Pneumatic high-pressure control valves as a key equipment in industrial process, its common faults and solutions can be summarized in the following aspects, should be combined with the characteristics of high pressure working conditions for targeted analysis:
Body structure malfunction
I.Internal leakage problem
Performance: after the valve is closed there is still a media leakage, high pressure conditions may significantly increase the leakage volume.
Reasons
valve core/seat wear (e.g. ball ball valve soft sealing gasket damage, ball valve bushing wear);
Stem seal failure (e.g. steam valves high temperature aging, packing leakage);
Dielectric pressure difference is too big, can cause valve core deformation or blockage.
Solutions
Replace worn cores/seats and select pressure-resistant, corrosion-resistant materials (e.g., hard alloy).
Repair valve stem seal with metal seal or high performance packing.
Optimize the design of the actuator, increase the pressure of the gas source and overcome the high pressure difference.
2.Jamming phenomenon
Performance: Valve is slow or cannot be fully opened/closed.
Reasons
Dielectric scale (such as steam steam valve muffler plate shedding;
The linkage mechanism is rusty or loose ;
High pressure media will cause the gap between the core and valve seat to narrow and friction to increase.
Solutions
Wash valve body regularly and install flushing water pipe.
Replace rusty parts and use corrosion resistant materials.
Adjust cylinder limit bolts to ensure accuracy of valve core stroke.
II. Pneumatic actuator
1. Cylinder leaks
Performance: Valve works poorly or does not meet the required opening.
Reasons
Cylinder's O-ring seal is damaged (easy to age under high pressure).
Limit bolts loose or fall off.
Insufficient cylinder capacity or spring failure.
Solutions
Replace the high-pressure resistant sealing ring;
Re-tighten limit bolts and calibrate cylinder stroke.
Choose high-volume cylinders or high-strength springs.
2. Moving slowly
Performance: the valve response speed is slow, cannot meet the requirements of rapid high-voltage truncation.
Reasons
Increased friction force of piston (such as cylinder surface finish or poor lubrication);
Insufficient air source pressure (high pressure valves require high drive pressure);
The stem is bent or packed too tightly.
Solutions
Grind the inside of the cylinder and repaint with grease.
Adjust gas source pressure to 0.4-0.5MPa (should be above normal working condition);
Correct valve stem and replace self-lubricating packing.
III. the positioner and control system failures
1. Locator malfunction
Performance: Valve opening is inconsistent with control signal and cannot be precisely regulated.
Reasons
Damage The positioner circuit board (e.g. due to humidity or vibration);
Small slip valve wear (the instrument air contains impurities);
The O-ring of the gas source interface broke.
Solutions
Improve the sealing performance of glans to prevent water from entering.
Install air filters and replace the filters periodically;
Select a separable positioner to separate the sliding rheostat from the circuit board.
2. Abnormal signal
Performance: Valves do not operate or have high fluctuation in opening.
Reasons
Inadequate The 4-20mA control signal load;
The DCS output unstable or control cable damage;
Malfunction of Solenoid valve failure.
Solutions
Signal load detection, guarantee ≥ 250 omega;
the DCS parameter setting and replace cable with damaged insulation.
Test the operation of the solenoid valve and adjust interlocking logic.
IV. Process and Design Defects
1. Too little pressure
Performance: Valves cannot be opened or closed.
This was due to poor pipeline design, which resulted in the pressure difference between the high and low pressure sides exceeding the valve rating.
Solutions
Install bypass valves front and back to balance pressure difference.
Re-select the type and select a special valve for high pressure differential (e.g. multi-stage relief core).
2. Improper selection
Performance characteristics: frequent valve malfunctions, short service life.
Reason
The specificity of high-pressure working conditions (e.g. material strength and sealing performance) was not taken into account.
Solutions
Select high pressure forging valve bodies to avoid casting defects.
Verify the match between valve diameter and flow coefficient (Cv value).
V. Maintenance and Operation Suggestions
Periodic maintenance: Check cylinder seal performance and valve stem flexure quarterly to replace ageing fillings.
Special high pressure inspection: A pressure test is conducted once a year to verify whether the valve's pressure resistance rating is in accordance with working conditions.
Operating Specification: Avoid frequent opening and closing to reduce high pressure shock; confirm stable gas source pressure (≥0.4MPa) prior to operation.
Spare parts management: Stock up on key spare parts such as high-voltage valve seals and locator circuit boards to reduce downtime.
