API RP 580 2023 PDF - Elements of a Risk-Based Inspection Program

Elements of a Risk-Based Inspection Program API RECOMMENDED PRACTICE 580 FOURTH EDITION, AUGUST 2023 Copyright American Petroleum...

Elements of a Risk-Based Inspection Program API RECOMMENDED PRACTICE 580 FOURTH EDITION, AUGUST 2023 Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Special Notes API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed. Neither API nor any of API's employees, subcontractors, consultants, committees, or other assignees make any warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the results of such use, of any information or process disclosed in this publication. 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Contact the Publisher, API Publishing Services, 200 Massachusetts Avenue, NW, Suite 1100, Washington, DC 20001-5571. Copyright © 2023 American Petroleum Institute ii Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Foreword Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent. Shall: As used in a standard, “shall” denotes a minimum requirement to conform to the specification. Should: As used in a standard, “should” denotes a recommendation or that which is advised but not required to conform to the specification. 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Suggested revisions are invited and should be submitted to the Standards Department, API, 200 Massachusetts Avenue, NW, Suite 1100, Washington, DC 20001, [email protected]. iii Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Contents Page 1 Scope............................................................................................................................................................. 1 1.1 Industry Scope............................................................................................................................................... 1 1.2 Purpose......................................................................................................................................................... 1 1.3 Flexibility in Application.................................................................................................................................. 1 1.4 Mechanical Integrity Focused........................................................................................................................ 2 1.5 Target Audience............................................................................................................................................. 2 1.6 RBI Assessment Benefits and Limitations..................................................................................................... 2 2 Normative References................................................................................................................................... 3 3 Terms, Definitions, Acronyms, and Abbreviations.......................................................................................... 4 3.1 Terms and Definitions.................................................................................................................................... 4 3.2 Acronyms and Abbreviations....................................................................................................................... 11 4 Risk Assessment Concepts......................................................................................................................... 11 4.1 What is Risk?............................................................................................................................................... 11 4.2 Risk Management and Risk Reduction........................................................................................................ 12 4.3 Relative Risk vs Absolute Risk.................................................................................................................... 12 5 Introduction to Risk-Based Inspection......................................................................................................... 13 5.1 from chapter 4 The Evolution of Inspection Intervals and Due Dates.................................................................................. 13 5.2 Consequence of Failure (COF) and Probability of Failure (POF) for RBI.................................................... 13 5.3 Precision vs Accuracy.................................................................................................................................. 15 5.4 Types of RBI Assessment............................................................................................................................ 18 5.5 Expected Outcome of the RBI Process....................................................................................................... 21 5.6 Using RBI for Risk Management................................................................................................................. 21 5.7 Using RBI as a Continuous Improvement Tool............................................................................................ 24 5.8 Relationship Between RBI and Other Risk-Based and Safety Initiatives.................................................... 25 5.9 Relationship with Jurisdictional Requirements............................................................................................ 27 6 Planning the RBI Program........................................................................................................................... 27 6.1 Organizing the Work Process...................................................................................................................... 27 6.2 Establishing Objectives and Goals of an RBI Assessment.......................................................................... 30 6.3 Initial Screening........................................................................................................................................... 32 6.4 Establish Operating Boundaries.................................................................................................................. 35 6.5 Selecting a Method of RBI Assessment....................................................................................................... 36 6.6 Factors Influencing the Resources and Time Required............................................................................... 37 6.7 from chapter 17 Pitfalls Keys for Success: RBI Program Planning................................................................................................... 37 7 from chapter 15 Roles, Responsibilities, Training, and Qualifications................................................................................... 38 7.1 Team Approach............................................................................................................................................ 38 7.2 Team Members, Roles, and Responsibilities............................................................................................... 38 7.3 Training and Qualifications for RBI Application............................................................................................ 40 7.4 Keys for Success: Roles, Responsibilities, Training, and Qualifications for RBI Team Members............... 41 from chapter 17 Pitfalls 8 chapter 7 Data and Information Collection for RBI Assessment.................................................................................. 41 8.1 General........................................................................................................................................................ 41 8.2 RBI Data Needs........................................................................................................................................... 42 8.3 Data Quality................................................................................................................................................. 