Physico–statistical models based on the residual defectiveness of structural materials - Probabilistic Safety Assessment for Optimum Nuclear Power Plant Life Management (PLiM) - page 150

d e , mm

d s , mm

5.34 Correlation between the equivalent diameter d e and its true
size in the cross section d s : 1) cracks in inspection with a single
piezoelectric transducer, 2) volume defects, 3) crack in tandem
inspection.

Table 5.7 Information content of methods and the reliability of
detection of defects in welded joints of pipelines

Information content

Reliability of detection
compared with opening,%

Minimum detected sizes of inter-
nal defects, mm Inspec-

tion
methd

Identification of
defects on the
basis of type and
appearance

Bulk
defects
(pores,
slag)

Planar defects
(cracks, narrow
incomplete fu-
sion, etc.)

Height, Length Width

￿ ￿ ￿ ￿ ￿

Radio-
graphy

Good 0.1-0.2 0.1-0.2 0.1-0.2 85-90 65-75

Gamma-
graphy

Satisfactory 0.2-0.3 0.2-0.5 0.3-0.5 75-85 60-70

Ultra-
sonic
testing

Good for thick-
ness 40 mm

0.8 0.5 10.5 65-70 85-90

Colour
flaw test*

Satisfactory 0.3-0.4 0.5-1 0.5-1 75-80 55-65

Eddy
current
testing*

Cannot be distin-
guished

2-3 5-10 2-3 30-40 45-55

*Colour flaw test and eddy current testing for joints of pipelines with diameter 57-108 mm, thickness
3.52-4.5 mm