The objective of this paper is to describe the inspection process and examine a piping elbow found to have metal loss within the context of Asset Integrity Management (AIM). During the last five years, Industry 4.0 technology involving mobile tablet and cloud technology has merged with the proven concepts of AIM enterprise systems. Before this shift inspectors, engineers and managers relied on pen and paper and spent time waiting for the final reports to arrive. That approach created delays and was susceptible to errors due to the multiple processes and remote locations being inspected. These new technologies allows inspectors and mangers to think, react, and communicate quickly as opposed to waiting to organize a meeting between inspectors, engineers, and management when integrity threats are discovered.

The advancement of digitalization and automation has helped improve key metrics across inspection reporting, planning and execution of inspection and repair work, risk based inspection studies, and fitness for service assessments. As an overall result, a benefit has been a reduction in cycle time for decision making by managers and inspectors. Based on the best practices in API and ASME standards, AIM software has created a logical, repeatable, and automated workflow. Such software can be used both at the office on desktop computers and on mobile tablets in the field. The tablets allow faster exporting and importing of inspection reports, and help provide recommendations and results from the processing facility back to the office. In addition, data between AIM software can be configured to communicate with one another at the appropriate time and decision points when triggered by the user.

The AIM process initiates by assessing the operational and inherent risk of all assets according to an approved model. Inspection planning based on the level of risk is developed and scheduled. The inspector, using a mobile tablet and cloud connection can venture out, inspect, report and communicate back to the head office. Inspection findings such as visual (VT) and NDT results can be shared in real time and if deemed necessary, a Fitness-for-Service (FFS) assessment can be applied. In this case a pipe elbow is used as an example of inspection leading to an assessment calculation. When necessary, a repair scope of work can be developed and used with the mobile tablet to validate that the work in the field has been performed correctly.

A piping elbow was identified at a thickness monitoring location (TML) within a larger system due to existing internal corrosion and/or erosion. Since the metal loss is internal, an external visual examination was not sufficient to monitor the metal loss. External ultrasonic (UT) inspection was used to measure the thickness at multiple points on a grid pattern drawn on the elbow’s external surface.

The measured thickness grid, pressure and system supplemental loads, and material data provide the input needed for a local metal loss assessment per the API 579/ASME FFS standard. The local metal loss assessment methodology uses critical thickness profiles from the thickness grid in the circumferential and sweep/longitudinal directions to compute a remaining strength factor (RSF) and to compute the reduced maximum allowable working pressure (MAWPr). The computed RSF and MAWPr were found to be acceptable for the current amount of metal loss, but would not pass with an additional corrosion allowance for anticipated continuing future metal loss. A further decrease of thickness or a change of operating conditions could easily change the assessment result to not-passing. Knowledge of the metal loss rate is needed to determine when the next inspection would need to be scheduled.  The analysis results and inspection methodology help to provide specific data needed to make a decision about when and how to repair the elbow. 

With a heightened understanding of the asset’s degradation pattern, the risk to the asset is reassessed and the process repeats itself until the risk has been reduced to an acceptable level as defined by the stake holders.


Asset Integrity Management and Fitness-for-Service Assessment of a Pipe Elbow With Metal Loss

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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