PSI - Issue 59

S.E. Donets et al. / Procedia Structural Integrity 59 (2024) 367–371 S.E. Donets et. alAuthor name / Structural Integrity Procedia 00 (2019) 000 – 000

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to prevent possible failures while keeping the systems running for as long as possible tolerating the risk. Monitoring and maintenance of pipeline networks and related facilities is rather a complex set of activities because operational stability and safety is of great importance, Latif (2022), Bazaleev (2023). The modern effective maintenance strategies are focused on optimization of inspections to detect possible failure points. One of the most popular NDT tools to assist with these tasks is thermal imaging, Prohorenko (2018). The objective of this research is to find the correlation between presence of pollution or defects on the pipe walls and fractal dimension mapping of thermal images of the pipe under heating and cooling. The experimental setup emulates real-world conditions when the operator can introduce warm water in the system and then force it cooling with introduction of cold water. Thermographic imaging captures surface temperature patterns along the pipe, facilitating identification and quantification of thermal anomalies. Fractal dimension analysis can be used to analyze the thermographic data, as it is a tool sensitive to temperature distribution complexity and irregularity, providing The piece of a steel water pipe was taken from an actual decommissioned water supply network from the apartment block in Kharkiv. It was operational for 9 years. Its diameter was 1½ ״ , thickness ~ 4 mm. This pipe was cold-formed from unknown low-alloyed steel from unknown producer . For our research, we‟ve selected a solid pipe, not welded. During exploitation under nominal conditions (cold water supply), it partially corroded internally, also there were layers of calcinated sediment and rust, and other typical pollutants of technical water systems as in Jachimowski (2017) and Shulyak (2021). Its external surface was protected with a paint coat all the time during operation, however, before the experiments, its surface was cleaned off the paint with a hard polish (Fig. 1a). No significant signs of corrosion or major defects were noticed on the external surface. The experimental stand was created. It consisted of an electric water heater and a piece of the pipe under study. The schema and the heating profile over the experiment duration were presented on Fig. 1. The pipe was extended with metal inlets via electric welding. The inlets themselves were connected to the water heater (220 V, 5 kW) using ½” diameter flexible pipes. The stand system was a not a closed system, but used a fresh cold-water supply of around 16 °C . At the beginning of the experiment, cold water flew in the pipe. Thermography camera started to take images of the setup Fig. 2, and the heater was turned on. Then, after a short heating, the heater was switched off. The water flow rate was around 0.14 liter/s. Only one single heating-cooling was applied. The thermal imaging measurements were performed using the Fluke Ti32 thermographic camera with a temperature sensitivity of 0.05 K and a matrix size of 240x320 pixels. The initial processing of thermograms was done using the Fluke SmartView software application. „macroscopic‟ insights. 2. Materials & Methods

Fig. 1. Left – Photo of pipe used for testing. Right – schema of the experimental stand with the target sample (pipe) mounted, with the average temperature of pipe surface – heating profile on top.