Probabilistic life assessment of GT vanes


  • Four heavy duty, 6-stage expansion GTs driving compressors at a UK chemical plant; installed in the 1960s with 112,000 hours service on the current set of vanes


  • To reduce maintenance costs by extending vane life from 100,000 to 130,000h, prior to retirement of the units


  • Inspection
  • Flow, thermal and stress analysis
  • Probabilistic creep life calculation, allowing for local hot-spots


  • Inspection revealed no cracking and little degradation or oxidation
  • One row demonstrated to be of a different material to that specified
  • Analysis showed life to be limited by creep under flow-induced bending
  • Risk calculated to increase by a factor of 5 from 112,000 to 130,000 h
  • Absolute risk level during extended life deemed tolerable by the operator
Predicted failure probability for GT vanes, individually and as a row, under two operating scenarios


Wood, M.I., Lant, R.P.D. and Brear, J.M., “Quantitative Risk Assessment and its Role in Plant Maintenance Decisions”, IMechE Conf ‘Power Station Maintenance 2000’, St. Catherine’s College, Oxford, September 2000

Plant Integrity