VALVE MAINTENANCE PROCEDURE

Regularly remove dust, oil, and rust from the external surface of the valve. Use a clean soft cloth or brush. For stubborn stains, use a mild detergent (alkaline cleaner for stainless steel valves; avoid damaging the paint on coated valves). Keep the nameplate legible (model, specification, pressure rating, manufacturing date) to facilitate maintenance and traceability.

Inspect the valve body, bonnet, flanges, etc., for cracks, deformation, or sand holes (especially for cast iron valves). Cracks may cause leakage, and deformation affects operation.

Check flange connection bolts for looseness, loss, or corrosion—tighten if loose, replace if severely corroded. Also, check the gasket for integrity; replace if aged or damaged.

Check operating parts such as handwheels, handles, or electric actuators for damage, deformation, or loss. Damage may prevent normal operation.

Apply leak detection fluid (e.g., soapy water) to the valve stem seal and flange connections, and observe for bubbles.

Stem leakage usually requires packing replacement. For flange leakage, first try tightening bolts; if ineffective, replace the gasket.

For globe valves and gate valves: After closing the valve, observe whether the downstream medium flows (for water systems, check for water seepage or pressure drop; for gas systems, use a detector).

For ball valves and butterfly valves: Check whether the position indicator is accurate after closing. If leakage occurs, it may be due to wear, scratches, or debris on the ball/butterfly plate and seat sealing surfaces—lap or replace the seat as needed.

Periodically open and close the valve to feel whether the operating force is even and whether there is any sticking. Sticking may be caused by over-tight packing, foreign object blockage, or component damage.

Check whether the opening indicator is accurate; if not, calibrate it.

For frequently operated valves, inspect handwheel/handle wear and replace if severe.

Check whether the power connection is normal and whether wires are damaged, aged, or loose. Confirm that control signals are transmitted normally and that the valve moves accurately as commanded.

Observe the operation process: whether the opening/closing speed meets requirements, and whether there is abnormal vibration or noise (may indicate internal actuator damage, mechanical failure, or improper installation).

Regularly check and adjust travel limit switches to prevent overstroke.

Common lubrication points: valve stem, bearings, gears, etc. For gate valves, also include contact surfaces between the gate and guides; for ball valves, include ball-seat contact surfaces and the stem.

Check whether lubrication points have sufficient lubricant (observe grease fittings or oil levels). Replenish promptly if insufficient.

Normal temperature and pressure: lithium grease.

High-temperature environment: polyurea-based grease or perfluoropolyether grease.

Low-temperature environment: ester-based lubricant (good low-temperature fluidity).

Chemically corrosive environment: fluorinated grease or other corrosion-resistant lubricants.

Ensure compatibility between lubricant and seal materials.

Use a grease gun or oil can to inject lubricant, avoiding excess overflow.

After lubrication, operate the valve several times to distribute lubricant evenly.

Clean up any excess lubricant to keep the environment tidy.

If a strainer is installed upstream, regularly check for blockage (observe differential pressure across it). If the differential pressure exceeds the limit, clean or replace the filter element, following procedures to avoid damage.

Pressure gauge pointer should indicate accurately, not fluctuate, and return to zero properly; otherwise, calibrate or replace.

Safety valve: Regularly check whether the set pressure meets the specified value, using manual testing or specialized equipment. Also, check sealing to prevent leakage under normal operating pressure.

In addition to daily inspections, the following describes the causes and corrective actions for frequent leakage issues in valve operation.

Daily valve maintenance is a systematic task. It requires regular inspections and upkeep following the "5 aspects, 11 key points" and mastering rapid diagnosis and handling of common leakage failures. Through preventive maintenance, valve service life can be significantly extended, unplanned downtime reduced, and the safety and stability of fluid conveyance systems ensured.