Figure 5: Multiple isolated cavities or pitting (red arrow) were observed at the welding joints on the left-side (view from the combustion chamber), connecting the water tubes and the water drum.

Figure 5: Multiple isolated cavities or pitting (red arrow) were observed at the welding joints on the left-side (view from the combustion chamber), connecting the water tubes and the water drum.

Figure 5: Multiple isolated cavities or pitting (red arrow) were observed at the welding joints on the left-side (view from the combustion chamber), connecting the water tubes and the water drum.