30%, the flow will enter 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°C and below PN40.
3. The sealing performance is poorer than that of ball valves and globe valves, so it is used in places where the sealing requirements are not very high.

3. Ball valve: It is evolved from a plug valve. Its opening and closing part is a sphere, and the sealing body is rotated 90° around the axis of the valve 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 the medium on the pipeline, and the ball valve designed with a V-shaped opening also has a good flow regulation function.

advantage :
1. Has the lowest flow resistance (actually 0);
2. Because it will not get stuck when working (in lubricant), it can be reliably applied to corrosive media and low boiling point liquids;
3. In a larger pressure and temperature range, it can achieve complete sealing;
4. It can realize fast opening and closing. 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 bench. When opening and closing the valve quickly, there is no shock in operation.
5. The spherical closing member can be automatically positioned on the boundary position;
6. The working medium is reliably sealed on both sides;
7. When fully open and fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, so the medium passing through the valve at high speed will not cause erosion of the sealing surface;
8. With 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 parts can withstand the high pressure difference when closing.
11. The ball valve with fully welded body can be directly buried in the ground, so that the internal parts of the valve will not be corroded, and the maximum service life can reach 30 years. It is the most ideal valve for oil and natural gas pipelines.

shortcoming:
1. Because the most important seat sealing ring material of the ball valve is polytetrafluoroethylene, it is inert to almost all chemical substances, and has small friction coefficient, stable performance, not easy to aging, wide temperature application range and sealing performance Excellent comprehensive features. However, the physical properties of PTFE, including high coefficient of expansion, sensitivity to cold flow and poor thermal conductivity, require that seat seals must be designed around these properties. Therefore, when the sealing material hardens, the reliability of the seal is compromised. Moreover, PTFE has a low temperature rating and can only be used below 180°C. Above this temperature, the sealing material will age. In the case of long-term use, it is generally not used at 120°C.
2. Its adjustment performance is worse than that of the globe valve, especially the pneumatic valve (or electric valve).

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

advantage:
1. During the opening and closing process, since the friction force between the disc and the sealing surface of the valve body is smaller than that of the gate valve, it is wear-resistant.
2. The opening height is generally only 1/4 of the seat channel, so it is much smaller than the gate valve;
3. Usually there is only one sealing surface on the valve body and the valve disc, so the manufacturing process is relatively good and it is easy to maintain.
4. Since the filler is generally a mixture of asbestos and graphite, the temperature resistance level is relatively high. Generally steam valves use globe valves.

shortcoming:
1. Since the flow direction of the medium through the valve has changed, the minimum flow resistance of the globe valve is also higher than most other types of valves;
2. Due to the longer stroke, the opening speed is slower than that of the ball valve.

5. Plug valve: It refers to a rotary valve with a plunger-shaped closing part. Through 90° rotation, the channel port on the valve plug is connected or separated from the channel port on the valve body to realize opening or closing. The shape of the valve plug can be cylindrical or conical. Its principle is basically similar to that of the ball valve. The ball valve is developed on the basis of the plug valve. It is mainly used in oilfield exploitation and also in petrochemical industry.

6. Safety valve: it is used as an overpressure protection device on pressure vessels, equipment or pipelines. When the pressure in the equipment, container or pipeline rises above the allowable value, the valve will automatically open and then fully discharge to prevent the equipment, container or pipeline and the pressure from continuing to rise; when the pressure drops to the specified value, the valve should automatically Close in time to protect the safe operation of equipment, containers or pipelines.

7. Steam trap: Some condensed water will be formed in the transport of steam, compressed air and other media. In order to ensure the working efficiency and safe operation of the device, these useless and harmful media should be discharged in time to ensure the consumption and safety of the device. use. It has the following functions: 1. It can quickly remove the condensed water; 2. Prevent steam leakage; 3. Remove air and other non-condensable gases.

8. Pressure reducing valve: It is a valve that reduces the inlet pressure to a certain required outlet pressure through adjustment, and relies on the energy of the medium itself to automatically maintain a stable outlet pressure.

9. Check valve: also known as reverse flow valve, check valve, back pressure valve and one-way valve. These valves are automatically opened and closed by the force generated by the flow of the medium itself in the pipeline, which is a kind of automatic valve. The check valve is used in the pipeline system, and its main function is to prevent the reverse flow of the medium, the reverse rotation of the pump and the drive motor, and the discharge of the container medium. Check valves are also used on lines that supply auxiliary systems where the pressure may rise above system pressure. It can be mainly divided into swing type (rotating according to the center of gravity) and lifting type (moving along the axis)