Detection of the thickness of scale on the inner surface of water pipes by infrared thermography
The infrared thermography technique developed in the present study was successfully applied to determine the scale thicknesses of the steel pipe. We aim to estimate the thickness of the scale on the inner surfaces by calculation of the maximum temperature of the infected pipe heated surface. Dimensions of the pipe and those of the layer of scale are taken as geometrical parameter. We have studied the effect of each one on the thermal response of the considered structure. These information are important for determining dangerous state of water distribution network.
The numerical modeling and the infrared thermography principle applied to the analysis of corrosion defects in oil Conduits
Currently the corrosion phenomenon becames a serious concern to several industries of metals and particularly of steel like nuclear, chemical and petrol industries. Such defects can occur severe economic and social damage, that’s why it’s so important to detect them as soon as possible to avoid those lost. The purpose of the study is to show by calculating of surface temperature the effect of corrosion defect which can exist in these conduits. To undertake the study we modelled conduit (tube) by a steel cylinder and the defect by a circular layer of rust. Dimensions of the cylinder and those of the layer of rust are taken as parameters. To see the effect of each geometrical parameter on the thermal state of the considered structure we studied the thermal state of the structure by taking this parameter like variable and all the others as constant. In fact, when a material is thermically requested (artificial excitation in the case of Laboratory measurements or natural excitation in the case of in-situ measurements), the heat diffuse in uniform way in material. The presence of a defect within the material (e.g. a crack or a rusted layer) acts like a heat insulator and idle this diffusion. It follows from there the appearance of a hotter region on the surface compared to the close one without anomaly. The study is undertaken on a cylindrical structure, as on the figure below, of geometrical parameters: external diameter d=254mm. The cylinder thickness ep =19mm, the length of tube l =1m. In order to detect the rust thermal effect on the thermal state of the steel pipe, many situations are considered. The study concerns the effect of rust thickness, rust depth and finally the number of rust layers in pipe on the surface temperature at the structure.
Application of laser-generated guided wave for evaluation of corrosion in carbon steel pipe
Local wall thinning of pipes, resulting from corrosion, is the major cause of accidents in nuclear power plants. In order to assure the integrity of pipes, a variety of NDE techniques have been proposed. It is well recognized that the utilization of guided waves to detect flaws in pipes has been a very effective tool for long-range inspection in NDE. Since most conventional research on guided waves has focused on long-range inspection, it is difficult to evaluate a defect in a local area. An objective of this study is to develop a non-contact inspection technique for the quantitative evaluation of defects on a local area in a cylindrical tube. Therefore, the purpose of this study is to introduce an advanced inspection system and a new signal processing method for the evaluation of defects such as corrosion in a pipe. In this study, an advanced non-contact method for pipe inspection is proposed, which generates the ultrasonic guided wave by laser and receives it by a dual air-coupled transducer. Information on each directional defect location and length is obtained by using a line scan along a circumferential and longitudinal direction. Received signals are analyzed by using the peak-to-peak amplitude of waveform and the maximum center frequency magnitude of the frequency spectrum. The optimal mode selection of guided waves based on a dispersion curve is also discussed. The experimental results using the proposed method show that the location and the size of the defect could be evaluated successfully in the 2-dimensional scanning images.