43 8.4 Codes and Standards—National and International..................................................................................... 43 8.5 Sources of Site-Specific Data and Information............................................................................................ 44 v Copyright American Petroleum Institute Provided by Accuris unde license with API ` No reproduction or networking permitted without license from Accuris  Contents Page 8.6 Keys for Success: Data and Information Collection..................................................................................... 45 9 chapter 8 Damage Mechanisms and Failure Modes Damage Mechanism Review....................................................................................................................... 46 9.1 General........................................................................................................................................................ 46 9.2 Identifying Corrosion Rates and Damage Mechanisms............................................................................... 47 9.3 DMR Outcome Documentation.................................................................................................................... 48 9.4 DMR Relationship with IOWs...................................................................................................................... 48 9.5 from chapter 17 Pitfalls Keys for Success—Damage Mechanisms and Failure Modes.................................................................... 48 10 chapter 9 Assessing Probability of Failure (POF)........................................................................................................ 49 10.1 Introduction to Probability of Failure (POF)................................................................................................. 49 10.2 Units of Measure in the POF Analysis......................................................................................................... 49 10.3 Types of Probability of Failure (POF)........................................................................................................... 50 10.4 Determination of POF.................................................................................................................................. 51 10.5 from chapter 17 Pitfalls Keys for Success—Assessing POF............................................................................................................. 52 chapter 10 11 Assessing Consequence of Failure (COF).................................................................................................. 53 11.1 Introduction to COF Analysis....................................................................................................................... 53 11.2 Types of Consequence of Failure (COF) Analysis....................................................................................... 54 11.3 Units of Measure in Consequence of Failure (COF) Analysis..................................................................... 55 11.4 Volume of Fluid Released............................................................................................................................ 58 11.5 Consequence of Failure Effect Categories.................................................................................................. 58 11.6 Determination of COF.................................................................................................................................. 62 12 chapter 11 Risk Determination, Assessment, and Management................................................................................... 65 12.1 Purpose....................................................................................................................................................... 65 12.2 Determination of Risk.................................................................................................................................. 65 12.3 Understanding Acceptable Levels of Risk................................................................................................... 66 12.4 Sensitivity Analysis...................................................................................................................................... 67 12.5 Assumptions................................................................................................................................................ 67 12.6 Risk Presentation......................................................................................................................................... 67 12.7 Risk Thresholds........................................................................................................................................... 69 12.8 from chapter 17 Pitfalls Keys for Success—Risk Determination, Assessment and Management..................................................... 69 13 chapter 12 Risk Management with Inspection Activities................................................................................................ 70 13.1 from 11.8 Risk Management........................................................................................................................................ 70 13.2 Managing Risk by Reducing Uncertainty Through Inspection..................................................................... 70 13.3 Identifying Risk Management Opportunities from RBI Results.................................................................... 72 13.4 Establishing an Inspection Strategy Based on Risk Assessment................................................................ 73 13.5 Managing Inspection Costs with RBI........................................................................................................... 73 13.6 Assessing Inspection Results...................................................................................................................... 74 13.7 Achieving Lowest Life Cycle Costs with RBI............................................................................................... 74 13.8 Modifying RBI Plans After a Failure Investigation........................................................................................ 74 13.9 from chapter 17 Pitfalls Keys for Success—Risk Management with Inspection Activities................................................................. 74 14 chapter 13 Other Risk Management Methods............................................................................................................... 75 14.1 General........................................................................................................................................................ 75 14.2 Equipment Replacement and Repair........................................................................................................... 75 14.3 Evaluating Flaws for Fitness-for-Service..................................................................................................... 75 14.4 Equipment Modification, Re-design, and Re-rating..................................................................................... 75 14.5 Emergency Isolation.................................................................................................................................... 76 vi Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Contents Page 14.6 Emergency Depressurizing/De-inventory.................................................................................................... 76 14.7 Modify Process............................................................................................................................................ 76 14.8 Reduce Inventory......................................................................................................................................... 