Which term refers to the amount of risk that is acceptable in risk management?
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Risk acceptance criteria are the limits above which an operator will not tolerate risk on the installation. These criteria must be defined for each type of risk to be assessed. Similar to the traditional pipeline RBI, the subsea equipment RBI quantifies risk from the aspects of Safety, environment, and economy. Most importantly, the safety level depends on product, manned condition, and location class. If the product is toxic or the location is in a sensitive area, then the safety class should be considered to be high. Show
The risk acceptance criteria are used to derive the time of inspection, which is carried out prior to the acceptance limit being breached. This would allow either the reassessment of the risk level based on better information, a detailed evaluation of any damage, or the timely repair or replacement of the degraded component. The acceptance criteria are defined for each of the different consequence categories. Acceptance criteria may be based on previous experience, design code requirements, national legislation, or risk analysis. The acceptance criteria for a function may be “broken down” into acceptance criteria for the performance of the individual items comprising the function. Generally, due to the quick reaction ability of extensive valves and sensors, the main risk is the economic loss of the subsea tree or manifold. For a pipeline and riser, however, safety, environmental, and economic risks should be considered. For each type of item and for each deterioration process, the acceptance criteria with regard to personnel risk, environmental impact, or economic risk may be represented by a risk matrix as illustrated in Figure 11.3.  Figure 11.3. Illustration of the Principle of Acceptance Criteria and Risk Matrix [2]. View chapterPurchase book Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780128126226000117 Risk Assessment MethodologyYong Bai, Wei-Liang Jin, in Marine Structural Design (Second Edition), 2016 38.3 Risk Acceptance Criteria38.3.1 GeneralHow safe is safe enough? Risk acceptance criterion defines the overall risk level that is considered acceptable, with respect to a defined activity period. The criteria are a reference for the evaluation of the need for risk reducing measures, and therefore need to be defined prior to initiating the risk analysis. Additionally, the risk acceptance criteria must reflect the safety objectives and the distinctive characteristics of the activity. The risk acceptance criteria may be defined in either qualitative or quantitative terms, depending on the expression for risk. The basis for their definition includes: •Governmental legislation applicable to the safety in the activity •Recognized industry standards for the activity •Knowledge of accidental events and their effects •Experience from now and past activities According to the purpose and the level of detail for the risk analysis, the acceptance criteria may be: •High-level criteria for quantitative studies •Risk matrices and the ALARP principle •Risk comparison criteria Fischhoff et al. (1981) identified and characterized various methods for the selection of risk acceptance criteria. They indicated that values, beliefs, and other factors all influence the selection of risk acceptance criteria. The complexity of defining risk acceptance criteria should be explicitly recognized, due to the uncertainty of their definition, lack of relevant facts, conflicting social values, and disagreements between technical experts and the public. The selection of risk acceptance criteria is subject to a rigorous critique, in terms of philosophical presuppositions, technical feasibility, political acceptability, and the validity of underlying assumptions made about human factors. 38.3.2 Risk MatricesThe arrangement of accident frequency and the corresponding consequences in a matrix (see Figure 38.3) may be a suitable expression of risk where many accidental events are involved or where single value calculations are difficult. The matrix is separated into three regions, including: Figure 38.3. Risk matrix. •Unacceptable risk •Acceptable risk •A region between acceptable and unacceptable risk, where evaluations have to be carried out in order to determine whether further risk reduction is required or whether more detailed studies should be conducted. The limits of acceptability are set by defining regions in the matrix, which represent unacceptable and acceptable risk. The risk matrix may be used for qualitative and quantitative studies. If frequency is classified in broader categories such as rare and frequent, and consequences are classified as small, medium, and catastrophic, the results from a qualitative study can be shown in the risk matrix. The definition of the categories is particularly important in the case of qualitative use. The categories and the boxes in the risk matrix can be replaced by continuous variables, implying a full quantification. An illustration of this is shown in Figure 38.4. Figure 38.4. Risk matrix in terms of continuous variables. The following are examples of situations where the use of a risk matrix is natural: •Evaluation of personnel risk for