Diagnose the Leakage Source

Before grinding, confirm that the leak originates at the wedge and seat interface rather than at the bonnet gasket or stem packing. Isolate and depressurize the valve, then remove the bonnet and withdraw the wedge. Inspect the wedge sealing faces and the body seat rings under magnification. Typical damage includes circumferential wear bands, radial scoring from trapped particles, and shallow erosion grooves. A uniform, shallow wear band is a good candidate for lapping. Deep grooves, cracks, or a warped wedge cannot be repaired by grinding and require replacement of the trim.The main gate valve product names of China gate valve Network include:Fire Special Rising Stem Resilient Seat Seal Gate Valve,Forged Steel Socket Welding Valve,Forged Steel Flange Gate Valve,GB Bellows Wedge Gate Valve,High Temperature & pressure Power Station Gate Valve,Inside Screw Non-rising Stem Wedge Gate Valve,Insulation Jacket Gate Valve,Lined Gate Valve,MZ44W Rising Stem Gas Quick Open&close Parallel,MZ48W Manual Non-rising Stem City Gas Quick Gate Valve,Manual Knife-shaped Gate Valve.

Prepare the Sealing Surfaces

Clean the wedge, seat rings, and stem with a solvent compatible with the process fluid. Remove all scale, grease, and embedded particles. Check the stem for straightness and the wedge guide for free movement. A misaligned wedge will produce an uneven grind and will continue to leak after lapping. Verify that the seat rings are accessible. In many gate valves the seats are integral to the body, which requires a specialized seat lap or controlled hand lapping.

Reassembly and Leak Testing

Clean all lapping compound from the parts with solvent and dry with oil-free air. Reinstall the wedge and stem, renew the bonnet gasket and packing if worn, and tighten the bonnet bolts in a crisscross pattern. Close the valve and pressurize the upstream side. Check for leakage at the downstream side and at the packing. A properly lapped gate valve should hold tight with minimal handwheel torque.

Summary

Gate valve leakage from worn sealing surfaces can be restored by lapping the wedge and seat with progressively finer compound, verifying the contact band, and leak-testing after reassembly. Deep grooves, cracks, and warped wedges cannot be repaired by grinding and require trim replacement. Upstream filtration and correct closing technique are the most effective prevention against recurrent seat damage.

Do you still need to know or purchase the following gate valve products:

• Fire Special Signal Relisient Seat Seal Gate Valve
• Fire Special Rising Stem Resilient Seat Seal Gate Valve
• Forged Steel Socket Welding Valve
• Forged Steel Flange Gate Valve