Risk Informed Work Selection

Asset integrity management is a life cycle concept typically initiated in the conceptual and detailed design phase of projects. Parallel with the development of equipment and system lists, the process of building maintenance job plans starts. Tools, such as criticality assessment, are used to identify the type of engineering deliverable from which the maintenance job plan is built. For a large majority of equipment and systems, original equipment manufacturer (OEM) recommended or fleet inspection, maintenance and testing (IMT) plans are adequate. For a smaller subset, more detailed plans leveraging risk-based inspection (RBI) and reliability-centered maintenance (RCM) concepts are developed building a regime of preventative maintenance focused on data collection in the commissioning and early operation of the facility. For an extremely limited subset of equipment, mostly machinery, but could include pipelines, electrical and product analyzers, the most detailed plans are developed which are highly specific to a particular equipment tag. Criticality assessment is commonly cited as a core process for prioritization of RBI/RCM plan development initially with spare parts inventories and work management later in the life cycle. International standards such as ISO 14224, Petroleum, petrochemical and natural gas industries — Collection and exchange of reliability and maintenance data for equipment, provide a framework for asset hierarchy and taxonomy which will prove to be important during the operating phase of the life cycle where surveillance and corrective maintenance data will be leverage to optimize maintenance job plans. ISO 14224 refers to IEC 60812, Failure modes and effects analysis (FMEA and FMECA), for treatment of Failure Mode Effects and Criticality Assessment (FMECA). To a large extent, ISO 60812 leaves determination of the variables to drive criticality assessment up to the operator saying only that two or more variables should be used. Variables used commonly include consequence of failure, but also maintainability and complexity. Benchmarks for criticality assessment suggest about 10% of equipment merits identification as critical (reference needed). Criticality is important as a foundation to integrity management as work linked to primary function carries an inherited technical characteristic of the equipment and systems. Over time, additional equipment and systems will be added (or removed) from critical equipment lists through continuous improvement processes such as root cause failure analysis (RCFA). With the prioritization of developing maintenance plans through fleet and RBI/RCM processes and their resultant deliverables defined, the detailed plans are identified through collaboration of technical, maintenance and operations staff specialists. Fundamentally, the process involves identification of hazards which can result in impaired primary and secondary functionality, estimation of unmitigated risk, identification of work to mitigate risk, estimation of mitigated risk, calculation of benefit-to-cost and documenting the analysis into the system of record. Consistency in the processes can be assured through application of procedures and references that typically reference a risk matrix. As each hazard is reviewed, there may be multiple failures modes (e.g. hole, crack, rupture) which needs to be considered independently. Consequence assessment is performed for a range of Safety Health Environmental and Security (SHES) scenarios associated with the failure mode. Probability assessment for the scenarios is performed using the available design parameters. The combined consequence and probability form the initial unmitigated risk basis for the scenario. Inspection, maintenance and testing activities are selected by the collaborating specialists with focus of input from technical on probability mitigation, maintenance on cost and operations on benefit. The scenarios is then revisited to document the mitigated risk.

Knowledge Criticality Assessment and Codification Framework for Major Maintenance Activities: A Case Study of Cement Rotary Kiln Plant

Maintenance experts involved in managing major maintenance activities such as; Major overhauls, outages, shutdowns and turnarounds (MoOSTs) are constantly faced with uncertainties during the planning and/or execution phases, which often stretches beyond the organisation’s standard operating procedures and require the intervention of staff expertise. This underpins a need to complement and sustain existing efforts in managing uncertainties in MoOSTs through the transformation of knowledgeable actions generated from experts’ tacit-based knowledge. However, a vital approach to achieve such transformation is by prioritising maintenance activities during MoOSTs. Two methods for prioritising maintenance activities were adopted in this study; one involved a traditional qualitative method for task criticality assessment. The other, a quantitative method, utilised a Fuzzy inference system, mapping membership functions of two crisp inputs and output accompanied by If-Then rules specifically developed for this study. Prior information from a 5-year quantitative dataset was obtained from a case study with appreciable frequency for performing MoOSTs; in this case, a Rotary Kiln system (RKS) was utilised in demonstrating practical applicability. The selection of the two methods was informed by their perceived suitability to adequately analyse the available dataset. Results and analysis of the two methods indicated that the obtained Fuzzy criticality numbers were more sensitive and capable of examining the degree of changes to membership functions. However, the usefulness of the traditional qualitative method as a complementary approach lies in its ability to provide a baseline for informing expert opinions, which are critical in developing specific If-Then rules for the Fuzzy inference system.

Criticality Assessment of the Life Cycle of Passenger Vehicles Produced in China

China is globally the largest and a rapidly growing market for electric vehicles. The aim of the paper is to determine challenges related to criticality and environmental impacts of battery electric vehicles and internal combustion engine vehicles, focusing not only on a global but also the Chinese perspective, applying the ESSENZ method, which covers a unique approach to determine criticality aspects as well as integrating life cycle assessment results. Real industry data for vehicles and batteries produced in China was collected. Further, for the criticality assessment, Chinese import patterns are analyzed. The results show that the battery electric vehicle has similar and partly increased environmental impacts compared with the internal combustion engine vehicle. For both, the vehicle cycle contributes to a large proportion in all the environmental impact categories except for global warming. Further, battery electric vehicles show a higher criticality than internal combustion engine vehicles, with tantalum, lithium, and cobalt playing essential roles. In addition, the Chinese-specific results show a lower criticality compared to the global assessment for the considered categories trade barriers and political stability, while again tantalum crude oil and cobalt have high potential supply disruptions. Concluding, battery electric vehicles still face challenges regarding their environmental as well as criticality performance from the whole supply chain both in China and worldwide. One reason is the replacement of the lithium-ion power battery. By enhancing its quality and establishing battery recycling, the impacts of battery electric vehicle would decrease.