77 14.9 Water Spray/Deluge..................................................................................................................................... 77 14.10 Water Curtain............................................................................................................................................... 77 14.11 Blast-resistant Construction......................................................................................................................... 77 14.12 Additional Risk Management Methods........................................................................................................ 77 14.13 from chapter 17 Pitfalls Keys for Success—Other Risk Management Methods................................................................................ 78 15 chapter 14 Updating the RBI Assessment..................................................................................................................... 78 15.1 The Difference Between Evergreening and Reassessment........................................................................ 78 15.2 Why Conduct an RBI Reassessment?........................................................................................................ 80 15.3 When to Conduct an RBI Reassessment.................................................................................................... 81 15.4 from chapter 17 Pitfalls Keys for Success—Updating the RBI Assessment...................................................................................... 82 chapter 16 ` 16 RBI Documentation and Recordkeeping..................................................................................................... 82 16.1 Documenting the RBI Management System................................................................................................ 82 16.2 Documenting the RBI Assessment.............................................................................................................. 83 16.3 Documenting the Outcome of the RBI Assessment..................................................................................... 84 16.4 from chapter 17 Pitfalls Keys for Success—RBI Documentation and Recordkeeping...................................................................... 84 Bibliography.............................................................................................................................................................. 85 Figures 1 Risk Plot....................................................................................................................................................... 15 2 Accuracy vs Precision.................................................................................................................................. 16 3 Continuum of RBI Methods.......................................................................................................................... 19 4 Management of Risk Using RBI................................................................................................................... 23 5 Risk-Based Inspection Analysis Process..................................................................................................... 29 6 Determination of COF.................................................................................................................................. 63 7 Example Risk Matrix Using POF and COF Categories to Display Risk Rankings....................................... 68 8 Risk Plot when Using Quantitative or Numeric Risk Values........................................................................ 69 Tables 1 Example of RBI Inputs................................................................................................................................. 17 2 Examples for Three Levels of Qualitative POF Ranking............................................................................. 50 3 Examples for Six Levels of Qualitative POF Ranking.................................................................................. 50 4 Examples for Three Levels of Qualitative COF Ranking............................................................................. 54 5 Examples for Six Levels of Qualitative COF Ranking.................................................................................. 54 6 Examples for Six Levels of Cost Consequence of Failure Ranking............................................................. 57 7 Example for Three Levels of Safety, Health, and Environmental Consequence Categories....................... 58 8 Examples for Six Levels of Safety, Health, and Environmental Consequence of Failure Categories......... 58 vii Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  ` Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Introduction The use of Risk-Based Inspection (RBI) methodologies for inspection planning is not compulsory. The use of RBI is entirely optional, subject to the requirements and limitations of the other inspection codes (such as API 510, API 570, and API 653). This recommended practice (RP) contains the requirements and expectations required to establish and maintain an API 580 compliant RBI program. RBI is a systematic process that begins with identification of facilities or equipment, continues with a determination of risk (via probability of failure and consequence of failure analysis). The process culminates in the creation of a risk- based management plan based on the credible damage mechanism(s) and the risk of failure. Owner-operators may utilize this output to prioritize the execution of the inspection programs effectively and efficiently. For the purposes of this document, RBI is synonymous with descriptions of other RBI programs used in the industry: risk-prioritized inspection, risk-informed inspection, and inspection planning using risk-based methods. ix Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Elements of a Risk-Based Inspection Program 1 Scope 1.1 Industry Scope This RP is specifically targeted to the application of RBI in the hydrocarbon and chemical process industries. The principles and concepts herein can be applied in other industries with appropriate documentation. 1.2 Purpose The purpose of this RP is to provide users with the recommended elements for developing, implementing, and maintaining an RBI program. This RP provides guidelines for establishing an RBI program which when implemented properly, will allow the owner-operator to integrate risk assessment and inspection planning into an existing inspection program. The approach emphasizes safe and reliable operation through risk-prioritized inspection. A spectrum of complementary risk analysis approaches (qualitative through fully quantitative) can be considered as part of the inspection planning process. This RP contains individual sections that describe the steps in applying concepts and principles of an RBI program which include: a) risk-based inspection analysis methods; b) planning the RBI program; c) roles, responsibilities, training, and qualifications; d) data and information collection for a risk assessment; e) damage mechanisms review; f) assessing probability of failure (POF); g) assessing consequence of failure (COF); h) risk determination, assessment, and management; i) other risk management activities; j) evergreening and reassessment of the risk assessment; and k) RBI documentation and recordkeeping. 1.3 Flexibility in Application Because of the broad diversity in organizational size, culture, and regulatory requirements, this RP offers users the flexibility to create and implement an RBI Program within the context of existing corporate risk management practices—including the selection and application of a specific RBI methodology. Various RBI methodologies exist and are currently being applied throughout industry. This RP is not intended to recommend nor endorse any specific methodology for implementing the assessment steps within an RBI program. However, this document is designed to provide a framework that specifies the minimum requirements and expectations needed for a quality risk assessment without imposing undue constraints on users. 