6. Potential Service Issues
6.1 Tube failures
The majority of problems facing a cooler are those of corrosion or erosion on the water
side. Common types of failure are:
a) Impingement attack (or erosion corrosion)
This is caused by water containing air bubbles flowing at high speed through the tubes. The
impingement of rapidly moving water may lead to a breakdown of the protective copper oxide film
built up by the tube thus allowing corrosion/erosion. This is worse with water containing sand or grit.
The effect of these conditions would be pockmarking and pin holing of the tubes. In Charge Air Cooler
applications, erosion problems could occur on the outer surface of the tubes due to localised high
velocity “wet” gas impingement attack, therefore it is important that the risk of overcooling is minimised.
b) Microbial corrosion and pitting corrosion
This is caused by water containing organic matter, such as that found in polluted estuaries, which cause
the surface films to be predominantly sulphide and less protective. Please avoid extended exposure to
stagnant water which can encourage sulphate reducing bacteria and in the presence of deposits, pitting
corrosion will take place under the deposits.
Titanium tube stacks
Titanium tube stacks are available as a replacement for standard cupro-nickel tube stacks, for
applications where corrosion issues are being experienced. Titanium provides a highly durable, long life
solution for the most demanding applications and comes with a full 10 year guarantee on all titanium in
contact with cooling water.
6.2 End covers
a) Galvanic corrosion
Avoid mixed metal connections where the end covers are more anodic, especially if it has a relatively
small surface area. Alternatively, insulate the connection or coat either the anode or cathode to prevent
electrical connections.
b) Localised corrosion
The end covers can also suffer erosion corrosion and therefore flow and velocity guidelines must be
adhered to. Avoid installation with tight angle bends or obstructions which can cause local areas of
turbulence.
This is only a brief introduction to corrosion problems. The subject is complex and the purpose of these
notes is to outline in very general terms what may occur under extreme conditions.
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