Api580 chapter 12 to 14

Charlie Chong/ Fion ZhangAPI 580

12 Risk Determination, Assessment and Management风险确定, 评估和管理


Contents

12 Risk Determination, Assessment, and Management 12.1 Purpose 12.2 Determination of Risk 12.3 Risk Management Decisions and Acceptable Levels of Risk 12.4 Sensitivity Analysis 12.5 Assumptions 12.6 Risk Presentation 12.7 Establishing Acceptable Risk Thresholds 12.8 Risk Management


12.1 Purpose 目的This section describes the process of determining risk by combining the results of work done as described in the previous two sections. It also provides guidelines for prioritizing and assessing the acceptability of risk with respect to risk criteria. This work process leads to creating and implementing a risk management plan. Risk should be determined by combining the POF (results of work done as described in Section 10) and the COF (results of the work done as described in Section 11). 此章节, 提供有关风险的优先次序的准则和评估风险的可接受性准则,这项工作过程导致建立和实施风险管理计划.

The general form of the risk equation should be as follows:风险方程的一般形式应该如下

Risk = Probability × Consequence 风险 = 概率 × 后果


12.2 Determination of Risk 风险的确定12.2.1 Determination of the Probability of a Specific Consequence测定特定后果的概率

Once the probabilities of failure and failure mode(s) have been determined for the relevant damage mechanisms (see Section 10), the probability of each credible consequence scenario should be determined. In other words, the loss of containment failure may only be the first event in a series of events that lead to a specific consequence. The probability of credible events leading up to the specific consequence should be factored into the probability of the specific consequence occurring.

可信的事件发生的概率,导致特定的”后果”(COF – specific scenario 特定的场景) 应考虑的具体(顺序进程) ”后果” 发生的概率(POF)


For example, after a loss of containment:例如, 溶液流失后

the first event may be initiation or failure of safeguards (isolation, alarms, etc.); 第一个事件可能引发或失败启动保护措施 (隔离, 警报, 等)

the second event may be dispersion, dilution or accumulation of the fluid; 第二个事件可能会是溶液的分散, 稀释或流体的积累

the third event may be initiation of or failure to initiate preventative action (shutting down nearby ignition sources, neutralizing the fluid, etc.);第三事件可以启动或启动失败的预防措施 (关闭附近的点火源, 中和液, 等)

and so on until the specific consequence event (fire, toxic release, injury, environmental release, etc.). 直到特定的后果事件发生(火灾, 有毒的释放, 损伤, 环境释放, 等)


It is important to understand this linkage between the POF and the probability of possible resulting incidents. The probability of a specific consequence is tied to the severity of the consequence and may differ considerably from the probability of the equipment failure itself. Probabilities of incidents (failure scenario) generally decrease with the severity of the incident. For example, the probability of an event resulting in a fatality will generally be less than the probability that the event will result in a first aid or medical treatment injury. It is important to understand this relationship.

认识, 设备故障概率 (POF) 和可能产生的事件的概率之间的联系是很重要. 一个特定的后果的概率与后果的严重程度和设备故障本身可能的概率大大不同.事件发生概率一般会随事件的严重程度, 减少.

事件发生概率设备故障概率


Personnel inexperienced in risk assessment methods often link the POF with the most severe consequences that can be envisioned. An extreme example would be coupling the POF of a damage mechanism where the mode of failure is a small hole leak with the consequence of a major fire. This linkage would lead to an overly conservative risk assessment since a small leak will rarely lead to a major fire. Each type of damage mechanism has its own characteristic failure mode(s). For a specific damage mechanism, the expected mode of failure should be taken into account when considering the probability of incidents in the aftermath of an equipment failure. For instance, the consequences expected from a small leak could be very different than the consequences expected from a brittle fracture.

每种类型的损伤机理有其自身失效模式特点. 缺乏风险评估方法经验的人员往往会错误的关联失效模式与损伤机理. 比如点蚀导致小孔泄漏, 错误的关联到重大火灾事件.


The example in Figure 5 serves to illustrate how the probability of a specific consequence could be determined. The example has been simplified and the numbers used are purely hypothetical. 说明一个特定的后果的概率的确定方法(简化和使用的数字是纯粹的假设)

Figu

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Figure 6—Example of Calculating the Probability of a Specific Consequence

EXAMPLE: An equipment item containing a flammable fluid is being assessed.

EXAMPLE: An equipment item containing a flammable fluid is being assessed.

The probability of a specific consequence should be the product of the probability of each event that could result in the specific consequence. In this example, the specific consequence being evaluated is a fire (an example event tree starting with a loss of containment is shown below). The probability of a fire would be:

Probability of Fire = (Probability of Failure) × (Probability of Ignition)Probability of Fire = 0.001 per year × 0.01 = 0.00001 or 1 × 10-5 per year

The probability of no fire encompasses two scenarios (loss of containment without ignition and no loss of containment). The probability of no fire would be:

Probability of No Fire = (Probability of Failure × Probability of Non-ignition) + Probability of No FailureProbability of No Fire = (0.001 per year × 0.99) + 0.999 per year = 0.99999 per year

NOTE The probability of all consequence scenarios should equal 1.0. In the example, the probability of the specific consequence of a fire (1 × 10-5 per year) plus the probability of no fire (0.999999 per year) equals 1.0.

If the consequence of a fire had been assessed at $1 × 107 then the resulting risk would be:

Risk of Fire = (1 × 10-5 per year) × ($1 × 107) = $100/year


Figure 6—Example of Calculating the Probability of a Specific Consequence


NOTE The overall risk must include the probability of loss of containment. For example, if the probability of loss of containment is 0.1, the overall risk above is 0.1 × $100/year = $10/year.


Typically, there will be other credible consequences that should be evaluated. However, it is often possible to determine a dominant probability / consequence pair, such that it is not necessary to include every credible scenario in the analysis. Engineering judgment and experience should be used to eliminate trivial cases.通常情况下, 会有很多其他可信的概率/后果组合,但是分析时,只需要选择较为显著的概率/后果组合. 真确的工程判断和经验应该用来消除微不足道的概率/后果组合.


