Pneumatic - valve daily maintenance needs to pay attention to what issues? What are the common fault?

Instrument and meter plant with you take a look at; Pneumatic control valve daily maintenance and pay attention to which common fault with the continuous development of industrial automation, control valve in the application of the control system is becoming more common, it is an important link in industrial automation systems. In order to make the production security and stability of reasonable control for a long period of operation, precise, stable work is inseparable from the regulator. So it is important to strengthen the maintenance of the regulator, if the regulator is poorly maintained or fault handling in time will affect the normal regulation of the whole control system. When repair key check which parts? Body wall in high pressure and corrosive medium, the body wall, diaphragm valve diaphragm often hit from the medium and corrosion, must check pressure point corrosion situation; Valve spool valve core is one of the moving parts of control valve, the erosion of the medium is relatively serious, carefully check whether the various parts of the valve core maintenance corrosion, wear and tear, especially under the condition of the high pressure difference, the valve core of the wear and tear caused by cavitation cavitation phenomenon more serious damage to the valve core should be replaced check packing: check whether the packing asbestos rope is dry, such as using ptfe packing, should pay attention to check whether the aging and whether the mating surface damage; When the seat because of work medium infiltration, fixed seat with thread is susceptible to corrosion on the inner surface and make the seat relaxation; Diaphragm and o-rings, parts, check whether the aging; To ensure that the valve movement flexible; If found that packing pressure cap pressure very low, should complement packing; Such as ptfe found dry packing hardening, should change in time; Air to equipped with adjustable valve locator to regularly check gas source, to ensure the quality of air, no water, and other sundry. Common faults and response regulator is different from the manual valve, it is in use process is in constant motion, state regulation, the moving parts, and to inherit from the impact of various forces, such as unbalanced force of medium, the hard to avoid all kinds of unexpected problems, these failures can be from executive mechanism, adjusting mechanism, may also be attachment device from the connection. Regulator is not reason 1: no air or air pressure is too small measures: should first check the source ( Instrument air) Whether whether unobstructed, air pressure to the valve use requirement. Reason 2: there is air, no air output signal pressure measures: 1) Of mechanical controller or locator, should be more mechanical pressure controller or locator. 2) Of mechanical controller regulating valve, check valve installed on the pipeline medium signal gathering pipeline valve is fully open or leak is serious, if there is anomaly should be processed in a timely manner. Reason 3: the output signal of gas pressure is normal, still don't. Steps: 1) Check the pneumatic diaphragm actuator diaphragm for serious leakage phenomenon, if the gas leak, should be timely replacement of the diaphragm and the related seals. 2) Check if the diaphragm in good condition does not leak, should be the main valve valve core is stuck with the bushings, valve seat, should check the main valve, disintegration of clear clutter. 3) Disintegration of stem bending deformation is serious, should check the main valve, replace the processing according to the inspection situation. 4) Funnelled signal air piping for leaks, check processing. 5) Signal amplifier failure or improper adjustment, the main gas source did not enter the diaphragm chamber, through amplifier should adjust or replace the amplifier. Regulating valve work adjustment range, control is not stable cause 1: air pressure change is bigger, or filter, pressure reducing valve don't work properly. Steps: 1) Check the compressed air system running state. 2) Check the replacement filters or relief valve. Reason 2: air pressure is stable and unstable signal pressure. Steps: 1) If it is unstable, after replace the intelligent positioner for the PID parameters setting. 2) Of mechanical controller or locator, should replace the mechanical controller or locator, and setting the controller. 3) After replacement of mechanical controller or locator is still unstable, should check replacement gas source signal amplifier, and carry on setting. Reason 3: pressure stable gas supply, signal, but the regulator is still unstable. Steps: 1) Check the pneumatic diaphragm actuator air tightness. Check carefully whether the driven push rod seal slight leakage phenomenon, if there is leakage should be replaced the collapse of the seal; Disintegration check diaphragm for scratches, stabbed the slight leakage phenomenon, caused by such as leak should replace the diaphragm. 2) Carefully check whether there is connected with main valve locator part clearance, should be to replace or tighten the positioner and the main valve fittings. 3) With soap and water check carefully whether the signal windpipe way slight leakage phenomenon, once discovered should handle in time. 4) Signal source unreasonable setting of the amplifier, adjust the balance screw signal source amplifier. 5) The regulator mechanism ( Including the main valve and pneumatic diaphragm actuator) Resistance is too big, should be the collapse of the main valve, check change abnormal elements, including the valve core and valve seat, valve stem and stem seal and driven push rod. 6) Check whether the pneumatic diaphragm actuator pressure balance in spring is damaged, have test spring fatigue deformation, if there is abnormal pressure balance springs should be changed.