Page 61 - Handbook of Materials Failure Analysis
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2 Case Studies 55
FIGURE 3.6
Caustic corrosion gouging. Severe localized gouging on the heat absorption side of this
SA-210 waterwall tube was caused by caustic corrosion beneath a deposit. Once the caustic
concentration within a deposit becomes grate enough to cause corrosion, the reaction
becomes self-perpetuating and causes a through-wall leak within a very short time [3].
parameters that may require determination by calculation, observation, or measure-
ment are as follows:
• Tube metal temperature
• Tube metal stress
• Tube metal thickness
• Tube metal diameter
• Tube metal material properties
• Tube metal microstructure
• Boiler water quality
• Boiler water flow
• Fuel constituents
• Fuel gas temperature
• Tube deposit constituents and
• Steam-side scale-thickness
2.1 CASE1: HIGH-TEMPERATURE CREEP
This investigation was conducted to determine the cause of failure of a platen super-
heater tube in a 140 MW thermal power plant. Visual examination along with dimen-
sional measurement, chemical analysis, and hardness measurement were carried out
to deduce the probable cause of failure. In addition, optical microscopy was a nec-
essary supplement to understand the reason for the failure. It was concluded that the
tube had failed due to severe creep damage. The tube metal had been exposed to a
