Knife-Gate Valve Seat Reclamation

The challenge

A knife-gate valve on a stock line wore out where the abrasive slurry runs hardest. The seat and the gate guides lost metal, so the blade no longer dropped square against a clean seat and the valve passed when it should have shut off tight. A valve that will not isolate cannot be trusted to take a section of the line out of service for work downstream, and the leak-by carries product where it does not belong. The usual fix is a new valve, which is costly and can sit on a lead time while the line waits.

Our approach

We pull the valve and open it up to see where the slurry took the metal. We blast the seat pocket and the guide faces back to clean, profiled metal so the repair bonds, then rebuild the worn seat and guides with a composite that stands up to the same abrasion that wore the originals. We reform the seat so it carries the blade evenly across its face and line the wetted pocket against the slurry. When we close the valve back up, the gate shuts off square, the guides hold the blade true, and the body goes back on the line instead of being scrapped for a replacement.

1. Open and assessWe pull the valve, open the body, and map where the slurry has worn the seat and the gate guides.
2. Blast to clean metalWe grit-blast the seat pocket and the guide faces back to a clean, profiled surface so the composite bonds to bare metal.
3. Rebuild seat and guidesWe rebuild the worn seat and guide faces with an abrasion-resistant composite, working cold with no welding on the body.
4. Reform and lineWe reform the seat so the blade seats evenly across its face and line the wetted pocket against the slurry.
5. Reassemble and return to serviceWe close the valve back up, confirm the blade shuts off square, and hand the body back to go on the line.