Thursday, July 21, 2011

Ron Selva, Director, TCR PP SIMTECH is interviewed in the prestigious NG Oil Gas Journal


Best practice risk-based inspection implementation

Ron Selva Photo_CorCon 2011-India_File0009a

RBI guru Ron Selva, Director of TCR PP SIMTECH Solutions, reveals what is RBI best practice and how to implement it successfully.

Risk-based inspection implementation (RBI) is still a developing technology. What are the decisive factors to consider for best practice RBI implementation?

Ron Selva. RBI implementation is a highly critical process, as it effectively manages through the assigned responsibilities of plant inspection, operations and process engineers the asset integrity safely, reliably and at the most optimum costs throughout a plant’s lifecycle.

In order to deliver this, certain aspects must not be compromised, as these are the ‘bottom line’ for implementing RBI successfully. To begin with, RBI technology should be reliable, incorporating best practices, and be user-friendly for plant engineers. Secondly, the RBI team study needs to be thorough. There is no short cut to this task – the required study time must not be compromised. In addition to an RBI engineer and corrosion specialist, the study team must include inspection, operations and process engineers from plant. The study output needs to be reliable and comprehensive, and match plant site objectives. Finally, RBI software needs to comprehensively support the foregoing and be transparent and auditable.

For example, compromising the quality of the RBI study by not providing sufficient study time – to reduce project timescales and costs – adversely affects correct identification of active and potential damage mechanisms (DMs) applicable to an item. This has a detrimental effect on the confidence that can be placed on the RBI study output, particularly on the risk profiles of DMs and the related inspection interval. As such, the claimed outcomes in improvements in equipment reliability, safety and financial benefits are questionable, as is the management decision to buy into RBI output and implement it in the hope of achieving the claimed benefits.

Various RBI methodologies are available, including API-581. Each has merits and weaknesses. What is the current industry status on RBI technology? Is there a recommended assessment level?

RS. Companies that have implemented RBI report varying outcomes. Consequently, the UK Health and Safety Executive (HSE) issued additional guidance for RBI implementation to help minimise inconsistencies. The latest API-580:2009 provides guidance for key aspects to be considered for implementing RBI, using Level-1 (qualitative), Level-2 (semi-quantitative) or Level-3 (quantitative) methods. API-581:2008 provides a method of RBI implementation using a Level-3 quantitative approach.

In theory, the accuracy, the detailed nature of the assessment and confidence in the results are supposed to increase with the increased level of assessment. Unfortunately, this is not the case in this instance if API-581 methodology is used. Noting that RBI is still a developing technology, the latest API-581 quantitative method has uncertainty in some of the technology used and is not end-user-friendly due to its technical complexity. Critical uncertainties include validity of ‘generic failure frequency data’ in relation to DMs and equipment types; ‘probability of failure’ assessment method; and ‘consequence of failure’ assessment in relation to each DM and its ‘failure mode’. Additionally, not all DMs applicable to a single industry sector are properly covered in API-581 methodology.

As per API-580:2009, any of the three assessment levels is acceptable; but plant site must ensure that the RBI methodology provided by the service provider is defendable, user-friendly, detailed, documented, transparent and auditable with facility for future updates of the initial implementation. Particularly, the selected service provider must have the RBI methodology to reliably assess the ‘probability of failure’ and ‘risk profiles’ of each of the DMs applicable to an item and the implementation must be supported by a comprehensive team study method. Failure to satisfy these important aspects means the confidence in the inspection interval derived for each item is fundamentally questionable.

Wider industry experience shows that a Level-2 (semi-quantitative) RBI methodology, which satisfies criteria outlined above, plus API-580:2009 and UK HSE guide, supported by a comprehensive multi-discipline team study, proves to deliver the required output and confidence in meeting plant site goals.

Due to the fact that API is again considering revamping the API-581:2008 Quantitative RBI (Level-3 methodology), it is recommended to avoid its use until this technology is stabilised and fully approved by the wider RBI service providers and relevant industry sectors, whilst ensuring all the relevant DMs applicable, at least to the refining and petrochemical industries, are included in it. However, API-581 is useful for obtaining damage rate and other relevant information on certain DMs when using Level-2 (semi-quantitative) RBI methodology.


Ron Selva has over 35 years of industry-recognised experience relating to static equipment integrity, with the last 20 years spent specialising in the development and application of best practice RBI and fitness-for-service assessment technologies. He has published many papers on these subjects. He is also a member of several relevant British Standards Technical Committees.

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