Environmental Engineering Reference
In-Depth Information
5.16 Diagram of radiographic inspection of the assembly weld
No. 1 in test sample DN 800. 
by automatic ultrasonic testing and radiography. However, the number
of detected defects can not be regarded as a complete characteristic of
detectability since it does not take into account the size and, hence, the
importance of the detected discontinuities. In this case, radiography did
not detect two defects.
The probability of detecting defects of the given lengthis determined
by the formula:
P = n det i / N emb i ,
where n det i is the number of detected defects with the given length; N emb i is
number of embedded defects with this length.
The results calculated by this formula are presented in Table 5.6 and
Fig. 5.17. The calculations were performed for radiography and automated
ultrasonic testing (NDT inspector Nos. 12, 18 and 11 who found the
maximum, minimum and average number of defects, respectively).
As seen in Fig. 5.17, the highest detectability was recorded for automatic
ultrasonic testing. Combined application of TOFD and the pulse-echo
technique in automatic ultrasonic testing allows conclusions to be drawn
about the type of detected defect. In the conclusion, drawn up by TRC
experts, the given type of defects is identical with the certificate data of
the test sample and is confirmed by radiography.
￿ ￿ ￿ ￿ ￿
Investigation of inspection methods to enhance their effectiveness
In this case, the effect of various elements of inspection methods (inspection
duration, scanning method, frequency, etc.). As an example, Fig. 5.7
and 5.18 presents the data on the impact on repeated inspection on the
detectability of defects.
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