12.2.2 Calculate Risk 计算风险Referring back to the risk equation:

Risk = Probability × Consequence

It is now possible to calculate the risk for each specific consequence. The risk equation can now be stated as:

Risk of a Specific Consequence = (Probability of a Specific Consequence) × (Specific Consequence)

The total risk is the sum of the individual risks for each specific consequence. Often one probability/consequence pair will be dominant and the total risk can be approximated by the risk of the dominant scenario. For the example mentioned in 12.2.1, if the consequence of a fire had been assessed at $1 ×107 then the resulting risk would be:

Risk of Fire = (1 × 10–5 per year) × ($1 × 107) = $100/yearOverall risk?


If probability and consequence are not expressed as numerical values, risk is usually determined by plotting the probability and consequence on a risk matrix (see 12.6). Probability and consequence pairs for various scenarios may be plotted to determine risk of each scenario. Note that when a risk matrix is used, the probability to be plotted should be the probability of the associated consequence, not the POF. Also note that the overall risk must include the probability of loss of containment. For example, if the probability of loss of containment is 0.1, the overall risk above is 0.1 × $100/year = $10/year. 使用风险矩阵, 要绘制的概率应该是相关情景的结果的概率而不是故障概率. 总体风险 = 情景风险 x 溶液流失概率

Note that when a risk matrix is used, the probability to be plotted should be the probability of the associated consequence, not the POF.


Prob

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Consequence of failureIncrease severity


12.3 Risk Management Decisions and Acceptable Levels of Risk风险管理决策和可接受的风险水平

12.3.1 Risk Acceptance 接受风险Risk-based inspection is a tool to provide an analysis of the risks of loss of containment of equipment. Many companies have corporate risk criteria defining acceptable and prudent 谨慎 levels of safety, environmental and financial risks. These risk criteria should be used when making risk-based inspection decisions. Because each company may be different in terms of acceptable risk levels, risk management decisions can vary among companies.

可接受的风险水平, 风险管理决策是以不同公司需要而别.


Cost-benefit analysis is a powerful tool that is being used by many companies, governments and regulatory authorities as one method in determining risk acceptance. Users are referred to “A Comparison of Criteria for Acceptance of Risk” by the Pressure Vessel Research Council (PVRC), for more information on risk acceptance. Risk acceptance may vary for different risks. For example, risk tolerance for an environmental risk may be higher than for a safety/health risk.

成本效益分析是一个用于风险管理, 功能强大的工具, 此分析笨被很多企业,政府和监管部门作为确定可接受的风险的方法.

“A Comparison of Criteria for Acceptance of Risk” by the Pressure Vessel Research Council (PVRC)

压力容器研究委员会出版的 “风险标准接受的比较” 是个很好的参考文件.

http://foreng1.securesites.net/pvrc/index.html


12.3.2 Using Risk Assessment in Inspection and Maintenance Planning运用风险评估于检查和维修计划

The use of risk assessment in inspection and maintenance planning is unique in that consequence information, which is traditionally operations-based, and POF information, which is typically engineering/maintenance/inspection-based,is combined to assist in the planning process. Part of this planning process is the determination of (1) what to inspect, (2) how to inspect (technique), (3) where to inspect (location), and (4) how much to inspect (coverage).

Determining the risk of process units, or individual process equipment items facilitates this, as the inspections are now prioritized based on the risk value. The second part of this process is determining when to inspect the equipment. Understanding how risk varies with time facilitates this part of the process. Refer to Section 13 for a more detailed description of inspection planning based on risk analysis.

传统的检验与维修方案: 故障结果被操作阶段注重, 失效概率被工程/维修/检验阶段注重. 然而 RBI 综合故障结果/失效概率, 开发更为有益的检验维修计划.


Typically:Consequence information - operations-based, POF - engineering/maintenance/inspection-based,

RBI Approach:Risk – Combined COF/POF into one for inspection and maintenance planning


12.4 Sensitivity Analysis 敏感性分析

Understanding the value of each variable and how it influences the risk calculation is key to identifying which input variables deserve closer scrutiny versus other variables which may not have significant effects. This is more important when performing risk analyses that are more detailed and quantitative in nature.

Sensitivity analysis typically involves reviewing some or all input variables to the risk calculation to determine the overall influence on the resultant risk value. Once this analysis has been performed, the user can see which input variables significantly influence the risk value. Those key input variables deserve the most focus or attention.

分析与筛选, 显著影响风险的输入变量值. 这些关键输入变量作为值得关注或焦点.


It often is worthwhile to gather additional information on such variables. Typically, the preliminary estimates of probability and consequence may be too conservative or too pessimistic; therefore, the information gathering performed after the sensitivity analysis should be focused on developing more certainty for the key input variables. This process should ultimately lead to a re-evaluation of the key input variables. As such, the quality and accuracy of the risk analysis should improve. This is an important part of the data validation phase of risk assessment.

为了避免过于开放或保守的风险分析结构, 对关键变量值的真确性质是非常重要的. 对这些变量值进行敏感度分析能更加保证风险数据的质量与准确度.


12.5 Assumptions 假定

Assumptions or estimates of input values are often used when consequence and/or POF data are not available. Even when data are known to exist, conservative estimates may be utilized in an initial analysis pending input of future process or engineering modeling information, such as a sensitivity analysis.

Caution is advised in being too conservative, as overestimating consequences and/or POF values will unnecessarily inflate the calculated risk values. Presenting over inflated risk values may mislead inspection planners, management and insurers, and can create a lack of credibility for the user and the RBI process. Appropriate members of the RBI team as outlined in Section 16 should agree on the assumptions made for RBI analysis and the potential impacts on the risk results.

在缺乏可信的输入值时, 一般上较为保守的变量值将会运用, 然而过于保守的变量值输入导致风险膨胀. 这不必要的膨胀给用户, 管理层, 检验策划者, 偷保险者误导, 也同时让 RBI 的可信/诚信度降低.


在缺乏可信的输入值时, 一般上较为保守的变量值将会被运用, 然而过于保守的变量值输入导致风险膨胀. 这不必要的膨胀给用户, 管理层, 检验策划者, 保险投保者误导, 也同时让 RBI 的可信/诚信度降低.


