Spray water temperature control valve installed in the boiler cooling system, by changing the throttling area to regulate the amount of water spray, steam temperature control to ensure the normal operation of the boiler. In order to further understand the performance of the control valve, our company draws on the advanced experience of foreign countries, set up a test stand, the valve of the flow characteristics, flow capacity, critical pressure and flow coefficient and other key performance indicators for accurate test for the design of the valve An important basis. 1 test prototype and test method The prototype for the test is DN32; PN25 and DN20; PN25 two kinds of water jet temperature control valve. DN32; PN25 sprinkler valve for the gate type, adjust the characteristics of a straight line. DN20; PN25 water control valve for the plunger, the adjustment is a parabolic nature. According to the American ASME, the British BS4740, the International Electrotechnical Commission IEC test requirements and methods for testing. Using two kinds of valve contrast test method. During the test of the data measured three times, whichever is the average calculated basis. Test medium is 5 ~ 40 ℃ of purified water. 2 Test items, results and analysis 2.1 Test project flow characteristics, flow capacity, critical pressure and flow coefficient test. 2.2 Test results 2.2.1 For DN32; PN25 gate valve, the flow characteristics of the data in Table 1, and according to the test data in Table 1 into the flow characteristics of the curve shown in Figure 1. Table 1 Valve Flow Rate Characteristics when Pressure Difference ΔP = 0.3MPa No. Valve stroke / mm Relative stroke /% Flow rate / t · h-1 Relative flow rate /% 1 2.25 8.7 0.425 10.6 2 6.4 24.8 1.165 21.8 3 10.44 40.2 1.94 32.5 4 14.36 55.5 2.52 46.7 5 18.36 70.9 3.4 57.8 6 22.42 86.6 4.17 74 7 25.9 100 4.83 100 Table 2 Adjusted Control Valve Operating Characteristics No. 1234567 Relative Stroke /% 8.724.840.2 55.570.986.6100 Q1 / Qmax (S = 0.5) 10.5821. 629.6 3944.857.551 Q1 / Qmax (S = 0.2) 10.5719.626.2 32.634.838.240.5 DN32; The flow characteristics of the PN25 gate valve are tested in the ideal case where the system resistance is compared to the valve only A small proportion. However, in actual operation, especially during the start-up process of the boiler, when the pressure drop of the whole system is a certain value, the resistance of the system is very large, which will cause the adjustment characteristic curve to be distorted and the working characteristic of the piping system to be distorted. Therefore, we adjust the characteristic data by the following formula. (1) - actual relative flow; - theoretical relative flow; S-valve resistance versus system resistance ratio. The above data and Figure 1 shows that for the linear characteristics of the water regulating valve, when the ratio of valve resistance and system resistance S = 0.2, the valve opening is 60%, the flow is equivalent to 33.2% of the valve fully open flow, and after 60 % ~ 100% opening, little change in traffic. When the ratio of valve to system resistance is S = 0.5 and the valve opening is 70%, the flow rate corresponds to 41% of the full-flow rate, and the flow rate increase is very small at 30% of the valve opening thereafter. In line with the requirements of automatic boiler control. The best regulating range of the regulating valve should be between 90% ~ 5%, so the water regulating valve used in the boiler superheater and reheater should not choose the straight line characteristic.
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