Risk-based Inspection Methodology Research Articles

Development of Risk-Based Methodologies for Highway Pavement Construction Inspection

Construction inspection plays a critical role in Portland cement concrete pavement (PCCP) and hot mix asphalt (HMA) pavement projects. To ensure the quality of pavement projects, state departments of transportation (DOTs) in the U.S. typically conduct construction material tests and inspect workmanship processes using quality assurance (QA) programs. Given today’s reality of reduced QA inspection resources such as funding, staff ability, and availability, several state DOTs have used a risk-based inspection (RBI) approach to optimize their QA processes. A thorough review of existing literature revealed limited studies examining RBI methodologies in highway pavement construction projects. The aim of this study is to investigate the use of RBI for pavement construction projects. It employed a triangulation research methodology, including an extensive literature review, a survey questionnaire of 50 state DOTs, focus groups, and a vetting workshop. A list of 16 core items in field inspection for both PCCP and HMA pavement projects was developed and verified. A generic risk rating of these critical inspection activities was determined. Additionally, inspection frequency, documentation effort, and inspector experience associated with these critical inspection activities identified through focus groups and the vetting workshop served as a reference point when conducting RBI for PCCP and HMA pavement projects. This study contributes to the body of knowledge and the highway construction industry by identifying and prioritizing 16 core inspection items for PCCP and HMA pavement construction. Construction project managers and inspectors may benefit from this study by analyzing the risks of core inspection items and implementing appropriate risk mitigation plans.

Quantitative research on stress failure risk assessment for girth welds with unequal wall thickness of the X80 pipeline under lateral load

The cumulative length of the X80 steel pipeline extends to 17,000 km, with a predominant portion traversing mountainous terrains characterized by intricate geological formations. Recurrent geological hazards significantly impede the safe operation of oil and gas pipelines. Landslides can induce substantial axial forces on steel pipelines, significantly increasing the risk of pipeline failure. Moreover, as a result of sudden changes in mechanical structure, the pipeline's unequal wall thickness leads to local stress concentration, making it more vulnerable to external loads than the steel pipeline itself. Therefore, to analyze the mechanical response of steel pipelines under different working conditions, we establish a smooth particle hydrodynamics, finite element transverse landslide pipeline model for girth welds with unequal wall thickness and investigate a tearing accident caused by a lateral landslide in a section of the large-diameter natural gas pipeline. The landslide volume is found to be the main controlling factor for the failure of pipeline circumferential welds. According to the genetic algorithm backpropagation neural network, the von Mises stress of the most dangerous section of the pipeline is calculated based on pipeline and landslide parameters, and the error is 11.67 %. According to the API RP 581–2016 Risk-Based Inspection Methodology, a failure risk assessment matrix is established using the pipeline statute as an evaluation indicator to evaluate the landslide risk to pipelines in different regions. A variable-wall-thickness girth weld on the ZG pipeline was selected for application. This method has good applicability for evaluating the failure risk of circumferential welds with wall thicknesses of 12.8/15.3 mm under the action of small landslides.

Probabilistic inspection planning for fatigue cracks in floating production, storage, and offloading units

Probabilistic inspection planning for fatigue cracks in floating production, storage, and offloading units

Materials for Hydrogen Storage and Transport: Implications for Risk-Based Inspection

The growing interest towards hydrogen technologies and their implementation in the hydrocarbon and chemical process industry makes maintenance planning of storage and transport equipment an emerging safety aspect. With respect to high-pressure working equipment, Risk-Based Inspection methodology (RBI) aims at minimizing the risk of loss of containment due to materials’ deterioration mechanisms. This set of procedures focuses on the mechanical integrity of equipment to achieve crucial risk mitigation by means of risk-informed inspection planning and maintenance activities. In addition, hydrogen-induced damages are often generalized or even neglected by the existing RBI standards and recommended practices. On this basis, high-pressure vessels, process piping and storage tanks working in gaseous or liquid hydrogen environments, which are exposed to hydrogen-induced deterioration mechanisms, might be subjected to an inaccurate evaluation of the associated risk and hazards when these RBI standards are applied. For this reason, this work proposes a review of the pipelines steels commonly used for gaseous hydrogen transport to investigate the possible limitations of the standard RBI planning methodologies, when applied to hydrogen technologies. More accurately, the pipeline steels’ susceptibility to hydrogen-induced degradations mechanisms will be discussed to underline assumptions and hypothesis limiting the conventional RBI applicability. Therefore, the overall suitability of standard RBI planning with respect to hydrogen equipment is discussed, highlighting possible relevant gaps as a general result.

