Page 390 - Challenges in Corrosion Costs Causes Consequences and Control(2015)
P. 390
368 CONSEQUENCES OF CORROSION
Figure 5.61 Close-up of dimpled surface (19).
Corrosion
products
Metal
90 μm
Figure 5.62 Longitudinal section showing extreme localized attack (19).
top of the tube sheet as shown in Figure 5.67. The condenser is installed vertically
with severe operating conditions at the inlet of the top tube sheet as the temperature
∘
reaches 150 C and pressure 250 psi.
Corrosion resulted in leak failures of many tubes and led to several shutdowns.
The corrosion attack was at the top 100 mm where the tube was expanded (rolled) to
join the top tube sheet with the rest of the tube intact. The rolled end of the tube is
the corrosion end.
Repairing the condenser by plugging leaking tubes was unsuccessful as seen by the
corrosion of plugs, top tube sheet, and seal welds. Plugging the tubes caused turbulent
flow, which eroded the passive film on the steel plugs and caused severe corrosion of
the plugs, top tube sheet, and steel welds.
A section of the tube with the inner surface covered by a mixed black/brown
scale is shown in Figure 5.68. Circumferential cracks growing in a zigzag fashion