different solutions such as integrated versus separate quarters. •Evaluation of risk in relation to operations such as exploration drilling. •Evaluation of risk in relation to a particular system such as mechanical pipe handling. •Evaluation of environmental risk. 38.3.3 The ALARP PrincipleThe ALARP (“as low as reasonably practicable”; see Figure 38.5) principle is sometimes used in the oil and gas industry (UK HSE, 1992). The use of the ALARP principle may be interpreted as, satisfying a requirement to keep the risk level “as low as possible” provided that the ALARP evaluations are extensively documented. In the ALARP region (between “lower tolerable limit” and “upper tolerable limit”), the risk is tolerable, only if risk reduction is impracticable or if its cost is grossly disproportionate to the improvement gained. The common way to determine what is practicable is to use cost–benefit evaluations as a basis for the decision on whether certain risk reducing measures should be implemented. A risk may not be justified in any ordinary circumstance, if it is higher than the “upper tolerable limit.” The “upper tolerable limit” is usually defined, whereas the “lower tolerable limit” may sometimes be left undefined. This will not prohibit effective use of the approach, as it implies that ALARP evaluations of risk reducing measures will always be required. The ALARP principle used for risk acceptance is applicable to risks regarding personnel, the environment, and assets. Trbojevic (2002) illustrated the use of the ALARP principle for a design. Figure 38.5. The ALARP principle. 38.3.4 Comparison CriteriaThis type of criteria is suitable for more limited studies that aim at comparing certain concepts or solutions for a particular purpose with established or accepted practices. The criteria are suitable in relation to operations that are often repeated such as drilling and well interventions, heavy lift operations, and diving. The use of the comparison criteria requires that the basis of the comparison be expressed precisely. The formulation of the acceptance criterion in this context may be that the new solution cannot represent any increase in risk, in relation to current practices. Examples of comparison criteria are: •Alternative design (or use of new technology) for a fire water system can be at least as safe as conventional technology •The risk level for the environment cannot be higher than with the existing solution •Alternative solutions can be at least as cost-effective as the established practice This type of risk acceptance criteria is also suitable for risk regarding personnel, the environment, and assets. View chapterPurchase book Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780080999975000381 Probability of ship collision and groundingShengming Zhang, ... Richard Villavicencio, in Probability and Mechanics of Ship Collision and Grounding, 2019 1.1.2 Risk acceptance criteriaFor a rational reduction of risk related to hazards, such as ship collisions and grounding events, it is necessary to establish a risk acceptance criterion. Without a generally agreed acceptance criterion, it is not possible to find the balance between safety in terms of risk reduction and the cost to the stakeholders. Usually, risk acceptance criteria must be established for three main types of risks: •Fatalities •Pollution of the environment The loss of property or financial exposure The acceptance criteria for fatalities related to shipping accidents are normally based on two principles: •The individual fatality risk shall be approximately the same as typical for other occupational hazards. •The frequency of accidents with several fatalities, that is, the societal fatality risk, shall not exceed a level defined as unconditionally intolerable, and moreover, the general as low as reasonably practicable (ALARP) risk management shall be applied. Fig. 1.1 illustrates the principle of the ALARP criterion. Fig. 1.1. Typical risk acceptance criterion, F-N diagram. The latter criterion is introduced because society is often more concerned about single accidents with many fatalities than many accidents with few fatalities per accident. If the risk is estimated to be in the ‘intolerable’ region in Fig. 1.1, then the activity should not be allowed. For risks that are not in the negligible region, the general ALARP risk management shall be applied. That is, in principle for all nonnegligible risks, it is required that measures for risk reduction are to be identified and analysed and their societal value assessed. In this ALARP region, an economic criterion can be applied to consider the effectiveness of safety measures or risk control options; see Eq. (1.2). Similarly, ALARP criteria have been used by authorities to reduce accidental oil spills from tankers. Here, the cost for preventing an oil spill accident must be based on the cost of oil, the clean-up cost, the environmental damage cost, etc. Shipping and grounding accident costs are often dominated by clean-up costs due to oil spillage. Authorities like International Maritime Organization (IMO), International Association of Classification Societies (IACS), and national administrations normally focus on these types of risks one after the other. That is, so far, the ALARP principle has