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Regulating valve of the main performance
Nov 23, 2017

Pneumatic control valve performance indicators: basic errors, return difference, death difference and leakage always spreads, rated stroke deviation, volume, sealing, compressive strength, appearance, rated flow coefficient, the inherent flow characteristics, vibration resistance and operating life, 13, 9 test items to the factory. Because of the transportation of regulating valve and the adjustment of working spring range, it is necessary to adjust and test the following performance before installation:

1) the basic error input the input signal smoothly according to the increase and decrease direction into the actuator gas chamber or locator, measure the corresponding stroke value, calculate the actual "signal stroke", and the relationship between the theory and the relationship between each point error. Its maximum value is the basic error. The experimental points should include at least 5 points of signal range 0, 25%, 50%, 75%, 100%, and so on. The basic error limit of measuring instrument should be less than 1/4 of the basic error limit of the test valve.

2) the experimental procedure of the return difference is the same as that of the above first points. The maximum difference between the positive and negative stroke measured on the same input signal is the backlash.

3) always point deviation method with the first point. The basic error of the upper limit of the signal is the starting point deviation; the basic error of the lower limit of the signal is the end point deviation.

4) the rated travel signal is added to the pneumatic actuator air chamber or positioner to make the valve stem go through the whole course. The difference between the actual stroke and the rated stroke and the rated stroke is the deviation of the rated stroke. The actual stroke must be greater than the rated stroke.

5) leakage test medium for clean gas "10~50 degrees of air and nitrogen" or "liquid water or kerosene"; the test pressure A program: when the valve allows the pressure greater than 350KPa, the test pressure according to 350KPa, less than 350KPa by allowing pressure to do; B test procedures according to the maximum working valve the pressure to do so. The test signal pressure should ensure that the valve is in the closed state. In the A test program, the opening valve actuator pressure is zero; the gas valve actuator pressure is the upper limit of the input signal plus 20KPa; the two bit valve actuator pressure should be the design specified value. In the B test procedure, the signal pressure of the actuator shall be the design specified value. The test medium shall flow into the valve according to the regulation, and the valve outlet can directly pass through the atmosphere or connect the outlet to the atmospheric pressure head loss measuring device. When the confirmation valve and the downstream connecting pipe are completely filled with the medium, the leakage can be measured.