Risk-Based Selection of Inspection Method for External Post-Tensioning System of Bridges

The increasing complexity associated with the maintenance of bridges with post-tensioning tendons, along with growing public awareness to ensure higher levels of safety in bridges, has put additional pressure on the designers and the owners to find innovative solutions to ensure safe as well as economically viable solutions. Risk-based inspection and maintenance helps in finding such solutions and, thus, it is gaining more importance in the field of infrastructure management. Within the framework of current risk-based inspection methodologies, it is normally assumed that the method by which the inspection is performed is known beforehand. However, the selection of the inspection method by itself should be given importance and viewed as the first key step for any inspection. The lack of quantitative data in the initiation step makes this selection uncertain and the decision making rather subjective. Despite recent release of comprehensive reports and other publications on condition assessment of bridges with post-tensioning systems, a quantitative approach and a decision-making framework for the selection of the inspection method and associated protocol are still missing, and the inspection strategy and methods are determined purely by the experience of the inspector or the owner. In this paper, a simple and structured risk-based selection methodology is presented that can bridge the existing knowledge gap. The proposed methodology uses a statistical approach to quantify the likelihood of the inspection error utilizing a variety of applicable NDE (Non-destructive Evaluation) methods. To give the methodology both accuracy and practicality, the specifications for the national bridge inventory (SNBI) condition rating was incorporated in this methodology and the accuracy of the inspection methods are measured against determining the correct SNBI condition. Application and effectiveness of the proposed methodology are demonstrated using a case study inspection conducted earlier by the authors. The results, in this case, converged to the selection of one of the NDE methods, which consequently was accepted by the bridge stakeholders.

Quantitative risk-based inspection approach for high-energy piping using a probability distribution function and modification factor

Risk-based inspection (RBI) offers the most cost-effective operation and maintenance strategy for minimizing overall risks and making financial and safety improvements within a power plant. Risk assessment may also benefit decision-making with regards to plant design and equipment manufacturing processes. The purpose of this study is to propose a quantitative RBI methodology that can be applied to a high-energy piping system operating at elevated temperatures and high pressures in power plants. Three major steps involved are: (i) using generic mean time to failure (MTTF), specified as the expected lifetime of the equipment obtained from a theoretical equation; (ii) adding a modification factor that identifies the specific conditions that can influence the failure rate; and (iii) incorporating individual inspection locations as a factor in risk evaluation.Probability-of-failure (POF) assessment was conducted using a Weibull distribution with MTTF and the modification factor. In addition, consequence-of-failure (COF) assessment was conducted based on financial consequences in terms of downtime costs per day and the length of downtime due to failure. The main steam piping system in a thermal power plant was selected as the case study unit. The actual inspection locations where damage to components could frequently occur were defined as risk evaluation targets for the RBI. The generic MTTF for the main steam piping system was evaluated using the Larson-Miller parameter (LMP) equation for creep rupture time. Piping system stress analysis was conducted to obtain the stress applied to the LMP. An equation for the modification factor applied to the main steam piping system was also proposed based on five subfactors.

Corrosion loop development of oil and gas piping system based on machine learning and group technology method

Purpose Corrosion loop development is an integral part of the risk-based inspection (RBI) methodology. The corrosion loop approach allows a group of piping to be analyzed simultaneously, thus reducing non-value adding activities by eliminating repetitive degradation mechanism assessment for piping with similar operational and design characteristics. However, the development of the corrosion loop requires rigorous process that involves a considerable amount of engineering man-hours. Moreover, corrosion loop development process is a type of knowledge-intensive work that involves engineering judgement and intuition, causing the output to have high variability. The purpose of this paper is to reduce the amount of time and output variability of corrosion loop development process by utilizing machine learning and group technology method. Design/methodology/approach To achieve the research objectives, k-means clustering and non-hierarchical classification model are utilized to construct an algorithm that allows automation and a more effective and efficient corrosion loop development process. A case study is provided to demonstrate the functionality and performance of the corrosion loop development algorithm on an actual piping data set. Findings The results show that corrosion loops generated by the algorithm have lower variability and higher coherence than corrosion loops produced by manual work. Additionally, the utilization of the algorithm simplifies the corrosion loop development workflow, which potentially reduces the amount of time required to complete the development. The application of corrosion loop development algorithm is expected to generate a “leaner” overall RBI assessment process. Research limitations/implications Although the algorithm allows a part of corrosion loop development workflow to be automated, it is still deemed as necessary to allow the incorporation of the engineer’s expertise, experience and intuition into the algorithm outputs in order to capture tacit knowledge and refine insights generated by the algorithm intelligence. Practical implications This study shows that the advancement of Big Data analytics and artificial intelligence can promote the substitution of machines for human labors to conduct highly complex tasks requiring high qualifications and cognitive skills, including inspection and maintenance management area. Originality/value This paper discusses the novel way of developing a corrosion loop. The development of corrosion loop is an integral part of the RBI methodology, but it has less attention among scholars in inspection and maintenance-related subjects.

