Confidence-based quantitative risk analysis for offshore accidental hydrocarbon release events

Quantitative risk analysis (QRA) has been widely used to conduct the assessment of offshore accidental risks. However, the accuracy and validity of QRA is significantly affected by uncertainties when subjective judgments are involved. Therefore, it is unrealistic to determine the probability of a hazardous event by using one single explicit value when safety experts have a relatively low confidence level in their judgments. This paper proposes a new methodology for incorporating uncertainties into conventional QRA using the concept of confidence level. Offshore hydrocarbon release hazards are focused on and a barrier and operational risk analysis (BORA-Release) method is selected as the basic model to illustrate the proposed methodology. A left–right (L–R) bell-shaped fuzzy number is employed and its membership curve is able to control its shape to represent different confidence levels. As to the complex geometry of the bell-shaped fuzzy number, an α-cut operation is introduced to conduct the arithmetic operations of the fuzzy number, and a defuzzification method with total integral value is chosen to match the α-cut operations and acquire complete information for the fuzzy numbers. In the meantime, an optimism index is used to describe the attitude of the decision-maker. One case study is provided in this paper to demonstrate the implementation of this method.     

Risk assessment in the offshore industry

This paper describes the implementation and use of risk assessment in the offshore industry in relation to safety aspects — safety to people's life and health, as well as environment and property. Although risk assessments may be based on both qualitative and quantitative methods, the main focus here will be on quantitative risk assessments (QRA). The development of offshore QRA has been lead by a mutual influence and interaction between the regulatory authorities for the UK and Norwegian sectors of the North Sea as well as the oil companies operating here. The experience from this area has been the main basis during the writing of this paper.     

定量风险评价技术在管道城市穿越段的应用

介绍了管道高后果区定量风险评价的方法和风险可接收标准.将定量风险评价技术在我国某长输原油管道城市穿越段的应用表明,定量风险评价方法适用于人口密集的管道高后果区,能对管道高后果区的风险管理、决策提供重要的参考.     

Risk indicators for major hazards on offshore installations

Major hazards risk indicators are proposed for offshore installations, based on what has been used by the Petroleum Safety Authority Norway for the Risk Level approach in the Norwegian offshore petroleum industry. Since 2002 also leading indicators are used, in the sense that indicators for barrier performance are included together with the lagging indicators. There are individual indicators for a number of barrier functions, including fire and gas detection, a number of safety valves, active fire protection and mustering of personnel. The performance of the leading indicators during several years of data collection as well as lessons learned from the project are discussed. This is followed by a review of how indicators may be used by individual companies, and how the lessons may be utilised by individual companies to develop risk indicators for individual installations as well as company wide indicators.     

Occupational injury risk in a blue collar, small business industry: Implications for prevention

Conflicting perceptions of risk in OHS generate barriers to occupational injury prevention. Occupational injury prevention strategies that fail to address workplace risk perceptions are likely to be ineffective. In this study, we ask whether employers' and employees' have conflicting risk perceptions that may produce barriers to injury prevention in workplaces and we explore underlying understandings of risk in OHS that produce conflicting risk judgements. A novel research methodology was utilised to compare and contrast risk judgements of employers and employees in a blue collar, small business industry. Participants were asked to rate ten OHS risks and the risk rating scores of the two groups were compared. They were also asked to explain their risk judgements and their responses were contrasted by a method of qualitative data analysis. Significant differences between the risk rating scores of employers and employees were found for four OHS risks. The focus of conflicting risk judgements was a distinction between risks with an immediate injury effect and those with a delayed disease effect. Employers tended to rate the former significantly higher than employees. Employees tended to rate the latter significantly higher than employers. Three themes emerged to explain underlying understandings of risk in OHS that produce conflicting risk judgements. Implications of these understandings for occupational injury prevention strategies in an Australian blue collar, small business industry are explored and a new approach is proposed.     

Associations between sleep,risk and safety climate: A study of offshore personnel on the Norwegian continental shelf

The demands and constraints of the offshore working environment can have adverse effects on health, particularly the quality of sleep. Perceived risk and safety are significant psychological stress factors which may interfere with and deteriorate the sleep quality of offshore personnel. The present study explores the relationship between risk perception, safety climate and sleep quality. Data were collected under the auspices of the Petroleum Safety Authorities in Norway using a cross-sectional design. A total of 9601 offshore workers from 52 offshore installations on the Norwegian continental shelf participated in the study. Our findings indicate that both risk perception and safety climate are significantly related to sleep quality. The results of the present study suggest that risk perception and safety climate not only are important aspects of safety performance in the offshore industry, but also have an impact on sleep quality.     

