Pneumatic control valve, electric valve positioner is one of the most primary attachment, the acceptance of precise positioning control signal valve stroke end bearing, the effect of pneumatic control valve factory, locator and manipulation of the valve are done calibration, but after loaded on the pipeline valve general demand for an additional calibration.
Conventional calibration method is: 5 points calibration is 4 ma, ma, ma, ma, 20 ma, locator reaction when 12 ma stem in a horizontal position, other groups of signal when the valve orientation should be respectively in % 0, 25, 75%, 100% of stroke, and reaction rod rolling viewpoint less than plus or minus 45 degrees.
Deviation about zero and full alone can adjust the screw corresponding corrections, under normal circumstances, if the valve stroke and the corresponding suggests that a given signal calibration is gone.
Valve closed occurs when a primary question that how to make the valve tightly closed seat full load.
General method is to calibrate the valve, so that the closed parts (
Such as plug, estrangement, valve plate, etc. )
Just locate on the seat, not admit that closed parts is completely against the seat.
Leakage quantity in order to adhere to the planning, to prevent the sealing surface corrosion, it is necessary to plan the appropriate sealing load.
Effect of single pneumatic actuators are generally choose spring reset planning, choose this kind of planning method, using spring is able to cut the seat of the load, also can accept all the closure pressure.
Typical double effect of pneumatic actuator piston planning, choose this kind of planning method, unlike type spring reset type planning, supply pressure does not demand constraint, in order to reach high closure pressure, to be able to use full load supply pressure.
About the piston type planning, the higher the pressure, stability and control, the better the sensitivity of the valve.
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