been applied separately for fatalities and for environmental impacts when considering new rules. The general economic costs associated with severe accidents have not been considered very often. With a significant percentage of all ships involved annually in a serious and costly accident, the economic loss will have a significant influence on the outcome of expressions such as Eq. (1.2). This indicates that it is often possible to introduce risk mitigation measures that can be cost-effective. One example is improved navigational safety measures that influence all three risk categories at the same time. Ideally, the additional cost of risk-reducing measures in the form of construction cost plus present value of operational costs is evaluated against the effect of the risk in the ALARP region. The condition for a decision to introduce risk-reducing measures could be. C where C is the cost of the considered risk-reducing measure X is the direct costs concerned with the accident I is the accumulated change of cost of all ‘individual’ user risks E is the quantified change in cost of ‘environmental’ impact D is the change in cost due to economic loss caused by ‘disruption’ where all costs are converted to present value costs. View chapterPurchase book Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780128150221000013 Pipeline Flow Risk AssessmentYong Bai, Qiang Bai, in Subsea Pipeline Integrity and Risk Management, 2014 Risk Acceptance CriteriaThe risk criteria define the level at which the risk can be considered acceptable or tolerable. During the process of making decisions, the criteria are used to determine if risks are acceptable, unacceptable, or need to be reduced to a reasonably practicable level. Numerical risk criteria are required for a quantitative risk assessment. As described previously, risk assessment involves uncertainties. It may not be suitable to use the risk criteria in an inflexible way. The application of numerical risk criteria may not always be appropriate because of the uncertainties of certain inputs. The risk criteria may be different for different individuals and also vary in different societies and alter with time, accident experience, and changing expectations of life. Therefore, the risk criteria are able to only assist with informed judgment and should be used as guidelines for the decision-making process [3]. In risk analysis, the risk acceptance criteria should be discussed and defined first. Three potential risk categories are proposed in DNV-RP-H101[2]: •Low. •Medium. •High. The categorization is based on an assessment of both consequence and probability, applying quantitative terms. The categories should be defined for the following aspects: •Personnel safety. •Environment. •Assets. •Reputation. A risk matrix is recommended for defining the risk acceptance criteria, a sample of which is presented in Table 14.2. Table 14.2. Sample Risk Matrix ConsequenceProbability (Increasing Probability →)DescriptivePersonnelEnvironmentAssetsReputationRemote (A) Occurred, UnlikelyUnlikely (B) Could OccurLikely (C) Easy to PostulateFrequent (D) Occurs Regularly1. ExtensiveFatalitiesGlobal or national effect Restoration time > 10 yrProject prod consequence costs > USD 10 millionInternational impact neg. exposureA1 = SB1 = SC1 = UD1 = U2. SevereMajor injuryRestoration time > 1y. Restoration cost > USD 1 millionProject prod consequence costs > USD 1 millionExtensive national impactA2 = AB2 = SC1 = SD2 = U3. ModerateMinor injuryRestoration time > 1 md. Restoration cost > USD 1K.Project prod consequence costs > USD 100KLimited national impactA3 = AB3 = AC3 =D3 = S4. MinorIllness or slight injuryRestoration time < 1 md Restoration cost < USD 1K.Project prod consequence costs < USD 1KLocal impactA4 = AB4 = AC4 = AD4 = S Source: DNV [2]. View chapterPurchase book Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780123944320000147 Risk-Based InspectionYong Bai, Qiang Bai, in Subsea Pipeline Integrity and Risk Management, 2014 3 Acceptance CriteriaIn RBI process, risk acceptance criteria need to be established previously to compare with the result of risk analysis to assist decision. The acceptance criteria are targets of risks reduction and help maintain the confidence in pipeline integrity. The acceptance criteria are developed by various regulatory bodies, design codes, and operators based on previous experience, design code requirements, national legislation, or risk analysis. Thus the acceptance criteria adopted is often dependent on the relevant authority and owner of the pipeline. In qualitative RBI progress, risk is commonly presented in a 5 × 5 matrix with PoF on the vertical axis and CoF on the horizontal axis as showed in Table 9.3. Risk matrices can graphically illustrate the progress of how the risk is evaluated and how the inspection priorities in the strategy are developed. The risk's reduction is also shown when effective measures have been taken to reduce the ranks of PoF or CoF. The risk matrix can be further broken down into individual matrices for safety, economic, and environmental risk, respectively as shown in Table 9.4. The acceptance criteria are generally expressed in terms of safety risk, economic risk, and environmental damage with respect safety. While in quantitative RBI