| Case | A spring of a steam valve was broken after several years of service. Conditions steam 80 bar at 500°C. The lowest winding of the spring, located inside the bonnet at atmospheric conditions, was broken. |
| Cause | The material of the spring was corroded near the fracture. SEM investigation revealed a typical intergranular fracture surface with pitting at the edges. The morphology is characteristic for hydrogen embrittlement, induced by the cathodic partial reaction of the corrosion process. |
| Advice | Waterproofing of bonnets and apply insulation to prevent condensation. |
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