The Challenge
Following an over-pressurization event, a nuclear power plant discovered significant damage to the pressure seal cavity of a 15-inch Class 900 main steam header shut-off valve.
The damage created conditions that made installation of a traditional metal pressure seal impractical.
Inspection revealed multiple challenges, including:
- Out-of-round conditions
- Oversizing
- Coning
- Ballooning of the cavity
The original valve manufacturer determined that machining the cavity back to its original dimensions was not feasible. Replacing the valve was also undesirable due to an estimated lead time of approximately 20 weeks.
A different solution was needed.
Engineering a Custom Solution
EGC engineers evaluated the damaged valve and determined that a custom graphite pressure seal could accommodate the distorted cavity geometry.
Unlike traditional metal seals, high-density flexible graphite can conform to irregular sealing surfaces while maintaining sealing performance under load.
Based on detailed measurements of the cavity, EGC designed and manufactured a custom 16-inch capped VSG Graphite Pressure Seal specifically for the application.
The seal’s end-cap design allowed the graphite to conform to the cavity geometry once compressed under operating load.
This capability helped compensate for:
- Out-of-round conditions
- Surface imperfections
- Dimensional inconsistencies
- Localized damage
without requiring extensive valve rework.
The Results
After installation, the facility reported:
✅ Zero leakage
✅ Successful operation under service conditions
✅ No reported seal failures
The project demonstrated how a custom-engineered graphite pressure seal can provide an effective sealing solution when severe cavity distortion prevents the use of a conventional metal seal.
Don’t Let Valve Damage Lead to Extended Downtime
Severe cavity distortion, oversizing, and surface irregularities don’t always require valve replacement. EGC’s custom graphite pressure seals are engineered to solve challenging sealing problems in critical power generation and industrial applications.
Speak with our engineering team to evaluate your valve sealing challenge and explore a custom solution tailored to your application requirements.
