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Elastic hard sealing butterfly valve maintenance
I. Overview With the development of China's capital construction, large-scale national projects have been put into operation so that more and more valves, such as electric power, petroleum, chemical industry, urban supply and drainage systems, are used, especially for butterfly valves. China's production of metal seal butterfly valve, from the seal structure can be divided into two categories, one is a flexible hard-seal structure, the second is a multi-level seal butterfly valve. Flexible hard-seal butterfly valve diameter is generally below the production of DN500, the use of large-caliber multi-level structure. The following amount of butterfly valve DN500 the largest, so users encounter more problems in use, here, the problems that often appear are summarized, and guide the correct installation and use. Second, the elastic structure analysis and problems where the elastic structure of the flexible butterfly valve seal by: valve body, valve plate, valve stem, flexible seat, pressure ring and other major components. The structure and role of the pressure ring: the pressure ring on the side of the sealing surface of the valve body and the pipe flange sealing surface to become a sealing pair, the side of the bolt holes, with a pressure ring from the bolt to secure the valve seat with the valve body Even as one, the total length of the valve structure. Due to the fact that the screw hole on the side of the pressure ring reduces the effective sealing surface diameter. Flange from the user's situation, most of the welding flange is used, and its pass through the public through a large 10-20mm. This use will reduce the effective sealing surface, if the installation process of the valve flange and the pipe there is a different heart, then the pressure will be placed in the bolt aperture above the hole diameter of the flange exposed at the bolt hole, causing leakage here. Leakage characteristics of the media flow from the back of the ring out. Third, the special flange At present, the country does not have flexible flange valve seal the corresponding special standards, according to the current national standards, the standard size in the flange the same circumstances, the use of its internal Classic socket. Flange diameter and nominal pass through the same basic, this is to increase the effective sealing surface, but also to provide convenient installation, while ensuring the normal use of the valve. Here, to remind users to use flexible hard sealing butterfly valve, the matching anti-flange must use a special flange, especially with the body pressure ring paired pipe flange, be sure to use a special flange. Fourth, the direction of the arrow on the body refers to the pressure direction of the medium Usually cast on the body of the arrow direction, refers to the flow of media, the user saw the arrow, the logical direction of the arrow according to flow consistent with the installation, so installed Has become a habit, the installer is easy to accept such instructions, according to national standards, there is nothing wrong. However, in the eccentric structure of the butterfly valve is concerned, there will be some problems when installed, the following to say an example: eccentric butterfly valve according to the flow and the media flow consistent installation, the media is liquid pipe, the valve is closed, if the original media import pressure, Reduce or zero, the export of the medium backflow reflux, if it is high-level supply, the medium in a high pressure, the pressure is greater than the inlet pressure, the valve will have to bear the role of reverse pressure, due to ordinary hard-sealed butterfly valve For one-way use of the valve, so use is not conducive to the sealing of the butterfly valve, and there will be leakage. The conclusion from the above example is that the arrow direction of the butterfly valve body means the pressure direction of the medium. Before installation, the user should know clearly the direction of the medium pressure after the valve is closed, and the direction of the arrow of the free valve body can be correctly used in the direction of the pressure of the medium, and the sealing performance remains good. Fifth, the flexible seal butterfly valve to the user acceptance Note users to purchase the valve to do sampling or all inspection is very necessary, the sampling of the quality of the product is: First, the quality of the product, and second, to reduce the valve is not installed Necessary repairs and updates, an installation success rate engage. However, the user checks the hard seal on the butterfly valve test, some did not pay attention to the place, resulting in the law of your quality, suspicion or rejection. Where is the reason? The pressure ring on the screw according to the size of the hole there are 4, 6, 8 and 12, the maximum bolt diameter does not exceed M10. These screws are mainly used to fix the elastic seat, can not withstand the pressure of all the media, when the valve is installed and then by the external flange bolts compaction, can withstand all the media power. Due to structural reasons, there is a difference in the acceptance of inspection operations when there is a leak. Users are often notified of non-conformities by manufacturers. After the communication, the products can be smoothly cleared and there is no problem in use. Therefore, in this case should pay attention to the matter, for users to better understand and use of flexible hard-sealed butterfly valve for the next exchange. When testing elastic hard sealing butterfly valve, the side of the pressure ring should be placed flatly on the flat surface, and a flat flange should be placed outside the flange. The valve passes through the pressure plate with the same size. If it is tested with a pressure tester, This pressure plate, so that the pressure evenly distributed on the pressure ring on the side of the body. If you are using the blind test, the general elastic clamp butterfly valve are used to clamp two pairs of flange clamping test, flange flexible hard seal butterfly valve Sometimes, for the convenience of the user only with a flange below And the valve bolt fixed, then the body of the pressure ring above the fixed screw to withstand the full pressure of the medium, as mentioned earlier, these few screws can not withstand the pressure of all the media, so with a blind Test valve does not leak, but also the actual use of the same state. These problems often encountered in the installation process, if you understand our valve structure, it will give you the convenience of installation, and the correct use of flexible hard-sealed butterfly valve.