Fluorine lined butterfly valve
Fluorine plastic lined butterfly valve shaft and disc design Determination of shaft diameter of fluorine lined butterfly valve The minimum diameter of the valve shaft is shown in Table 4. The minimum diameter is determined according to the calculation result of the butterfly valve shaft and modified according to the relevant regulations of AWWAC504. After years of use, it has been proved to be reliable. The connection between the disc and the valve shaft of the fluorine-lined butterfly valve (1) The design of the disc and the valve shaft of the fluorine-lined butterfly valve is separate, as shown in Figure 6(a). pin connection. If the fluoroplastic lined butterfly valve adopts such a connection method, not only the fluorine lining is not good in manufacturability, but also has problems in the use effect. The lining layer is easily damaged during the repeated alternating stress on the part connecting the butterfly plate and the valve shaft, which causes the steel skeleton to be corroded by the corrosive medium and fail, thus shortening the service life of the valve. Therefore, the valve shaft and disc of the fluoroplastic lined butterfly valve are usually designed in a conjoined shape, as shown in Figure 6(b). Practice has proved that this design has a better effect. (2) The connection between the disc of the fluorine-lined butterfly valve and the valve shaft should be firm and reliable. Under the working conditions of pressure, it should be ensured that no part of the valve shaft will be ejected from the valve. The connection between the disc and the valve shaft should be completed before the fluoroplastic lining. There are various ways to connect. The butterfly plate and the valve shaft can be cast integrally, or the butterfly plate and the valve shaft can be welded or riveted. The premise is that it is firm and reliable, not loose. (3) In order to ensure that the fluoroplastic layer on the disc is tightly combined with the substrate, a small twist drill of φ6mm can be used to drill some perforations evenly, and the number of holes is determined according to the area of u200bu200bthe disc. (4) The fluorine-lined butterfly valve is particularly good due to the insulation of fluorine plastics. When the butterfly plate and the valve seat are opened and closed, the static electricity generated by friction is difficult to release. Therefore, an electrostatic communication structure should be designed between the butterfly plate and the valve shaft and the valve body, so as to be grounded through the pipeline and eliminate the accumulation of static electricity. Flow resistance and flow coefficient The size of flow resistance and flow coefficient is an important indicator to measure the quality of fluoroplastic lined butterfly valve. my country's JB/T53171 standard includes the flow resistance and flow coefficient of ISO/TC153/SCIGT8-37 (see Table 5) as an indicator for evaluating valve performance for users to choose. For fluoroplastic lined valves, the flow resistance and flow coefficient values u200bu200bshould be listed in the valve performance indicators to check whether the designed and manufactured products meet the standard requirements. Torque of fluorine lined butterfly valve Small opening and closing torque is a major feature of fluorine plastic lined butterfly valve. In the manuals of many foreign products, the valve torque is listed as a technical parameter. In the valve samples of some well-known brands in my country, the valve opening and closing torque designed and manufactured by our company is also listed, which is convenient for users to choose. Some valves with flexible opening and small torque are very popular among users. Butterfly valve torque can be approximated by the following formula: MDu003dMM+MC+MT In the formula: MD—butterfly valve shaft torque, N Mm; MM—friction torque between sealing surfaces, N mm qM—sealing surface must be pressure-specific, MPa; R—disc radius, mm; bM—contact width of sealing surface, mm; fM—friction coefficient between sealing surfaces; h—eccentric distance between the valve shaft and the center of the disc, (central line is 0), mm; Mc— Valve shaft bearing friction torque, N•mm MCu003dQCfCdF/2 QC—load acting on valve shaft bearing, N•mm; fC—bearing friction coefficient; dF—valve shaft diameter, mm; MT—friction torque of sealing packing , N mm MTu003dQT dF/2 MT—friction between valve shaft and packing, N; QTu003dφdFbT; φ—coefficient; bT—filling depth, mm; p—calculated pressure, MPa The torque of the butterfly valve can also be used Torque testing machine directly measured. Compare the calculated value with the measured value to verify the performance of the product. It is worth noting that, affected by factors such as processing technology and material selection, the actual torque of the valve shaft is slightly different from the calculated torque when the nominal size is less than DN300, and the torque difference is larger when the nominal size is greater than or equal to DN300. The data listed in Table 6 are typical cases of domestic and foreign manufacturers, which are limited to DN65～DN300 for reference in design and manufacture.
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