I. Structural characteristics from the standard requirements and the actual use of the situation analysis: Low-load regulating butterfly valve for the regulation of the media when the sealing performance requirements and the metal seal butterfly valve there are some differences. As the pipe network flue gas dust control equipment in the closed position there is still a certain gap will not affect the regulation of opening to achieve automatic control of furnace pressure. Low-load butterfly valve and metal seal butterfly valve fluid characteristics similar to the relationship between the butterfly valve opening and the flow rate is basically a linear ratio. If used to control the flow of its flow characteristics and supporting piping flow resistance coefficient is closely related. If the two pipe installation valve diameter and form exactly the same pipe loss factor is different, the valve flow difference will be very different. If the valve is in a state of large throttling, when the butterfly plate is in the middle opening, the upper and lower sides of the butterfly plate can form completely different states. One side of the forward flow of the disc forward flow of media, the other side of the reverse flow of media and move. Therefore, one side of the valve body and the butterfly valve is formed like a nozzle-shaped opening, the other side is similar to the throttle-shaped opening. The nozzle side is much faster than the throttling side and the throttling side tends to generate negative pressure. Therefore, the low-load butterfly valve should be installed horizontally when the nozzle side of the lower part of the pipeline, pipe valves can be connected to prevent the phenomenon of gray clogging. Low-load butterfly valve mainly from the closure and regulation of the role of flow. In particular, large-diameter butterfly valve, the working conditions affect the deformation of the valve more and deformation is not easy to control, so the structural design should take into account environmental factors. Low-load butterfly valve radial seal and metal seal butterfly valve structure is similar to the temperature of the application process easy to produce thermal resistance, affecting the normal valve opening and closing. Low-load butterfly valve seal in the form of a flat seal is ideal can be designed as a vertical plate or inclined plate structure of the valve body, butterfly plate to the side plane for the sealing pair. The diameter of the disc can be smaller than the diameter of the valve body, even if the wall of the valve cavity has a bond can be easily opened. Pipe deformation on the main valve sealing performance without radial sealing effect is obvious. The structure of the sealing surface of the valve symmetry requirements are high, especially the inclined plate structure of the valve body sealing side of the plane in ordinary machinery and equipment difficult to process. Reasonable process must be arranged in order to achieve the desired assembly accuracy sealing effect. Plane seal structure if the use of leverage, whether vertical or inclined plate structure can solve the sealing plane in the process of existing problems. The structure has many advantages, the lever structure of the valve sealing surface sealing side will not produce radial jamming. In addition the valve body and the butterfly seal side plane for the continuous plane overall processing disc diameter design is smaller than the body diameter. The process of closing the disc first rotates and then moves the sealing surface more to press the more tightly to open the disc. Low-load butterfly valve is generally low pressure, high temperature conditions work will not affect the valve opening and closing. Two. The installation of low-load regulating butterfly valve structure design should be combined with the working conditions of the valve conditions. Under the conditions of high temperature dust content, the design of low load regulating butterfly valve can adopt the plane inclined plate structure. The structure of the disc and valve body leaving a gap between the gap value based on the valve diameter and conditions of use to determine the general control of the channel area of ​​less than 0.5%, to meet the low load regulation butterfly valve installation and temperature conditions change And smelting process requirements. In the higher temperature and dust content of small acid conditions, the design of low load butterfly valve can be used vertical plate structure. The structure of sealing surface processing easy, the sealing surface gap value controlled within 0.2% of the channel area. Valve body, butterfly seal size accuracy can be achieved through machining design requirements. For high temperature, low pressure and sealing requirements of the operating conditions, low-load control butterfly valve design using lever-type planar structure. The sealing companion and disc running track to meet the high sealing performance of pipe network equipment process requirements. Low load regulating butterfly valve body seal according to different conditions choose different structures, is conducive to valve production and working conditions. The low-load regulation butterfly valve shaft end structure design adopts the external support structure with excellent heat insulation and sealing effect, which can seal and support the two-shaft end of the valve first, which facilitates the adjustment function and does not cause the shaft end jam. In the direct connection or crank linkage and transmission mechanism connection, the installation of insulation sleeve can effectively away from the impact of high temperature environment on the transmission, to ensure the normal operation of the valve. Large diameter low load regulating butterfly valve body and butterfly valve should be based on the conditions required by the use of cast or welded form, should be configured ribs, select a reasonable process options and materials to improve product rigidity and prevent product deformation Low load regulating butterfly valve Installation location in the pipe network and the layout of the pipe also has an impact on the use of the valve, large pipe dust in the valve opening or the valve connecting the corner of the design of the closed funnel, regular ash can prevent dust accumulation too much, in order to facilitate the butterfly plate The rotation. Low load regulation butterfly valve installation should also pay attention to several issues: ①The use of metal washers must ensure uniform load, to avoid the influence of temperature and weight or welding stress to the valve to bring additional pressure, the valve flange and pipe deformation. ② valve installed in the place of longer pipes, should be installed support frame. ③ valve installation should pay attention to the flow of media, the direction of opening of the disc and pipe media flow direction is conducive to the role of self-cleaning of the flow rate of the medium. ④ Strengthen the overall network of pipe insulation, so that the wall temperature above the dew point, you can reduce the low-temperature dust cohesion dust. If the tube wall temperature is higher than the acid dew point of the flue gas, acid condensation on the wall of the heated tube can be avoided and the generation rate of sulfur trioxide can be controlled, the valve effect will be better. Low load butterfly valve installation location With the design of the pipeline has a horizontal, vertical and corner of the different positions, the general installation of low load butterfly valve with vertical well, the effect is better, less fouling, followed by horizontal, corner effect Worst. Valve inlet and outlet on both sides of the corner of the most easy to form drift and gray block, the valve operating torque will be increased. III. Conclusion Low load regulation Butterfly valve structure is simple, small size, light weight, generally used in places with high temperature and low working pressure. Low load regulation butterfly valve design structure and working conditions have a great relationship, the specific structure should be based on working conditions. From the use of analysis, as the regulation of the control valve, the main structure of the seal, regardless of the vertical plate or inclined plate structure, the general structure of the valve body seal ring structure is better than no seal diameter seal structure. For the melting conditions, flue gas temperature, high dust content, easy to choose inclined plate plane seal structure. Refining and chemical acid conditions Relatively low temperature and dust content can be used to seal the valve body structure of the vertical plate seal structure. For refining equipment sealing strict requirements, high temperature conditions, the choice of lever-type plane seal structure. Low-load regulation butterfly valve shaft structure, combined with external support structure is more reasonable. Low load regulating butterfly valve in the use of temperature changes in the heat generated by the resistance and pipe wall dust adhesion and pipe plugging, is the impact of low-load regulating butterfly valve opening and closing the main reason for the normal.
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