Damaged cables, power sources and overloaded power supply can all lead to welding instability and
general frustration. In some cases unusual and completely unexpected problems arise from deficient
equipment. An extreme example is shown in Fig. 11, which shows a photomacrograph taken from a weld
repair which had been excavated by air-arc gouging. In this instance the air flow had not been sufficiently
powerful to eject the molten metal pool. The remaining highly carburised material had solidified as hard
cementite which contaminated the subsequent repair welding, producing a martensitic structure and severe
cracking problems.
Piecemeal correction of faults is inefficient, expensive and unpredictable. Planned maintenance systems
are essential to ensure that all plant is working to its declared efficiency at all times.