Non-Intrusive Inspection – An Effective NII Process

Tyron Kimble, Sonomatic 

Internal Visual Inspection (IVI) has historically been used as the main method for determination of the condition of pressure equipment as part of the integrity management process. IVI can however be a hazardous, time consuming and costly exercise. Non- Intrusive Inspection (NII) is increasingly being considered as an alternative to the traditional IVI approach. The benefits of NII in comparison to IVI are significant and include the following.
– Reduced production losses associated with shut-down.
– Reduced manpower requirements – this can lead to reduced shut-down cost and
– Shorter overall shut-down times since greater capacity is available for other tasks.
– Removal of hazards associated with man entry of vessels.
– Removal of the need to clean vessels internally.

It is widely recognised that NII is different in many respects to IVI hence a different approach to planning is needed. For example, while IVI has the capability to detect a range of different defect types without specific knowledge of what to expect, the capability of NII is very much technique driven. Hence an up-front knowledge of what degradation may be present takes on added significance when planning an inspection by NII. This also means that successful NII is very much dependent on knowledge of the capabilities and limitations of available inspection techniques so that the most appropriate is selected. Definition of the inspection requirements is also linked closely to what defects are of concern and what represents a threat to integrity. In order to ensure effective NII, a multidisciplinary approach is required that combines skills and knowledge in corrosion engineering, inspection technology and mechanical integrity.


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