12.6 Risk Presentation 风险表达12.6.1 General 总则

Once risk values are developed, they can then be presented in a variety of ways to communicate the results of the analysis to decision-makers and inspection planners. One goal of the risk analysis is to communicate the results in a common format that a variety of people can understand. Using a risk matrix or plot is helpful in accomplishing this goal.

把分析到的风险数据, 运用风险矩阵或绘图来表达是被接受的有效方法.


12.6.2 Risk Matrix 风险矩阵

For risk ranking methodologies that use consequence and probability categories, presenting the results in a risk matrix is a very effective way of communicating the distribution of risks throughout a plant or process unit without numerical values. An example risk matrix is shown in Figure 7. In this figure, the consequence and probability categories are arranged such that the highest risk ranking is toward the upper right-hand corner.

It is usually desirable to associate numerical values with the categories to provide guidance to the personnel performing the assessment(e.g. probability category C ranges from 0.001 to 0.01). Different sizes of matrices may be used (e.g. 5 × 5, 4 × 4, etc.). Regardless of the matrix selected, the consequence and probability categories should provide sufficient discrimination (辨别力) between the items assessed.

运用风险矩阵作为表达风险, 是有效的沟通方式. 这样的方式不带数值的单位. 然而对进行评估提供指导, 对每个风险类别一般上都关联相应的数值.


Risk categories may be assigned to the boxes on the risk matrix. An example risk categorization (higher, medium, lower) of the risk matrix is shown in Figure 7. In this example, the risk categories are symmetrical. They may also be asymmetrical where for instance the consequence category may be given higher weighting than the probability category. A risk matrix depicts results at a particular point in time.

Figure 7—Example Risk Matrix Using Probability and Consequence Categories to Display Risk Rankings


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Consequence of failureIncrease severity


12.6.3 Risk Plots 风险绘图

When more quantitative consequence and probability data are being used, and where showing numeric risk values is more meaningful to the stakeholders, a risk plot (or graph) is used (see Figure 7). This graph is constructed similarly to the risk matrix in that the highest risk is plotted toward the upper right-hand corner. Often a risk plot is drawn using log-log scales for a better understanding of the relative risks of the items assessed. In the example plot in Figure 8, ten (10) pieces of equipment are shown, as well as an iso-risk line (line of constant risk). If this line is the acceptable threshold of risk in this example, then equipment items 1, 2, and 3 should be mitigated so that their resultant risk levels fall below the line.


Figure 7—Example Risk Matrix Using Probability and Consequence Categories to Display Risk Rankings


Figure 8—Risk Plot when Using Quantitative or Numeric Risk Values

Item no. 2

Line of constant risk – acceptable level


12.6.4 Using a Risk Plot or Matrix 使用风险绘图或矩阵

Equipment items residing towards the upper right-hand corner of the plot or matrix (in the examples presented) will most likely take priority for inspection planning because these items have the highest risk. Similarly, items residing toward the lower left-hand corner of the plot (or matrix) will tend to take lower priority because these items have the lowest risk. Once the plots have been completed, the risk plot (or matrix) can then be used as a screening tool duringthe prioritization process.

分析完成后的风险绘图(或矩阵)可以用为筛选优先次序的工具


Risk may be described in terms of dollars or other numerical values as described in 10.2 even if a qualitative analysis has been performed, and the results have been plotted on a risk matrix. Numerical values associated with each of the probability and consequence categories on the risk matrix may be used to calculate the risk. For cost related risk, a net present value savings vs inspection time plot may be used to time the inspection activities.

不管是定性或定量分析,风险可能以美元或其它的数值来描述. 牵涉,成本相关的风险, 净现值的节约与检查时间绘图, 可以用来决定检验活动的时间额.


12.7 Establishing Acceptable Risk Thresholds 建立可接受的风险临界

After the risk analysis has been performed, and risk values plotted, the risk evaluation process begins. Risk plots and matrices can be used to screen, and initially identify higher, intermediate and lower risk equipment items. The equipment can also be ranked (prioritized) according to its risk value in tabular form. Thresholds that divide the risk plot, matrix or table into acceptable and unacceptable regions of risk can be developed.

Corporate safety and financial policies and constraints or risk criteria influence the placement of the thresholds. Regulations and laws may also specify or assist in identifying the acceptable risk thresholds. Reduction of some risks to a lower level may not be practical due to technology and cost constraints. An “as low as reasonably practical” (ALARP) approach to risk management or other risk management approach may be necessary for these items.

企业安全, 金融政策, 约束或风险指标的影响临界线的位置. 一些设备, 把风险降低到较低到可接受水平, 可能由于技术或成本的约束是不实际的, 这时, “ 低合理可行的” (ALARP) 风险管理或其他风险管理方法可以用来处理这些设备.


Reduction of some risks to a lower level may not be practical due to technology and cost constraints. An “as low as reasonably practical” (ALARP) approach to risk management or other risk management approach may be necessary for these items.

一些设备, 把风险降低到较低到可接受水平, 可能由于技术或成本的约束是不实际的, 这时, “ 低合理可行的” (ALARP) 风险管理或其他风险管理方法可以用来处理这些设备.


http://www.hse.gov.uk/risk/theory/alarp.htm


http://www.hse.gov.uk/risk/theory/alarp.htm

ALARP Suite of Guidance

With these six pieces of guidance HSE is addressing its own staff, explaining the concept 'reasonably practicable' and providing guidance about what they should expect to see in dutyholders demonstrations that the risk has been reduced ‘as low as reasonably practicable’(ALARP).

Assessing compliance with the law in individual cases and the use of good practice

Policy and guidance on reducing risks as low as reasonably practicable in Design

Principles and guidelines to assist HSE in its judgements that duty-holders have reduced risk as low as reasonably practicable

HSE principles for Cost Benefit Analysis (CBA) in support of ALARP decisions

Cost Benefit Analysis (CBA) Checklist ALARP "at a glance"


12.8 Risk Management 风险管理

Based on the ranking of items and the risk threshold, the risk management process begins. For risks that are judged acceptable, no mitigation may be required and no further action necessary. For risks considered unacceptable and therefore requiring risk mitigation, there are various mitigation categories that should be considered.

