Important Elements of RBI
There are a handful of elements that should be adequately addressed in all RBI applications starting with documented management systems for implementing and maintaining an RBI program. Key examples, as outlined in API RP 580, include:
- Documented methods for PoF and CoF determination.
- Documented methodologies for managing risk through inspection, process control, and other mitigation activities.
- Management systems for maintaining documentation, personnel qualifications, data requirements, program consistency, and analysis updates.
Additional elements required for implementing and maintaining an RBI program include the RBI team, data & information inputs, damage mechanisms & failure modes, PoF & CoF analyses, and risk assessment & evaluation. These elements help form and drive the RBI Work Process (shown below), which is simply a collection of essential steps and elements for inspection planning derived from the RBI program.
The RBI Team
RBI is a team-based approach that requires a competent team comprised of individuals with complementary backgrounds from various departments. Not all team members are required full time; rather, their presence is based on the scenario or stage of the work. The following, as detailed in API RP 580, is useful for building a team:
| Team Member | Role |
| Team Leader |
The team leader should be a full-time team member and is considered a specialist in the RBI process and facilitation. Their main function should be to integrate the inputs, outputs, organizational structure, reporting facilities, and communications of the assessment team. Other responsibilities of the team leader may include, but are not limited to:
|
| Equipment Inspector or Inspection Specialist | The equipment inspector or inspection specialist is generally responsible for gathering data on the condition and history of the equipment included in the study, assessing the effectiveness of previous inspections, and often implementing the recommended inspection. |
| Corrosion Specialist | The corrosion specialist is responsible for assessing the types of damage mechanisms and their applicability and severity to the equipment. They should compare the results to the actual condition of the equipment, identify the reasons for any differences between the predicted and actual condition, and provide guidance on damage mechanisms, rates, or severity to be used in the assessment. The corrosion specialist should also be able to provide recommendations on how and where to inspect as well as mitigation methods. |
| Process Specialist | The process specialist is responsible for the provision of process condition information. They should also be responsible for documenting variations in the process conditions due to normal occurrences (e.g., start-ups and shutdowns) and abnormal occurrences. Their responsibilities also include describing the composition and variability of the fluids/gasses as well as their potential toxicity and flammability. Lastly, the process specialist should also evaluate and recommend risk mitigation methods through changes in process conditions. |
| Operations & Maintenance Personnel | The operations & maintenance personnel responsibilities include verifying that the facility is being operated within the parameters set out in the process operating window. They’re also responsible for providing data on occurrences when the process deviated from the limits of the operating windows and any operating data trends over the past unit run. They should also verify that equipment repairs, replacements, and/or additions have been included in the equipment condition data supplied by the equipment inspector. |
| Management | Management is responsible for providing sponsorship and resources (e.g., personnel and funding) for the RBI analysis. Their responsibilities also include making decisions on risk management, establishing risk acceptance criteria, and/or providing the framework for other team members to make these decisions based on the RBI assessment results. |
| Risk Analyst |
The risk analyst, who could be a separate specialist or one of the other team members, is responsible for pulling together all of the data and carrying out the RBI analysis. Their responsibilities typically include:
|
| Environment & Safety Personnel |
Environment & safety personnel are responsible for providing data on environmental and safety systems and regulations. They should also provide recommendations for mitigating the consequence of failures. |
| Financial/Business Personnel |
Financial/business personnel are responsible for providing data on the cost of the facility/equipment being analyzed and the costs associated with having pieces of equipment or the facility shut down. They should also provide recommendations for mitigating the financial consequence of failures. |
Data & Information
Key information is needed to ensure a system is functioning safely and reliably. Information is generated by structured and unstructured data from documents, databases, drawings, reports, and spreadsheets. Data is collected from inspection, process, design, maintenance and repair documents, and Management of Change (MOC) documentation. Important considerations include:
- Ensuring that well-trained, qualified personnel are processing data
- Ensuring the right data is captured and available
- Storing and managing data in a single location
- Reducing the number of databases to eliminate redundant data and the potential for conflicts
- Streamlining data-input for easy search queries and calculations
- Consistently updating data
- Incorporating a strong MOC program
Damage Mechanisms & Failure Modes
Damage mechanisms lead to problems or failures with process equipment. Damage mechanisms can range from corrosion, to cracking, to heat damage, and everything in between. Identifying damage mechanisms are integral to conducting RBI and important for the following:
- The analysis for determining the PoF
- Selecting appropriate inspection intervals/due dates, locations, and techniques
- Making decisions that can remove or reduce the probability of a specific damage mechanism
Failure modes identify the manner in which a damaged equipment will fail (i.e., small hole, leakage, rupture, etc.). Identifying failure modes are integral to conducting RBI and important for the following:
- The analysis for determining the PoF
- Decision making for run-or-repair
- Selecting the proper repair techniques
Probability & Consequence
An objective of RBI involves the combined consideration of the consequence(s) of failure with the probability that the failure may occur. In an RBI context, failure refers to the loss of contained material to the external environment. The PoF and CoF are the two fundamental parts that define risk and when calculated together, helps operators establish the risk level for a particular piece of equipment and set inspection intervals based on the calculated risk.