Optimizing the design of storage facilities through the application of ISD and QRA

Four strategies can be used to achieve safety in chemical processes: inherent, passive, active and procedural. However, the strategy that offers the best results is the inherent safety approach, especially if it is applied during the initial stages of a project. Inherently Safer Design (ISD) permanently eliminates or reduces hazards, and thus avoids or diminishes the consequences of incidents. ISD can be applied using four strategies: substitution, minimization, moderation and simplification. In this paper, we propose a methodology that combines ISD strategies with Quantitative Risk Assessment (QRA) to optimize the design of storage installations. As 17% of major accidents in the chemical industry occur during the storage process and cause significant losses, it is essential to improve safety in such installations. The proposed method applies QRA to estimate the risk associated with a specific design. The design can then be compared to others to determine which is inherently safer. The risk analysis may incorporate complex phenomena such as the domino effect and possible impacts on vulnerable material and human elements. The methodology was applied to the San Juanico tragedy that occurred in Mexico in 1984.     

Risk measures constituting a risk metrics which enables improved decision making: Value-at-Risk

In this work, a novel approach is proposed for expressing the risks of process plants consisting of a large number of scenarios, in the form of a risk metrics of leading indicators to prevent potential high profile industry accidents. The methodology includes: 1) risk estimation of a portfolio by CPQRA (or QRA), 2) monetization of the tangible risks with the inclusion of the lost time of production, 3) estimation of the maximum portfolio loss using Value-at-Risk approach, 4) inclusion of intangible risks using FN-curve and, 5) generation of F$-curve of tangible risks. The proposed methodology can particularly help in understanding the stakes at risk by performing the overall cost-benefit analysis, for identifying the most risky scenarios and identifying critical equipments to enable better risk-informed decision making in order to adopt appropriate risk mitigation measures. This work establishes the groundwork for developing measures for understanding and comparing the large number of risk values derived from QRA studies for large portfolios. It will aid in less subjective decision making as it enables the decision maker to choose the most preferred portfolio option among alternatives. Decisions made with the accurate understanding of the consequences of risks can significantly reduce potential work-related fatalities, property losses and save millions of dollars.     

Frequency data and modification factors used in QRA studies

The source data for QRA’s is important to assure meaningful risk assessment results, particularly when the result is to be compared against quantitative risk acceptance criteria. The author’s company is one of the largest global QRA providers and we have concluded that the UK HSE Hydrocarbon Release Database (HCRD) provides the basis for the best leak frequency data as it offers complete leak data collection in a systematic manner, against a known population of equipment and facilities in the UK sector of the North Sea for which there is an accurate parts count estimate. The LEAK program is described. It screens HCRD to remove leak events not associated with full operations inventories and flows (e.g. when isolated for maintenance) and further uses a distribution function that permits frequencies for any arbitrary hole size range to be determined (e.g. 25 mm leaks, 50 mm leaks, full-bore ruptures). An important factor is that leak frequency data is not stationary, offshore operators have improved their control of leak events and the HCRD shows a declining leak rate over time.DNV often uses frequency modification techniques, termed MOR - Modification of Risk. This paper reviews 4 methods developed by the company internationally. These are the Manager Method, the API 581 method, a barrier based method, and a proprietary management system based method. These all permit localization of UK North Sea data to apply to other facilities (onshore or offshore) and with different management systems and mechanical integrity programs.Overall, localized data using MOR is considered more accurate than direct use of UK North Sea data, however validation is an issue. There are no direct comparisons that compare leak statistics over a sufficiently long period with static management systems and integrity programs. Thus MOR techniques remain judgment based approaches, but transparent in methodology and assumptions. The barrier based modification technique is the most directly verifiable of the four MOR methods presented.     

The oil and gas industry,the competence assessment of Offshore Installation Managers (OIMs) and Control Room Operators (CROs) in emergency response,and the lack of effective assessment of underpinning technical knowledge and understanding