process, all the chosen traditional criteria should be transformed to risk matrices and the most important thing is to design the risk limit of unacceptable risk area. Table 9.4. Risk Ranking Matrix (For color version of this table, the reader is referred to the online version of this book.) View chapterPurchase book Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780123944320000093 Risk Management ProcessBijan Elahi, in Safety Risk Management for Medical Devices (Second Edition), 2022 13.3.1 Criteria for Risk AcceptabilityAs described in Section 13.1.1, ISO 14971 [1] requires that a policy for establishing risk acceptance criteria be defined and documented. The policy could be applied to the entire range of a manufacturer’s medical devices, or be specialized for different groupings of the manufacturer’s medical devices. Similarly, the policy may be the same for individual and Overall Residual Risks, or be distinct. The manufacturer can take into account the applicable regulatory requirements in the regions where a medical device is to be marketed. To maintain objectivity, the criteria for risk acceptance should be established before starting the risk assessment and be documented in the RMP. For some hazards, harmonized or recognized international standards can provide specific safety requirements, and criteria to demonstrate compliance to the standard. The risks of these hazards are deemed acceptable for medical devices which satisfy the requirements and compliance criteria of the standards. The requirements of the standards (such as engineering or analytical processes, specific output limits, warning statements, or design specifications) can be considered Risk Control measures established by the standards writers that are intended to address the risks of specific Hazardous Situations. In many cases, the standards writers have performed and completed elements of risk management and provide manufacturers with solutions in the form of design requirements and test methods for establishing conformity. When performing risk management activities, manufacturers can take advantage of the work of the standards writers and need not repeat the analyses leading to the requirements of the standard. International standards, therefore, provide valuable information on risk acceptability that has been validated during a worldwide evaluation process, including multiple rounds of review, commenting, and voting. In the absence of an applicable harmonized or recognized international standard, depending on where the medical device is going to be marketed, it is also possible to apply a similar strategy which is specific to a geography. That is, it is possible that a particular country has an applicable national product safety standard. Therefore, compliance to that standard would establish acceptability of risk in that country. Evaluation of Overall Residual Risk comes after the evaluation of the individual risks. Depending on the policy of the manufacturer, the criteria for risk acceptability of Overall Residual Risk may, or may not, be the same as individual risks. In the BXM quantitative method, the Overall Residual Risk is a computed probability number which is compared against the maximum acceptable probability of Harm to determine acceptability. If quantitative methods are not used, an alternative method is to create a safety risk-profile for the device and compare it against a reference profile. An example risk profile could look like Fig. 14. The method to create this type of risk profile is as follows. Figure 14. Example Risk Profile. Use a Severity scale, such as Table 27, and a probability scale, such as Table 28. Determine the risk of Harm(s) for every Hazard. If your process uses a single Harm-Severity method, then R describes the probability of occurrence of the Harm in one class of Harm, e.g., Critical (rank 4). For all the Hazards of the System, count the number of risks that fall in each cell of the matrix in Fig. 14. Populate the matrix as in Fig. 14. This would be the risk profile for the device in question. Compare it against the reference profile to determine acceptability. The reference risk profile would be the profile of a comparable approved device on the market. If your device is a first-of-a-kind, you would engage a panel of experts to determine if the risk profile is acceptable when compared to the Benefits of the device. When your device gets regulatory approval, its risk profile would become the reference risk-profile for future products. Comparison of the risk profile of a new product with a reference risk profile is not so obvious. One way of comparison is to engage a panel of experts to give opinion as to whether the new profile is equal to, or better than the reference profile. A better way is to create an algorithm to objectively compare the new risk profile against the reference risk profile. For example, one possible algorithm is to assign a score to each risk profile which is the sum of the products of the entry in each cell of the matrix by its Severity and occurrence rankings. In other words: Score=∑(N×S×O)forallcells where: N=the entry in the cell S=the Severity ranking for that cell O=the occurrence ranking for that cell A lower score would be better than a higher score. This is an