Boiler Tube Failure

Boiler Tube Failure Investigation
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Boiler tubes

undergo abrupt failures by rupture or leakage. The problem is generally detected during operation rather than during hydro test or other inspection activities. This calls for immediate attention and can often require shutdown of the boiler leading to down time and loss of production. It is essential to understand the various modes and mechanisms by which the boiler components such as tubes, headers, pipes, turbines fail. Having proper understanding of the damage mechanisms, the inspection activities and on-line monitoring tools as necessary are addressed in a more systematic manner.
Metallurgical root-cause investigation helps to narrow down the reasons of failure and provides inputs to make proper corrective action. TCR has vast experience in undertaking complex failures of boiler tube, turbine shaft & blades and have helped power plant and utility boiler users to solve the problems.
Following is a brief classification of frequently encountered causes of

Boiler Tube Failure

Fluid side corrosion

  • Oxygen pitting
  • Under deposit corrosion-caustic gouging
  • Under deposit corrosion-hydrogen damage
  • Under deposit corrosion-phosphate corrosion
  • Acid cleaning corrosion
  • Internal deposit/corrosion product build up fireside wastage
  • Flow accelerated corrosion

Fireside corrosion of super heater and reheater tubing

  • Fireside oxidation
  • Fly ash corrosion
  • Soot blower erosion
  • Coal particle corrosion
  • Steam impingement

Fireside corrosion of water-wall tubing

  • Erosion
  • Low temperature (dew point) fireside corrosion
  • Falling slag damage
  • Tube rubbing

Rupture

  • Short-term overheating (stress rupture)
  • Long-term overheating (creep rupture)

Metallurgical degradation

  • Graphitization
  • Sigma phase embrittlement cracking

Corrosion with metallurgical aspect

  • Dissimilar metal weld stress rupture
  • Stress-corrosion cracking
  • Stress induced corrosion
  • Polythionic Acid Stress Corrosion cracking

Fatigue

  • Corrosion fatigue-waterside
  • Corrosion fatigue-fireside
  • Thermo mechanical fatigue
  • Vibration fatigue