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Métodos de Mantenimiento y Causas de Fallos de las Válvulas de Control Neumáticas
Creado 10.10
[Overview Description]
Pneumatic control valves are one of the most widely used instruments in petrochemical enterprises. Their accurate and normal operation is of great significance for ensuring the normal functioning and safe production of process units. Therefore, it is essential to strengthen the maintenance of pneumatic control valves.
I. Key Inspection Areas During Overhaul
- Inspection of Valve Body Inner Wall
- Inspection of Valve Seats
- Inspection of Valve Trim
- Inspection of Sealing Packing
- Inspection of Rubber Diaphragms in Actuators
II. Daily Maintenance of Pneumatic Control Valves
- When graphite-asbestos packing is used, lubricating oil should be added to the packing approximately every three months to ensure the control valve operates smoothly. If the packing gland is found to be pressed down too low, additional packing should be added. If Teflon packing is found to have hardened, it should be replaced promptly.
- During routine inspections, pay attention to the operating conditions of the control valve, checking whether the valve position indicator matches the regulator output.
- For control valves equipped with positioners, frequently inspect the air supply and address any issues promptly.
- Regularly maintain the cleanliness of the control valve and ensure all components are in good working condition.
III. Common Faults and Their Causes
(I) Control Valve Inaction
- No Signal, No Air Supply
- Air Supply Present, No Signal
- No Air Supply to Positioner
- Air Supply to Positioner, No Output
- Signal Present, No Action
(II) Unstable Operation of Control Valve
- Unstable Air Supply Pressure
- Unstable Signal Pressure
- Stable Air Supply and Signal Pressures, but Unstable Valve Operation
(III) Control Valve Vibration
- Vibration at Any Valve Opening
- Vibration Near Full Closure
(IV) Sluggish Operation of Control Valve
- Sluggishness in Single Direction
- Sluggishness in Both Directions
(V) Increased Leakage in Control Valve
- High Leakage at Full Closure
- Inability to Reach Full Closure
(VI) Reduced Flow Adjustment Range
- The primary reason is the corrosion and reduction in size of the valve trim, leading to an increase in the adjustable minimum flow rate.
Understanding the fault phenomena and causes of pneumatic control valves enables targeted measures to be taken for resolution
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