Bow-tie Method Research Articles

Validity and consistency assessment of accident analysis methods in the petroleum industry

Background. Accident analysis is the main aspect of accident investigation. It includes the method of connecting different causes in a procedural way. Therefore, it is important to use valid and reliable methods for the investigation of different causal factors of accidents, especially the noteworthy ones. Objective. This study aimed to prominently assess the accuracy (sensitivity index [SI]) and consistency of the six most commonly used accident analysis methods in the petroleum industry. Methods. In order to evaluate the methods of accident analysis, two real case studies (process safety and personal accident) from the petroleum industry were analyzed by 10 assessors. The accuracy and consistency of these methods were then evaluated. The assessors were trained in the workshop of accident analysis methods. Results. The systematic cause analysis technique and bowtie methods gained the greatest SI scores for both personal and process safety accidents, respectively. The best average results of the consistency in a single method (based on 10 independent assessors) were in the region of 70%. Conclusion. This study confirmed that the application of methods with pre-defined causes and a logic tree could enhance the sensitivity and consistency of accident analysis.

Hazard-Based Design of the Bow-Tie Method to Prevent and Mitigate Mine Accidents

The mining trade involves many complicated and interrelated variables—its complex environment, abundant machinery and a plethora of other contributors to accidents. In both developed and developing countries, mining accidents have caused many casualties. However, a universal risk assessment method for mining accidents is has not yet been implemented. Among risk assessment methods, the bow-tie has been used in different industry processes and systems and has proven effective. In this paper, the bow-tie model is utilized to investigate the relationship among mining accident risks, safety measures and possible consequences. The paper illustrates the hazards of mining accidents using US mine accident data. It also shows how the consequences of mine accidents are summarized by laws and regulations of different countries. This paper also introduces a series safety measures from Chinese safety standards and how the safety measures prevent and mitigate risks. At the end of the paper, a case of mine water inrush is applied using the bow-tie approach. The results show that the method is effective for analyzing mine safety.

“And DPSIR begat DAPSI(W)R(M)!” - A unifying framework for marine environmental management

The marine environment is a complex system formed by interactions between ecological structure and functioning, physico-chemical processes and socio-economic systems. An increase in competing marine uses and users requires a holistic approach to marine management which considers the environmental, economic and societal impacts of all activities. If managed sustainably, the marine environment will deliver a range of ecosystem services which lead to benefits for society. In order to understand the complexity of the system, the DPSIR (Driver-Pressure-State-Impact-Response) approach has long been a valuable problem-structuring framework used to assess the causes, consequences and responses to change in a holistic way. Despite DPSIR being used for a long time, there is still confusion over the definition of its terms and so to be appropriate for current marine management, we contend that this confusion needs to be addressed. Our viewpoint advocates that DPSIR should be extended to DAPSI(W)R(M) (pronounced dap-see-worm) in which Drivers of basic human needs require Activities which lead to Pressures. The Pressures are the mechanisms of State change on the natural system which then leads to Impacts (on human Welfare). Those then require Responses (as Measures). Furthermore, because of the complexity of any managed sea area in terms of multiple Activities, there is the need for a linked-DAPSI(W)R(M) framework, and then the connectivity between marine ecosystems and ecosystems in the catchment and further at sea, requires an interlinked, nested-DAPSI(W)R(M) framework to reflect the continuum between adjacent ecosystems. Finally, the unifying framework for integrated marine management is completed by encompassing ecosystem structure and functioning, ecosystem services and societal benefits. Hence, DAPSI(W)R(M) links the socio-ecological system of the effects of changes to the natural system on the human uses and benefits of the marine system. However, to deliver these sustainably in the light of human activities requires a Risk Assessment and Risk Management framework; the ISO-compliant Bow-Tie method is used here as an example. Finally, to secure ecosystem health and economic benefits such as Blue Growth, successful, adaptive and sustainable marine management Responses (as Measures) are delivered using the 10-tenets, a set of facets covering all management disciplines and approaches.

A Total Safety Management framework in case of a major hazards plant producing pesticides

The aim of this paper is to present the framework for Total Safety Management through its application to a major hazards chemical plant, namely a pesticides producing unit. This framework was developed within the European Project entitled “Total Operation Management for Safety Critical Activities” (TOSCA) aiming at an innovative approach able to integrate and enhance safety, quality and productivity. The cornerstone of this framework is the “Common Operation Picture” notion, which involves a useful synthesis of the unit risk assessment, with the intention to provide understandable information to the relevant stakeholders and decision-makers. This framework has been applied to the storage area of a hazardous substance called dichloropropene, a flammable material used for pesticides production. The Fault Tree and the Bowtie methods have been used for the risk assessment of various accidental releases from the dichloropropene storage tanks. Production data, safety barrier information and results of risk analysis are stored in a database linked with accident sequences visualization tools.

