Anomaly Description:
Steam leak from the glands and bonnet of a very old valve.

Root causes:
A worn-out bonnet gasket caused steam to leak from the valve. The valve was previously repaired by pinning a wire between the bonnets and injecting polymer compound through the bonnet. Because of the aging valve, the steam leak was discovered despite the previous repair that was done on the valve.

Integrity concerns:
The valve bonnet forms part of the piping pressure system. Failure of the bonnet would result in a catastrophic explosion of the valve and uncontrolled excessive service leak.

Clamp Design:
Failure of the previous repair system resulted in the need for a new and improved repair method. A 2” valve enclosure was designed according to ASME VIII Div 1 to cover the entire valve section. The enclosure would contain the process service should the bonnet fail completely. A strongback system was also designed to keep the clamp (and the piping system) in place should there be a complete failure of bonnet bolting.

Seal:
A successful seal was obtained by injecting a polymer compound into a sealing groove that runs throughout the valve flanges. The polymer compound was also injected into the cavity space of the enclosure resulting in a tight seal of the leak.