Within the UKCS offshore oil and gas industry there exist key personnel who perform critical roles in an emergency as part of the installation's emergency response team (ERT), two of these personnel are the Offshore Installation Manager (OIM) and the offshore Control Room Operator (CRO). The OIM is responsible for the safety and well-being of all persons onboard and within 500 m of the installation. Should an emergency situation arise, the OIM performs one of the most critical roles in emergency response - management of the response to the emergency to mitigate and make safe the installation to secure a place of safety for persons onboard or organise their safe evacuation. Such emergency response shall also include limiting the loss of hydrocarbons to the environment. The CRO monitors and interprets the output from an installation's Distributed Control System (DCS) and Fire and Gas Panel (FGP), responding to alarms and deviations from steady state. In many instances, an offshore CRO's actions in response to these deviations can determine whether or not the situation deteriorates into a disaster. Should an emergency occur, the CRO will act in accordance with an installation's emergency response procedures and OIM instructions.The persistence of incidents, a number leading to disasters, in the industry highlights the importance of both OIM and CRO competence in controlling emergencies. Both positions require an effective system to assess the competence of job holders. Research at the University of Aberdeen identified potential barriers that can prevent the effective competence assessment of an OIM in emergency response. An extension to this research analyses the two offshore industry standards for competence in emergency response: OPITO 7025 – OIM Controlling Emergencies and OPITO 9004 – Control Room Operator Emergency Response, and associated documentation, applying a critical hermeneutic approach, focusing on the assessment of underpinning knowledge and understanding within the roles. The key findings are that there currently exists no effective means to assess the underpinning technical knowledge and understanding of either OIMs or CROs in emergency response within the offshore industry. Knowledge and, in particular, understanding are poorly defined within the relevant OPITO standards. There exists no validation of evidence collated to support an individual's underpinning knowledge and understanding and no truly independent audit of collated evidence or the process of assessment.The research is important to Duty Holders (see also OSD Installation Operators under UK Offshore Safety Directive Regulations) and employers within the offshore oil and gas industry, organisations associated with the offshore industry, safety engineers and UK Government departments with regard to the effectiveness of competence assessment of appointed OIMs and CROs. It is also significant to risk engineers when considering the probable competence of key emergency response personnel in a given environment at a given point in time. The research is not just applicable to the UKCS offshore industry but also to the global offshore oil and gas industry.     

化工园区定量风险评价中危险源初选方法的研究

在进行化工园区定量风险评价中,危险源的梳理和筛选是首要步骤。分析了欧盟ARAMIS方法、荷兰PURPLE BOOK方法和新西兰的HFSP方法在危险源初选中的适用性,指出对于区域危险源初选用HFSP方法可以全面考虑区域中的各类危险源,快速准确地对危险源进行排序,并提出了HFSP方法用于区域危险源初选的调整方法,给出了危险设施单元的定义和进行QRA的选择判据。     

用FSA方法优化油库安全管理

在油库燃爆研究的基础上,利用FSA方法的理念,对油库安全管理过程中的客观危险因素进行识别,即对油库燃爆事故的基本原因进行综合分析,然后对识别出的各危险因素采取定性分析的方法进行风险评估,以基本事件的结构重要度系数表示。根据事故树的最小径集,得出防止油库燃爆的各种风险控制方案,然后对各方案进行成本与效益评估,从而对各风险控制方案进行比较,从中选择出科学合理的油库安全管理方案。     

Workplace Hazards and Prevention Options From a Nonrandom Sample of Retail Trade Businesses

Employer commitment is a key factor in an effective safety program, yet limited research has focused on the safety priorities of retail store managers. To address this, the U.S. National Institute for Occupational Safety and Health recruited 4 experienced ergonomists, who met and interviewed 9 retailers in different parts of the eastern USA. The reports from the 9 interviews were used to document the hazards facing retailers and the interventions they attempted. Those interviewed were managers/owners of establishments that ranged from a small bakery with 11 employees to a supermarket with 85 or more employees. The main hazards across all establishments included overexertion, contact-with-objects, and falls-to-the-same-level. We also compared the retailers’ perceptions of safety hazards with injuries from actual hazards as supplied by the U.S. Bureau of Labor Statistics. This report provides insight into the retailers ‘ perceptions of safety hazards as well as their commitment to the prevention of workplace injuries.     

A hybrid decision-making approach based on FCM and MOORA for occupational health and safety risk analysis

IntroductionWith the development of industries and increased diversity of their associated hazards, the importance of identifying these hazards and controlling the Occupational Health and Safety (OHS) risks has also dramatically augmented. Currently, there is a serious need for a risk management system to identify and prioritize risks with the aim of providing corrective/preventive measures to minimize the negative consequences of OHS risks. In fact, this system can help the protection of employees’ health and reduction of organizational costs. Method: The present study proposes a hybrid decision-making approach based on the Failure Mode and Effect Analysis (FMEA), Fuzzy Cognitive Map (FCM), and Multi-Objective Optimization on the basis of Ratio Analysis (MOORA) for assessing and prioritizing OHS risks. After identifying the risks and determining the values of the risk assessment criteria via the FMEA technique, the attempt is made to determine the weights of criteria based on their causal relationships through FCM and the hybrid learning algorithm. Then, the risk prioritization is carried out using the MOORA method based on the decision matrix (the output of the FMEA) and the weights of the criteria (the output of the FCM). Results: The results from the implementation of the proposed approach in a manufacturing company reveal that the score at issue can overcome some of the drawbacks of the traditional Risk Priority Number (RPN) in the conventional FMEA, including lack of assignment the different relative importance to the assessment criteria, inability to take into account other important management criteria, lack of consideration of causal relationships among criteria, and high dependence of the prioritization on the experts’ opinions, which finally provides a full and distinct risk prioritization.     