Quantitative risk analysis on leakage failure of submarine oil and gas pipelines using Bayesian network

Submarine pipeline is the major transportation way of subsea oil and gas production. Due to the internal and external factor, the failure probability of submarine pipeline is increasing, which could lead to the spill accidents of oil and gas. Efficient risk analysis is vital for preventing and mitigating such potential accident. This paper presents a risk-based accident model to conduct quantitative risk analysis (QRA) for leakage failure of submarine pipeline. Firstly, we employ bow-tie method to model the causal relationship between pipeline leakage and potential accident scenarios. Subsequently, in order to overcome the difficulties of bow-tie in modeling uncertainties and conditional dependency, a Bayesian network model for pipeline leakage is developed through mapping from the former bow-tie. Meanwhile, an object-oriented Bayesian network that has a smaller and more clarified structure is also constructed by modularizing the primary Bayesian network. Eventually, the probability updating is implemented in risk analysis using Bayesian network when a new evidence or observation occurs, and an experience learning from accident precursor data is also conducted through Bayesian approach. The proposed accident model based on Bayesian network can provide a more case-specific and realistic analysis consequence compared to bow-tie method, since it could consider the common cause failures and conditional dependency in accident evolution process of pipeline leakage.

The bowtie method: A review

The bowtie method is becoming more popular, but it lacks a consistent approach. This article reviews the available literature and identifies the different approaches that are taken. There are two main types of bowties. Quantitative bowties and Qualitative bowties. Most Quantitative bowties use a fault tree together with an event tree and barriers to calculate risk. The ORM bowtie can also be considered a Quantitative bowtie, although its structure is different from a fault and event tree. Qualitative bowties use simpler cause–effect scenarios with barriers to communicate the risk to an audience. It is proposed to allow these variations of the method to exist and be used when applicable. It is also proposed that people using the bowtie method give an additional qualification as to whether they’re using a qualitative or quantitative variant.

The Bowtie method in safety management system: A literature review

The Bowtie method is a qualitative incorporating management system technique. The theory behind the bow tie approach can be found in the “Swiss cheese model” of Reason. The Royal Dutch/Shell Group was the first major company to integrate fully the total bow-tie methodology into its business practices and then the bowtie has become popular as a structured method to assess risk where a quantitative approach is not possible or desirable. Its essence is to establish how many safety barriers there are available to prevent, control or mitigate the identified scenarios, and the quality of those barriers.

A reliability model for safety instrumented system

Safety analysis in the companies is an important issue besides the quality, productivity and profitability. Safety integrity function in many industries is based on safety instrumented systems. Uncertainty is the main problem of safety analysis. In this paper, a new mathematical model is developed to compute the probability of failure on demand (PFD) following the three steps. First, KHALFI (Characteristics of Hazard Analysis based on Logic Frequency Initiative) mathematical model is formulated to identify the real PFD at any geographical location considering five intermediate factors: temperature, humidity, pressure, wind speed and time which can affect the PFD. Second, probability binary state (PROBIST) is used to precise the values of PFD. Third, Bowtie method is employed to carry out the safety analysis for examining the safety of some scenarios by determining the PFD of safeguards, where new classification for the safety integrity level is proposed. Finally, Simulink model is developed implementing the proposed model to facilitate the automatic computation and analysis. Results indicate that all the atmospheric elements are significant and need to be taken into consideration to attain the best reliability in the calculation of PFD. The effectiveness of the proposed model gives the opportunity for the analysts to conduct safety analysis at any geographical location.

Mechanical investigation of tunnels: risk analysis and notation system

The current mechanical investigation strategy applied to RATP (Régie Autonome des Transpots Parisiens) tunnels is mainly based on visual inspection. All the works are inspected and every apparent fault is located and reported in inspection reports. However, this type of inspection detects only apparent faults without linking them to their causes. A new methodology of mechanical investigation is proposed in the framework of the ANR project MEDITOSS (Méthodologie de Diagnostic des Tunnels et Ouvrages Souterrains en Service), consisting in integrating mechanical investigation tools to better characterise the geometrical and mechanical state of the tunnel. This new strategy combines four techniques (ground penetrating radar, light dynamic penetrometer, endoscopy and geo-mechanical impedance). These techniques are applied to panels to obtain a ‘panel score’. This paper presents a risk analysis of the system studied (network of corridors and tunnels), by applying the bow-tie method in order to obtain information on its elements, its function and its pathologies. This analysis incorporates a quantitative characterisation method (scoring) to assess the state of corridors and tunnels. These methods are tested on infiltration and cracking pathologies for the risk analysis and on the notation of a corridor for the quantitative quantification.