1 Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  2 API Recommended Practice 580 This RP is also intended to promote consistency of the process and quality in the identification, assessment, and management of risks pertaining to material deterioration that could lead to failure. Further, the document provides guidance on the recommended work process for conducting and sustaining a successful RBI program. 1.4 Mechanical Integrity Focused The RBI process is focused on maintaining the mechanical integrity of pressure equipment and minimizing the risk of loss of containment due to deterioration. RBI is not a substitute for a process hazards analysis (PHA) nor is it a substitute for hazard and operability assessment (HAZOP). Typically, PHA risk assessments focus on the process unit design, operating practices, and the adequacy of the practices, given the unit’s current or anticipated operating conditions. RBI complements the PHA by focusing on the mechanical integrity related damage mechanisms and managing risk through inspection and complimentary mitigation and/or monitoring programs. There are other relevant relationships between RBI and other equipment reliability or risk assessment programs in the industry. For example, RBI is complementary to reliability centered maintenance (RCM) programs in that both programs are focused on understanding failure modes, addressing the modes, and therefore improving the reliability of equipment and process facilities. Relevant relationships between RBI and other equipment reliability or risk assessment programs in industry are discussed in 5.8. 1.5 Target Audience The primary audience for this RP is inspection and engineering personnel who are responsible for the mechanical integrity and operability of equipment covered by this RP. While an organization’s inspection or materials engineering group may champion the RBI initiative, RBI is not exclusively an inspection activity. RBI requires the involvement of various segments of the organization such as engineering, maintenance, and operations. Implementation of the resulting RBI product (e.g. inspection plans, replacement/upgrading recommendations, other mitigation activities, etc.) may rest with more than one segment of the organization. RBI requires the commitment and cooperation of the organization. In this context, all stakeholders who are likely to be involved should be familiar with the concepts and principles embodied in the RBI methodology to provide the necessary support for the RBI assessment and in the interpretation and application of the results as it relates to their specific function. 1.6 RBI Assessment Benefits and Limitations An RBI program can provide the following benefits: a) identification of risk drivers; 1) damage mechanisms and damage modes 2) equipment with insufficient or inadequate inspection history 3) consequence driven equipment not impacted by inspection 4) safety, health, environmental and/or economic consequences b) development of an inspection plan; 1) techniques and methods to be used for proper detection and quantification 2) establishment of the extent of inspection (e.g. percent of the total area to be examined or specific locations) 3) provision of the inspection interval or next inspection date (timing) c) optimization of resources; Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Elements of a Risk-Based Inspection Program 3 d) identification of mitigation activities which can further reduce risk for the facilities and equipment assessed; e) acceptance/understanding of the current risk; and f) provision for other applicable risk mitigation activities (including but not limited to): 1) establishing and maintaining Integrity Operating Windows (IOWs); 2) reducing personnel exposure to high-risk areas; 3) upgrading to materials of construction less susceptible to degradation; 4) reducing the consequence of failure (e.g. limiting inventory, detection, and mitigation controls); 5) repair or replacement. The risk assessment can identify equipment that does not require inspection or mitigation because of the acceptable level of risk associated with the equipment’s operation. In addition, there can be synergies between the RBI process and process safety management and turnaround activities that may further decrease the amount of inspection related activities. These synergies can lead to a potential decrease in operating expenses, while also reducing the facility risk. An RBI assessment is limited by and will not compensate for: 1) inaccurate or missing information; 2) inadequate design, faulty equipment installation, or inadequate testing or commissioning of equipment; 3) operating outside the acceptable process limits (e.g. not to exceed limitations, IOWs, etc.); 4) not effectively executing the plans; 5) lack of qualified personnel or teamwork; 6) lack of sound engineering or operational judgment; 7) lack of follow-up on inspection findings or recommendations; and 8) construction and fabrication errors. 2 Normative References The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any addenda) applies. API 510, Pressure Vessel Inspection Code: In-service Inspection, Rating, Repair, and Alteration API 570, Piping Inspection Code: In-service Inspection, Rating, Repair, and Alteration of Piping Systems API Recommended Practice 571, Damage Mechanisms Affecting Fixed Equipment in the Refining Industry Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  4 API Recommended Practice 580 3 Terms, Definitions, Acronyms, and Abbreviations 3.1 Terms and Definitions For the purposes of this document, the following terms and definitions apply. 3.1.1 absolute risk An ideal and accurate description and quantification of risk. 3.1.2 acceptable risk A level of risk that is acceptable to the owner-operator. 3.1.3 as low as reasonably practicable ALARP A concept of minimization where that attributes (such as risk) can only be reduced to a certain minimum under current technology and with reasonable cost. 3.1.4 components Parts that make up a piece of equipment or equipment item. For example, a pressure boundary may consist of components (pipe, elbows, nipples, heads, shells, nozzles, stiffening rings, skirts, supports, etc.) that are bolted or welded into assemblies to make up equipment items. 3.1.5 consequence The outcome of an event. 3.1.6 consequence of failure COF The outcome of a failure event such as safety, environmental, financial, damage to reputation or other negative outcomes. 3.1.7 corrosion specialist A person acceptable to the owner-operator who is knowledgeable and experienced in specific process chemistries, degradation mechanisms, materials selection, corrosion mitigation methods, corrosion monitoring techniques, and impact on equipment. 3.1.8 cost-effective An activity that is both effective in resolving an issue (e.g. some form of mitigation) and is a financially sound use of resources. 3.1.9 credible A descriptor where the term being modified has been determined to have a reasonable likelihood of occurrence. EXAMPLE Credible damage mechanism, credible consequence Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Elements of a Risk-Based Inspection Program 5 3.1.10 credible damage mechanism deterioration mechanism Any type of deterioration encountered in the refining and chemical process industry can result in flaws/defects that can affect the integrity of vessels (e.g. corrosion, cracking, erosion, dents, and other mechanical, physical, or chemical impacts). NOTE 1 See API 571 for a comprehensive list and description of damage mechanisms affecting the refining industry. Other sources of damage mechanisms and their descriptions exist in ASME PCC-3, WRC 488, WRC 489, WRC 490, ASM Volume 6, ASM Volume 11, and ASM Volume 13 among industry accepted documentation. NOTE 2 Mechanism assignment is typically completed by a corrosion specialist. NOTE 3 See Section 9 for further information. 