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Shenyang Taike Fluid Control Co.,Ltd

Summary Of Control Valve Troubleshooting

In the industrial field, the process parameters such as medium flow, pressure, temperature and liquid level are very important as several meridians in the production process. Regulating valves are important acupoints distributed in these meridians. Once there is a problem in that parameter, it needs to be mobilized These regulating valve to be conditioning.


Regulating valve, also known as control valve, in the field of industrial automation process control, by receiving the control signal output control unit, with the power to change the media flow control, pressure, temperature, liquid level and other process parameters of the final control element. In many systems, regulating valves are subjected to more severe operating conditions than temperature, pressure, corrosion and contamination.


Air source system failure


1, the meter wind blockage. As the ball valve at the end of the wind instrument branch has throttling effect, the stolen goods in the wind here easily stacked accumulation. Resulting in instrument pressure is too low, the valve can not be fully closed, and even control valve does not move.


2, air filter pressure regulator failure. Air filter pressure regulator for a long time to use too much booty, air leakage valve, pressure relief valve set the output pressure over the end of the output pressure gauge less than the prescribed pressure. Resulting in sluggish control valve, can not fully open the whole or even closed.


3, copper connection failure. Aging copper leakage, loose joints or stolen goods to block the brass so that the wind instrument signal pressure caused the valve does not move, can not fully open the whole, the manual state valve instability generated oscillation.


4, instrument wind system failure. Abnormal air pressure station, purifying device abnormal tank, water cut is not timely to make the icy lines, instrument air leakage or stolen goods blocked, resulting in low or no pressure instrument wind pressure.


5, instrument wind branch valve is not open, causing the valve does not move. Often occurred in the device overhaul, after the transformation of driving.


Power system failure

1, the power cord terminals loose, short circuit, fall off, polarity reversed fault.


Due to the on-site vibration, the wiring is not strong, resulting in loose wiring or too much dust caused by poor contact to the control room when the signal arrives at the scene from time to time, resulting in regulation of the chaos generated vibration regulation.


Due to wiring errors, equipment, water or moisture and other reasons to short-circuit the power cord so that the signal received by the regulator valve than the signal will be low, resulting in the valve can not be fully closed.


2, the middle of the power cord connector or the middle of the injury at fault.

The power cord by the environment vibration, pull the external force, the insulating tape failure of the insulation properties and high temperature baking joints and other reasons to make the power cord connector loose or broken off, short circuit between the power lines or short to ground, the terminal or Broken power cord. Resulting in the control valve is not continuous action, can not be fully closed, no action. In the maintenance process, the middle of the power line connected reverse, causing the control valve does not move.


3, the control valve from the regulator control failure.

In the device overhaul, after the transformation of the power line in the process of driving the wrong car or control the configuration error caused by the control valve regulator is not controlled.


Electrical converter problem


1, zero, the range is not allowed. Due to the installation and debugging are not allowed or on-site vibration, temperature changes and other reasons so that the converter output signal zero, range is not allowed. Resulting in the valve can not be fully closed, the amount of leakage, limited and so on.


In the converter field adjustment should first ensure that the converter signal small table indicates accurate. Normally small signal table should be maintained.


2, throttle blocked. Wind instrument stolen plug throttle orifice. Resulting in the valve does not move.


3, the output is not linear. As the coil in the converter, the aging of components or by the site vibration, ambient temperature, so that the output of the converter is not linear, resulting in its zero point, range adjustment process can not achieve the required value, the valve action is not linear, can not Fully open.


Valve positioner failure


Electrical valve positioner

1, zero, the range is not allowed.


As the locator installation process is not allowed to debug or on-site vibration, temperature changes and valve stem stroke changes, changes in the location of the feedback lever and other reasons the minimum valve opening and maximum opening and control room signal is inconsistent. Resulting in the valve positioner output signal can not make full-closed control valve, resulting in a large amount of leakage, limited and so on.


In the locator field adjustment should first ensure that the control valve action well, the feedback system installed firmly and well, and then through the standard signal to be adjusted. The control valve stroke and the control signal.


2, throttle blocked. Booty blocked the throttle. So that there is no output signal locator, resulting in control valve does not move.


3, nozzle, baffle between the stolen goods. Affected by the site environment, the locator will be attached to the use of a period of time after a layer of dust, affecting the nozzle baffle back pressure, thus affecting the locator output. Caused by the instability of the control valve, resulting in shock.


4, the seal is not good. Long-term use of the locator Various fastening nut, gasket prone to loosening, aging phenomenon, resulting in locator air leakage. So that the valve can not be fully closed, valve instability, resulting in regulation of oscillation.


