The valve classification valve has an important position in the petrochemical industry, and it is a device with a large amount of zui in the device. Through the control of the valve, the gas and liquid medium can be adjusted or blocked according to the production needs. Valves in petrochemical production can be divided into two categories: general purpose valves and special valves. General valves include: pressure reducing valves, butterfly valves, ball valves, gate valves, globe valves, check valves, safety valves, etc.; special valves include slide valves, high temperature butterfly valves, four-way switching valves, and plugs used in various special devices. Coke valve, high temperature cracking slab gate valve, cryogenic valve, solid valve, high temperature and high pressure angle cut-off valve and throttle valve.
Analysis of Valve Leakage There are two types of valve leakage, namely external leakage and internal leakage. The internal leakage of the valve means that the sealing surface between the valve seat and the valve core is not tightly closed, so that the fluid cannot flow through the valve and cannot be completely cut off to cause internal leakage. The external leakage of the valve refers to the leakage of the medium in the pipe from the inside to the outside through the packing. Under normal circumstances, the leakage of the valve will make the internal leakage of the valve more serious. The leakage of the valve will cause great waste of raw materials and products, and will also seriously affect the environment, and even cause explosion, fire, poisoning and other life-threatening. Major accident.
The cause of leakage of the valve and the analysis of the leakage of the valve often appear in the connection part of the valve body, the valve stem, the stuffing box and the valve body. The external leakage of the valve body originates from the manufacturing form of the valve body. Most of the valves are cast, so it is inevitable that sand holes are easy to produce. However, the flow rate of the valve body leaking out through the sand hole is relatively small, so the influence is relatively small, and the sand eye can be detected by the water pressure test. The external leakage of the valve stem stems from the design and selection of the valve stem. The up and down movement of the valve stem will open and close the valve. Therefore, if there is a problem in the design and selection of the valve stem, there may be a phenomenon that the valve stem is stuck during use and the valve cannot be completely closed, resulting in leakage. . The amount of leakage caused by this situation is generally large. Therefore, the impact on the device and the surrounding environment is relatively large. The external leakage of the stuffing box is caused by: (1) the packing gland is loose; (2) the sealing packing is not tight; (3) the material of the packing is improperly selected or has quality problems; (4) the filler is aged or worn. . The external leakage of the valve body connection originates from: (1) improper selection of the type, material or size of the gasket; (2) quality problems with the flange sealing surface; (3) loose bolt connection; (4) due to the pipeline Unreasonable size selection results in four aspects of excessive load on the valve body joint.
The cause of the internal leakage of the valve and the analysis of the internal leakage of the valve often appear in the valve seal, the valve plate, the sealing surface and the medium in the pipeline. Poor sealing of the valve can lead to leakage of small flow of the medium, which depends mainly on the design and manufacturing process of the valve. Deformation of the valve plate or sealing surface can also cause leakage of small flow of the medium. Damage to the sealing surface of the valve will also result in a tight seal, resulting in small flow leakage and high flow leakage, depending on the valve manufacturing, transportation, inspection, installation and use. If the medium in the process pipeline contains a large amount of solid impurities, the valve cannot be completely closed, and there will be leakage of large flow or small flow to varying degrees. Based on the above analysis of the causes of valve leakage, we can see that the internal leakage of the valve is often a small flow leakage, and there will be very few large flow leakage, so the impact on the process equipment and the surrounding environment is still smaller. Most of the leakage of the valve will have a more serious impact. The leakage of the valve not only causes great waste of raw materials and products, but also seriously affects the environment and even causes major accidents such as fire, explosion and poisoning.
Valve Leak Detection Methods There are many methods for valve leak detection, but there is no uniform classification method. The three recognized classification methods are now discussed:
1 According to the detected parameters, the detection method is divided into direct detection method and indirect detection method. The direct detection method uses a detector to detect the gas or liquid leaking from the periphery of the valve to determine whether it is caused by leakage of the valve. The indirect detection method determines whether there is a valve leakage condition by changing the operating parameters such as pressure and flow rate of the valve medium.
2 The detection method is divided into an internal detection method and an external detection method according to different positions where the detection device is located.
