Large-scale fertilizer plant imports regulating valve made a case

Large-scale fertilizer plant imports control valve localization case A case of Sichuan Chemical Machinery Factory Xu Hongtao On the localization of imported control valve, I plant has done work in the medium-sized urea plant, and achieved the desired success, such as my factory production with an annual output of 110,000 T for urea plant control valve referred to as P4 valve is an example. In large-scale fertilizer plant with an annual output of 480,000 tons of urea plant, U-LRCA-401 control valve is another example. The U-LRCA-401 regulator is installed on the secondary line between the ammonium pump outlet and the high pressure absorber cooler to control the high pressure absorber cooler level. U-LRCA-401 regulating valve in an annual output of 480,000 tons of urea plant in importance, according to user introduction, second only to the urea synthesis tower outlet pressure regulating valve U-PRCA-101, ranking second place. U-LRCA-401 control valve conditions of use are as follows: Fluid: Methylammonium fluid flow (Max / Normal): 38000 / 18300kg / h Valve pressure P1: 240kg / cm² Pressure difference △ P (normal / maximum): 200 / 250kg / cm² Temperature: 100 ℃ Specific Gravity: 1.15 Cv: 4.0 Flow Characteristics: Equal Percentage Mode of action: Air-off type with Actuator Effective area: 950cm² Travel: 19.05mm It can be seen from the above that the valve has large differential pressure before and after, Fast flow at the hole, ammonium methylate has such a strong corrosive characteristics. In addition, from the damage profile of the valve seat used by the chemical plant in Sichuan (made by Honeywell, Yamatake, Japan), there is a serious cavitation phenomenon. All in all, the valve operates poorly in view of the effects of erosion, corrosion and cavitation. To this end, Japan's Yamatake - cut Nigel company uses a special alloy (according to user analysis for the cast alloy) as the valve seat material. But even its life is only 150 days or so. I plant for the U-LRCA-401 control valve in the use of the existing problems, combined with China's national conditions, to ensure the connection size, flow capacity, flow characteristics, pressure and other conditions unchanged, the U-LRCA-401 adjustment Valve has been greatly modified. The main approach is described as follows: First, the effective area of ​​the membrane chamber, U-LRCA-401 control valve actuator chamber effective area of ​​950cm ², while China's stereotypes of high-pressure 5-type actuator chamber area of ​​?? 1000cm ², it seems quite Close to, and slightly larger than the valve 50cm ². So decided to change the effective area of ​​the membrane chamber. Using domestic stereotypes of high-pressure type 5 actuator film cover and diaphragm. Doing so, on the one hand, can speed up trial production and, on the other hand, save on the cost of making new molds for film covers and diaphragms. Second, due to the change in the effective area of ​​the actuator chamber, the heart-spring of the actuator was redesigned in order to maintain its original characteristics. And for the U-LRCA-401 valve seat life is very short (because the flow is side into the bottom, the damage is mainly manifested in the seat), we conducted an analysis that the main selection is not very appropriate. Because Japan Yamatake - Honeywell may over-focus on corrosion-resistant negligence cavitation erosion, resulting in its service life of only 153 days. From the corrosion point of view, in this occasion the choice of zirconium alloy is beyond reproach, the problem is the valve there is a serious cavitation, which requires the material to be harder. We made some damage to the valve seat hardness test, the HB only 143 or so. The choice of valve seat material mainly depends on two factors, one is the pressure difference, and the other is the circulation medium. In general, the greater the pressure difference, you should use high hardness of the material; corrosive circulating media, you should use corrosion-resistant materials. Therefore, we use the U-LRCA-401 control valve conditions were considered, decided to use corrosion-resistant materials. A4 steel has good corrosion resistance to urea and methyl ammonium liquid, and has better comprehensive mechanical properties and process properties, especially HB greater than 250 is the main steel in China's current urea steel. Finally, the stuffing box structure was modified with a Teflon V-ring to make the seal even harder. The revised design of the U-LRCA-401 control valve used in chemical plant in Sichuan so far, in good condition, did not find any failure to adapt to a variety of production load, and its price is only one-twelfth of the inlet valve.

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