Ageing equipment or structure is that for which there is evidence or likelihood of significant deterioration and damage taking place since new, or for which there is insufficient information and knowledge available to know the extent to which this possibility exists. It is not necessarily characterised by physical age.
Life extension refers to continued operation of an installation beyond the design life assumed at the time of design or revised following a reassessment.
The ageing process is depicted simply and effectively by the ‘bathtub curve’. This shows the following characteristics:
A suitable asset integrity management programme should ensure that loss of integrity due to ageing does not occur during the design life of the component or structure.
Figure 2 illustrates possible variations of deterioration of integrity with time. The principal concern for ageing installations is the increased uncertainty associated with their performance in the later stages, characterised by the life extension phase.
Ageing processes can be considered as systematic changes that alter the risk profile of an installation. The integrity management of ageing installations and the successful implementation of an asset integrity management plan for life extension require consideration of:
and depend on:
Further information can be found on the publications webpage and in the KP4 Policy and KP4 Strategy documents.
Offshore installations on the UKCS by age
Bathtub curve
The KP4 Technical Policy