Page 55 - Handbook of Materials Failure Analysis

CHAPTER

Boiler tube failures: Some

case studies 3

Atanu Saha
CSIR-Central Mechanical Engineering Research Institute, Durgapur, West Bengal, India

CHAPTER OUTLINE
1 Introduction ....................................................................................................... 49
1.1 Short-Term Overheating ......................................................................51
1.2 High-Temperature Creep .....................................................................51
1.3 Hydrogen Damage ..............................................................................53
1.4 Caustic Corrosion/Gouging ..................................................................53
2 Case Studies ...................................................................................................... 54
2.1 Case 1: High-Temperature Creep .........................................................55
2.1.1 Examination Details ..................................................................56
2.2 Case 2: Hydrogen Damage ..................................................................62
2.2.1 Examination Details ..................................................................62
3 Conclusion ......................................................................................................... 67
Acknowledgments .................................................................................................... 67
References .............................................................................................................. 67

1 INTRODUCTION

The principal route for producing electricity is the conversion of mechanical energy
of rotation into electrical energy using a generator. The rotation of the generator shaft
is achieved by coupling it to a turbine where the kinetic energy of the moving fluid is
converted into mechanical energy of rotation. The working fluid may be wind, water,
steam, or combustion gases. The most common fuel used to produce steam in the
boiler is coal. In USA, 70% of the electricity is produced from fossil fuel power plant;
in India also, it is about 80%, and the rest from other sources, such as, wind, water,
nuclear, etc. [1,2]. The schematic illustration of a boiler is shown in Figure 3.1.
The severe service environment in fossil fired boilers is largely the reason for
these failures as the effect of stress, temperature, corrosion, erosion, and vibration
combine to produce degradation of the tubing steel. Corrosion by oxidation, by com-
bustion products, and by impure boiler water can significantly reduce the tube wall
thickness and result in failure of a tube many years before the expected end of its
useful service life.

Handbook of Materials Failure Analysis With Case Studies from the Chemicals, Concrete, and Power Industries. 49
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