被认为是不可接受的风险,缓解类别有

a) Decommission - Is the equipment really necessary to support unit operation?使退役(冗余设备).

b) Inspection/ Condition Monitoring - Can a cost-effective inspection program, with repair as indicated by the inspection results, be implemented that will reduce risks to an acceptable level? 经济有效的检查计划与由检验结果标出维修项.

Probability Mitigation- with repair as indicated by the inspection results?


c) Consequence Mitigation - Can actions be taken to lessen the consequences related to an equipment failure? 后果缓解

d) Probability Mitigation - Can actions be taken to lessen the POF such as metallurgy changes or equipment redesign? 故障概率缓解

Risk management decisions can now be made on which mitigation actions to take. Risk management/mitigation is covered further in Section 13 and Section 14.


13 Risk Management with Inspection Activities检查活动的风险管理


Contents

13 Risk Management with Inspection Activities 13.1 Managing Risk by Reducing Uncertainty Through Inspection 13.2 Identifying Risk Management Opportunities from RBI Results 13.3 Establishing an Inspection Strategy Based on Risk Assessment 13.4 Managing Risk with Inspection Activities 13.5 Managing Inspection Costs with RBI 13.6 Assessing Inspection Results and Determining Corrective Action 13.7 Achieving Lowest Life Cycle Costs with RBI


13.1 Managing Risk by Reducing Uncertainty Through Inspection管理风险, 通过检查减少不确定性

In previous sections, it has been mentioned that risk can be managed by inspection. Obviously, inspection does not arrest or mitigate damage mechanisms or in and of itself it does not reduce risk, but the information gained though effective inspection can better quantify the actual risk. Impending failure of pressure equipment is not avoided by inspection activities unless the inspection precipitates risk mitigation activities that change the POF. Inspection serves to identify, monitor, and measure the damage mechanism(s).

Also, it is invaluable input in the prediction of when the damage will reach a critical point. Correct application of inspections will improve the user‘s ability to predict the damage mechanisms and rates of deterioration. The better the predictability, the less uncertainty there will be as to when a failure may occur.


Mitigation (repair, replacement, changes, etc.) can then be planned and implemented prior to the predicted failure date. The reduction in uncertainty and increase in predictability through inspection translate directly into a better estimate of the probability of a failure and therefore a reduction in the calculated risk. However, users should be diligent to assure that temporary inspection alternatives, in lieu of more permanent risk reductions, are actually effective.

检验不能直接的降低风险. 然而检验可以确定, 监测并测量损伤机理(损坏率) 来提供有

用的信息,通过准确估计失效的概率更好的量化实际风险. 从而降低计算风险.


http://www.dnv.com/services/software/training/synergicourses/sy12

_onshore_rbi_dnv_api_581_may_rotterdam.asp


检验不能直接的降低风险. 然而检验可以确定, 监测并测量损伤机理(损坏率) 来提供有用的信息,通过准确估计失效的概率 (POF) 更好的量化实际风险 (RISK). 从而降低计算风险.


The foregoing does not imply that risk-based inspection plans and activities are always the answer to monitoring degradation and therefore reducing risks associated with pressure equipment. Some damage mechanisms are very difficult or impossible to monitor with just inspection activities (e.g. metallurgical deterioration that may result in brittle fracture, many forms of stress corrosion cracking, and even fatigue).


Other damage mechanisms precipitated by short-term, event-driven operatingchanges can happen too fast to be monitored with normal inspection plans, be they;

(1) risk-based, (2) condition-based or (3) time-based.

Hence the need for a establishing and implementing

(A) comprehensive program for IOW, along with (B) adequate communications to inspection personnel when deviations

occur and a (C) rigorous MOC program for changes from the established parameters.

检验的限制有; 有的损伤机理很难或不能被检验探测到(比如; 冶金损伤, 很多的应力腐蚀开裂等). 有的, 由于短期的,操作变化事件驱动的损伤模式, 可能发生太快不在正常的检验计划所能监控范围. 基于上述理由,建立和实施一个全面的IOW计划, 适当的信息沟通和变革管理师很有必要的.


happen too fast to be monitored with normal inspection plans


http://www.sv.vt.edu/classes/MSE2094_NoteBook/97ClassProj/anal/kelly/fatigue.html

Some damage mechanisms are very difficult or impossible to monitor with just inspection activities


Some damage mechanisms are very difficult or impossible to monitor with just inspection activities


OPERATING WINDOW

Hence the need for a establishing and implementing a comprehensive program for IOWs, along with adequate communications to inspection personnel when deviations occur and a rigorous MOC program for changes from the established parameters.


Risk mitigation (by the reduction in uncertainty) achieved through inspectionpresumes that the organization will act on the results of the inspection in a timely manner. Risk mitigation is not achieved if inspection data that are gathered are not properly analyzed and acted upon where needed. The quality of the inspection data and the analysis or interpretation will greatly affect the level of risk mitigation. Proper inspection methods and data analysis tools aretherefore critical. 通过检验, 风险缓解 (通过减少不确定性), 假定管理层对检验结果采取及时的措施. 选用适当的检验方法与资料分析是检验资料的关键点.


a) equipment type; 设备种类b) active and credible damage mechanism(s); 活跃和可靠的损伤机制c) rate of deterioration or susceptibility; 恶化率或敏感率d) inspection methods, coverage and frequency; 检查方法,频率和覆盖

13.2 Identifying Risk Management Opportunities from RBI Results 确定风险管理的机会

As discussed in Section 12, typically a risk priority list is developed as a result of the RBI process. RBI will also identify whether consequence or POF or both is driving risk. In the situations where risk is being driven by POF, there is usually potential for risk management through inspection. Once an RBI assessment has been completed, the items with higher or unacceptable risk should be assessed for potential risk management through inspection, or other risk management strategies. Whether inspections will be effective or not will depend on:

确定操纵风险关键因素: 故障结果或POF? 当风险分析完成后, 高或不可接受风险应评估风险管理所需要的方法. 一般上, POF 使用检验方法降低, 故障结果COF 运用其他风险管理策略. 检验的有效性取决于;


e) accessibility to expected damage areas; 损害的区域可达性f) shutdown requirements; 停机要求g) amount of achievable reduction in POF (i.e. a reduction in POF of a low POF

item is usually difficult to achieve through inspection). 对故障概率的降低效果 (低故障概率的设备一般上对检验带来的益处不多)


active and credible damage mechanism(s); 活跃和可靠的损伤机制rate of deterioration or susceptibility; 恶化率或敏感率

