Environmental Engineering Reference
In-Depth Information
whose amplitude of the echo signal exceeded the recording level were
recorded.
Radiographic inspection of the test sample was carried out by specialists
of the Expert Centre for Technical Diagnostics of Metals (MIKIMT) at
three angles to the normal to the circumference of the joint: 0, +20 and
-20
o
(sensitivity 0.3 mm).
The results of all experiments were used to prepare charts of defects
in the weld test specimen. The following factors were taken into account
when analyzing the results:
• inaccuracy in the coordinates of the defect location introduced during
sample preparation;
• measurement inaccuracy in radiographic inspection, for example,
if the radiographs were taken with overlapping of the sector size,
the inaccuracy in the range of ± 17 mm was also made in the
coordinates of defects on the overall chart;
• measurement inaccuracy in the coordinates of the detected dis-
continuities in manual and automatic ultrasonic testing, for example,
the effect of the wall thickness of the sample.
In addition to the defects mentioned in the producer certificate, additional
discontinuities can form in the welded joint of the test sample. The positive
conclusion on the existence of such discontinuities was made if indications
from discontinuities in the near coordinates were recorded by at least two
different methods of ultrasonic testing and/or radiography.
The detectability of discontinuities was assessed using the coefficient of
overall detection of discontinuities (i.e., the ratio of the number of detected
discontinuities from the number taken into consideration to the number of
discontinuities taken into account).
Table 5.4 and Fig. 5.12 show the results of detection of different types
Sumiad
(MVTU)
VNIIAES
(MVTU)
Slag
VNIIAeS
(YuTE)
Pores
Hot cracks
Radiography
Fatigue cracks
5.12
Detection of discontinuities of different types using different
methods.
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