Valve Bonnet and Seat Reclamation
Rebuilding a passing gate valve's worn seat and bonnet faces cold to restore shutoff and a tight bonnet seal, with no new casting.
What was failing
A gate valve on a process line was passing across a worn seat, and the bonnet face no longer pulled up tight against the body. Once a valve will not shut off and the bonnet weeps, it stops doing the one job it is there for, which is to isolate the line safely. The sealing faces were pitted past the point where they could be lapped back true, and the body was too far gone to recover by hand work alone. Replacing the valve was the obvious answer, but the lead time on a fresh casting was long enough to hold up the line, and the cost of the swap was hard to justify for a body that was otherwise sound.
How AAS approaches it
We took the valve down and looked at where the metal had actually gone, both on the seat and on the bonnet mating surface. Rather than chase a casting, we strip those areas back to clean, bright metal and rebuild the pitted sealing faces and the bonnet face cold with a machinable composite that keys to the steel. We hold the body off any hot work the whole way through, so there is no heat into the casting and no distortion to fight. Once the rebuild is in and cured, we reform the profile so the seat carries an even line of contact again and the bonnet pulls up flat, then put the valve back together so it shuts off and the bonnet seals.
Assess the body
We dismantle the valve and check the seat, the bonnet face, and the body to confirm what is worn, what is pitted, and what is still sound enough to keep.
Strip to clean metal
We take the seat and bonnet areas back to clean, profiled metal so the rebuild keys to the steel and not to old corrosion.
Rebuild the faces cold
We rebuild the pitted sealing faces and the bonnet mating surface with a machinable composite, with no hot work into the body.
Reform the profile
We work the cured rebuild back to profile so the seat carries an even line of contact and the bonnet face pulls up flat and tight.
Reassemble and return to service
We put the valve back together and hand it back so it shuts off and the bonnet seals, without waiting on a fresh casting.
The result
From the job
Repair and protection work of this kind, performed by AAS crews across Louisiana.
Capabilities used here
Where this work happens
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