Globe Valve Sealing Surface Wear Leakage: Grinding Repair Methods
When the leak is caused by surface wear rather than a bent stem or cracked body, grinding and lapping can restore the sealing geometry at a fraction of the cost of replacement.The main globe valve product names of China globe Valve Network include:Flange Straight-through Throttle EmptyingGlobe Valve,Flange, Internal Thread Straight-through Plastic Globe Valve,GB Cast Steel Flange Globe Valve,GB Stainless Steel Flange Globe Valve,GB Bellows Globe Valve,High Temperature and Pressure Power Station Electric Globe Valve,Insulation Globe Valve,Inner Thread Straight-through Stainless Steel Globe Valve,Internal Thread Ammonia Globe Valve,Liquefied Gas Globe Valve.
Diagnose the Wear Pattern
Before grinding, confirm the leak originates at the disc and seat interface. Depressurize the valve, remove the bonnet and disc assembly, and inspect the sealing surfaces under magnification. Typical wear patterns include a circumferential groove on the disc face, a matching ring on the seat, and radial scoring from entrapped particles. A shallow, uniform wear ring is a good candidate for lapping. Deep grooves, chipped edges, or a warped disc cannot be repaired by grinding and require replacement of the trim.
Prepare the Parts
Clean the disc, seat, and stem thoroughly with a solvent compatible with the process fluid. Remove all scale, grease, and metal particles. Check the stem for straightness by rolling it on a flat surface; a bent stem will produce an uneven grind and must be replaced first. Verify that the seat is accessible or removable. In many globe valves the seat is integral to the body, which limits lapping to the disc alone or requires a specialized seat lap.
Grinding and Lapping Procedure
Select the abrasive grade based on damage depth. Begin with a medium grit lapping compound, typically 320 to 400 grit, to remove the wear ring. Finish with a fine compound of 800 to 1200 grit to produce a smooth sealing surface. Use a compound compatible with the valve material; aluminum oxide suits stainless steel, while diamond compound is suitable for hardfaced seats.
Apply a small amount of compound to the seat. Lap the disc against the seat using a light oscillating motion combined with intermittent rotation. Maintain even pressure and keep the disc concentric with the seat. Work for 30 to 60 seconds, then wipe clean and inspect. Repeat until the original wear ring is replaced by a continuous, matte contact band.
For the seat, use a matching lap or the disc itself with fine compound. Rotate in a figure-eight pattern to avoid directional grooves. Check the contact pattern by applying a thin marking compound to the disc and rotating it lightly against the seat. The contact band should appear as a continuous, even ring of consistent width. An interrupted or uneven band indicates misalignment and requires further lapping or replacement.
Reassembly and Leak Testing
Clean all lapping compound from the parts with solvent and dry with oil-free air. Reinstall the disc 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 globe valve should hold tight with minimal handwheel torque.
Summary
Globe valve sealing surface wear is repairable by lapping when the damage is a shallow wear ring. The procedure is to diagnose the wear pattern, clean the parts, check stem straightness, lap the disc and seat with progressively finer compound, verify the contact band with marking compound, and leak-test after reassembly. Deep grooves, chipped seats, and bent stems cannot be restored by grinding and require replacement. Upstream filtration and correct closing technique are the most effective prevention against recurrent wear.
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