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Control valve failure analysis and processing
(A) diaphragm membrane type actuator First, the level control valve out of control can not open the level measurement instructions are high, the regulator output is also great, but the control valve still can not open, had to fight mechanical hand wheel control. Check the valve positioner (remove the membrane connector, plugging), move the nozzle baffle mechanism, locator output changes, check the orifice is unobstructed, open the amplifier found the amplifier diaphragm is broken. Replace the diaphragm, the control valve re-input automatic control. Valve positioner amplifier diaphragm broken, back pressure chamber no back pressure, amplifier output, so the control valve out of control. Second, the valve positioner feedback slider rust level fluctuations, inspection found that the valve positioner feedback mechanism slide bar is fully rusty can not be rotated, had to use the handwheel control. Try to knock out the slider, rust and refueling back, the control valve back to normal. Valve positioner feedback mechanism, with the valve opening size changes into the corresponding positioner feedback. Slider rust, the feedback force can not change with the size of the valve opening, but can not make the valve opening at the regulator output signal corresponding position, resulting in fluid level fluctuations. Third, the pressure control valve can not move a process of reducing load, natural gas volume can not be reduced, the natural gas pressure regulating valve can not move due. Inspection found that the output signal to the valve is normal, it is estimated that the valve core is only carbon stuck, after the increase of pneumatic signal, coupled with the hand wheel force to close the valve. To be opened parking valve inspection, not surprisingly, due to the valve load usually stable little switch, carbon black brought in the gas in the stem and the guide sleeve between the small gap in the carbon stuck. Therefore, every major overhaul, the valve will be opened to clean, to avoid similar accidents. Fourth, the loss of control spool Absorption of liquid level control can not, record fluctuations in the curve, check the transmitter, the regulator are no problem. Hand wheel control when found hand wheel pressure or lift are not as heavy as usual, floating, the judge is the spool rupture, forced to open the parking control valve is split, the valve plug and stem connection at the disconnect. Had to replace the spool, and spool valve spool connected to increase the strength of a circle, so as to avoid similar accidents. Spool breakage is caused by unbalanced forces under medium pressure. Fifth, the Canadian gas root more regulation valve can not open after the overhaul of the car, the liquid ammonia flash tank high, the scene check valve is not open, hurried hand control to make the liquid level is normal, the instrument found to be in the control valve Maintenance, fear of leakage of ammonia, packing plus too much pressure too tight, large friction. Appropriate loose packing pressure ç–¬ let its action flexible, re-vote automatic control. Six, flow control fluctuations Air compressor anti-surge flow control vent valve, frequent switching in the car, resulting in unstable traffic. Check the regulator, control valve are no problem, but the control valve opening has been small. When air flow rises, the regulator outputs a signal of up to 1 MPa / cm 2 to the regulator valve (purge valve), similar to the phenomenon of integral saturation. When the locator received a signal to open the valve, the locator to go through a period of dead zone before the control role, the dead zone so that the regulator output becomes smaller, to be adjusted valve action and over, this repeated process, coupled with Low control valve linearity poor, so the valve must frequent switching, the flow control instability. The solution is only suggested to increase the compressor speed, increasing the amount of vent, the control valve off the low-end control. Seven, the absorption tower liquid level low alarm check valve is closed, but with the process down to B valve operation. Disassembled valve check is serious damage to the spool erosion, replacement of the new cartridge installed a good backup. Spool erosion, can not afford to control the role, if not handled in time, the liquid level below the interlocking liquid level will cause parking. Eight, the valve stem bending can not open After overhaul, when driving the absorption tower liquid level control valve can not open, the valve stem found in the inspection pressure bend, had to disassemble and remove the stem alignment and then re-installed, put into service. Overhaul the control valve must be careful, especially this non-splice valve structure, the film is heavy, the first few turns screw head need to turn the film head, accidentally bend the valve stem. In addition, after adjusting the valve overhaul finished school, should be repeatedly switched several times, convinced that its action is very flexible to give up. Nine, the control valve can not move After the overhaul of the vehicle and found that the absorption tower liquid level control valve can not move, was forced to open the control valve check, is the guide sleeve and stem fell into the iron stuck. In the overhaul of the valve, the lower flange was pressed down with a lathe to remove the old guide sleeve and put on a new guide sleeve. When assembling the valve, it was not carefully cleaned. There was also fallen iron falling below the guide sleeve. When checking the valve, Iron below the valve action without obstacles, did not find the problem. Drive into the media, the media into the guide sleeve from the balance hole, but also by the guide sleeve out of the balance hole, iron filings in the guide sleeve back and forth, stuck in the stem and the guide sleeve between the valve can not move It's Ten, the control valve can not drive the car process, the carbon dioxide pressure control valve can not open, the pressure force high, vent valve is opened. Check the reasons that the mechanical hand wheel control latch is not unplugged, the control valve is in the mechanical hand off position, of course, can not open. The regulator output signal is adjusted to zero, unplug