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.

Our approach

We take the valve down, strip the disc and the seat back to clean metal, and look at exactly where the corrosion has eaten the faces. We rebuild the pitted disc edge and the corroded seat land with Belzona composite, restoring the metal that was lost. Then we reform the contact line so the disc sits evenly against the seat all the way around, and we coat the wetted disc and body 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 facesWe inspect the disc edge and the seat land to map the pitting and corrosion and find where the contact line is no longer meeting evenly.
2. Strip to clean metalWe grit-blast the disc and seat back to clean, profiled steel so the composite and the coating bond to bare metal.
3. Rebuild disc and seatWe rebuild the pitted disc edge and the corroded seat land with Belzona 1000 Series composite, working cold with no welding or heat distortion.
4. Reform the contact lineWe reform the seating surfaces so the disc sits evenly against the seat around the full contact line and shuts off tight.
5. Coat and return to serviceWe coat the wetted disc and body to hold back the water that caused the corrosion, then return the valve to the line.