3.1.11 damage mode deterioration mode The physical manifestation of damage (e.g. wall thinning, pitting, cracking, rupture). 3.1.12 damage tolerance The amount of deterioration that a component can withstand without failing. 3.1.13 design premise Assumptions made during the design (e.g. design life and corrosion allowance needed). 3.1.14 deterioration The reduction in the ability of a component to provide its intended purpose of containment of fluids. NOTE This can be caused by various damage mechanisms (e.g. thinning, cracking, mechanical). Damage or degradation may be used in place of deterioration. 3.1.15 equipment An individual item that is part of a system (such as pressure vessels, relief devices, piping, boilers, and heaters) or an assemblage of components. 3.1.16 event An incident or situation that occurs in a particular place during a particular interval of time. 3.1.17 event tree An analytical tool that organizes and characterizes potential occurrences in a logical and graphical manner and shows the events relationship to each other. 3.1.18 external event ` Events resulting from forces of nature, acts of God, sabotage, or other events usually beyond the direct or indirect control of persons employed at or by the facility. EXAMPLE Neighboring fires or explosions, terrorism, neighboring hazardous material releases, electrical power interruptions, forces of nature, and intrusions of external transportation vehicles, such as aircraft, ships, trains, trucks, or automobiles. Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  6 API Recommended Practice 580 3.1.19 facility Any location containing equipment and/or components to be addressed under this RP. 3.1.20 failure The loss of function of a system, structure, asset, or component to perform its required or intended function(s). NOTE Though there are many definitions for failure of equipment, in this document failure is defined as loss of containment. 3.1.21 failure mode The manner of failure. For RBI, the failure of concern is loss of containment of equipment items. EXAMPLE Small hole, cracks, and ruptures. 3.1.22 Fitness-For-Service Evaluation FFS A methodology whereby damage or flaws/imperfections contained within a component or equipment item are assessed to determine acceptability for continued service. 3.1.23 functional failure The inability for a component, equipment, or system to perform its intended function. 3.1.24 hazard A physical condition or a release of a unsafe material due to a component failure and which may result in human injury or death, loss or damage, or environmental degradation. NOTE The hazard is the source of harm. Components that are used to transport, store, or process hazardous material can be a source of the hazard. Human error and external events may also create a hazard. 3.1.25 hazard and operability study HAZOP A structured brainstorming process of assessing the existence of dangers and/or risks (i.e. hazard) in equipment and vulnerability of operation. NOTE The process uses a list of guidewords to focus on process parameters such as flow, level, temperature, and pressure and then branch out to include other concerns, such as human factors and operating outside normal parameters. 3.1.26 inspection The external, internal, or on-stream assessment (or any combination of the three) of the condition of an asset conducted by the authorized inspector or his/her designee in accordance with the appropriate code. NOTE 1 Includes activities performed to verify that materials, fabrication, erection, examinations, testing, repairs, and any other data relevant to the equipment conform to applicable codes, engineering, and the owner-operator’s written procedure requirements. NOTE 2 Inspection also includes the planning, implementation, and evaluation of the results of inspection activities. 3.1.27 inspection plan Strategy defining how and when an asset or component will be inspected, repaired, and/or maintained. Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Elements of a Risk-Based Inspection Program 7 NOTE For the purposes of this document, the inspection plan is the product of an RBI analysis that details the scope, extent/locations, methods, and timing of specific inspection/monitoring activities for determining the condition of a specific piece of equipment. It is the essential part of a risk-based management plan. 3.1.28 integrity operating windows IOWs Established limits for process variables (parameters) that can affect the integrity of the equipment if the process operation deviates from the established limits for a predetermined amount of time. 3.1.29 ISO-risk A line of constant risk and method of graphically showing probability of failure (POF) and consequence of failure (COF) values in a two-dimensional plot where risk increases toward the upper right-hand corner. 3.1.30 logic model A tool used to depict the effectiveness in depicting a combination of events that could result in a loss of containment event. 3.1.31 management of change ` MOC A documented management system for review and approval of changes (both physical and process) to equipment prior to implementation of the change. NOTE Alteration of inspection plans may occur as a result of the change. 3.1.32 management system The framework of work processes and procedures is used to provide assurance that an organization can fulfill all tasks required to achieve its objectives. 3.1.33 mechanical integrity MI The management systems, work practices, methods, and procedures established to protect and preserve the integrity of operating equipment (i.e. avoid loss of containment due to the effect of equipment damage mechanisms). NOTE MI is one part of a process safety program. 3.1.34 mitigation Limitation of any negative consequence or reduction in probability of a particular event. 3.1.35 physical model A tool used to depict the progression of events and the release of a hazardous material to the environment. 3.1.36 probabilistic Systematic and comprehensive methodology to evaluate risks associated with a complex engineered entity, which is based on or adapted to a theory of probability; subject to or involving chance variation. Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  8 API Recommended Practice 580 3.1.37 probability likelihood Extent to which an event is likely to occur within the timeframe under consideration (i.e. events/year). NOTE 1 The mathematical definition of probability is “a real number in the scale 0 to 1 attached to a random event.” For a high degree of belief, the probability is near one (1.0). NOTE 2 Frequency rather than probability may be used in describing risk. NOTE 3 Degrees of likelihood of probability can be chosen as classes or ranks like “rare/unlikely/moderate/likely/almost certain” or “incredible/ improbable/remote/occasional/probable/frequent.” 3.1.38 probability of failure POF Likelihood of an equipment or component failure due to a single damage mechanism or multiple damage mechanisms occurring under specific operating conditions. 3.1.39 process monitoring Observing and tracking operating variables such that they are maintained within defined operating limits to minimize damage. 3.1.40 process unit A group of systems arranged in a specific fashion to produce a product or service. EXAMPLE Power generation, acid production, fuel oil production, and ethylene production. 3.1.41 qualified person A competent person who has met the knowledge and skill requirements and expectations of the owner-operator. 3.1.42 qualitative risk analysis A risk analysis using primarily subject matter expertise and experience to assign broad categorizations for POF and COF. 3.1.43 quantitative risk analysis QRA A risk analysis that uses primarily model-based methods where numerical values are calculated, and more discreet input data used. 3.1.44 reassessment The process of integrating inspection data or other changes into the risk analysis. 