gate

Gate valve refers to a valve whose closing part (gate) moves along the vertical direction of the channel axis. It is mainly used for cutting off the medium in the pipeline, that is, fully open or fully closed. Generally, the gate valve cannot be used for regulating flow. It can be applied to low temperature and pressure as well as high temperature and high pressure, and can be based on different materials of the valve. But gate valves are generally not used in pipelines that transport mud and other media.　　

Advantages: ① small fluid resistance; ② small torque required for opening and closing; ③ can be used in the ring network pipeline where the medium flows in both directions, that is to say, the flow direction of the medium is not restricted; ④ When fully opened, the sealing surface is affected by the work The erosion of the medium is smaller than that of the stop valve; ⑤The body structure is relatively simple, and the manufacturing process is better; ⑥The structure length is relatively short.　　

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

Butterfly valve

The butterfly valve is a valve that uses a disc-type opening and closing member to reciprocate about 90° to open, close and adjust the fluid channel.　　

Advantages: ①Simple structure, small size, light weight, saving consumables, suitable for large-diameter valves; ②Quick opening and closing, low flow resistance; ③It can be used for medium with suspended solid particles, and can also be used for powder according to the strength of the sealing surface And granular media. It can be applied to the 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, and petrochemical systems.　　

Disadvantages: ①The flow adjustment range is not large. When the opening reaches 30%, the flow will enter more than 95%. ②Due to the limitation of the structure of the butterfly valve and the sealing material, it is not suitable to be used in the high temperature and high pressure pipeline system. The general working temperature is below 300℃ and below PN40. ③The 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.

Ball valve

It is evolved from the plug valve. Its opening and closing part is a sphere, which uses the sphere to rotate 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 direction of the medium flow in the pipeline. The ball valve designed with a V-shaped opening also has a good flow adjustment function.

Advantages: ①It has low flow resistance (actually 0); ②Because it will not get stuck when working (when there is no lubricant), it can be used in corrosive media and low boiling point liquids; ③Under higher pressure Within the range of temperature and temperature, it can be completely sealed; ④It can realize fast opening and closing, and the opening and closing time of some structures is only 0.05~0.1s 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. ⑤Spherical closure can be automatically positioned at the boundary position; ⑥Double-sided sealing; ⑦When 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 ⑧Compact structure and light weight, it can be considered as a reasonable valve structure for low-temperature media systems; ⑨The valve body is symmetrical, especially the welded valve body structure, which can well withstand the stress from the pipeline; ⑩The closure can withstand High pressure difference when closing. ⑾The ball valve with fully welded body can be directly buried in the ground, so that the internal parts of the valve are not corroded, and the service life can reach 30 years. It is an ideal valve for oil and natural gas pipelines.

Disadvantages: ①Because the main seat sealing ring material of the ball valve is polytetrafluoroethylene, it is inert to almost all chemical substances, and has a small friction coefficient, stable performance, not easy to age, wide temperature application range and sealing performance Excellent comprehensive characteristics. However, the physical properties of PTFE, including higher expansion coefficient, sensitivity to cold flow and poor thermal conductivity, require the design of valve seat seals to revolve around these characteristics. Therefore, when the sealing material becomes hard, the reliability of the seal is damaged. Moreover, PTFE has a low temperature resistance grade and can only be used at less than 180°C. Above this temperature, the sealing material will deteriorate. When considering long-term use, it will generally only be used at 120°C. ② Its adjustment performance is worse than that of the stop valve, especially the pneumatic valve (or electric valve).

Shut-off valve

It refers to the valve whose closing part (disc) moves along the center line of the valve seat. According to this movement form of the valve disc, the change of the valve seat port is proportional to the valve disc stroke. Since 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 port 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 off or regulating and throttling.

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

Disadvantages: ①Due to the change in the flow direction of the medium through the valve, the small flow resistance of the globe valve is also higher than that of most other types of valves; ②Because of the longer stroke, the opening speed is slower than that of the ball valve.

Diaphragm valve

It means that a flexible membrane or combined diaphragm is installed in the valve body and the valve cover, and the closing part is a compression device connected with the diaphragm. The valve acne can be weir-shaped, or it can be a pipe wall that passes through the flow channel.　　

Advantages: ①The control mechanism is separated from the medium passage, which not only ensures the purity of the working medium, but also prevents the possibility of the medium in the pipeline from impacting the working parts of the control mechanism. There is no need to adopt any form of separate seal at the valve stem, unless it is in the control It is used as a safety facility in hazardous media; ②Since the working medium is only in contact with the diaphragm and the valve body, both of which can use a variety of different materials, the valve can ideally control a variety of working media, especially suitable for chemical corrosion Or the medium of suspended particles. ③Simple structure, only composed of three parts: valve body, diaphragm and valve cover assembly. The valve is easy to quickly disassemble and repair, and the replacement of the diaphragm can be completed on site and in a short time.

Disadvantages: ①Due to the valve body lining process and diaphragm manufacturing process and restrictions, larger valve body lining and larger diaphragm manufacturing process are difficult, so the diaphragm is not suitable for larger pipe diameters, generally used in DN≤200mm On the following pipeline. ②Due to the limitation of diaphragm material, diaphragm valve is suitable for low pressure and low temperature occasions. Generally, it does not exceed 180°C; ③The adjustment performance is relatively poor, and it can only be adjusted in a small range (generally, it can be used for flow adjustment when it is closed to 2/3 opening).

The auxiliary system of the system pressure is provided on the supply pipeline. Mainly can be divided into swing type (rotating according to the center of gravity) and lifting type (moving along the axis).