PTASCC – Polythionic acid stress corrosion cracking


accessibility to expected damage areas; 损害的区域可达性shutdown requirements; 停机要求


accessibility to expected damage areas; 损害的区域可达性


accessibility to expected damage areas; 损害的区域可达性shutdown requirements; 停机要求


POF为风险关键因素: 使用

检验方法降低

COF为风险关键因素: 运用其他风险管理策略


Inspection Limitations


Depending on factors such as the remaining life of the equipment and type of damage mechanism, risk management through inspection may have little or no effect. Examples of such cases are: 根据设备损伤机理类型或设备剩余寿命的因素, 有的时候运用检验作为风险管理不能带来任何或很小的效果. 以下为例子;

a) corrosion rates well-established with equipment nearing end of life, 设备的腐蚀速率准确的预测设备接近设备剩余寿命.

b) instantaneous failures related to operating conditions such as brittle fracture, 快速脆裂损伤机理

c) inspection technology that is not sufficient to detect or quantify deterioration adequately, 检验工艺的限制或可探能力

d) too short a time frame from the onset of deterioration to final failure for periodic inspections to be effective (e.g. high-cycle fatigue cracking), 牵涉到快速导致失效模式的损伤机理 (比如, 高频率疲劳)

e) event-driven failures (circumstances that cannot be predicted), 事件驱动的故障 (不可预测的事件-操作失误/ 人为破坏等)


In cases such as these, an alternative form of mitigation may be required. The most practical and cost effective risk mitigation strategy can then be developed for each item. Usually, inspection provides a major part of the overall risk management strategy, but not always.

在上述的情况下, 其他风险管理策略应开发与执行.


corrosion rates well-established with equipment nearing end of life, 设备的腐蚀速率准确的预测设备接近设备剩余寿命


检验工艺的限制或可探能力

event-driven failures (circumstances that cannot be predicted), 事件驱动的故障 (不可预测的事件-操作失误/ 人为破坏等)


检验工艺的限制或可探能力


检验工艺的限制或可探能力检验工艺的限制或可探能力


13.3 Establishing an Inspection Strategy Based on Risk Assessment建立基于风险评估的检测策略

The results of an RBI assessment and the resultant risk management assessment are normally used as the basis for the development of an overall inspection strategy for the group of items included. The inspection strategy should be designed in conjunction with other mitigation plans so that all equipment items will have resultant risks that are acceptable. For the development of their inspection strategy, users should consider the following:

RBI分析带来的风险管理评估用于全面检查策略开发的基础, 应与其它非检验缓解计划共同设计, 检验策略开发考虑项有

risk criteria and ranking,风险准据和排名 risk drivers, 风险因素(POF或COF主导) item history,设备历史 number and results of inspections,检查数量和结果 type and effectiveness of inspections,检查类型和有效性 equipment in similar service and remaining life. 类似服务的设备和剩余寿命


Inspection is only effective if the examination technique chosen is sufficient for detecting the damage mechanism and its severity. As an example, spot thickness readings on a piping circuit would be considered to have little or no benefit if the damage mechanism results in unpredictable localized corrosion (e.g. pitting, ammonia bisulfide corrosion, local thin area, etc.). In this case, ultrasonic scanning, radiography, etc. will be more effective. The level of risk reduction achieved by inspection will depend on:

选用真确的检验方法是很重要的, 比如点蚀管线上用测厚仪抽检,并不能有效的检验方法, 在此情况, 应当选用超声或射线探伤. 通过检验减少风险水平将取决于

a. mode of failure of the damage mechanism, 损伤机理和失效模式b. time interval between the onset of deterioration and failure (i.e. speed of

deterioration), 开始退化至失效之间的时间间隔c. detection capability of examination technique, 检查技术检测能力d. scope of inspection, 检验范围e. frequency of inspection. 检验频率


Organizations should be deliberate and systematic in assigning the level of risk management achieved through inspection and should be cautious not to assume that there is an unending capacity for risk management through inspection. The inspection strategy should be a documented, iterative process to assure that inspection activities are continually focused on items with higher risk.

管理层,被提醒检验的可探性限制.在策划检验计划时,应记录与从迭代过程中,选择佳的检测方法. 优先专注高风险的项目风险缓解.


13.4 Managing Risk with Inspection Activities 通过检验活动管理风险

The effectiveness of past inspections is part of the determination of the present risk. The future risk can now be influenced by future inspection activities. RBI can be used as a “what if” tool to determine when, what and how inspections should be conducted to yield an acceptable future risk level. Key parameters and examples that can affect the future risk are as follows.

过去的检查的有效性是确定当前风险的一部分. 往后的风险指望于后续的检验活动. 评估过去的检验有效性作为改进后续的检验活动,有助于降低风险. 检验活动影响风险的关键参数/例子有

a) Frequency of Inspection—Increasing the frequency of inspections may serve to better define, identify or monitor the damage mechanism(s) and therefore better quantify the risk. Both routine and turnaround inspection frequencies can be optimized. 检验频率, 增加频率能更加的对损坏机理的认识与评估,因此更好地量化风险.常规和周转检验频率可以被优化.


b) Coverage - Different zones or areas of inspection of an item or series of items can be modeled and evaluated to determine the coverage that will produce an acceptable level of risk. For example: 覆盖范围 ; 设备可以分区, 位置建模进行执行检验工作.

a higher risk piping system may be a candidate for more extensive inspection, using one or more NDE techniques targeted to locating the identified damage mechanisms; 对风险高的管线系统进行较多的检验投入(聚焦)

an assessment may reveal the need for focus on parts of a vessel where the highest risk may be located and focus on quantifying this risk rather than focusing on the rest of the vessel where there are perhaps only low risk deterioration processes occurring. 对风险较高的容器设备的位置/区域进行较多的检验投入(聚焦)


c) Tools and Techniques - The selection and usage of the appropriate inspection tools and techniques can be optimized to cost effectively and safely quantify the POF. In the selection of inspection tools and techniques, inspection personnel should take into consideration that more than one technology may achieve risk mitigation. However, the level of mitigation achieved can vary depending on the choice. As an example, profile radiography would typically be more effective than digital ultrasonic for thickness monitoring in cases of localized corrosion.

