Bolt failures – root cause analysis and remediation


  • Coal-fired, 4 x 550MW, located in the UK


  • Explosive ejection of a governor valve due to progressive bolt failures
  • History of individual bolt failures on comparable units
Fractured bolt, with cross section of cracked bolt


  • Multi-disciplinary investigation of the failure, in the context of utility-wide bolt experience


  • Mechanical, metallurgical and compositional factors identified
  • Revisions to design, heat treatment and detailed chemistry recommended
  • Major revision to bolt life management procedure implemented, and rolled-out to other utilities and operators

Plant Integrity