Investigations of flame front propagation between interconnected process vessels. Development of a new flame front propagation time prediction model

For the case where a dust or gas explosion can occur in a connected process vessel, it would be useful, for the purpose of designing protection measures and also for assessing the existing protection measures such as the correct placement, to have a tool to estimate the time for flame front propagation along the connecting pipe. Measurements of data from large-scale explosion tests in industrially relevant process vessels are reported. To determine the flame front propagation time, either a 1 m³ or a 4.25 m³ primary process vessel was connected via a pipe to a mechanically or pneumatically fed 9.4 m³ secondary silo. The explosion propagation started after ignition of a maize starch/air mixture in the primary vessel. No additional dust was present along the connecting pipe. Systematic investigations of the explosion data have shown a relationship between the flame front propagating time and the reduced explosion over-pressure of the primary explosion vessel for both vessel volumes. Furthermore, it was possible to validate this theory by using explosion data from previous investigations. Using the data, a flame front propagation time prediction model was developed which is applicable for:

• •gas and dust explosions up to a K value of 100 and 200 bar m s⁻¹, respectively, and a maximum reduced explosion over-pressure of up to 7 bar;
• •explosion vessel volumes of 0.5, 1, 4.25 and 9.4 m³, independent of whether they are closed or vented;
• •connecting pipes of pneumatic systems with diameters of 100–200 mm and an air velocity up to 30 m s⁻¹;
• •open ended pipes and pipes of interconnected vessels with a diameter equal to or greater than 100 mm;
• •lengths of connecting pipe of at least 2.5–7 m.

     

The relationship between speeding behaviour (as measured by violation convictions) and crash involvement

While it seems rational to assume that crash involvement risk and outcome are influenced by the way one drives, nevertheless there is continuing controversy over the validity of certain categories of traffic law infractions as true measures of such behavior. Specifically, does the accumulation of tickets for speeding identify drivers as high risk for becoming culpably involved in speed-related crashes? Further, does a proclivity for exhibiting speeding behavior in the presence of police translate into a greater risk for involvement in high-severity collisions?The research reported in this paper attempted to address these issues. Several years of crash and conviction data were utilized to examine

• 1.(a) the risk of culpable crash involvement by severity of outcome during a 2-year period following 3 years of conviction record,
• 2.(b) the degree to which an increasing level of speeding convictions per driver relates to an increasing propensity for speed to be a factor in drivers' crash involvements.

The results of the research identified a clear distinction between the conviction categories of “exceeding the speed limit” and “excessive speed” in terms of these accident-violation relationships.     

Management of change: Lessons learned from staff reductions in the chemical process industry

Increasing global competition and shareholder pressure are causing major changes in the chemical industry. Over the last decade companies have been continuously improving staff efficiency. As a result, most modern chemical plants can be regarded as lean. Plans to further reduce the number of staff have come under increasing criticism by personnel for safety reasons, and there is strong resistance to further staff reductions. It is clear that management and workers often have conflicting viewpoints for more than just safety reasons; technologists and safety engineers also have different points of view. This results in complex decision-making processes and makes it difficult to realize changes.What can the chemical industries learn from their experiences of decision-making and management with regard to staff reductions?In our exploratory research that used four case studies, we were able to identify and analyse three distinct patterns, with some variations:

• •Fragmented and incomplete decision-making.
• •Unintended and undesirable side effects generated by the decision-making and management of change.
• •Development of difficult dilemmas and ambiguous issues.

In this paper, we present a conceptual model that includes factors important for optimizing shifts. This model can serve as a common frame of reference for all agents involved in the decision-making and management process with regard to staffing.The present study was based on four cases, which means our findings serve to form rather than test hypotheses. At this early stage it is not yet possible to generalize from or validate the results, but we plan to go beyond these preliminary results in future research.     

