PSI - Issue 17

C. Medrea et al. / Procedia Structural Integrity 17 (2019) 526–531 C. Medrea, E. Pappa, D.G. Papageorgiou, C. Stergiou / Structural Integrity Procedia 00 (2019) 000 – 000

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For visual inspection of the inner area, the piece was fragmented in three parts. Vertical cracks (marked with red arrows) were detected on the cross section of the bottom, between the first and second part (Fig. 4). Some marks observed on fig 4b, most probably have been caused during cutting (marked with yellow arrows).

Fig. 4. (a) Images showing the first fragment, (b) Vertical cracks detected on the cross section of the pipe bottom.

Numerous welding defects were detected. Lack of welding material was detected between the pipeline and the tees high temperature inlet side (arrows on Fig. 5a). Furthermore, a specific area exhibits wear. Lack of welding material (point I on Fig. 5b) and lack of base metal (point II on Fig. 5b), spatters and material’s detachment on heat affected zone (point III on Fig. 5b), can be observed on the internal side of tee’s outlet area. In the opposite side of the welding line, signs of extended wear on the bottom edge of the part are noticed (arrows on Fig. 5c). Additionally, on the internal side of the tube possible signs of thermal fatigue are present (Fig. 5d).

Fig. 5. Welding defect on first fragment; (a) Lack of welding material, (b) Lack of welding and base metal material, m aterial’s detachment , (c) Fatigue cracks on the internal side.

A network of cracks originated on the inlet side of high temperature steam line (arrow on Fig. 6a) and propagated on the mixing area (Fig. 6b). In some regions, material was detached due to the expansion of the cracks (Fig. 6c).

Fig. 6. (a) The internal area of the second fragment, (b) Network of cracks on the internal area of second fragment , (c) Material detachment.

Welding material is missing of the tee joint of outlet area on both sides of lower and higher temperature lines (Fig. 7a, e). Many cracks originate from different points that can be observed on the same area (Fig. 7 b,c,d).