Pneumatic high-pressure control valves needs to consider its structural characteristics (such as pneumatic actuators and high pressure seals) and operating conditions (such as high pressure differentials and corrosive media). Regular inspection, cleaning, lubrication and replacement of components are key to ensuring stable long-term operation.
Daily Inspection and Cleaning
Visual inspection:
Check the valve body, actuator and air supply pipe for leaks (e.g., air supply interface, diaphragm seals).
Observe smooth, adhesion or abnormal vibration of valve stem movement.
Make sure pressure gauges, locators and other accessories are functioning properly and are not damaged or loose.
Clean Air Supply system
Maintenance of filters and Pressure Regulator: weekly venting of condensates from filters and pressure regulator to prevent moisture from entering the pneumatic system and causing corrosion or diaphragm damage.
Oil mist Inspection: If a lubricated pneumatic actuator used, the oil level of the oil mist should be checked regularly to ensure adequate lubrication of cylinder piston and diaphragm.
Middle-end cleaning:
For media containing particles or prone to crystallization (e.g. mud, brine solutions), the valve body must be periodically removed to remove sediment from valve seat, valve core and sealing surface and to prevent seal failure or valve stem jamming.
Clean with a soft brush or non-metallic tool to avoid scratching metal surfaces.
Key Component Maintenance
Seal inspection and replacement
High pressure seal: Check the valve seat and valve core sealing surfaces for wear or corrosion (such as spot or scratch). If the surface roughness exceeds Ra0.8 micron, the surface needs to be ground or replaced.
Dynamic Seal: Replace stem stuffing (e.g. graphite packing or PTFE packing) periodically and adjust the packing gland bolt preload every 1-2 years or according to leakage conditions.
Actuator Seals: Check cylinder diaphragm or piston seals for aging and cracking. Usually replaced once every 3 to5 years (depending on frequency of use and media corrosion).
Actuator Maintenance
Diaphragm actuator: Check if the diaphragm is cracked or deformed. Replace the diaphragm if the thickness is reduced by more than 20%.
Piston Actuator: Clean dirt from piston rod surface and apply special grease (such as molybdenum disulfide grease) to prevent leakage due to wear and tear.
Spring Inspection: Make sure the actuator spring is not damaged or permanently deformed. If the spring force decreases by more than 10%, replace the spring.
Positioner and Accessory Calibration: The power valve locator is calibrated annually at zero point and range to ensure an accurate correspondence between the control signal (e.g. 4-20mA) and valve position feedback.
Check the reliability of solenoid valves, limiter switches and other accessories and clean the oxide layer on the contact.
Special maintenance of high-pressure operations
High-Pressure Differential Adaptability Check: Under high pressure differential conditions (such as steam pipelines and high pressure water systems), check regularly the pretension of valve body cavity and valve cover bolts to prevent bolt loosening or valve body deformation due to pressure fluctuations.
Make sure the gap between the core and valve seat meets design requirements (usually 0.1 -0.3mm) to avoid accelerating wear on the sealing surface due to differential corrosion at high pressure.
Corrosion Prevention Measures
For media containing chloride ions (Cl−) or hydrogen sulfide (H2S), the valve body material (e.g., titanium, Hastelloy) shall be inspected for pitting or stress corrosion cracking.
Periodically passivate valve body surface (e.g. acid wash, then applyrust oil) to extend its service life.
Emergency Shutdown function test
If the valve is used for emergency closure, a full opening/full closing operation test must be conducted quarterly to confirm that the response time ≤0.5 seconds must not be leaked.
Check gas supply reserve (such as pressure on gas tank pressure) to ensure that at least one complete operation can be completed in the event of a power outage or gas supply failure.