the latch, the control valve into operation. Eleven, found that the control valve friction natural gas pressure control valve, repair found that the friction is not good, resulting in pressure fluctuations. Friction is due to maintenance and assembly, the gland flange friction phenomenon eliminated. General regulating valve stem and the gap between the guide sleeve is very small, gland flange must be flattened during assembly, otherwise it is not leakage is the stem and guide sleeve is not the heart and cause friction. Second, the sudden closure of the control valve caused a sudden closure of natural gas flow control valve, natural gas flow dropped to zero, was forced to stop the whole system. Check the regulator output, but the valve is fully closed, hit the hand wheel operation, with the process to resume production. The locator output duct removed, plugged by hand, move the nozzle baffle mechanism, the output signal up to 1MPa / cm 2, indicating that the problem is in the control valve to the membrane head gas supply signal, the membrane vent gas Release to prove that the patch is broken. Replace diaphragm control valve put into operation. Thirteen, vote automatically cause the system to disturb the steam flow control valve, a section for the hand wheel control, check the locator after re-vote automatically, release the hand wheel, causing system disturbances. The reason is that the regulator output signal is kept in front of the manual value of the fight, the operator did not see the output locator, the hand wheel quickly released, the control valve then open large. Because the film is too large, there is a process of inflated lag, causing the gas valve suddenly open a lot of big, to the system once disturbed. Fourteen, deal with the problem of air leakage Leak in the treatment of valve positioner gas source leaks, due to excessive force to make joint slider, gas source tube was washed away, the regulating valve immediately began to move. Instrumentation workers immediately select the source tube plug back, press tight by hand, restored the original position of the control valve, and then with the control valve operator hand wheel control, replacement of joints. It is also very effective in emergency situations. Fifteen, the diaphragm valve can not open the water treatment valve does not open the regeneration valve, open the inspection and found that the diaphragm is pulled bad, after the replacement of the new film, not open a few days, the above re-occurred. Diaphragm diaphragm pull analysis is due to the reason, the diaphragm valve head limit bolt loose, limit position has changed, the stem stroke is too large, the tensile force exceeds the elastic range of the diaphragm, so the film pull bad. Re-adjust the limit bolt, re-replace the diaphragm, diaphragm valve back to normal. (B) cylinder-type actuator First, the hydraulic control valve can not turn off During driving, the steam pressure regulator automatically opens, plus the signal can not be shut. Check found to be the wrong throttle O-ring due to long-term immersion in high temperature aging, can not afford to seal the role of replacement O-ring, returned to normal. The role of the wrong throttle is the high-pressure control oil and pressure relief after the introduction of low-pressure control oil were introduced into the upper and lower cylinder cylinder to control the valve opening. When the wrong throttle seal O-ring aging oil leakage, high pressure oil and pressure relief oil can not be isolated, resulting in no pressure difference between the upper and lower piston cylinder, of course, the control valve can not be closed. Second, the butterfly valve oscillating hearth negative pressure control valve amplitude oscillation, the section for the hand wheel control, inspection found that dual orifice amplifier orifice is somewhat blocked, resulting in cylinder balance pressure is too small, the cylinder pressure is too small at both ends, it can not Make the valve stable, causing equal amplitude oscillation. After cleaning the clogged orifice, the amplifier output increases and the butterfly valve operates normally. Third, check the broken splint threaded check valve, the need to adjust the stem position, then the calibration signal should be reduced to zero, on the loose stem plywood, just a song heard a loud noise, A look at the splint thread has been broken, had to rework plywood assembly and then check. The reason is that the calibrator with the signal down to 0.2 MPa / cm 2, but the role of the upper cylinder piston pressure on the role of the membrane valve stem, loose some of the plywood care, so the thread playing Bad. The correct operation should be the balance between the upper and lower cylinder piston open, so that the upper and lower cylinder pressure balance. Or remove the connector to deflate, and then loose the lever to adjust the valve stem. Fourth, the cylinder balance valve leakage control valve can not move] check valve after maintenance check, send signal control valve can not be opened. Checked only to find the upper and lower cylinder balance valve leaks, so the upper and lower cylinder can not form a pressure difference. Replace the balance valve, back to normal. Fifth, the butterfly valve can not open the valve after opening when the refined butterfly valve can not open the operation, the inspection found to be installed after the maintenance of upper and lower cylinder air supply and pneumatic signal line reversed, to take over the normal operation of the valve. Due to the pneumatic signal pressure plus spring pressure is greater than the pressure of the air supply, the butterfly valve is closed. When the pneumatic signal and the gas source is reversed, it is always the pressure of the air source plus the spring pressure is greater than the pneumatic signal pressure, so the two-position butterfly valve is closed. Sixth, vent valve dead pressure regulation vent valve, in a maintenance, the grinding, compression test, sealing performance is very good. Replaced, the process of driving normal, the need to close the valve, but found serious leakage. It is estimated that the spool valve seat card into the foreign body, decided to switch several times washed away foreign objects, the test was successful, the valve is strictly closed to operation.