Joining technologies often play a vital role in the repair and maintenance of structures. Parts can be replaced, worn or corroded parts can be built up, and cracks can be repaired.
When a repair is required it is important to determine two things: firstly, the reason for failure and, secondly, can the component actually be repaired? The latter point infers that the material type is known. For metals, particularly those to be welded, the chemical composition is vitally important. Failure modes often indicate the approach required to make a sound repair. When the cause-effect analysis, however simple, is not followed through it is often the case that the repair is unsafe - sometimes disastrously so.
In many instances, the Standard or Code used to design the structure will define the type of repair that can be carried out and will also give guidance on the methods to be followed. Standards imply that when designing or manufacturing a new product it is important to consider a maintenance regime and repair procedures. Repairs may be required during manufacture and this situation should also be considered.
Normally, there is more than one way of making a repair. For example, cracks in cast iron might be held together or repaired by: pinning, bolting, riveting, welding, or brazing. The method chosen will depend on factors such as the reason for the failure, the material composition and cleanliness, the environment and the size and shape of the component.
Repair and maintenance is also important in relation to the joining processes themselves. For example, the jigs and fixtures used for welding automotive components may suffer cyclic loading that exceeds that which will be seen by the parts being joined. They should, therefore, be carefully maintained during operation and properly repaired when necessary. Furthermore, poorly maintained welding equipment cannot be expected to hold components in tolerance.
It is very important that repair and maintenance welding are not regarded as activities which are simple or straightforward. In many instances a repair may seem undemanding but the consequences of getting it wrong can be catastrophic failure with disastrous consequences.