Risk = Probability of Failure (PoF) × Consequence of Failure (CoF)
Probability of Failure (PoF) is the likelihood that a piece of equipment will fail at a given time and is dependent on the stage of the lifecycle of the components (e.g., the PoF will generally be higher for aging infrastructure in comparison to new assets). The PoF is used to determine the type and rate of potential damage mechanisms to a system. Since most operations are dynamic and degradation rates and operating practices change from time-to-time, the analysis should not be static and the data should be updated at the appropriate intervals (i.e., when conditions or materials change that could have a significant impact on the PoF).
RBI also analyzes the Consequence of Failure (CoF), which is simply the most probable consequence scenario from a loss of containment. The CoF analysis considers and evaluates the consequences of various types of outcomes (e.g., health and safety, environmental damage, equipment damage, and economic loss).
In a qualitative assessment, consequences are categorized and typically shown as areas in a matrix, such as “insignificant,” “minor,” “significant,” “serious,” “major,” and “catastrophic.” In a quantitative assessment, CoF may be evaluated and the results shown in areas affected by personal injury, equipment damage, and/or financial impact (e.g., remediation, equipment replacement costs, loss of profit/production opportunity in economic terms).
RBI Assessment Methods
Determining risk in RBI can be approached using qualitative, quantitative, and/or semi-quantitative methods. These methods are applied to systems to determine, or calculate, the PoF and CoF. The choice of approach can depend on multiple factors (i.e., objective of the study, available resources, assessment timeframe, nature and quality of the available data, etc.). It’s possible to select an approach and carry it through to completion or change it as the analysis progresses (i.e., the analysis may become more or less quantitative); however, consistency will be vital when comparing the results to future assessments.
In practice, an RBI study will likely use aspects from all three approaches. These approaches shouldn’t be considered as competitors, but rather they should be used in complement to one another. For example, a high-level quantitative approach may be used at the facility level to find its unit that presents the highest risk; however, the unit’s systems and equipment may be screened using a qualitative approach and a more quantitative approach used for the higher risk items. The team must exercise caution when performing a risk analysis across different equipment unless they apply the same or very similar methodologies and assumptions. Also, the accuracy of any type of RBI approach depends on having quality data, qualified personnel, and using a sound methodology.
Qualitative
The qualitative approach requires a high level of credible judgement, skill, and experience from personnel. The objective of utilizing a qualitative method is to deliver a credible RBI analysis using expert opinion/judgement (i.e., inputs are given in data ranges instead of discrete values). The value of this approach enables the completion of an assessment without needing detailed quantitative data; however, the accuracy of the results will depend on the background and expertise of the team members.
The more qualitative the study is, the more engagement it requires from highly knowledgeable people. Since this approach is heavily opinion-based, it is often a challenge to achieve the level of consistency required to achieve reproducibility. Since RBI is based on relative risks, a high level of consistency in work processes and calculation is a must. Things to help achieve this level of consistency include a clear and consistent procedure as well as proper training of RBI team members to ensure everyone is on the same page.
Quantitative
The quantitative approach is a more data-driven assessment where numerical values are calculated and more discrete input data is used. An advantage of the quantitative method is that it provides the same basis for comparison between equipment at a more detailed level. This helps drive accuracy and consistency and lends itself towards automation as key inputs, as they change, can be updated. These methods typically supply more value, such as Key Performance Indicator (KPI) outputs (e.g., relative probabilities of failure), with more discretion for benchmarking and evaluating "sister" equipment and other discrete queryable outputs (e.g., show all crude vacuum towers with more than 4 corrosion circuits, a PoF of greater than 1.0 X 10-3.5, and corrosion rates greater than 7 mils per year with sulfidation as the primary damage mechanism).
Semi-Quantitative
The semi-quantitative approach uses aspects from both the qualitative and quantitative approach. This approach requires the same type of data as a quantitative assessment but is less detailed. In response, this approach provides the major benefits of the other approaches (e.g., quickness of the qualitative approach and the thoroughness of the quantitative approach).
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