Cold Welds Hot Welds Failure was as the weld Poor fusion of the filler rod / wire to the tubes Weld bead radius is smaller than tube wall thickness Little to no heat discoloration The fitted / coped edges of the tube are visible after separation Failure was at the weld Weld / tube thickness was very small at point of failure Weld bead radius is distinctly larger than tube wall thickness Extreme heat discoloration 0 Examples of Failing Welds: Sample #1 (Destructive Testing)

1 Inconsistent and unclearly defined fusion line Weld bead radius is smaller than tube wall thickness Weld bead does not adequately contact and fuse the both tubes Examples of Failing Welds: Sample #2 (Destructive Inspection)

2 Examples of Passing Welds Sample #1 – Destructive Testing Sample #2 – Destructive Inspections Failure was not at the weld Weld bead radius is approximately the same as tube wall thickness Moderate Heat Discoloration Weld bead radius is approximately the same as tube wall thickness Clearly defined and substantially uniform width fusion line, no burn - through