3.1.45 relative risk The comparative risk of a facility, process unit, system, equipment item, or component to other facilities, process units, systems, equipment items, or components, respectively. 3.1.46 residual risk The risk remaining after all specified risk management activities have been performed and/or implemented. Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Elements of a Risk-Based Inspection Program 9 3.1.47 risk A combination of the POF and COF associated with that failure. In some situations, risk is a deviation from the expected. When probability of failure and consequence of failure are expressed numerically, risk is the product. 3.1.48 risk acceptance A level of risk accepted by the owner-operator whether by pre-determined risk threshold or by appropriate approvals to operate with risk above threshold levels. 3.1.49 risk assessment risk analysis Systematic use of information to identify sources to estimate the risk, provide a basis for risk evaluation and develop inspection planning, risk mitigation, and risk acceptance. NOTE Information can include historical data, theoretical analysis, informed opinions, and concerns of stakeholders. 3.1.50 risk-based inspection RBI A risk assessment and management process that considers both the probability of failure and the consequence of failure due to material deterioration. 3.1.51 risk based management plan Prescriptive task(s) used to manage risk for fixed equipment. NOTE This could include, but is not limited to inspection, examination, replacement, process monitoring, material upgrade, and/or re-rating. 3.1.52 risk criteria Terms of reference by which the significance of risk is assessed. NOTE Includes associated cost and benefits, legal and statutory requirements, socio-economic and environmental aspects, concerns of stakeholders, priorities, and other inputs to the risk assessment. 3.1.53 risk driver The primary contributor(s) responsible for a significant share of the equipment’s or component’s risk value. 3.1.54 risk evaluation The process is used to compare the estimated risk against a risk criteria to determine the significance of the risk. 3.1.55 risk identification Process to find, list, and characterize factors of risk. NOTE Factors may include source, event, COF, and POF and/or stakeholder concerns. 3.1.56 risk management Coordinated activities to direct and control an organization with regard to risk. Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  10 API Recommended Practice 580 NOTE The coordinated activities may include risk evaluation, risk mitigation, risk acceptance, inspection planning, process monitoring and communication. 3.1.57 risk mitigation Process of selection and implementation of measures to modify risk. NOTE The term is sometimes used to refer to the measures themselves. 3.1.58 risk reduction Actions taken to lessen the POF, COF, or both associated with a particular risk. 3.1.59 risk threshold Criteria which depict acceptable versus unacceptable risk. 3.1.60 semi-quantitative A risk analysis using aspects of both--a qualitative and quantitative risk analysis. Calculations may be used but can be based on the input of subject matter experts. NOTE API Recommended Practice 581 is an example of a semi-quantitative risk analysis methodology. 3.1.61 service life The expected lifetime or the acceptable period during which an asset and/or component can safely and reliably perform within its intended operating envelope. 3.1.62 source Thing or activity with a potential for consequence. Source in a safety context is a hazard. 3.1.63 stakeholder Any individual, group or organization that may affect, be affected by, or perceive itself to be affected by the risk. 3.1.64 system A collection of equipment assembled for a specific function within a process unit. EXAMPLE Service water system, distillation systems, and separation systems. 3.1.65 toxic chemical Any chemical that presents a physical or health hazard or an environmental hazard according to the appropriate material safety datasheet. 3.1.66 turnaround A period of downtime to perform inspection, maintenance, or modifications and prepare process equipment for the next operating cycle. 3.1.67 unmitigated risk The risk prior to mitigation activities. Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Elements of a Risk-Based Inspection Program 11 3.1.68 user The individual that is readily applying the principles, recommendations, and requirements herein to establish and maintain an RBI Program. 3.2 Acronyms and Abbreviations ACC American Chemistry Council ALARP as low as reasonably practicable BLEVE boiling liquid expanding vapor explosion CCPS Center for Chemical Process Safety COF consequence of failure DMR damage mechanism review EPA environmental protection agency FMEA failure modes and effects analysis HAZOP hazard and operability assessment IOW integrity operating window LOPA layers of protection analysis MOC management of change MSD material selection diagrams NDE nondestructive examination OSHA occupational safety and health administration PASCC polythionic acid stress corrosion cracking PHA process hazards analysis PMI positive material identification POF probability of failure PSI process safety information PSM process safety management PVRC Pressure Vessel Research Council QA/QC quality assurance/quality control QRA quantitative risk assessment RBI risk-based inspection RCM reliability centered maintenance RMP risk management plan SIL safety integrity level UT ultrasonic testing 4 Risk Assessment Concepts 4.1 What is Risk? Risk is the product of the probability of an event occurring during a time period of interest (or POF) and the consequences (generally negative) associated with the event (or COF). Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  12 API Recommended Practice 580 In the context of this document, probability refers to the Probability of Failure (POF) and consequence refers to the Consequence of Failure (COF). In mathematical terms, risk can be calculated by the equation: ​Risk = Pr obability ⋅ Consequence​ Risk is assessed by identifying credible damage mechanisms, estimating the POF, assessing the COF, and identifying the risk drivers to enable development of effective risk management strategies. 4.2 Risk Management and Risk Reduction Once the risk is known and the magnitude of the risk is established, risk evaluation allows for the determination of whether or not risk reduction is needed or desired, and risk management provides methodologies to maintain risks at or below an acceptable level. Risk reduction is typically accomplished using mitigation, the results of inspection activities and/or process control. Mitigation efforts can reduce risk by changing the variable conditions used to evaluate risk. Examples of effective management strategies may include material upgrades to reduce or eliminate damage and reduce POF or process changes (which reduces COF). Inspecting an asset for a specific damage mechanism can further quantify the estimated or expected rate of deterioration. Since conservative values are often used during initial risk assessments, inspection typically better quantifies risk as the deterioration rate used for analysis is more representative of the actual rate. Process control can reduce risk by keeping the operation within the defined operating limits (e.g. IOW). Risk is reduced as compared with operating with upsets or instability. Modifications to the inspection plan can better ascertain the risk by improving the information used to establish the POF. For example, if the damage mode is localized metal loss, a mitigation plan may require the equipment operate at a reduced inventory to lower risk to an acceptable level until a thorough inspection could validate the equipment condition and allow any repairs to be made. IOWs could be used in the example above to define the operating limits required to maintain the risk of the equipment at an acceptable level. By using risk management, some risks may be identified as acceptable so that no risk reduction is required within ` the risk assessment timeframe. Further discussion about risk management can be found in Sections 12, 13, and 14. 