Manual Slide Gate Valve

Working Principle

• Opening: Rotate the handwheel clockwise. The screw stem lifts the gate plate upward, aligning the plate opening with the valve passage to allow material flow.

• Closing: Rotate the handwheel counterclockwise. The gate plate descends to block the passage. The sealing surface compresses the seal to cut off the medium completely.

Common Faults, Causes & Solutions

1. Stuck or sluggish operation 

• Phenomenon: Handwheel is hard to turn, gate plate cannot move.

• Causes: Material accumulation & caking; rust or poor lubrication on screw stem; foreign matter trapped; valve body/plate deformation; misaligned flanges.

• Solutions: Clean accumulated materials and foreign objects; clean and lubricate the screw stem regularly; correct deformed parts; re-install and calibrate flange coaxiality.

2. Leakage when fully closed 

• Phenomenon: Material leakage with valve fully closed.

• Causes: Seal aging, wear or damage; dirt/scratches on sealing surface; gate plate not fully closed; operating pressure/temperature exceeding rated value.

• Solutions: Replace damaged seals; clean and grind sealing surface; adjust travel limit to ensure full closure; keep working conditions within rated range.

3. Malfunction of screw stem 

• Phenomenon: Handwheel idles, stem cannot lift or lower.

• Causes: Thread wear, rust or tooth breakage; worn stem nut; bent stem; over-tight packing gland.

• Solutions: Repair or replace the screw stem and nut; straighten bent stem; properly loosen the packing gland.

4. Leakage at stuffing box 

• Phenomenon: Dust/medium leaks from the stem gap.

• Causes: Packing aging or improper installation; stem surface scratch/rust; loose gland bolts.

• Solutions: Replace and repack packing; repair defective stem; tighten gland bolts evenly.

5. Flange & body leakage 

• Phenomenon: Leakage at flange or valve body welds.

• Causes: Gasket aging/damage; loose or uneven tightened bolts; welding defects.

• Solutions: Replace flange gasket; fasten bolts diagonally and evenly; repair welding defects.

• Daily Maintenance

1. Lubricate the screw stem and bearings regularly, especially in dusty environments.

2. Remove accumulated materials inside the valve cavity periodically.

3. Inspect seals and packing regularly, replace worn parts in time.

4. Operate gently; do not use extended lever for forced opening/closing.