工具与技术 – 挑选合适的检验工具与技术, 有助于费用节省与更加有效的量化故障概率(POF). 在选择检验方法时, 除了选择合适的技术, 多个检验技术可能被动用来缓解风险.


d) Procedures and Practices - Inspection procedures and the actual inspection practices can impact the ability of inspectionactivities to identify, measure and/or monitor damage mechanisms. If the inspection activities are executed effectively by well-trained and qualified inspectors, the expected risk management benefits should be obtained. The user is cautioned not to assume that all inspectors and NDE examiners are well qualified and experienced, but rather to take steps to assure that they have the appropriate level of experience and qualifications.

程序和做法 – 检验可探性受检验程序与实际操作影响. 实用的检验作业指导书, 合格的检验人员是检验工作的先决条件.


http://myicp.api.org/inspectorsearch/


e) Internal, On-stream, or External Inspection—Risk quantification by internal, on-stream and external inspections should be assessed. Often external inspection with effective on-stream inspection techniques can provide useful data for risk assessment. It is worth noting that invasive inspections, in some cases, may cause deterioration and increase the risk of the item. Examples where this may happen include:

内部,外部,在职检验 – 按照实际要求进行合适的检验方法(内,外,在职)筛选. 很多时候外部在职检验能提供有用的风险评估信息. 很多时候内部检验可能导致设备的恶化与增加风险, 例子有;

moisture ingress to equipment leading to stress corrosion cracking or polythionic acid cracking, 水分渗入导致如腐蚀应力开裂(连多硫酸开裂)

internal inspection of glass lined vessels, 玻璃容器内部检验导致损坏 removal of passivating films, — human errors in start up (re-streaming),钝化

膜去除 (开机导致损坏) increased risks associated with shutting down and starting up equipment.

设备关机和启动带来的机械完整性负面影响


The user can adjust these parameters to obtain the optimum inspection planthat manages risk, is cost effective, and is practical. 用户可以按照实际情况优化检验方法和筛选佳的方法.


13.5 Managing Inspection Costs with RBI 运用 RBI 管理检查的费用

Inspection costs can be more effectively managed through the utilization of RBI. Resources can be applied or shifted to those areas identified as a higher risk or targeted based on the strategy selected. Consequently, this same strategy allows consideration for reduction of inspection activities in those areas that have a (1) lower risk or where the inspection activity has (2) little or no effect on the associated risks. This results in inspection resources being applied where they are needed most and thereby increased inspection cost effectiveness.

合理的把检验活动关注与高风险设备与那些能有效通过检验活动降低风险的设备, 在(1) 低风险和检验活动(2) 不能显著地降低风险的设备, 减少或完全取消检验活动, 能节约检验费用.


POF为风险关键因素: 使用检验方法降低 – 检验关注点

COF为风险关键因素: 运用其他风险管理策略- 非检验关注点

低风险区- 非检验关注点

高风险区- 检验关注点


Another opportunity for managing inspection costs is by identifying items in the inspection plan that can be inspected non-intrusively on-stream. If the non-intrusive inspection provides sufficient risk management, there is a potential for a net savings based on not having to blind, open, clean, and internally inspect during downtime. If the item considered is the main driver for bringing an operational unit down, the non-intrusive inspection may contribute to increased uptime of the unit. The user should recognize that while there is a potential for the reduction of inspection costs through the utilization of RBI, increased equipment integrity and inspection cost optimization should remain the focus.

另个节约检验费用的来源是, 外部在职检验替代设备内部检验 (内部检验的准备工作, 关机导致停产, 等). 用户应当注意的是, 虽然外部在职检验在替代内部检验带来成本节约, 设备机械完整性与检验成本佳平衡是终目标.


检验如何降低检验费用:

注重高风险项目,减少或忽略对低风险项目. 不能显著地降低风险的设备, 减少或完全取消检验活动. 外部在职检验替代设备内部检验.


13.6 Assessing Inspection Results and Determining Corrective Action评估检测结果并确定纠正措施

Inspection results such as the (1) identification of damage mechanisms, (2) rate of deterioration and (3) equipment tolerance to the types of deteriorationshould be used as variables in assessing (A) remaining life and (B) future inspection plans. The results can also be (C) used for comparison or validation of the models that may have been used for POF determination.

检验结果如, 损伤机理的识别, 劣化率, 设备容忍性能用来评估剩余寿命和策划未来的检验计划. 在此同时, 相关的资料可以用来, 比较与核实 POF 数据的准确性.

A documented mitigation action plan should be developed for any equipment item requiring repair or replacement. The action plan should describe the extent of repair (or replacement), recommendations, the proposed repair method(s), appropriate QA/QC and the date the plan should be completed.

每个需要维修或更换作为风险缓解的设备, 应当有缓解计划书. 化解计划书应, 详细的说明, 返修/更换范围, 建议, 修复方法, QAQC 要求和计划完成时间.


Reducing Uncertainty

Assessing Inspection Results and Determining Corrective Action评估检测结果并确定纠正措施检验结果如,(1) 损伤机理的识别, (2) 劣化率, (3) 设备容忍性能用来;

1. 评估剩余寿命和2. 策划未来的检验计划. 在此同时, 3. 相关的资料可以用来,比较与核实 POF 数据的准确性.

(1) indication characterized as a crack or zone of incomplete fusion or penetration;

(2) any other elongated indication on the radiograph which has length greater than:

(a) ¼ in. (6 mm) for t up to ¾ in. (19 mm)

(b) ⅓ t for t from ¾ in. (19 mm) to 2 ¼ in. (57 mm)

(c) ¾ in. (19 mm) for t over 2 ¼ in. (57mm)

(3) any group of aligned indications that have an aggregate length greater than “t” in a length of 12t, except when the distance between the successive imperfections exceeds 6L where L is the length of the longest imperfection in the group;

(4) rounded indications in excess of that specified by the acceptance standards given in Appendix 4.

Full

Unacceptable imperfections Degree of RadiographicExamination.

