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TOFD
Phased array
Testing levels Acceptance levels
ISO 10863
ISO 15626
Testing levels
B C 1 B /
C B as a minimum 2 A /
D A as a minimum 3 A /
Quality levels
ISO 5817
Acceptance levels
ISO (not available)
Figure 5.17 Example of levels to apply for TOFD or phased array in agreement with ISO 17635
When the replacement of a NDT technique by another one is not defined within a standard or a construction
code, the approach suggested in the IIW V-1502-11 document can be applied. For a specific weld on a given
welded construction, the proposed actions are to carry out a systematic analysis called OPC consisting in
assessing:
The Occurrence of flaws liable to appear while welding (in the conventional risk assessing analysis,
this represents the probability of the feared event).
The detection Performance of such flaws for each of the used NDT technique/method.
The Consequence(s) liable to result from the non detection of these flaws by the NDT technique
applied and the alternative one when using construction weld or welded equipment.
After this analysis, risks are assessed combining parameters by means of a set of rules allowing comparison
of, at least qualitatively, the NDT techniques. This approach is advantageous since it is global and allows a
better assessment of the criticality resulting from a undetected flaw and thus to compare the risk induced
by changing the NDT method.
5.3.2.2 Ultrasonic testing of austenitic welds
The need to test austenitic welds by means of ultrasonic testing is growing in various industry sectors such
as nuclear, LNG tank storage and oil and chemical industries.
IIW Sub Commission VC has prepared a Handbook published in 2012 by DVS media GmBh (Handbook on the
examination of austenitic and dissimilar welds – ISBN 978-3-87155-969-3).
This handbook covers the ultrasonic inspection of austenitic butt welds. The objective of the handbook
is to provide all those involved in the volumetric examination of austenitic welds with the background
knowledge necessary to perform effective ultrasonic inspections of austenitic welds and to inform them of
the limitations caused by the acoustic properties of the material.
The handbook is particularly addressed to technicians, engineers and scientists involved in austenitic weld
inspection. It should be of particular value to those responsible for preparing inspection procedures, but it
does not provide a detailed inspection procedure for any particular weld.
The handbook deals mainly with butt welds but the theory and practice presented can be applied to welds
with more complex geometries providing the additional difficulties of the geometry are taken into account.
The handbook also covers dissimilar-metal welds, which are generally more difficult to examine than a
straight butt weld due to the buttering layer. The scope of the handbook includes fabrication and in-service
inspections.
ISO 22825 was recently revised and issued in May 2012 and specifies the approach for the development
of procedures for ultrasonic inspection of welds: stainless and austenitic steel - nickel-based alloys -
duplex - dissimilar metals. The objectives of the tests may differ, for example: assessing the level of quality
(manufacturing) or detection of specific indications produced during the service.
Through Optimum Use and Innovation of Welding and Joining Technologies
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