Remote inspection by the magnetic tomography method (MTM) to prevent the risks imposed by exploitation of Arctic offshore pipelines

Cold climate areas that provide opportunities for the remote inspection of pipelines include the Barents Sea, the Russian Arctic, the Alaskan Chukchi Sea, the Beaufort Sea and the Canadian Arctic offshore. First, an analysis of several actual projects of contactless diagnostics using the magnetic tomography method of pipelines in Arctic conditions is done. Second, the Risk-Based Inspection methodology for Arctic offshore pipelines is discussed. It involves ensuring pipeline reliability on the basis of data on the technical condition of the metal in actual operating conditions. The magnetic tomography method allows not only to remotely identify areas of anomalies with metal defects, but also to register mechanical stress levels taking into account actual loads. This reduces the risk for the structure to come to the critical state in terms of exceeding local loads. Finally, magnetic tomography technology allows managing risks in cases of local corrosion, stress cracking or loss of stability of underwater pipelines in areas with free spanning. The qualitative indicators of the inspection include the probabilities of identifying, interpreting the degree of danger, missing a dangerous defect. The pipeline diagnostics report provides the parameters of reliability forecasting: the period of incident-free operation, safe working pressure, and pressure coefficient.

Dynamic risk-based inspection methodology

Inspection methodologies have evolved in the past decades to explore optimal interval and inspection methods. The American Petroleum Institute has published several standards such as API-510, API 653, API 570 and API-580 to assist in determining inspection intervals based on equipment life, consequences of failure, degradation rate, and environmental impact. The most recent approach is the Risk Based Inspection, API-580 and API-581. The underlying assumption of this approach is that risk remains acceptable between two planned inspection or maintenance intervals. This condition may not hold true in a complex, fast-changing or degrading engineering system. This study presents an innovative method to assess risk for a dynamically changing system based on the system parameters that are continuously monitored. The calculated dynamic risk can be used to plan optimal inspection and maintenance intervals more efficiently. The proposed method is tested on several possible combinations of an engineering system. Efforts are also made to align and integrate the proposed method with API-581. This would help to implement a more accurate approach while maintaining the required industry standard to ensure safe operation with low uncertainty.

A new risk-based inspection methodology for offshore floating structures

ABSTRACTThe Risk-Based Inspection (RBI) programme is a part of the overall Asset Integrity Management (AIM). The RBI programme offers benefits such as providing a rational basis for inspection plans and efficient tools for updating those plans. The ultimate goal of the RBI programme, coupled with a more generic approach to asset integrity management, is to verify the integrity of the facility and its fitness for service. The present study attempts to address a step by step approach which can be followed for RBI planning inspection. Guidelines regarding the various steps of the RBI process are also provided in order to assist in preparing and maintaining the RBI programme. An advanced tool for semi-quantitative risk assessment of offshore floating structures is developed, where the user guide is presented.

Application of Risk-Based Inspection method for gas compressor station

According to the complex process and lots of equipment, there are risks in gas compressor station. At present, research on integrity management of gas compressor station is insufficient. In this paper, the basic principle of Risk Based Inspection (RBI) and the RBI methodology are studied; the process of RBI in the gas compressor station is developed. The corrosion loop and logistics loop of the gas compressor station are determined through the study of corrosion mechanism and process of the gas compressor station. The probability of failure is calculated by using the modified coefficient, and the consequence of failure is calculated by the quantitative method. In particular, we addressed the application of a RBI methodology in a gas compressor station. The risk ranking is helpful to find the best preventive plan for inspection in the case study.