UW-51 (b)

UW-51

UW-51 (b2) any other elongated indication on the radiograph which has length greater than:(a) ¼ in. (6 mm) for t up to ¾ in. (19 mm)(b) ⅓ t for t from ¾ in. (19 mm) to 2 ¼ in. (57 mm)(c) ¾ in. (19 mm) for t over 2 ¼ in. (57mm)

Unacceptable imperfections

UW-51 (b2)

UW-51

1. indication characterized as a crack or zone of incomplete fusion or penetration.

2. Welds having indications characterized as slag inclusions or cavities are unacceptable when;

a. the indication length exceeds 2/3 t, where t is defined as shown in UW-51(b)(2).

b. For all thicknesses, indications less than ¼ in. (6 mm) are acceptable, and indications greater than ¾ in. (19 mm) are unacceptable.

c. Multiple aligned indications meeting these acceptance criteria are acceptable when the sum of their longest dimensions indications does not exceed t within a length of 6t (or proportionally for radiographs shorter than 6t), and when the longest length L for each indication is separated by a distance not less than 3L from adjacent indications.

(3) Rounded indications are not a factor in the acceptability of welds not required to be fully radiographed.

Spot

Unacceptable imperfections Degree of RT

UW-52 (c)

UW-52


API 510 Clause 3.20 examiner: A person who assists the inspector by performing specific nondestructive examination (NDE) on pressure vessel components but does not evaluate the results of those examinations in accordance with API 510, unless specifically trained and authorized to do so by the owner/user.

What were the differences in inspection?


13.7 Achieving Lowest Life Cycle Costs with RBI 低周期寿命成本

Not only can RBI be used to optimize inspection costs that directly affect life cycle costs, it can assist in lowering overall life cycle costs through various cost benefit assessments. The following examples can give a user ideas on how to lower life cycle costs through RBI with cost benefit assessments. 周期寿命成本

节约的贡献因素有

a) RBI should enhance the prediction of failures caused by damage mechanisms. This in turn should give the user confidence to continue to operate equipment safely, closer to the predicted failure date. By doing this, the equipment cycle time should increase and life cycle costs decrease. 提高故障预测率, 让用户有信心的安全操作设备, 临近预测的失效日期. 这样设备的使用周期时间增加和寿命周期成本降低


http://www.dnv.com/services/software/training/synergicourses/sy12

_onshore_rbi_dnv_api_581_may_rotterdam.asp


b) RBI can be used to assess the effects of changing to a more aggressive fluid. A subsequent plan to upgrade construction material or replace specific items can then be developed. The construction material plan would consider the optimized run length safely attainable along with the appropriate inspection plan. This could equate to increased profits and lower life cycle costs through reduced maintenance, optimized inspections, and increased unit/equipment uptime.

通过设备材料的更加认识, 从而优化设备/溶液/检验之间的互联组配, 来减少维修, 优化检查, 增加单元/设备的正常可用时间.

c) Turnaround and maintenance costs also have an effect on the life cycle costs of an equipment item. By using the results of the RBI inspection plan to identify more accurately where to inspect and what repairs and replacements to expect, turnaround and maintenance work can be preplanned and, in most cases, executed at a lower cost than if unplanned.

风险分析能正确的鉴定设备需要检验的位置与间隔, 这样检修和维护工作可预先计划. 预先合理时间安排往往导致成本节约.


14 Other Risk Mitigation Activities 其他的风险缓解活动


Contents

14.1 General14.2 Equipment Replacement and Repair 14.3 Evaluating Flaws for Fitness-For-Service 14.4 Equipment Modification, Redesign, and Rerating 14.5 Emergency Isolation 14.6 Emergency Depressurizing/Deinventorying 14.7 Modify Process 14.8 Establish Integrity Operating Windows 14.9 Reduce Inventory 14.10 Water Spray/Deluge 14.11 Water Curtain 14.12 Blast-resistant Construction 14.13 Others


14.1 General 总则

As described in the previous section, inspection is often an effective method ofrisk management. However, inspection may not always provide sufficient risk mitigation or may not be the most cost effective method. The purpose of this section is to describe other methods of risk mitigation. This list is not meant to be all inclusive. These risk mitigation activities fall into one or more of the following:

检验虽然一般上有效的降低风险, 但在检验并不能胜任时, 其他缓解措施将被动用.这些风险缓解活动主要分为以下

a) reduce the magnitude of consequence, 减少的后果的严重性b) reduce the POF, 减少故障率c) enhance the survivability of the facility and people to the consequence,

提高设备和人对事故后果的生存率d) mitigate the primary source of consequence. 缓解故障后果的主要来源


1. 14.2 Equipment Replacement and Repair 2. 14.3 Evaluating Flaws for Fitness-For-Service 3. 14.4 Equipment Modification, Redesign, and Rerating 4. 14.5 Emergency Isolation 5. 14.6 Emergency Depressurizing/De-inventorying 6. 14.7 Modify Process 7. 14.8 Establish Integrity Operating Windows 8. 14.9 Reduce Inventory 9. 14.10 Water Spray/Deluge 10.14.11 Water Curtain 11.14.12 Blast-resistant Construction 12.14.13 Others


14.2 Equipment Replacement and Repair 设备的更换和维修When equipment deterioration has reached a point that the risk of failure cannot be managed to an acceptable level, replacement/repair is often the only way to mitigate the risk. 当设备损伤导致失效风险不能管理到可接受的水平时, 设备维修或更换往往是唯一的风险缓解选择.

其他的风险缓解活动 – 设备维修!


Other Risk Mitigation Activities 其他的风险缓解活动


14.3 Evaluating Flaws for Fitness-For-Service 适用性评估

Inspection may identify flaws in equipment. A Fitness-For-Service assessment (e.g. API 579-1/ASME FFS-1) may be performed to determine if the equipment may continue to be safely operated, under what conditions and for what time period. A Fitness-For-Service analysis can also be performed to determine what size flaws, if found in future inspections, would require repair or equipment replacement.

适用性评估可以用于评估当前的设备缺陷 (不受理/维修/更换), 也可以用来定量缺陷大小的极限, 这有助于对未来检验测量到的缺陷变化,做出更换或维修的决定.


