A single circle or multiple
sectors?
For 360° inspection of tubes or
bars, either a single encircling probe or an arrangement of
several probes each covering a sector, typically 45° to
90°, can be considered.
Both possibilities offer various advantages and disadvantages.
The sectorial probes require a certain overlap
for a homogeneous inspection of the whole circumference. They
must therefore be placed in at least two rows, which requires
greater axial space. Because of the necessary overlap, a greater
total number of electronic channels are also required.
A single probe has the advantage of needing
less space, and of optimizing the number of useful channels
since no overlap is needed.
The inspection of bars or tubes often requires
the use of several simultaneous
beams on the same circumference. In the case of a single probe,
the
reflexions of a beam may cause interference to the inspection
with other
beams. Arranging the probes over several rows enables this
effect to be
limited where necessary.
Finally, while the purchase price of each
option is not very different, the maintenance
cost of the sectional curved probes is markedly lower, as
only part of the circumference
can be replaced.
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Immersion
transducers
