By definition, erosion or wear and tear is the progressive loss of material from the surface of a solid object. If mechanical forces affect this base body, i.e. contact and relative movements of a solid, liquid or gaseous counter body, this results in erosion.
Amongst others, this undesired change of the surface occurs on tubes and tubeworks. Wear and tear is one of the main reasons for tube damages and causes the associated downtimes of heat exchangers and their connected components. Erosion on pipes can be manifold, with more or less severe consequences.
Erosion at support plates
This kind of tube damage is a type of erosion that is caused by support plates and insert plates that bang against the tubes. Support plates normally support and stabilise the fitted tubes in common heat exchangers. However, under certain conditions, for example if there is clearance between boring and tube or if other thermal and mechanical influences are present, the tubes can vibrate in the support plates and get damaged due to the banging, and thus wear out. This quickly results in undesired leakages, with associated financial and possible environmental damages.
Particularly the first inches of a heat exchanger tube are subject to severe erosion stresses. This is due to the fact that the influx of media is exposed to strong velocities and turbulences on the first few inches. These in turn can result in dangerous thinning out of the inlet area, causing erosion.
Steam and wet steam erosion
Steam erosion is mostly found on the external of heat exchanger tubes, which are subject to steam or condensate. Depending on the design of the cooler or heat exchanger, there could be increased steam concentrations at the support plates or the free tube areas, which in turn results in leakages.
Erosion through deposits and inclusion of foreign objects in tubes
If deposits or foreign objects accumulate in a tube, the inflowing medium washes around these. This results in velocities and turbulences directly behind the point blocking the free flow. In combination with water or abrasive particles, this can lead to severe wear and tear.
Erosion through droplets mostly occurs on power plant condensers. Due to condensation, microscopic steam droplets form, which hit the external tube surface with tremendous speed and energy. The force of these droplets can be so high that the tube surface is damaged with pinholes that can result in leakages.