Human factors integration – Bridging the gap between system designers and end-users: A case study

Within any high hazard industry such as chemical, oil and gas, rail or nuclear, it is necessary to involve system end-users within the design process if system design is to be optimised. To facilitate the identification and assessment of end user requirements it is necessary to integrate human factors (HF) into design from the start of the design lifecycle.During 2004, the author facilitated the integration of HF into a development project being implemented at a major gas processing facility on mainland Britain. The approach taken to HF integration on the project is commonly applied across the high hazard industries. This paper will provide information on this process and the benefits that this provided to the operator. Details will be provided on the approach taken in terms of:

• –Liaison between HF and other design disciplines.
• –Analysis undertaken and tools used.
• –HF topic areas covered.
• –Specific issues raised and how these were resolved.

It will demonstrate the advantage of the early integrated approach as compared to the later auditing or assurance approach sometimes taken in relation to HF.     

Problems with identifiying a standard procedure for determining KG values for flammable vapors

Assessing the effect of potential confined fuel–air explosions involves the examination of several essential parameters. These include the limits of combustion, maximum pressure and the deflagration index or K_G. Accurate measurement of these parameters can be influenced by numerous experimental conditions. This paper describes the sensitivity of one of these parameters (K_G) to several experimental influences. The deflagration index, K_G, is important since it is the main design parameter for explosion protection systems. These studies used a highly automated 20 liter combustion sphere, with a 10 mm fuse wire igniter. Our results for methane combustion show that the deflagration index, K_G, is very sensitive to

• •the gas composition; a 1% change in nitrogen composition changed the index value by 12 bar-m/s along the stoichiometric line. Our studies also identified some problems with mixing gases to the desired composition.
• •the moisture content of the gas, which can change the index by 13 bar-m/s.

For some combustion gas compositions, it was difficult to describe a K_G value due to significant fluctuations in the pressure vs time data. Finally, an extensive study of fuse wire igniter dynamics identified a means to provide a consistent energy delivery to the igniter. All of these problems contribute significantly to specifying a standard procedure for determining the deflagration index.     

How the management aspects can affect the results of the QRA

This paper describes a procedure to include into the quantitative risk assessment (and namely in the construction and solution of the Fault Trees) the Safety Management System (SMS) aspects.The parameters used for probabilistic assessment of the Expected Number of Failures (ENF) of a Top Event are parameterised depending on:

• 1.a weight assigned to each SMS section with reference to the parameter;
• 2.a judgment about the correct application of the same SMS section.

Each probabilistic parameter (e.g. failure rates, mean time to repair, and so on) is thus modified using a mathematical algorithm, where an overall parameter including all the SMS sections influencing each single parameter is defined.The application of the procedure to a formaldehyde plant allowed the validation of the method and is here entirely reported.     

The oil and gas industry,the Offshore Installation Manager (OIM) and the management of emergencies - Changes necessary to achieve effective competence assessment of OIMs in controlling emergencies

Within the UK offshore oil and gas industry all installations require to be under the charge of a ‘competent’ installation manager in accordance with the Offshore Installations and Pipeline Works (Management and Administration) Regulations (MAR) 1995. The Offshore Installation Manager (OIM) is responsible for the safety of all persons onboard and within 500 m of an installation. Should an incident arise, the OIM performs one of the most critical roles within the offshore industry - 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. The emergency response also includes limiting the loss of hydrocarbons to the environment.Research at the University of Aberdeen has identified 8 potential barriers to the effective competence assessment of OIMs in controlling emergencies. These underlying barriers are a consequence of current UK legislation and industry practices in the assessment of OIM competence and result from:

• •multiple definitions of competence,
• •competence assessment predominantly by observation,
• •lack of specific and unambiguous competence requirements for trainers and assessors,
• •complexity in UK legislation and complicated interpretation of terms,
• •lack of statutory competence requirements for OIMs in controlling emergencies,
• •lack of ownership of OIM competence and competence assessment,
• •complex interactions across multiple UK Government departments, and
• •lack of regulation and independent audit of the competence assessment process of OIMs in controlling emergencies.