Real-World Application of the Bow-Tie Method

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 154549, ’Lessons Learned From Real-World Application of the Bow-Tie Method,’ by Gareth Book, Risktec Solutions, prepared for the 2012 SPE Middle East Health, Safety, Security, and Environment Conference and Exhibition, Abu Dhabi, 2-4 April. The paper has not been peer reviewed. Also known as barrier diagrams, bow-tie diagrams provide an understandable visualization of relationships between the causes of business upsets, the escalation of such events to a range of possible outcomes, the controls preventing the event from occurring, and the preparedness measures in place to limit consequences. Preventive and mitigating measures are linked to tasks, procedures, responsible individuals, and competencies. This crucial connection between risk controls (whether hardware or human intervention) and the management system ensures ongoing effectiveness. Introduction The primary motivation for the use of bow-tie diagrams was to seek assurance that fit-for-purpose risk controls were consistently in place throughout all operations worldwide. Their use has spread between companies, industries, and countries and from industry to regulators. This paper aims to demonstrate the practical uses and benefits of this versatile tool, which can be used to qualitatively assess and to demonstrate control of all types of risk in many industries and business sectors. The complete paper details an example case. Bow-Tie Method The bow-tie method shown in Fig. 1 provides a readily understood visualization of the relationships between the causes of business upsets, the escalation of such events, the controls preventing the event from occurring, and preparedness measures to limit the business effects. In its most common use, the ultimate aim is to demonstrate control of health, safety, and environmental (HSE) hazards; therefore, it is first necessary to identify those hazards requiring bow-tie analysis. Once hazards have been identified, the bow-tie method can be applied to assess risks further and provide a framework for demonstrating effective control. Typically, bow ties are developed by asking a structured set of questions that build the diagram in a step-by-step fashion, detailed in Figs. 2 through 4 in the complete paper. Applying the Technique. Development of the bow-tie diagrams and critical tasks should be carried out in a structured manner to obtain quality information and best represent the actual risk-control arrangements. Fig. 2 summarizes an effective building process, which has been developed and refined through experience with a variety of companies, industries, and work groups.

Scanning laser polarimetry with variable corneal compensation: identification and correction for corneal birefringence in eyes with macular disease.

In scanning laser polarimetry with variable corneal compensation (SLP-VCC), the macula is used as an intraocular polarimeter to calculate and neutralize corneal birefringence based on an intact Henle's layer. The purpose of this investigation was to validate this strategy in eyes with macular structural disease. A nerve fiber analyzer was modified to enable the measurement of corneal polarization axis and magnitude so that compensation for corneal birefringence was eye specific. Normal subjects and patients with a variety of pathologic macular conditions underwent complete ocular examination, SLP-VCC, and direct measurement of the corneal polarization axis (CPA), with a slit-lamp-mounted corneal polarimeter. Macular birefringence patterns were classified as well defined, weak, or indeterminate bow ties. A new "screen" method is described that determines the anterior segment birefringence without relying on the presence of macular bow-tie patterns. Forty-seven eyes (20 normal, 27 with maculopathy) of 47 patients (mean age, 59.0 +/- 19.0 years; range, 24-88) were enrolled. The correlation between CPA measured with corneal polarimetry (CPA by P(IV) [fourth Purkinje image]) and SLP-VCC was less in eyes with macular disease (R(2) = 0.22, P = 0.024) compared with normal eyes (R(2) = 0.72, P < 0.0001). Eyes with macular disease had significantly (P = 0.007) more indeterminate macular bow ties (8/27; 29%) than did normal eyes (0/20). The magnitude of difference between CPA by P(IV) and CPA by SLP-VCC was significantly (P = 0.0007) greater in eyes with indeterminate bow-tie patterns than in weak and well-defined patterns. Although no relationship was observed between CPA and 12 retardation parameters obtained with SLP-VCC in normal eyes (P > 0.05), eyes with macular disease showed a significant association between CPA and average thickness (R(2) = 0.27, P = 0.005), ellipse average (R(2) = 0.24, P = 0.0085), superior average (R(2) = 0.24, P = 0.009), inferior average (R(2) = 0.28, P = 0.004), and superior integral (R(2) = 0.37, P = 0.0008), suggesting incomplete corneal compensation. Greater correlation between CPA by P(IV) and CPA derived by SLP-VCC was found by using the screen method (R(2) = 0.83, P < 0.0001) compared with the bow-tie method (R(2) = 0.22, P = 0.024) in eyes with maculopathy. Macular strategies for neutralization of corneal birefringence using SLP-VCC can fail if Henle's layer is disrupted by macular disease. The screen method provides a more robust measure of the anterior segment birefringence in some eyes with macular disease.

Advanced experimental techniques for measuring oscillator strengths of vacuum ultraviolet lines

Advanced experimental techniques for measuring oscillator strengths of atomic and ionic transitions in the vacuum ultraviolet (VUV) are described. A VUV time-resolved laser-induced-fluorescence experiment for radiative lifetime measurements on atoms and ions in a beam is operational. Recent work on VUV transitions of Si I and B I is described. These lifetimes provide the essential absolute normalization for converting relative oscillator strengths to absolute transition probabilities. Emission measurements of branching fractions at VUV and longer wavelengths are proposed. A large echelle spectrograph equipped with a CCD detector array will be used. This experiment will provide the sensitivity, resolving power, and data handling capability required for extensive high quality emission branching fraction measurements. We further propose to use absorption measurements on hollow cathode discharges to determine relative absorption oscillator strengths. A demonstration of a new technique for absorption spectroscopy on glow discharges is reported. The new technique provides the sensitivity, dynamic range, and data handling capability required for extensive high quality absorption measurements. Relative absorption and emission oscillator strengths will be least-square adjusted using the bowtie method and normalized with accurate radiative lifetimes.