Called Risk-based Inspection (RBI), it enhances the traditional periodic approach to inspection planning and helps to achieve higher reliability and a longer operating time; minimising downtime and reducing risk. The new service is expected to be of interest to operators of floating units at a fixed location, such as FPSO and FLNG vessels.
“RBI techniques may be used to provide justification for the assignment of Class, and may be systematically applied to a hull structure and associated components or to individual systems, sub-systems or components,” says Tim Walsh, COO of Assurance Services for Lloyd’s Register.
RBI detects and monitors systems, subsystems, equipment and component degradation and results in the application of appropriate decision making criteria to manage risk to acceptable levels. To carry out a successful RBI program, certain tasks need to be performed including:
- - identification and definition of functional and physical relationships, interactions and dependencies of components
- - definition of the operating conditions and loading associated with each inspectable component
- - identification of the Common Cause Failure (CCF) of components
- - identification of the failure modes and degradation mechanism associated with individual components or group of components
- - identification of possible consequences due to failure of components.
“The most common deterioration mechanisms associated with hull structure components can range from coating failures, through to fatigue and stress built in to the structure during construction,” says Walsh. “RBI can help assess all of these issues and prioritise inspection needs.”
Walsh continues: “The key to understanding how classification, verification and integrity fit together is in understanding what differences there are between integrity management and classification schemes. We have investigated this in detail and have launched this new service because these two schemes can be integrated, and the overall result will optimise survey and inspection activities.”
The introduction of an RBI approach aligns the requirements for Class, verification and hull integrity management into a single survey and inspection programme.
“While the marine industry focuses on Class, the oil and gas industry applies asset integrity management and more often than not, a risk-based approach,” highlights Walsh. “To overcome this disparity in maintenance and management regimes there is a requirement of the Class societies to understand and appreciate what the FOI operators need and conversely the FOI operators need to understand what Class ‘does’. We are leading this approach for industry.”
Building to a higher standard
Industry feedback has highlighted that some operators chose to design and build to an enhanced standard in order to minimise operational costs and maximise asset life. For example, they can decide to use a better coatings specification and better structural details. However, under existing time based survey cycles, operators don’t receive credit from the Class society for these enhanced standards. Our new service enables the operator to develop a survey and inspection regime which is based on the current and expected future condition of the unit.
Rebecca Allison, Product Development Manager, Asset Integrity Services at Lloyd’s Register explains: “Class gives operators a common standard set to a maximum risk level however, risk is very much dependant on where the unit is located and not just build standards. When adopting an RBI approach, it must be taken into consideration that units located in different regions will perform in a very different way. Site specific assessments and environmental factors must be taken into account.”
From design through to asset life extension
Operators need to consider when to implement RBI - whether it’s at the design stage or part way through life – experts endorse the earlier the better. Implementing at the design stage means that the RBI programme is tailored to the asset. Risk-based design can help build a more robust structure, and at this stage the design can also be modified around the risk based inspection regime.
Allison says: “RBI and Class regimes can work in tandem to optimise inspection and maintenance regimes, reduce costs, minimise downtime, mitigate risk and shutdowns. However, adopting an RBI approach does require a mind-set change for both Class societies and operators. It is no longer about undertaking surveys at specific times. Rather, they are undertaken based on assessment of risk that each equipment and structural item poses.”
“The net is also being cast wider. RBI methodology isn’t limited to the oil and gas industry, the military and defence industry and cargo shipment sector have also shown interest in this new approach with the realisation of the operational efficiencies and cost savings that can be achieved.”
Source: Lloyd's Register