Enhancing offshore process safety by selecting fatigue critical piping locations for inspection using Fuzzy-AHP based approach

Topside piping is the single largest source of the hydrocarbon releases (HCRs) on the offshore oil and gas (OOG) platforms in the North Sea region. Consequently, if the leaked hydrocarbons from the process pipework are ignited, it may lead to a catastrophic event, thereby causing significant economic losses, environmental damage, and posing serious threat to the safety of the onboard personnel. In order to avert such a fateful event and to enhance process safety, it is vital to maintain the technical integrity of the topside piping. In regard to this, risk based inspection (RBI) plays a vital role, as the inspection locations and frequency are decided based on the risk of potential failure. However, international standards such as API 570, API 581 and DNV RP-G101 provide limited guidance in regard to inspection of the fatigue degradation of the offshore topside piping. Due to the aforementioned, selection of the fatigue critical piping locations for inspection, is currently done either on the ad-hoc basis or using the three staged Risk Assessment Process (RAP) mentioned in the Energy Institute (EI) guidelines. Nevertheless, it has been revealed that the methodology for stage 1 of the RAP is laborious and time consuming. Thus, to reduce the toil of the practicing inspection engineer and with the aim of mitigating the dearth of RBI methodologies for topside piping fatigue, this manuscript proposes a Fuzzy-Analytical Hierarchy Process (FAHP) centered approach for selecting the fatigue critical piping locations for inspection and repair. The usability of the proposed approach is demonstrated by an illustrative case study.

Information structuring and risk-based inspection for the marine oil pipelines

The proposed work is incorporated into the research theme concerning the maintenance and inspection of sensitive facilities in production systems. It is essential to promote the methodological deployment of inspection techniques to ensure the good functioning of services provided by complex production systems as well as their different components. We use a risk-based inspection methodology offering an organized analysis with knowledge sharing for collaborative possibilities in a multidisciplinary context and it consists of the following steps: data acquisition and information collection, failure analysis (probability and consequences), risk assessment, inspection plan, mitigation and revaluation. The application of this methodology can improve the maintenance management strategies of industrial companies. The inspection department is able to forecast its potential failure, root causes and impacts on the safe operation of the considered production system, based on a reliable inventory of existing situations and review options for continuous improvement in maintenance management. In particular, we addressed the application of a Risk-Based Inspection (RBI) methodology in the French petroleum company with operations on the west coast of central and southern Africa. The incorporation of expert knowledge into risk assessment is helping to find the best preventive plan for pipeline inspection in the case study.

Benchmarking PRAISE-CANDU 1.0 With Nuclear Risk Based Inspection Methodology Project Fatigue Cases

A probabilistic fracture mechanics (PFM) code, PRAISE-CANDU 1.0, has been developed under a software quality assurance (QA) program in full compliance with Canadian Standards Association (CSA) N286.7-99, and was initially released in June 2012 and officially approved for use in August 2013. Extensive verification and validation has been performed on PRAISE-CANDU 1.0 for the purpose of software QA. This paper presents the fatigue benchmarking against NURBIM (nuclear risk based inspection methodology for passive components) fatigue cases between PRAISE-CANDU 1.0 and six other PFM codes. This benchmarking is considered to be an important element of the validation of PRAISE-CANDU. Excellent agreement is observed in spite of the differences between the codes. The comparison of the predicted leak probability at the 40th year shows that PRAISE-CANDU not only captures the same trend but also bounds (higher predicted failure probability) the majority of the NURBIM results. In addition to the leak probability, the rupture probability, and uncertainty analysis, which were not reported in the NURBIM Project, are also calculated with PRAISE-CANDU and presented.

Application of Risk-Based Inspection in Olefins Conversion Plant

Inspection strategy is an important activity in processing plants, and one of the key tools used for such strategy is the risk-based inspection (RBI) methodology. Risk-based inspection is a methodology for optimization of inspection strategy. Based on principle of the risk-based inspection methodology in API 581, the risk assessment for vessels and pipelines in olefins conversion plant is carried out. The main failure modes and damage mechanisms of vessels and pipelines are identified. All vessels and pipelines in this plant are prioritized based on the level of risk. Risk reduction measures and optimal inspection strategy are proposed. This application of risk-based inspection will provide reference for the inspection of the olefins conversion plant.

Comparison of API 510 pressure vessels inspection planning with API 581 risk-based inspection planning approaches

To ensure mechanical integrity, all pressure vessels shall be inspected at the intervals provided in inspection codes or based on a risk-based inspection (RBI) assessment. The RBI assessment may allow previously established inspection intervals to be extended.This paper describes the methodology, analysis and results of two RBI studies conducted on 293 pressure vessel components in two crude oil distillation units. Based on API RBI methodology in API 581 (2008), risk target concept was used for determining inspection dates. It was shown that when thinning is the major active damage, the RBI recommended intervals are as long as twice the API 510 intervals. This paper summarizes that, as a fundamental step in the risk calculation, RBI has a more defined methodology for evaluating equipment for multiple damage mechanisms and a more defined approach to specify the use of other inspection technologies beyond the traditional visual, ultrasonic, and radiography tests.

