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I. Common Faults and Solutions
Valve leakage (not tightly closed)
Possible causes: Wear or damage to the valve seat sealing surface; aging or damage to the butterfly plate sealing ring; impurities blocking the sealing surface within the pipeline.
Maintenance method:
Minor impurities: You can try opening and closing the valve rapidly several times to use the fluid to wash away the impurities.
Seal surface damage: The valve needs to be disassembled to inspect the sealing rings on the valve seat and the butterfly plate. If it is a rubber or PTFE soft seal, a new sealing ring is usually required. If the valve body is damaged, the entire valve may need to be replaced.
The valve cannot be operated (the handwheel/actuator does not turn)
Possible causes: The valve stem is rusted or severely corroded; the butterfly plate is stuck with the valve body; foreign objects are blocking.
Maintenance method:
Do not force the operation, as it may damage the valve stem or the actuator.
Try spraying a loosening agent (such as WD-40) on the valve stem and its threads. Gently tap and vibrate to allow it to penetrate. Then try to rotate it slowly.
If it is caused by medium crystallization or solidification, the valve body can be heated with steam or hot water (note: it is necessary to confirm whether the valve material can withstand the temperature).
If it still fails to rotate, usually the valve needs to be removed from the pipeline and disassembled for inspection, cleaning, or replacement of internal parts such as the valve stem and bearings.
Leakage at the valve stem (external leakage)
Possible causes: Wear or aging of the valve stem packing (gland packing); Loosening of the packing gland bolts.
Maintenance method:
First, try to tighten the nuts on both sides of the packing gland. Be careful not to tighten it too much at once; instead, do it gradually and symmetrically until the leakage stops and the handwheel can still rotate freely.
If the tightening is ineffective, it indicates that the packing has failed. Replacement of the packing is necessary. During operation, the system should be at a non-pressurized state. Loosen the pressure cover, remove the old packing, insert the new packing ring, and make the cut edges offset by more than 90°. Finally, re-tighten the pressure cover.
Difficult to operate or too strenuous
Possible causes: The packing is compressed too tightly; the valve stem lacks lubrication; the bearing is damaged.
Maintenance method:
Loosen the packing gland nut appropriately.
Add lubricating grease to the valve stem bearing through the oiling port (if present).
If the situation does not improve, it may be necessary to disassemble and inspect the component and replace the bearing.
II. General Maintenance Procedures and Safety Instructions
Safety First:
It is essential to isolate the system before maintenance: close the front and rear stop valves, and depressurize and empty the pipe section where the valves are located (especially for high-temperature, toxic or corrosive media).
Make sure that the drive mechanism (such as electric heads or pneumatic heads) has been de-energized and the gas source has been cut off, and perform proper safety locking (Lockout/Tagout).
Disassembly and Inspection:
Symmetrically and in stages, loosen the valve body connection bolts.
Carefully remove the valve core assembly to avoid damaging the sealing surface.
Thoroughly clean all the parts, and inspect the wear conditions of the valve stem, butterfly plate, valve seat, sealing ring, bearing and packing.
Replacing parts and assembly:
Replace with original or equivalent specification parts, especially the seals.
Apply the appropriate lubricating grease (such as silicone grease) on the valve stem and sealing surface to facilitate installation and subsequent operations.
Tighten the bolts symmetrically and in stages to ensure uniform force on the flange and prevent leakage.
Test:
After the maintenance is completed, pressure tests and switch operation tests should be conducted to ensure there is no internal or external leakage and the operation is flexible. Only then can it be put into formal use.
III. When Professional Assistance is Required?
If the valve is of the welded type or is an integral structure with the pipeline.
If there is a lack of specialized tools or replacement parts.
If the medium is highly dangerous (such as highly toxic substances, strong acids, high-temperature and high-pressure steam).
If the problem still persists after the above basic repairs have been carried out.
In summary, for the maintenance of the mid-line butterfly valve, one should start with the simplest operations (such as flushing and tightening) first. If the problem is complex or requires disassembly, it is essential to follow safety procedures and, when necessary, contact professional valve maintenance personnel or the manufacturer's technical support to ensure the maintenance effect and personal safety.