The potential barriers were identified by qualitative analysis of key documentation, including legislation, using a critical hermeneutic approach. Hermeneutics has historically been used to analyse texts within the domains of theology, business and law. It arguably, however, represents a powerful approach to the study of documents within the engineering domain and the offshore oil and gas industry.This paper discusses the identified potential barriers, research conclusions and recommendations and represents the culmination of three years of doctoral research investigating the competence assessment of OIMs in controlling emergencies within the offshore oil and gas industry. The research, in particular, is relevant to Duty Holders within the offshore industry, safety engineers and UK Government departments.     

A method,DEB analysis,for proactive risk analysis applied to air traffic control

Introduction: Complex production systems as, for instance, those used in health care, in off shore industry, in nuclear power industry or in aviation suffer now and then from severe system breakdowns. Lessons learnt from these often lead to changes in the “system”. A more rational approach would be to identify these “system weaknesses” before accidents happen.A new proactive method, DEB analysis, for identifying hazards in a complex system was applied to an air traffic control unit in Malmoe, Sweden. The system weaknesses (i.e. latent system failures and insufficient safety barriers), which could cause these hazards, were identified. The effectiveness of the method was assessed by comparing these “prospective” identified system weaknesses with “retrospective” identified system weaknesses in a consecutive series of loss of separation cases (n=15), investigated by the central aviation administration.Main findings: The system weaknesses in 14 out of the 15 cases were found with the proactive method. One sub-task was missed.Discussion: The method is an effective tool in disclosing system weaknesses that can give rise to hazards. The method should be modified with increased engagement of operators. It might be applied to other complex systems as well.     

Perceptions of personal vulnerability to workplace hazards in the Australian construction industry

Introduction

The importance of risk perception for workplace safety has been highlighted by the inclusion of risk appraisals in contemporary models of precautionary behavior at work. Optimism bias is the tendency to think that negative events are less likely to happen to oneself than to the average person, and is proposed to be related to the reduced use of precautions.

Method

Building on studies of optimism bias for workplace hazards using samples with heterogenous risk profiles, the current study aimed to investigate whether optimism bias is present in a sample of workers exposed to similar workplace hazards. 175 Australian construction workers completed a brief survey that asked them to rate the likelihood of common construction industry hazards occurring to them and to the average worker of the same age doing the same job. Significant levels of optimism bias were found for many hazards (including being electrocuted, being trapped in a confined space, falling from heights, and causing someone else to have an injury).

Results

Optimism bias was not related to perceived controllability, contrary to findings in other domains, yet consistent with findings of optimism bias for workplace hazards. Optimism bias was not found to be related to a reduction in safe work behaviors, though this may be due to difficulties in measuring safe or precautionary behavior, such as social desirability.

Impact on industry

That most workers think that hazards are less likely to happen to them than to the average worker presents a significant problem because it may ameliorate the efficacy of safety programs, yet constitutes a largely unexplored opportunity for improving workplace safety performance.     

“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.     

长株潭城市群核心区重大危险源安全规划研究

笔者结合《长株潭城市群区域规划》,从城市的安全功能区划、重大危险源辨识、重大危险源安全规划对象、风险评价、风险控制等5个方面,初步探讨该市重大危险源安全规划的一般方法和技术要点,初步提出长株潭核心区重大危险源安全规划的编制程序的构想:①重大事故的统计分析和基础资料调查;②确定重大危险源和区域性重大事故风险评价;③确定安全功能区划,提出各类规划对象可接受的风险标准;④确定整治规划方案及实施措施。     

Literature review on risky driving videos on YouTube: Unknown effects and areas for concern?

Objective: Entry of terms reflective of extreme risky driving behaviors into the YouTube website yields millions of videos. The majority of the top 20 highly subscribed automotive YouTube websites are focused on high-performance vehicles, high speed, and often risky driving. Moreover, young men are the heaviest users of online video sharing sites, overall streaming more videos, and watching them longer than any other group. The purpose of this article is to review the literature on YouTube videos and risky driving.

