Plant:

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

Problem:

• Explosive ejection of a governor valve due to progressive bolt failures
• History of individual bolt failures on comparable units

Solution: 

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

Benefits:

• 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