3 based on hardware and software detection methods. Hardware-based detection methods include direct observation method, fiber leak detection method, oil-soluble pressure tube method, and infrared leak detection method. Software-based detection methods include negative pressure wave method, mass balance method, statistical leak detection method, pressure point analysis method and acoustic emission method.
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Analysis of Valve Leakage There are two types of valve leakage, namely external leakage and internal leakage. The internal leakage of the valve means that the sealing surface between the valve seat and the valve core is not tightly closed, so that the fluid cannot flow through the valve and cannot be completely cut off to cause internal leakage. The external leakage of the valve refers to the leakage of the medium in the pipe from the inside to the outside through the packing. Under normal circumstances, the leakage of the valve will make the internal leakage of the valve more serious. The leakage of the valve will cause great waste of raw materials and products, and will also seriously affect the environment, and even cause explosion, fire, poisoning and other life-threatening. Major accident.
The cause of leakage of the valve and the analysis of the leakage of the valve often appear in the connection part of the valve body, the valve stem, the stuffing box and the valve body. The external leakage of the valve body originates from the manufacturing form of the valve body. Most of the valves are cast, so it is inevitable that sand holes are easy to produce. However, the flow rate of the valve body leaking out through the sand hole is relatively small, so the influence is relatively small, and the sand eye can be detected by the water pressure test. The external leakage of the valve stem stems from the design and selection of the valve stem. The up and down movement of the valve stem will open and close the valve. Therefore, if there is a problem in the design and selection of the valve stem, there may be a phenomenon that the valve stem is stuck during use and the valve cannot be completely closed, resulting in leakage. . The amount of leakage caused by this situation is generally large. Therefore, the impact on the device and the surrounding environment is relatively large. The external leakage of the stuffing box is caused by: (1) the packing gland is loose; (2) the sealing packing is not tight; (3) the material of the packing is improperly selected or has quality problems; (4) the filler is aged or worn. . The external leakage of the valve body connection originates from: (1) improper selection of the type, material or size of the gasket; (2) quality problems with the flange sealing surface; (3) loose bolt connection; (4) due to the pipeline Unreasonable size selection results in four aspects of excessive load on the valve body joint.
The cause of the internal leakage of the valve and the analysis of the internal leakage of the valve often appear in the valve seal, the valve plate, the sealing surface and the medium in the pipeline. Poor sealing of the valve can lead to leakage of small flow of the medium, which depends mainly on the design and manufacturing process of the valve. Deformation of the valve plate or sealing surface can also cause leakage of small flow of the medium. Damage to the sealing surface of the valve will also result in a tight seal, resulting in small flow leakage and high flow leakage, depending on the valve manufacturing, transportation, inspection, installation and use. If the medium in the process pipeline contains a large amount of solid impurities, the valve cannot be completely closed, and there will be leakage of large flow or small flow to varying degrees. Based on the above analysis of the causes of valve leakage, we can see that the internal leakage of the valve is often a small flow leakage, and there will be very few large flow leakage, so the impact on the process equipment and the surrounding environment is still smaller. Most of the leakage of the valve will have a more serious impact. The leakage of the valve not only causes great waste of raw materials and products, but also seriously affects the environment and even causes major accidents such as fire, explosion and poisoning.
Valve Leak Detection Methods There are many methods for valve leak detection, but there is no uniform classification method. The three recognized classification methods are now discussed:
1 According to the detected parameters, the detection method is divided into direct detection method and indirect detection method. The direct detection method uses a detector to detect the gas or liquid leaking from the periphery of the valve to determine whether it is caused by leakage of the valve. The indirect detection method determines whether there is a valve leakage condition by changing the operating parameters such as pressure and flow rate of the valve medium.
2 The detection method is divided into an internal detection method and an external detection method according to different positions where the detection device is located.
3 based on hardware and software detection methods. Hardware-based detection methods include direct observation method, fiber leak detection method, oil-soluble pressure tube method, and infrared leak detection method. Software-based detection methods include negative pressure wave method, mass balance method, statistical leak detection method, pressure point analysis method and acoustic emission method.
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