Remediation of a vibration problem

Three-axis accelerometer in place on the bump-stop


  • A 400MW single-shaft combined-cycle plant, including a 150MW three-pressure HRSG with reheat


  • Irregular movement of a reheater header at maximum load, with potential for reduced fatigue life of tube-to-header welds


  • Team approach with the prime contractor, OEM and operator
  • Design review; plant instrumentation and monitoring
  • External observation during operation; internal inspection off-load
  • Investigation of the effect of operational parameters


  • Flow induced vibration of tube-bank identified as prime cause, being predicted to generate displacements and frequencies comparable to those observed
  • Addition of tube spacers implemented, leading to elimination of problem and allowing operation at full power to be resumed
  • Secondary effect of attemporator performance identified as requiring further investigation
Variation in reheater attemporator flow


Brear, J.M. and Jarvis, P.
“Tracing a vibration problem back to source”
ETD Int Conf ‘Heat Recovery Steam Generator Technology’, Woburn House, London, 10-12 Nov 2003

Plant Integrity