Commissioning
Boiler Tube

Travelling Across Boiler Tube

Travelling Across A Boiler Tube

Ready for an amazing journey?

Take a minute to travel across a preheater boiler tube affected with severe under deposit corrosion and overall oxygen pitting at early stages of development. This journey shall help you to become aware of the importance of having a deep understanding of the natural chemical reactions involved in a power plant. Only this way you will be able to identify potential failures and take proactive actions. In this particular case, the internal corrosion pattern in the tube is mainly due to the effect of high dissolved oxygen concentration in the presence of excessive non-volatile constituents in the quality of the make-up water. Enjoy!!   click here

Boiler Tube
Commissioning
exfoliation

Exfoliation Corrosion

Exfoliation & Lamellar Corrosion

During Inspection

Severe leakages in a steam generator superheater were the leading cause of a major outage a few months after first operation of a power plant. In the course of a visual inspection, the first section of the superheater was observed to develop several sharp perforations, impingement and general abrasion on the baffle/tube interface.

Heavy deposits were also found all over the steam drum along with serious surface exfoliation.

Conclusions

Failure investigation was conducted to reveal that unsatisfactory chemical cleaning left a heterogeneous layer of calcium carbonate, sodium phosphate, silica and iron citrate.

This layer inhibited the formation of a consistent magnetite layer that was partially developed across the surface.

All these layers present dissimilar thermal coefficient with regard to the steel surface creating exfoliation and lamellar corrosion which was intensified with vibrations and temperature changes experienced during hot commissioning (see photo).

As a result, scales detached from surface and passed to steam side leading to significant damage in the superheater and dramatic consequences to the project.

exfoliation