Page 365 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

CORROSION DAMAGE, DEFECTS, AND FAILURES 343

Figure 5.20 Close-up view of upright column with missing tie rod. (Reproduced by permis-
sion of the Society of Petroleum Engineers (20).)

1. Different metals and alloys such as copper galvanized steel, cast iron pipes, and
brass joints are used in hot water distribution line.
2. A noticeable temperature difference is observed in the heat exchanger loop
where the water in the hot water tank is circulated to a heater. No mechanical
pump is used in this loop and the water flow is by convection. Slow water
circulation results in a larger temperature difference between the upper and
lower pipe sections. A temperature difference is also seen in the heat circulation
loop where the circulated hot water is mixed with incoming cold water. Severe
corrosion is observed in these areas.
3. In some sections of the pipe, a large area of the copper pipe was in contact with
a relatively small area of galvanized iron and steel pipe.

Water samples taken from various locations (23) indicated high iron content in
samples taken from locations where the cold water and hot water are mixed, for
example, the heat exchange loop and hot water recirculation pump (Fig. 5.22).
Visual examination and the metal ion content of the water samples shows inter-
nal corrosion of pipe in various locations in the hot water distribution system that
compromises the quality of hot water. The internal pipe corrosion is because of the
following factors or a combination of the factors.