Improving Global Quality of Life
Improving Global Quality of Life
Improving Global Quality of Life
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5 Needs and challenges in welding and joining technologies<br />
5.3 Advanced technologies for maintenance, repair and life extension<br />
As mentioned in the previous section, the revolutionary developments in microelectronics and computer<br />
science are the reasons for advanced NDT technologies becoming available during the last decade. NDT has<br />
been developed for maintenance, for better quality inspection after repair and for more reliable lifetime<br />
prediction. The main areas <strong>of</strong> progress in NDT techniques applied in practice and reflecting the work in the<br />
sub-commissions <strong>of</strong> IIW Commission V “NDT and <strong>Quality</strong> Assurance” are covered below.<br />
5.3.1 NDT <strong>of</strong> welds by use <strong>of</strong> radiography, technical radiology & computer tomography<br />
As long as radiography means irradiating a component by X-rays or Gamma rays and sensing the information<br />
on a film, developing the film and analysing the developed film by human eye, the technique will suffer high<br />
errors due to human factor influences. Some quality standards for instance in nuclear technologies, have<br />
asked for film storage to have long-term documentation. Following the example <strong>of</strong> medical doctors who<br />
have changed their standards, adopting the digitisation <strong>of</strong> the film material has tremendously enhanced<br />
the technology. By applying automatic online working pattern recognition s<strong>of</strong>tware, considerable success in<br />
detecting imperfections can be achieved using the best trained NDT inspector as a benchmark.<br />
After online digital radiology gained popularity, the more pixelised solid state flat panel devices became<br />
available. Here also, by the use <strong>of</strong> pattern recognition s<strong>of</strong>tware, reliability comparable to the best film<br />
application can be achieved. The highest achievable capability for inspection is obtained by use <strong>of</strong> computing<br />
tomography because <strong>of</strong> the multi-angle information taking into account imperfections that can lay with an<br />
individual angle to the direction <strong>of</strong> the incoming energy. Here the synergic combination <strong>of</strong> digital detectors,<br />
optimised reconstruction algorithms test and high-speed computing power is responsible for the progress.<br />
A first inspection qualification according to the European Network for Inspection and Qualification (ENIQ)<br />
recommendations in Europe for multi-angle radioscopic inspection <strong>of</strong> primary circuit pipe welds in Nuclear<br />
Power Plants in Germany was successfully performed.<br />
5.3.2 NDT <strong>of</strong> welds by use <strong>of</strong> ultrasound<br />
5.3.2.1 Advanced UT techniques<br />
In ultrasonic testing (UT) with the development <strong>of</strong> the so called array transducer the most intelligent and<br />
flexible inspection probe was introduced into practice. The piezoelectric sensor membrane is divided into<br />
multiple single source elements which individually are controlled in the amplitude and phase <strong>of</strong> the electric<br />
pulses used for transmitting and receiving ultrasound. As micro-electronics becomes more miniaturised and<br />
computing power becomes cheaper, systems are now available at reasonable prices. The advantage <strong>of</strong> the<br />
transducer is the quick multi-angle-beam inspection which can detect individually oriented flaws.<br />
Industrial phased arrays have been in development for decades, following medical phased arrays and other<br />
areas like radar, sonar and geophysics. In the past, a small market, considerable flexibility demands, data<br />
handling, s<strong>of</strong>tware, and extensive training and experience requirements have hampered the wide use <strong>of</strong><br />
phased arrays for industrial applications. The first industrial commercial phased array systems appeared in<br />
the early 1990s, but were large, expensive, and required good s<strong>of</strong>tware skills. Most <strong>of</strong> these units were used<br />
in the nuclear industry on specific advanced applications.<br />
Currently, the phased array industry is maturing rapidly and phased arrays are becoming pervasive in<br />
inspection markets worldwide. This is true both for industrial field applications as well as for more academic<br />
applications in universities and research institutes. From a technical perspective, this is being driven by the<br />
flexibility that they bring to an inspection task, with their ability to generate a wide range <strong>of</strong> ultrasonic beam<br />
characteristics with one phased array unit.<br />
Through Optimum Use and Innovation <strong>of</strong> Welding and Joining Technologies<br />
<strong>Improving</strong> <strong>Global</strong> <strong>Quality</strong> <strong>of</strong> <strong>Life</strong><br />
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