4.3 Relative Risk vs Absolute Risk The complexity of risk assessment and its associated calculations is a function of the number of factors that can affect the risk. Absolute risk, which is an ideal and precise description and quantification of risk, is very time- consuming, and often cannot be done with a high degree of accuracy due to the uncertainty of associated inputs. Additionally, many variables are involved with loss of containment in hydrocarbon and chemical facilities and determining an accurate value for absolute risk is often not possible nor cost-effective. When the risk calculations and methodology are conducted similarly, the risk values of similar studies can be compared as they relate to similar items. This is considered ‘relative risk’. RBI is focused on a systematic determination of relative risk. In this way, RBI will allow facilities, process units, systems, equipment, or components to be comparatively ranked to other facilities, process units, systems, equipment, or components based on relative risk. This type of methodology forces a focus of the risk management efforts on the higher ranked risks and allows decisions to be made on the value of risk management efforts on lower ranked risks. Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Elements of a Risk-Based Inspection Program 13 5 Introduction to Risk-Based Inspection 5.1 The Evolution of Inspection Intervals and Due Dates In process plants, inspection and testing programs and process monitoring are established to detect and evaluate equipment deterioration due to the effects of in-service operation. The effectiveness of inspection programs varies widely, ranging from reactive programs, which concentrate on known areas of concern, to broad proactive programs covering a variety of equipment. One extreme of this would be the “don’t fix it unless it’s broken” approach. The other extreme is complete inspection of all equipment items on a frequent basis. Setting the intervals/due dates between inspections has evolved over time. With the need to periodically verify equipment integrity, organizations initially resorted to time-based or “calendar-based” intervals/due dates. With advances in inspection approaches, and better understanding of the type and rate of deterioration, inspection intervals/due dates became more dependent on the equipment condition (i.e. condition-based inspection), rather than what might have been an arbitrary calendar date. Codes and standards such as API 510, API 570, and API 653 evolved to an inspection philosophy with attributes such as: a) inspection intervals/due dates based on some percentage of equipment life (such as half-life calculations); b) on-stream inspection in lieu of internal inspection; c) internal inspection requirements for damage mechanisms related to process environment induced cracking; and d) consequence-based inspection intervals/due dates. RBI represents a methodology that combines the probability of a loss of containment event and the resulting consequence. This combination represents the risk to a facility due to loss of containment. This risk value is used in setting specific inspection approaches and due dates to help achieve safe and reliable operating facilities. RBI, as a risk-based approach, focuses attention specifically on the equipment and associated damage mechanisms representing the most risk to the facility. In focusing on risk and its mitigation, RBI provides a better linkage between the mechanisms that lead to equipment failure (loss of containment) and the inspection approaches that will effectively reduce the associated risks. There are many industry definitions for failure of pressure equipment, but in this document, failure is defined as loss of containment. 5.2 Consequence of Failure (COF) and Probability of Failure (POF) for RBI The objective of RBI is to determine what loss of containment incident could occur, and how likely the incident could occur. In determining the COF, the following are generally true: a) There may be one or more consequences from an event. b) Consequences are always negative for safety aspects. c) Consequences may be expressed qualitatively or quantitatively. For example, if a pressure vessel subject to a loss of containment event from corrosion under insulation develops a leak, a variety of consequences should be considered. Some of the examples of possible COF events to consider are as follows: 1) release of a flammable process fluid that could ignite, causing injury and equipment damage; 2) leak of a fluid with release to environment without escalation; Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  14 API Recommended Practice 580 3) release of a toxic chemical that could cause injury or long-term health problems; 4) release of a chemical that has an adverse economic impact; or, 5) release of a chemical as a minor leak of nonflammable or nontoxic fluid that triggers other minimal safety, health, environmental, and/or economic impacts. When determining the POF, the following are generally true: i) The mathematical definition of probability is “a real number in the scale 0 to 1 attached to a random event.” ii) Probability can be related to a long-run relative frequency of occurrence or to a degree of belief that an event will occur. iii) Degrees of belief about probability can be chosen as classes or ranks such as: — rare, unlikely, moderate, likely, almost certain, or — incredible, improbable, remote, occasional, probable, frequent. iv) Frequency rather than probability may be used in describing risk. v) Probabilities may be expressed qualitatively or quantitatively. Staying with the CUI example from above, some of the possible probabilities of failure (POF) are as follows: ` a) Low, medium, high, etc.; b) Occurs once every year in this facility; c) Occurs once every 10 years in this facility; d) Occurs 10 times every year in this facility. Loss of containment may occur relatively frequently without significant adverse safety, environmental, or economic impact. Similarly, other failures have potentially serious impact; but if the POF of the incident is low, the risk may not warrant immediate or extensive action. However, if the loss of containment risk is high enough to be unacceptable, then the determination of the appropriate action to reduce the POF (e.g. inspection activities and/or repairs) and/or the COF (e.g. design upgrades) of the event is appropriate. Understanding the two-dimensional aspect of risk provides insight into the use of risk for inspection prioritization and planning. POF and COF are plotted on an iso-risk plot or risk matrix to demonstrate the risk contribution. Figure 1 displays an example of the risk associated with the operation of several equipment items in a process plant. In the example, the POF and COF have been determined for 10 equipment items, and the results have been plotted in an iso-risk plot. The numbered points represent the risk associated with each equipment item. Figure 1 provides a basic visual guidance for a risk plot to demonstrate that: 1) Ordering by risk from high POF/high COF to low POF/low COF produces a risk-based ranking of the equipment items to be inspected. From this list, a risk-based management plan can be developed that focuses attention on the areas of highest risk. 2) An “ISO-risk” line is also depicted on Figure 1. An ISO-risk line represents a constant risk level, as shown across the iso-risk plot. Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Elements of a Risk-Based Inspection Program 15 i) All items that fall on or very near the ISO-risk line illustrates that all of the different combinations of POF and COF on that line are roughly equivalent in risk, even though the level of POF and COF can vary widely. ii) A user-defined acceptable risk level could be plotted as an ISO-risk line. In this way the acceptable risk line would separate the unacceptable from the acceptable risk items. 3) Due to the nature of the magnitude differences along each axis, a risk plot is often drawn using log-log scales for a better understanding of the relative risks of the items assessed. Figure 1—Risk Plot 5.3 Precision vs Accuracy An RBI assessment involves collecting data that is used to monitor changes in a company’s processes, so it is essential that the systems used for collecting and reporting measurements are valid and reliable. If the measurement system cannot be trusted, then the data that it produces cannot be trusted. RBI relies on data that can be trusted. To that end, the user needs to understand the difference between precision and accuracy when it comes to risk analysis. a) Accuracy—how close data measurements are to the “true” value (“the state of being correct”, a description of systematic errors, a measure of statistical bias). In RBI, accuracy is a function of the analysis methodology, the quality of the data, and consistency of application. b) Precision—how close measurements are to each other (“the state of being exact”, a description of random errors, a measure of statistical variability). In RBI, precision is a function of the selected metrics and computational methods. In other words, accuracy describes the difference between the measurement and the actual value, while precision describes the variation between repeated measurements using the same method or technique. The accuracy of any type of RBI analysis depends on using a sound methodology, quality data, and qualified personnel. Precision can be broken down further into two components: 1) Repeatability—the variation observed when the same operator measures the same part repeatedly with the same device. 2) Reproducibility—the variation observed when different operators measure the same part using the same device. Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris `  16 API Recommended Practice 580 Concerning precision in RBI data, the basis for predicted damage and rates, the level of confidence in inspection data, the technique used to perform the inspection are all factors that should be considered. For example, API Recommended Practice 581 is an example of a semi-quantitative RBI method that is highly reproduceable due to rigorous calculations. Conversely, a qualitative RBI method is less reproduceable due to the subjectivity introduced by expert opinion. Note Quantitative analysis uses logic models to calculate probabilities and consequences of failure. These logic models, which are used to characterize materials damage of equipment and to determine the COF, can have significant variability and therefore can introduce error and inaccuracy that impacts the quality of the risk assessment. Measurement systems can suffer from both accuracy and precision problems. The dart boards in Figure 2 help us visualize the difference between the two concepts: Figure 2—Accuracy vs Precision NOTE Risk presented as a precise numeric value (as in a quantitative analysis) implies a greater level of accuracy when compared with a risk matrix (as in a qualitative analysis). The procedure used to execute the RBI methodology can have significant impact on both accuracy and precision. If no procedure exists, the likely output for both semi-quantitative and qualitative RBI processes would be neither accurate nor precise. A detailed and complete procedure for a qualitative program will likely give an output that is accurate, but not precise. This is due to the amount of subject matter expert input into the program that could cause variance based upon the individual’s experience. A detailed and complete semi-quantitative procedure (e.g. API Recommended Practice 581 methodology) that does not check the data inputs into the program would give consistent results that are precise but may not be accurate. Examples of RBI inputs that can affect accuracy and precision are shown in Table 1. Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  Elements of a Risk-Based Inspection Program 17 Table 1—Example of RBI Inputs Example Impact on Accuracy Impact on Precision NDE use of radiography vs. straight Straight beam ultrasonics, from a The precision of radiography largely beam ultrasonics qualified technician, provides more depends on the procedure being accurate thickness results than used and the reproducibility of the radiography. inspection results executed by the same NDE technician. NDE use of radiography vs angle Depending on the type of flaw being Individual technician variance in beam ultrasonics detected the accuracy between these executing and interpreting the NDE two NDE techniques will differ e.g. results. radiography is better at detecting porosity vs. UT angle beam is better at detecting lack of side wall fusion. Use of NDE screening techniques Screening techniques for wall Usage of GUL at interval inspection thickness that detect volumetric vs. GUL fixed mounted sensor will corrosion wall losses, infer a wall impact the precision of NDE results. loss based upon estimated defect Five % vs 1 % making the fixed dimensions e.g. guided wave or PEC. mounted sensor more precise. Thus, screening techniques are not as accurate as direct measurement techniques. NDE technician to technician Qualification tests will determine how From a qualification test it can differences and qualification test accurate a technician is at detecting be determined if the technician flaws and anomalies as the test consistently over or under sizing flaws. have sizing limits a technician needs This data could be offset by a constant to remain within to obtain credit for to make the measurements more finding the flaw. accurate. Pressure and temperature sensors/ Having redundant sensors providing A pressure or temperature sensor gauges two readings for pressure and sending real time data provides more temperature. accurate real time data for analysis Calibration and maintenance of than operator rounds taking readings sensors maintains sensor/gauge from gauges. accuracy. Pressure and temperature sensors can drift over time providing either consistently higher or lower readings; thus, being highly precise, but not accurate. Process composition (e.g. weight/mole Accuracy largely will depend upon the Type of device being used to measure precents type of device being used to measure process contaminants can have process contaminants e.g. Draegor variation when measuring the same tubes vs. gas chromatograph for sample e.g. Draegor tubes vs gas measuring H2S. chromatograph for measuring H2S. Calibration of measurement devices also impacts accuracy. Examples of variables impacting accuracy of RBI assessment: 1) Competency of personnel supplying and validating the inputs causing poor data that will likely lead to inaccurate RBI results. 2) Process excursions potentially missing credible damage mechanisms as part of the RBI assessment. 3) Equipment Information: a) Materials of construction—improper identification of materials of construction (either through improper management of documents or documentation of repairs) can impact the selection of credible damage mechanisms. Copyright American Petroleum Institute Provided by Accuris unde license with API No reproduction or networking permitted without license from Accuris  18 API Recommended Practice 580 b) Correct damage mechanism assignment—poor process or competency of individuals executing damage mechanism assessment can impact the identification of credible damage mechanisms and thus, impact the accuracy of the ov