“Total risk of death”—Towards a common and usable basis for consequence assessment

Assessment of the risk of exposure to a “dangerous dose” (DD) is the basis of the UK Health and Safety Executive's HSE's current risk assessments for land-use planning (LUP). Some years ago, a hybrid approach using both DD and “significant likelihood of death” (SLOD) was proposed as an improvement, but was not adopted.Here, an alternative, weighted multiple threshold approach, provisionally titled “total risk of death” (TROD), is described. TROD improves the comparability of assessed risks from diverse hazards. This is achieved by first performing assessments for more than one threshold of consequence (such as DD assessment and SLOD assessment). The predicted risk for each threshold is then combined into a single risk value (at a specified location) by weighting the contributions to risk according to the predicted consequences for each threshold.This paper makes the case, in principle, for using TROD and illustrates how TROD values are constructed.TROD overcomes some of the objections that have barred progress to more widespread use of risk assessment, it is more comparable between different installations and hazards than DD, it is more sensitive than SLOD and more adaptable than probits (which can introduce a false sense of precision). It could support more direct comparison with other risks (e.g. everyday risks and transport risks) in the future.The appropriate “weightings” for addition of risks predicted for different consequence thresholds (contributing to TROD) are discussed here. A three-threshold scheme for evaluation of TROD is described. The thresholds are DD (assumed to approximate to a dose leading to ～1% fatal consequences or LD₁), LD₁₀, and SLOD (～LD₅₀).TROD has been used in HSE sponsored research and in HSE's exploration of societal risks.     

History of Dutch process equipment failure frequencies and the Purple Book

In the middle of 70s concerns of the public in the Netherlands about fire, explosion and toxic risks due to mishaps in the expanding process industry, causing political pressure led to the embracement of quantitative risk analysis as tool for licensing and land-use planning. Probabilistic treatment of risk had been exercised before to design flood defense. A ‘test’ on six different plants, the COVO study, favored the idea. Failure rate values were in immediate need. For storage vessels AKZO’s chlorine vessel data and British steam boiler data have been the first. Risk criteria to make decisions on were also developed and in 1985 embodied in legislation. As licensing and land-use planning are tasks of provincial authorities, under the auspices of the Inter-Provincial Consultation (IPO), further details such as failure frequency values have been worked out. In the late 90s the Purple Book consolidated the information as a guideline for Dutch quantitative risk assessment of process installations.The paper will give a condensed historical overview, guidance to published papers; it will further make comments, explain policy backgrounds, present comparison with other data and will briefly indicate in which direction developments should go to improve QRA.     

Quantitative risk analysis of urban natural gas pipeline networks using geographical information systems

This paper presents a novel quantitative risk analysis process for urban natural gas pipeline networks using geographical information systems (GIS). The process incorporates an assessment of failure rates of integrated pipeline networks, a quantitative analysis model of accident consequences, and assessments of individual and societal risks. Firstly, the failure rates of the pipeline network are calculated using empirical formulas influenced by parameters such as external interference, corrosion, construction defects, and ground movements. Secondly, the impacts of accidents due to gas leakage, diffusion, fires, and explosions are analyzed by calculating the area influenced by poisoning, burns, and deaths. Lastly, based on the previous analyses, individual risks and social risks are calculated. The application of GIS technology helps strengthen the quantitative risk analysis (QRA) model and allows construction of a QRA system for urban gas pipeline networks that can aid pipeline management staff in demarcating high risk areas requiring more frequent inspections.     

海上平台烟气组合工况扩散安全性分析

海上平台的压缩机透平、发电机透平、热介质锅炉等高温设备较多,多点排放的高温烟气,很有可能成为平台安全的隐患。这其中包括高温烟气对直升机起降的影响,或者对有人通行区域安全性的影响。因此很有必要针对海上平台烟气组合工况进行扩散安全性分析。本文就是利用三维数值模拟FLUENT软件,针对某海上平台多点排放源组合工况的烟气扩散问题进行数值模拟研究,并根据模拟结果分析高温废气对海上平台安全性的影响,从而为工程设计提供参考和依据。