BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI - Universitatea ...

180 Mihai Florin Mănescu and Valeriu Panaitescu
2. Damage Detection Technologies
2.1. Non-destructive Technologies for Monitoring
2.1.1. Thermal scanning technology. This technology is used to detect
anomalies, based on the differences in the temperature of the inspected areas,
such as the blades of the wind turbine, with the help of infrared sensors or heat
detecting cameras [6]. The differences in temperature are correlated with the
diffusion of heat and, as a result, they indicate abnormalities or damage.
Specialized equipment, called thermovision or thermographic camera and
similar in size and appearance to the very familiar video camera of everyday
life, is used to obtain thermal images. In this way, objects are viewed in terms
of the infrared radiation (IR) emitted by them and not in that of the visible
radiation, which can be effortlessly detected with the naked eye.
The thermographic method is extremely useful in practice because it
permits the achievement of the so-called "predictive maintenance", a term
which is applicable to all industries. The first sign of a defect or an operating
problem is often given by the increased heat in that particular area, therefore an
increase in the emission of infrared radiation. In other cases, the unjustified
lower temperatures of some areas or of some parts of the device may be a sign
of negative phenomena occurring at their level. After having been generated,
the termograma is digitally processed in order to locate the points where heat
stress is present and the defects. It should also be noted that the assessment of
the termograme obtained by scanning the device, system or facility during
proper functioning, can provide extremely valuable information on the normal
thermal map, which will serve as reference for future evaluation and will also
help with the remediation of any potential failure.
Fig. 1 – Image of wind turbine produced by thermography.
Additionally, the thermographic method is a non-invasive technique for
measuring the infrared radiation emitted by the object under examination and
generates, after a very short thermal analysis performed in real time, a thermal
paper which may be sometimes of vital importance to the wind turbines. This
method enables the precise measurement of surface temperature; the high
resolution is a valuable advantage in detecting differences in the temperature of