Termografia a korekta pomiarów pionowości kominów stalowych

Nasłonecznienie powoduje ugięcie trzonu komina i przemieszczenie jego wierzchołka względem położenia spoczynkowego. Opisane w literaturze próby określenia poprawek uwzględniających wpływ nasłonecznienia nie dały w pełni satysfakcjonujących rezultatów. Autorzy niniejszej pracy mierzyli wychylenia osi stalowego komina przez cały dzień. Na podstawie pomiaru termograficznego wyznaczyli temperaturę płaszcza i obliczyli spodziewane wychylenie wierzchołka spowodowane zróżnicowaniem temperatury. Obliczone wartości były zbliżone do wyników pomiaru geodezyjnego.

Industrial chimneys can be characterized as slim buildings with a vertical axis. The most important part of surveying during chimney construction is making sure that its axis is actually vertical. A chimney should be constructed in such a way that its axis is vertical in the resting position. Conditions like wind and insolation cause deflection of the chimney shaft and displacement of its top from the resting position. If the shape of the chimney axis is measured during a sunny day, the measured values have to be adjusted to take uneven temperature distribution within the chimney shaft into consideration. The change of the object’s size caused by a temperature change can be many times larger than the measurement precision. In the past, there were attempts to calculate the adjustments required to counterbalance the effect of insolation that relied on thermography [3, 4, 5], but they did not give fully satisfactory results. The authors of the present paper measured the deflection of the steel chimney axis (Fig. 1) once every hour for one day. At the same time, they captured thermographic images of the chimney shaft surface. They started the measurements before the sunrise, obtaining the deflection in resting position. During the day, the largest chimney top displacement from the resting position was 10 cm (Fig. 2). Using the thermographic images, the authors determined the chimney shaft temperature and calculated the expected chimney top displacement caused by the uneven temperature distribution (formula 1). The calculated values were close to the results of survey (Figs. 5 and 6). The largest difference was 10 mm what equaled to 33% of the permitted deflection for the measured chimney.