extremely simple algorithm. Consider using a more sophisticated algorithm. Another approach could be a policy statement such as: no red-zone risks, and no more than 1/3 of the risk could be in the yellow zone. View chapterPurchase book Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780323857550000138 Quantitative Risk Analysis Based RBIYong Bai, Qiang Bai, in Subsea Pipeline Integrity and Risk Management, 2014 3 Quantitative Risk Analysis Based RBI ProcessAs shown in Figure 12.2, the following steps are carried out for a quantitative risk analysis based RBI analysis [3]: FIGURE 12.2. QRBI Process. (For color version of this figure, the reader is referred to the online version of this book.) •Develop risk acceptance criteria. •Collection of information. •Determine pipeline segmentation. •Quantitative risk assessment for all sections. •Identify major degradation mechanisms and high-risk locations in the infant mortality phase. •Generating an inspection plan. •Use these as input into the inspection management system. Collection of InformationThe information mainly includes pipeline design data, operation data, pipeline alignments, and a corrosion study report. These data are used to determine the PoF and CoF, also to predicate the risk and establish an optimized inspection plan. Risk Acceptance CriteriaSimilar to the traditional RBI, the QRBI risk quantifies from the aspects of individuals, environment, and economy. The safety class depends on the product, personnel, and location class. If the product is toxic or the location is a sensitivity area, then the safety class should be taken as high. Figure 12.3 shows a quantitative risk acceptance, because the failure consequence is quantitative. Figure 12.4 shows a qualitative risk acceptance. FIGURE 12.3. Quantitative Risk Acceptance Criteria. (For color version of this figure, the reader is referred to the online version of this book.) FIGURE 12.4. Qualitative Risk Acceptance Criteria. (For color version of this figure, the reader is referred to the online version of this book.) Pipeline SegmentationPipeline segmentation is determined to save effort in analyzing inapplicable damage causes in some parts. A pipeline usually does not have a constant hazard potential over its entire length; as conditions along the line route change, so does the risk ranking, Thus, damage causes may be applicable for only some sections or components of a pipeline system. In QRBI assessment, each pipeline system should be divided into several components, as the following components address different damage causes and degradation mechanisms being encountered: •Riser above water. •Riser in splash zone; •Riser below water and pipeline in location class 2 (within 500 m of installation). •Pipeline in location class 1 (beyond 500 m of installation). •Pipeline approach the sensitive location, for example, park and city. •Pipeline passes the trawling zone. •Onshore part of pipeline. The detailed segmentation apply to the condition of individual pipeline. Quantitative Risk AssessmentIn the QRBI assessment, PoF and CoF are determined for different failure mechanisms in different sections of the pipeline system. The following degradation mechanisms are considered: •Internal corrosion. •External corrosion. •External impact(anchor, wreck, and trawler). •Material defect(material-weld defect and material-steel defect). PoF DeterminationThe PARLOC Database 2001 is considered the starting point in calculation of the PoF. In the PARLOC database, the failure rate is divided into three categories: lower bound, best estimated, and upper bound. Which category should be taken depends on the condition of the individual pipeline and the experience of engineer; for example if one section is not buried and is in the trawling zone, the upper bound of trawling PoF should be taken. Also the equivalent hole size for incidents to operating pipelines is divided into three categories: small (0–20 mm), medium (20–80 mm), and large (larger than 80 mm). So the failure rates should consider the equivalent hole to further reflect the probability of failure. Similarly, the failure rates of a pipeline in the riser, pipeline, and shore zone or sensitivity zone can be determined according to the PARLOC Database 2001. The preceding failure rates are statistic results deduced from the PARLOC database. However, note that individual pipelines may have quite different histories, properties, characteristics, and functions. Therefore, these values require further modification based on the special conditions of the oil export pipeline and the experience of the engineer. For example, in a concrete coating section where no impact comes from the external environment to the pipeline, the external impact can be neglected. In the PoF modification of degradation mechanisms, the details are as follows. Damage from external impact may arise from several causes, such as dropped objects, anchor impact, anchor dragging, trawling, boat impact to risers, or fish bombing. External impact is an event-based damage cause, the failure rate tends to vary with a changing environment, and the underlying mechanism is usually random and should exhibit a constant failure rate as long as the environment stays constant. So, to predicate the risk is very