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.
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.
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
Advanced modern industry is marked by production automation. From the development history and progress of automation system, the change of technical tools plays a very important role. All kinds of advanced control means appear constantly, but the basic control law has not changed, but the improvement of technical tools is changing with each passing day. The development and application of intelligent instrument will be a better future for industrial automation. The typical automatic control system mainly has three links: detection, control and execution. In recent years, the detection and control instruments are affected by digital technology and microprocessor technology, and the actuator, especially the control valve, has made great progress. The traditional control valve basically meets the needs of many industrial systems, but with the large-scale development of valve modern industry.
How to judge the quality of all welded ball valve
First, we can test the quality of buried all welded ball valve through a strength test. First of all, we can weld high-pressure caps on the sleeves of both sides of the valve of the buried all welded ball valve. After the valve is opened to 45 ℃, water is injected into the ball valve through the pressure test valve on the sleeve. The pressure is increased to 1.5 times of the nominal pressure of the ball valve, and the pressure is maintained for 15 minutes. If there is no leakage, then the ball valve is qualified.
Second, we can also test the quality of the buried all welded ball valve by testing its tightness. The specific operations are as follows: first, close the ball, then inject nitrogen into the ball valve through the pressure test valve on the sleeve until the pressure rises to 1.1 times of the nominal pressure of the ball valve, and then connect the middle cavity pressure relief valve to the water container for testing, and the insertion depth is 1cm If no bubble is produced within minutes, the product is qualified.
Recently, the international standard "ISO22153 "General Requirements for Industrial Valve Electric Devices"" led by the Hefei General Machinery Research Institute on behalf of China was officially released with the approval of the International Organization for Standardization (ISO). This is the first international standard for industrial valve electric devices led by my country. It is a major breakthrough in the field of international standards for the valve industry in my country. It is of great significance for promoting my country's valve electric devices to "go global."
Hefei General Machinery Research Institute is the secretariat of the International Organization for Standardization/Refrigeration and Air Conditioning Technical Committee/Refrigeration Compressor Testing and Evaluation Committee (ISO/TC86/SC4) and the United States ASME Boiler and Pressure Vessel Code Volume Ⅷ Committee China International Working Group The affiliated units are also the counterparts in China of the 7 International Organization for Standardization, including valves, overpressure protection safety devices, compressors, and packaging machinery. In recent years, their influence and voice in international standardization work have continued to increase. (Yi Ming)