14.4 Equipment Modification, Redesign, and Rerating设备改造, 重新设计和压力重估

Modification and redesign of equipment, utilizing a rigorous MOC process, canprovide mitigation of POF. Examples include: 利用严格的变更管理程序,备改造, 重新设计和压力重估作为缓解 POF,例子有

a) change of metallurgy,改变冶金b) addition of protective linings and coatings, 添加涂层和保护衬垫c) removal of deadlegs, 拆除盲流点(死角)d) increased corrosion allowance, 增加腐蚀余量e) physical changes that will help to control/minimize deterioration,

有助于控制/减少恶化的设备物理变化f) insulation improvements, 保温层的优化g) injection point design changes, 注入点设计优化h) resizing of the relief device.减压装置大小优化

Sometimes equipment is over designed for the process conditions. Reratingthe equipment may result in a reduction of the POF assessed for that item.有的时候,设备设计过于保守, 设计重估可能导致POF降低.


14.5 Emergency Isolation 紧急关断

Emergency isolation capability can reduce toxic, explosion or fire consequences in the event of a release. Proper location of the isolation valves is key to successful risk mitigation. Remote operation is usually required to provide significant risk reduction. To mitigate flammable and explosion risk, operations need to be able to detect the release and actuate the isolation valves quickly (within a few minutes). Longer response times may still mitigate effects of ongoing fires or toxic releases.


14.6 Emergency Depressurizing/De-inventorying 应急减压/ 清仓(溶液)

This method reduces the amount and rate of release. Like emergency isolation, the emergency depressurizing and/or de-inventory should be achieved within a few minutes to affect explosion/fire risk.


14.7 Modify Process 工艺修改

Mitigation of the primary source of consequence may be achieved by changing the process towards less hazardous conditions. As with physical modifications, any process changes should be conducted only after the application of a rigorous MOC process. Some examples include:

a) reduce temperature to below atmospheric pressure boiling point to reduce size of cloud; 降低温度

b) substitute a less hazardous material (e.g. high flash solvent for a low flash solvent); 更换工艺原材料

c) use a continuous process instead of a batch operation, where applicable;连续而不是一个间歇操作工艺过程

d) dilute or eliminate hazardous substances.淡化或消除有害物质

以上修改必须经过严格的 MOC 变更管理程序审核.


Mitigation of the sources of corrosion can be achieved by changing the process towards less corrosive conditions. Some examples include: 通过更改腐蚀性较弱的工艺过程

a) process water washing to remove corrosive materials (e.g. salts); 清水清理b) addition of neutralizing or inhibitor chemicals; 添加中和剂 /抑制剂c) removal of contaminants with process equipment (e.g. absorbers, filters);

污染物去除d) protection of downtime corrosion (e.g. PTASCC protection).

停机保护(比如:硫酸应力腐蚀)


14.8 Establish IOWs 建立操作完整性窗口

IOWs should be established for process parameters (both physical andchemical) that could impact equipment integrity if not properly controlled. Examples of the process parameters include temperatures, pressures, fluidvelocities, pH, flow rates, chemical or water injection rates, levels of corrosive constituents, chemical composition, etc. Key process parameters for IOWsshould be identified and implemented, upper and lower limits established, as needed, and deviations from these limits should be brought to the attention of inspection/engineering personnel. Particular attention to monitoring IOWsshould also be provided during start-ups, shutdowns and significant processupsets.

操作完整性窗口(参数) 应确定和实施. 特别注意监测在开机, 关机与工艺颠覆的工艺参数的异常. 当关键工艺参数偏离允许上下限,应及时提醒检验/设计人员.


14.9 Reduce Inventory 减少库存

This method reduces the magnitude of consequence. Some examples include:

a) reduce/eliminate storage of hazardous feedstocks or intermediate products;减少/消除储存危险原料或中间产品,

b) modify process control to permit a reduction in inventory contained in surge drums, reflux drums or other inprocess inventories; 减少缓冲罐, 回流罐的库存,

c) modify process operations to require less inventory/hold-up; 修改工艺以减少工艺流程库存,

d) substitute gas phase technology for liquid phase. 液相替代气相技术,


14.10 Water Spray/Deluge 水喷/消防水

This method can reduce fire damage and minimize or prevent escalation. A properly designed and operating system can greatly reduce the probability that a vessel exposed to fire. 这方法减少火灾的伤害或升级.

14.11 Water Curtain 水幕

Water sprays entrap large amounts of air into a cloud. Water curtains mitigate water soluble vapor clouds by absorption as well as dilution and insoluble vapors (including most flammables) by air dilution. Early activation is required in order to achieve significant risk reduction. The curtain should preferably be between the release location and ignition sources (e.g. furnaces) or locations where people are likely to be present. Design is critical for flammables, since the water curtain can enhance flame speed under some circumstances.


14.12 Blast-resistant Construction 防爆结构

Utilizing blast resistant construction provides mitigation of the damage caused by explosions and may prevent escalation of the incident. When used for buildings (see API 752), it may provide personnel protection from the effects of an explosion. This may also be useful for equipment critical to emergency response, critical instrument/control lines, etc.


14.13 Others 其他

a) spill detector; 泄漏检测器b) steam or air curtains; 蒸汽或空气幕c) fireproofing; 耐火层装置d) instrumentation (interlocks, shutdown systems, alarms, etc.);

仪表 (联锁, 关断系统, 警报, 等)e) inerting/gas blanketing;惰气/气掩盖f) ventilation of buildings and enclosed structures; 建筑物封闭结构的通风g) piping redesign; 管道设计h) mechanical flow restriction; 机械流量限制i) ignition source control; 燃点源头控制j) improved design, assembly and installation standards;

改进的设计, 装配和安装标准k) improvement in process safety management (PSM) program;

工艺安全管理程序的改进


l) emergency evacuation; 紧急疏散m) shelters (safe havens); 庇护所(避难所)n) toxic scrubbers on building vents; 在建筑通风有毒洗涤器o) spill detectors and containment; 泄漏检测器和遏制p) facility siting and/or layout; 设施选址和/或布局q) condition monitoring; 状态监测r) improved training and procedures; 改进,训练和程序s) emergency feed stops; 紧急原料补给关断t) improved fire suppression systems. 改进的灭火系统

Api580 chapter 12 to 14

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