5, feedback bar failure. Long-term operation of the feedback lever fastening nut gradually loose or even fall off, resulting in loose feedback bar, skew, with the fixture card touch, off. So that the controlled parameters is difficult to stabilize, especially in regulating valve action requires accurate temperature control have a greater impact.


6, loose nut. Locator fixing nut is loose due to loose installation, resulting in tilting of the positioner, affecting the action of the feedback lever and causing the phenomenon of collision of the card. So that the valve action instability, resulting in the phenomenon of limit.


Locator in a variety of spring fastening screws loose in the vibration environment, changing the amount of spring preload, affecting the spring tension and status. So that locator zero range changes, the locator is not linear, resulting in full-closed control valve can not be fully closed, the regulator valve action is not linear.


7, permanent magnet position changes. As a result of external forces, so that the location of two magnets change, changing the location of the magnetic field is unbalanced coil, locator output is not linear, resulting in the valve action is not linear. Magnet adsorption of impurities such as iron pin, the formation of a card touch impede the movement of the bezel, so that the output of the locator is not allowed, so that the control valve action and control signals are inconsistent.


Smart locator

1, feedback lever failure.


Feedback lever fastening nut loose or even fall off, resulting in loose feedback bar, skew, with the fixture card touch, off. Slowly regulating valve action, frequent fluctuations, regulating valve limit or even lose control.


Locator is not fixed loose skew loose, affecting the activities of the feedback lever, causing the phenomenon of the card touch the limit valve.


Feedback limit spring on the board off, or the feedback lever from projectile, resulting in poor contact with the feedback lever and the feedback plate, resulting in lag, resulting in frequent action regulating valve. So that the controlled parameters is difficult to stabilize, especially in regulating valve action requires accurate temperature control have a greater impact.


2, locator calibration is not good. Adjustment in the middle position did not find good, manual output when the control valve did not go all the way, open gas off the wrong choice. So that the valve can not be fully closed, resulting in a large amount of leakage, limit and so on.


3, the intelligent positioner calibration complex, a long time, and the need for multiple full-on, the process fluctuations, so the adjustment valve should be cut out, especially in the control of temperature control valve must be adjusted To be adjusted offline.




Regulating valve itself is faulty

1, the control valve leakage, valve closed all the time there is a gap between the valve core and valve seat, resulting in the valve fully closed when the flow of media, the controlled parameters is difficult to stabilize.


1>, adjust the valve regulating valve stroke adjustment improper use or spool valve core wear and tear caused by long-term use of corrosion. Usually adjust the stem down to reduce the leakage to reduce the purpose.


2>, the valve core is subject to more serious corrosion of the medium around the spool by the media in the welding slag, rust, slag and other scratch injury. Should remove the valve core for grinding, the serious should replace the new valve core.


3>, the valve seat by the more serious erosion of the medium, or medium welding slag, rust, slag and other scratches produce scars, seal between the valve seat and the body is damaged. The valve seat should be removed for grinding, replace the gasket, a serious new valve should be replaced.


4>, the valve slag, rust, slag and other stolen goods block, so that the valve can not be fully closed, the control valve should be disassembled for cleaning, while observing the valve seat is scratched wear phenomenon.


5>, sleeve valve seat and seat gasket seal damage, disc valve seal damage to the throttle when the valve clearance is relatively large.


2, regulating valve packing failure. Friction between the valve stem and the packing valve makes the small signal of the valve difficult to operate, and the large signal jumps and vibrates, causing the regulating valve to fluctuate greatly during the adjustment process, and the parameters are difficult to be stabilized. Friction caused by large-scale control valve movement does not even move. Routine maintenance should regularly increase the oil or grease, packing serious aging, serious leakage should be replaced packing.


3, the stem and the connector loose or fall off, due to the scene vibration or loose coupling nut, too close to the stem and the connecting part of the connection is too small, in operation stem and actuator push rod is not synchronized or off Move, affect the control valve action or even failure.


4, there is a foreign body stuck or blocked valve.


5, regulating valve film head failure. Control valve corrugated diaphragm aging metamorphism for a long time, elasticity becomes smaller, tightness worse, and even crack the air leakage serious. Compression spring aging elastic coefficient changes, or even broken.


6, PID control valve control system settings. PID set improperly affect the action of the control valve or even cause the adjustment valve turbulence, affecting the life of the valve. .


7, confirm the process status. In the control valve leakage is large, confirm the secondary line valve is closed, the control valve limit, confirm the valve before and after the opening degree of the valve. Confirmed if there is any big fluctuation in the process flow when the charged parameters change frequently.


8, heating furnace fuel oil control valve for maintenance, it is best to cut off the control valve used to run secondary line to prevent the impact of production. If you do not cut out to open a little deputy line valve, maintenance must ensure that the valve does not turn off due to the full control valve.


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