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