difficult. However, the following items can be calculated and used to predict the risk from the external impact: •Impact frequency from a dropped anchor (DNV GL 13). Impact frequency from trawling (DNV GL 13). •Probability of a direct dropped anchor impact calculation. •Dropped anchor impact assessment (DNV-RP-F107). •Trawler impact dent assessment (concrete coating and non-concrete). •Trawler impact frequency calculation. •Trawler pullover force calculation. In the PoF modification of internal corrosion, the following items should be considered: •Internal corrosion rate prediction. •Prevention strategies, water removal, and corrosion inhibition. Generally, in the infant mortality years for a pipeline, external corrosion is not a problem due to the cathodic protection and external coating. However, in the splash zone, the external corrosion is high, so this zone should be inspect frequently. In the PoF modification of external corrosion, the following items should be considered: •Coating system. •CP system. •External corrosion rate prediction. CoF DeterminationIn the QRBI assessment, the CoF is measured in terms of safety, environmental pollution, and business for gas pipelines and oil pipelines, respectively [4]. Safety consequences include individual and social consequences (Table 12.1). Table 12.1. The Safety Consequence Model ProductSafetyWith PersonnelOccasional PersonnelNo PersonnelGas, well fluidEDBGas, semi-processedECAGas, dryECAOil, well fluidDCBOil, semi-processedCBAOil, dryCBACondensate, well fluidEDBCondensate, semi-processedECACondensate, dryECATreated seawaterBAARaw seawaterBAAProduct waterBAA It is assumed that individual consequences are applicable to just riser and safety zone segments when considering the likelihood of people in the vicinity. Safety consequences for risers and safety zones may be considered to be similar to the topside failure consequences; however, their inventories may be much larger. These components are in close proximity to both human activity and potential ignition sources. Safety consequences are usually presented in terms of potential loss of life (PLL). The spill volume of oil and gas can be determined by the software of POSVCM and HGSYSTEM, respectively. Environmental consequences are concerned with the impact of various types of product release to the environment. The volume of oil spill dispersed in water can be modeled using the software Adios. Environmental pollution severity is determined by the oil spill volume dispersed in water and the local conditions, for example, the fishing resources. The environmental pollution ranking is determined by the recovery years of natural resources, which are decided by the recovery of local resource and local government effort. How to determine the pollution severity is illustrated in the “Quantitative Risk Assessment” subsection. Table 12.2 gives a qualitative environment consequence model. Table 12.2. The Environment Consequence Model ProductEnvironmentPipe sizeD < 8-in.D > 8-in.D > 16-in.D > 32-in.Gas, well fluidBBBCGas, semi-processedAAABGas, dryAAABOil, well fluidBCDEOil, semi-processedBCDEOil, dryBCDECondensate, well fluidBBCDCondensate, semi-processedBBCDCondensate, dryBBCDTreated seawaterAAAARaw seawaterAAAAProduct waterBBBC Economic consequences are concerned with repair costs and business loss due to interruption in production. The repair can be divided into two parts, consequence for leak and consequence for rupture. The repair consequences also depend on the location of the failure (e.g., above water, splash zone area, or underwater). Economic consequences due to business interruption or deferred production relate to the costs due to the shutdown of pipeline. An important factor to be considered is redundancy in the system, whereby production is maintained by using bypass lines. Table 12.3 gives a qualitative economy consequence model. Table 12.3. Economy Consequence Model ProductEconomyPipe sizeD < 8-in.D > 8-in.D > 16-in.D > 32-in.Gas, well fluidBCDEGas, semi-processedBCDEGas, dryBCDEOil, well fluidBCDEOil, semi-processedBCDEOil, dryBCDECondensate, well fluidCDEECondensate, semi-processedCDEECondensate, dryCDEETreated seawaterABCDRaw seawaterABCDProduct waterABCD High-Risk Locations and Major Failure MechanismsRisk is the product of PoF and CoF. In QRBI risk assessment, every section and every degradation mechanism of the pipeline system is determined to identify the major failure mechanisms and high-risk locations. Inspection PlanThe result from the QRBI assessment defines a proposed inspection plan for pipelines that are new or without inspection records. For the QRBI assessment, the major objective is to identify the main degradation of every pipeline section, so the inspection plan of QRBI gives recommendation for inspection scheduling, describing [5] •Which pipeline section is the high-risk location in infant years. •Which failure mechanism is major for different sections. •Which degradation mechanisms should be inspected first. View chapterPurchase book Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780123944320000123 Risk Assessment Applied to Offshore StructuresYong Bai, Wei-Liang Jin, in Marine Structural Design (Second Edition), 2016 40.6.1 GeneralA risk assessment may be conducted as part of the offshore field