The Failure That Had Nothing to Do With the Alloy Grade A heat exchanger in a refinery developed through-wall pitting within 18 months of commissioning. The tubes were specified correctly, the mill certificate confirmed the right alloy, and the installation inspection showed nothing unusual. The plant team replaced the bundle and assumed it was a manufacturing defect. It wasn't. The metallurgical testing on the failed tubes told a different story entirely. EDS analysis of the

In the first two parts of this series, corrosion was driven by chemistry and by flow. In the refinery hot-exchanger, a third agent takes command — temperature itself. Above a few hundred degrees, steel stops being a passive bystander to its environment and begins to react with it: sulphur attacks it, hydrogen invades it, and under sustained load it slowly deforms and tears. And in a final irony, the most dangerous crack of all appears not while the exchanger is running hot, b

In Part 1 of this series I argued that a heat exchanger failure is rarely proportional to the size of the leaking tube. Nowhere is that truer than in the condenser. A condenser does not fail because the whole bundle is bad — it fails because a few tubes, in three very specific situations, see conditions the rest never do. Across the condenser investigations my teams have closed, the same three culprits recur: the inlet end that erodes, the air-removal zone that grooves, and t