Butterfly Valve Disc and Seat Restoration

The challenge

A large butterfly valve stopped shutting off tight and passed water past the disc when it was supposed to be closed. Corrosion had pitted the edge of the disc and eaten into the seat land, so the two faces no longer met evenly around the full contact line. Once a valve passes by, the operator cannot isolate the line for downstream work, flow control suffers, and the corrosion keeps spreading across both faces. Left alone, the only remaining option is to cut the body out and drop in a replacement valve, which is costly and ties up the line.

The Belzona approach

The valve comes down, the disc and the seat are stripped back to clean metal, and the faces show exactly where the corrosion has eaten them. Belzona composite rebuilds the pitted disc edge and the corroded seat land, restoring the metal that was lost. The contact line is then reformed so the disc sits evenly against the seat all the way around, and the wetted disc and body are coated against the water that caused the damage. The body goes back into the line shutting off tight, with the corrosion held back, and the operator keeps the valve instead of buying a new one.

1. Assess the facesThe disc edge and the seat land are inspected to map the pitting and corrosion and find where the contact line is no longer meeting evenly.
2. Strip to clean metalGrit-blasting takes the disc and seat back to clean, profiled steel so the composite and the coating bond to bare metal.
3. Rebuild disc and seatBelzona 1000 Series composite rebuilds the pitted disc edge and the corroded seat land, worked cold with no welding or heat distortion.
4. Reform the contact lineThe seating surfaces are reformed so the disc sits evenly against the seat around the full contact line and shuts off tight.
5. Coat and return to serviceThe wetted disc and body are coated to hold back the water that caused the corrosion, and the valve returns to the line.