Pre-Service Inspection and In-Service Inspection 

PSIPre-Service Inspection is the application of NDT to plant once all the manufacture and construction activities have been completed but before the plant is actually commissioned. PSI is used to provide a final check that the plant is safe to operate. PSI also establishes an NDT fingerprint by using the same techniques that will be used during In-Service Inspection – ISI.

ISIIn-Service Inspection is performed during the operating life of the plant. ISI looks to detect any degradation occurring during the operation of the plant and to confirm that the plant is performing in accordance with the assumptions made in the design. If indications are observed in an ISI, the results can be compared to those of the PSI to confirm that changes have occurred.

Both PSI and ISI look for in-service defects which can have different characteristics to the defects which inspections performed during manufacture seek to detect.

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