development and includes the following: •All critical elements are appropriately selected and the corresponding performance standards are adequately defined for the life cycle of the Floating Production Systems (FPS) in terms of its functionality, availability, structural integrity, survivability, dependency, and influence on the other critical elements. It is demonstrated that the critical elements fit for purpose and meet the performance standards. •Risk acceptance criteria are defined prior to the execution of the risk assessment, and provide a level of safety is equivalent to that defined in the prescriptive rules and codes. •All hazards with a potential to cause a major incident have been identified, their risks are evaluated and measures have been taken (or will be taken) to reduce the risk to the level that complies with the risk acceptance criteria. Types of risks for FPS depend on the type of vessel used and the geographical region where it is sited. FPSOs used in the North Sea are mainly new vessels with turret systems. The offloading tankers come to empty the storage tanks (approximately) once per week. Offloading tankers may represent a collision hazard to the FPSO with medium frequency and potentially high consequences. So far, FPSOs in the West African offshore region are mainly based on spread mooring systems and a single-point mooring for oil exports. FPSOs used in other geographical regions are mainly based on converted tankers. In the following, an FPSO for the Gulf of Mexico illustrates the methods of risk assessment. The methods illustrated in this section can also be applied to other types of floating production systems such as TLPs, SPARs, and semisubmersibles. A risk assessment of FPSOs may include an evaluation of the following systems: Process SystemsProcess systems include: •Process plant with three-stage separation, gas compression for export and gas turbine-driven power generation on deck •Piping, pressure vessels in production and storage facilities •Cargo tanks and crude pumping systems, offloading systems and its operation Process risk is mainly initiated by a hydrocarbon containment loss, which might escalate to explosions and/or fire accidents. The risk assessment for process systems can be conducted using a conventional offshore QRA approach (Wolford et al., 2001). •Development of isolatable sections •Summarize the loss of containment frequency by using a parts count approach •Identifying spatial interactions that could lead to escalation Leak frequencies may be derived primarily from generic databases that are available to offshore industries. Emergency detection and process control response to a loss of containment needs to be accounted for. API RP 14J (1993) has been used by the industry for the design and hazards analysis for facilities on offshore production installations. This RP mainly deals with the prevention of fire risk due to hydrocarbon ignition. Methodologies for hazard analysis are recommended. The API methodologies can be applied to assess explosion risk as well. Guidance is given for everything from risk management to platform equipment arrangement, hazard mitigation, and personnel evacuation. Detailed checklists are given in the appendix regarding the facility layout (and emergency response/medical, escape and rescue), process equipment, safety and electrical systems, fire and gas leakage protection, and mechanical systems, etc. Marine SystemsThe marine systems may include: •Cargo tanks, crude pump room, boilers and engine room, power generation/supply systems, ballast system and wing tanks, etc. •Escape and evacuation system and equipment The risk assessment of marine systems is similar to that for process systems. The exception is, the scope of the marine system’s risk is broader than the hydrocarbon containment loss. The majority of the marine system’s risk is fire due to fuel leakage and electrical systems. However, there is a lack of FPSO fire initiator frequency data for the appropriate quantification of fire risk. What is acceptable risk in risk management?Definition(s):
the level of Residual Risk that has been determined to be a reasonablelevel of potential loss/disruption for a specific IT system. (See Total Risk, Residual Risk, and Minimum Level of Protection.)
What is an acceptable amount of risk?Acceptable risk: That risk for which the probabil- ity of a hazard-related incident or exposure occur- ring and the severity of harm or damage that may result are as low as reasonably practicable (ALARP) and tolerable in the setting being con- sidered.
What is another term for risk acceptance?Risk acceptance is also known as risk retention. It is simply accepting the recognized risk without taking any measures to avoid loss or the probability of the risk happening. It includes a decision by management to accept a given risk without more mitigation or transfer, for a period of time.
Which term refers to the amount of risk that is acceptable in risk management * 1 point valid tolerance acceptance threshold?Risk tolerance is a measure of the level of risk an organization is willing to accept, expressed in either qualitative or quantitative terms and used as a key criterion when making risk-based decisions.
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