How can a technician correct a valve seat that is wider than specifications?

• A. By single-angle grinding
• B. By increasing the seat width
• C. By replacing the seat
• D. Three-angle grinding of the seat

Answer: (D)

When a valve seat is wider than specification, you need to remove material to restore the proper seating surface and width so the valve can seal evenly and flow correctly. The best way to do this is three-angle grinding. This method uses three different cuts to shape the seat: the first cut sets the overall width, the second defines the seating surface, and the third finishes the edge to produce a precise, sharp sealing contact with the valve face. This approach recreates the correct seat geometry and edge without over-depleting material or creating an improper profile.

Using a single-angle grind isn’t ideal because it only creates one angle and often won’t produce the correct seat width or the proper profile needed for reliable sealing and flow. Replacing the seat would be necessary only if the seat is damaged beyond repair, and increasing the seat width would worsen sealing rather than fix it. After grinding, the seat width should be measured to ensure it matches the specification.