Risk based inspection for offshore structures

Floating Production Storage and Offloading Units (FPSOs) are specific installations regarding their operating conditions and functions in comparison with classic ships. One of these particularities is the lack of opportunity to dry-dock. Operating continuously whilst at the same time safely presents therefore a particular challenge which ultimately led to the development of new Inspection, Maintenance and Repair (IMR) procedures to be applied to FPSOs. This has encouraged major companies and class societies to adopt Risk Based Inspection (RBI) as one of the most appropriate procedures for IMR planning of FPSOs. As a consequence, the challenge for both parties is to develop and implement RBI methodologies which guarantee profitability and competitiveness of FPSOs whilst ensuring the required structural integrity throughout the service life. Objective of this paper is not to present a state-of-the-art review of RBI but rather to give some strong insights about all ingredients which have to be used to support the development of relevant RBI practices. Emphasis is put on quantitative fatigue RBI which is a good basis to highlight these ingredients. The model example, the RBI theoretical framework and the state-of-the-practice dealing with component quantitative RBI form a whole for which the objective is to open the door to other RBI issues which are briefly mentioned in the conclusion.

확률분포에 따른 불확실한 변수를 고려한 위험도기반의 정성적 평가

Plants which are having conditions of high temperature and pressure always are exposed to danger. In order to prevent unexpected accidents, safety management that can effectively and appropriately examine facilities is required in plant operation. RBI(Risk-Based Inspection) technology in API 581 is one of standard management technique for evaluating risk on petroleum plants. There are qualitative and quantitative assessments in RBI methodology. Quantitative evaluation step is complex and required much information, so high-risk facilities in plant are selected firstly by qualitative method. Qualitative RBI is performed by choosing the answer in prepared questionnaire. However, it is difficult to believe thoroughly results from survey including ambiguous information. In this study, the procedure of qualitative RBI analysis with considering probability distribution concept were proposed by using Monte Carlo simulation method in order to increase reliability in spite of uncertain factors. In addition, qualitative risk of cooling system for LNG plant was evaluated using proposed procedure. Although 20 items of total 39 assessment items are applied to uncertain factors, risk section of high probability(89%) were verified. The detailed results were described in manuscript.

Risk Based Inspection Methodology and Software Applied to Atmospheric Storage Tanks

A new risk-based inspection (RBI) methodology and software is presented in this paper. The objective of this work is to allow management of the inspections of atmospheric storage tanks in the most efficient way, while, at the same time, accident risks are minimized. The software has been built on the new risk framework architecture, a generic platform facilitating efficient and integrated development of software applications using risk models. The framework includes a library of risk models and the user interface is automatically produced on the basis of editable schemas. This risk-framework-based RBI tool has been applied in the context of RBI for above-ground atmospheric storage tanks (AST) but it has been designed with the objective of being generic enough to allow extension to the process plants in general. This RBI methodology is an evolution of an approach and mathematical models developed for Det Norske Veritas (DNV) and the American Petroleum Institute (API). The methodology assesses damage mechanism potential, degradation rates, probability of failure (PoF), consequence of failure (CoF) in terms of environmental damage and financial loss, risk and inspection intervals and techniques. The scope includes assessment of the tank floor for soil-side external corrosion and product-side internal corrosion and the tank shell courses for atmospheric corrosion and internal thinning. It also includes preliminary assessment for brittle fracture and cracking. The data are structured according to an asset hierarchy including Plant, Production Unit, Process Unit, Tag, Part and Inspection levels and the data are inherited / defaulted seamlessly from a higher hierarchy level to a lower level. The user interface includes synchronized hierarchy tree browsing, dynamic editor and grid-view editing and active reports with drill-in capability.

Multilevel Risk-Based Inspection Scheme for FPSOs

As the floating, production, storage, and off-loading (FPSO) fleet matures, the challenge of how to more rationally and efficiently manage the life-cycle integrity of an FPSO attracts more attention. Risk-and reliability-based approaches are regarded as very powerful tools to help optimize an integrity program and offer flexibility in helping better manage the integrity management regime. This paper presents a multilevel risk-based inspection (RBI) methodology ranging from simplified deterministic approaches using standard design analysis up to sophisticated probabilistic approaches. Each approach has various levels of usefulness ranging from the definition of critical areas for a single inspection campaign up to the generation of an optimized inspection schedule and work scope covering the entire life cycle of a particular unit. These RBI methodologies have been successfully applied in inspection planning for several FPSO installations. A wide range of engineering analyses were involved, depending on the needs of individual projects and client requests, inspection objectives, condition of the asset, availability of design analysis information, and so forth.