The demand for mechanised
ultrasonic wall thickness measurement is fulfilled with the introduction
of the Mapscan.
Mapscan applies a mechanical link between transducer and computer to
record the thickness data for each predetermined measurement position.
The transducer is scanned manually over the surface and the thickness
readings are stored on disk. After the scanning is finished, the data is
plotted on a wall thickness map. Each thickness level is colour coded
and wall thinning by corrosion or erosion is readily recognised. High
reproducibility (within 0.3 mm wall loss) enables accurate monitoring
and calculation of corrosion rates. This input is very important to
Mapscan is applied on vessels, pipework (bends), tank walls etc, for
exact documentation of corroded regions. It can be applied in service at
temperatures up to 250°C. Corrosion phenomena such as general wall
thinning, pitting corrosion, flow accelerated corrosion (FAC), hydrogen
induced corrosion (HIC) and hot hydrogen attack have been revealed
successfully by Mapscan.
Because of its high accuracy, Mapscan is accepted in lieu of internal
visual inspection of vessels. Based on the on stream Mapscan results,
off stream inspection interval extension is often accomplished.