Internal erosion can occur when high velocity process streams come in contact with the vessel shell. Entrainment of solid particles in the fluid stream and direct impingement of the stream on the shell can greatly increase the severity of erosion. Concurrent corrosion can also greatly increase the severity of erosion, due to the continuous removal of corrosion scales.
Wear plates are frequently provided to protect pressure vessel shells, especially at locations where high velocity process streams enter and impinge on the shell. The wear plates are usually fillet welded to the vessel shell and can be made from a high-alloy material that has greater erosion resistance than the shell.
Visual examination (VT) is adequate to detect internal erosion of a pressure vessel shell. Ultrasonic examination (UT) using a longitudinal wave procedure can be used to determine the remaining shell thickness in eroded areas, or to monitor erosion from the outside surface.
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