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Non-Intrusive Inspection (NII) of offshore process vessels

ABB identifies process vessels suitable for NII and defines inspection plans using Risk Based Inspection (RBI) methodology.

The client operates offshore and onshore oil and gas processing facilities. ABB was engaged to assess the major process vessels across the assets for suitability for NII and to define appropriate inspection plans and inspection intervals using a RBI methodology. The assessments provide a thorough understanding of all the potential degradation mechanisms that could affect each vessel. This new understanding enabled appropriate risk mitigation strategies such as NII to be defined and justified.



“ABB took our complex situation of uncertain pressure vessel history and used a professional and structured approach to NII and RBI to put us in a much better place where future inspection requirements are now mapped out and risk is managed better.”


Integrity Engineer


The initial requirement was to define the scope of the detailed RBI and NII assessments. ABB undertook a screening study to identify the process vessels that, due to their design, operating conditions and consequences of failure, warranted thorough analysis in order to derive an inspection plan. The screening study confirmed that 261 process vessels across assets should be subject to the detailed RBI / NII assessments.

RBI+© methodology
The assessments were delivered using ABB’s RBI+© software tool ensuring an efficient and robust assessment process. ABB has over 20 years experience of carrying out RBI reviews and has applied the RBI+© methodology to over 100,000 equipment items. 
The methodology adopts a qualitative approach and requires a detailed understanding of equipment specific data such as current and historical operating conditions. The tool has been recently upgraded to enable the assessment and documentation for suitability of NII according to the guidelines in DNV-RP-G103.

Data gathering
Gathering of all relevant data was the first stage of the assessment process. This work was undertaken remotely and consisted of the provision and review of data (vessel design, operating conditions, corrosion management and inspection histories) and teleconferences with the client’s operations and integrity personnel. This ensured that ABB had a full understanding of the key current and historical issues. Teleconferences were held with corrosion engineers, inspection engineers, process engineers and offshore operations engineers. 

Deterioration mechanisms
Following the review of data gathered, ABB completed an analysis of the potential deterioration mechanisms for each vessel and assessed the risks associated with each mechanism. The consequence assessments were undertaken according the the client’s models for EHS and business consequences.

NII assessments
DNV-RP-G103 is recognised good practise for the implementation of NII strategies. ABB assessed each vessel for suitability for NII according to the guidance given in DNV-RP-G103. The output of these assessments concluded that 145 of the 261 vessels were suitable for NII.

Risk mitigation plans
ABB then defined suitable risk mitigation plans for all credible deterioration mechanisms identified for each vessel. In addition to inspection plans, the mitigation plans included upgrades to operational controls such as extending the chemical analysis routines including sampling for MIC. 

The fully drafted RBI and NII assessments were then reviewed by the combined client and ABB team. The review validated the assessments and confirmed the clients ownership of them. The validation reviews were carried out at the client’s offices and required 28 days to review the 261 assessments.

The output of these assessments concluded that 145 of the 261 vessels were suitable for NII. Since the RBI assessment process results in a thorough understanding of the risks associated with vessel failure, the assessment team is able to prioritise inspections based upon risk and determine appropriate inspection plans and intervals, actively reducing the risk profile for the platforms.

Main data

Customer:  Major oil and gas company
Site:  Global
Customer need:  To assess the major process vessels across the assets for suitability for NII
Scope:  The assessments provide a thorough understanding of all the potential degradation mechanisms that could affect each vessel
Application:  Oil and Gas
Customer benefits:
Increased availability
Reduced total cost of inspection
Turnaround complexity
Man entry into the vessel (a potentially hazardous activity) is avoided
Commissioning year: 2016