HOIS successfully developed and issued a Recommended Practice (RP) to support the implementation of non-intrusive inspection of pressure vessels. The recommended practice provides a structured, auditable process to carry out an integrity review of degradation threats and inspection history prior to inspection, develop a statistically based inspection plan and carry out evaluation of inspection data. Initial work was carried out from around 2000 onwards, with the recommended practice becoming a HOIS branded document in 2020.
The Non-Intrusive Inspection Recommended Practice has now been in use for over 20 years. HOIS has previously run projects and trials to improve the confidence in the use of NII over internal visual inspection (IVI), including trials on high temperature vessels (HOIS-G-054), reviewing the suitability of NII for corrosion resistant clad vessels (HOIS(14)R5, HOIS-R-002, HOIS-R-014, HOIS-G-026) and comparing the effectiveness of NII against IVI (HOIS(15)R1). These projects have mainly focussed on the techniques used for NII and have been limited to a small selection of test samples and vessels. While very useful for confirming that NII can detect corrosion of concern as effectively as IVI, the trials did not examine the effectiveness of the NII plan (i.e. choice of inspection coverage and location).
HOIS members and some anonymous contributors provided over 60 case studies for examination. The focus of this project was to review how the HOIS-RP-103 has been used in practice, whether the NII process has been implemented effectively, identify any learning points to improve the practical application and to make recommendations for the next update of the Recommended Practice.
Case studies have been collated and examined. As the studies are selected by NII practitioners they largely demonstrate successful implementation of the current HOIS-RP-103 and earlier iterations. Nonetheless they provide a valuable insight into how the RP has been used, identifying sections to focus on when updating the RP and highlighting some collective learning points which are shared to aid successful implementation of the NII of pressure vessels.
The final report is expected to be issued Q3 2026.