Methods: A systematic search was performed using the following specialized database sources—Scopus, PubMed, Web of Science, ERIC, and Google Scholar—for the years 2005–2015 for articles in the English language. Search words included “YouTube AND driving,” “YouTube AND speeding,” “YouTube AND racing.”

Results: No published research was found on the content of risky driving videos or on the effects of these videos on viewers. This literature review presents the current state of our published knowledge on the topic, which includes a review of the effects of mass media on risky driving cognitions; attitudes and behavior; similarities and differences between mass and social media; information on the YouTube platform; psychological theories that could support YouTube's potential effects on driving behavior; and 2 examples of risky driving behaviors (“sidewalk skiing” and “ghost riding the whip”) suggestive of varying levels of modeling behavior in subsequent YouTube videos.

Conclusions: Every month about 1 billion individuals are reported to view YouTube videos (ebizMBA Guide 2015 ebizMBA Guide. Top 15 most popular websites. 2015. Available at: http://www.ebizmba.com/articles/most-popular-websites [Google Scholar]) and young men are the heaviest users, overall streaming more YouTube videos and watching them longer than women and other age groups (Nielsen 2011 Nielsen. State of the media: the social media report. Q3. 2011. Available at: http://www.nielsen.com/us/en/insights/reports/2011/social-media-report-q3.html [Google Scholar]). This group is also the most dangerous group in traffic, engaging in more per capita violations and experiencing more per capita injuries and fatalities (e.g., Parker et al. 1995 Parker D, Reason J, Manstead ASR, Stradling SG. Driving errors, driving violations and accident involvement. Ergonomics. 1995;38:1036–1048.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]; Reason et al. 1990 Reason J, Manstead A, Stradling S, Baxter J, Campbell K. Errors and violations on the roads: a real distinction? Ergonomics. 1990;33:1315–1332.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]; Transport Canada 2015 Vingilis E, Yilderim-Yenier Z, Fischer P, et al. Self-concept as a risky driver: Mediating the relationship between racing video games and on-road driving violations in a community-based sample. Transp Res Part F Traffic Psychol Behav. 2016;43:15–23. [Google Scholar]; World Health Organization 2015 World Health Organization. Road traffic injuries. Fact sheet no. 358. 2015. Available at: http://www.who.int/mediacentre/factsheets/fs358/en/# Accessed March 14, 2016. [Google Scholar]). YouTube also contains many channels depicting risky driving videos. The time has come for the traffic safety community to begin exploring these relationships.     

Studded and unstudded winter tires in fatal road accidents in Finland

Objective: The aim of the study was to compare the safety effects of studded and unstudded winter tires based on fatal road accidents.

Methods: The data included 958 road accidents involving a passenger car or van that occurred in Finland from November to March between 1997 and 2012.

Results: Comparing the proportions of winter tire type in accidents and in general traffic showed that the overall effect of tire type on the number of accidents was not significant, although studded tires reduced fatal accidents by 10–15%. Compared to unstudded tires, studded tires reduced accidents significantly only on bald ice in 2005–2012. Drivers using unstudded tires were more experienced and their profession was more frequently related to driving. In addition, the vehicle age was lower for vehicles with unstudded tires. On the other hand, the state of repair was less pertinent for unstudded than for studded tires. These confounding factors offset their effects to some degree.

Conclusions: The risk of fatal road accidents in winter between studded and unstudded tires does not differ significantly. However, the accident risk has recently been substantially higher on bald ice for unstudded than for studded tires. The magnitude of this risk difference is difficult to determine without specific information on exposure by road surface.     

Perspectives on safety: The impact of group membership,work factors and trust on safety performance in UK and Norwegian drilling company employees

This study is anchored in a contractor company providing well services for platform drilling on the Norwegian (NCS) and the UK Continental Shelves (UKCS). The research project has as its point of departure the potential influences of group level characteristics, structural work factors, trust, and safety behaviour on safety performance. Do perceptions and performance differ across Shelves? Are “nomadic” groups or employees that have more unpredictable shift rotations more exposed to accidents than others? Is high trust and sound safety behaviour enhancing good safety performance? The results are based on questionnaire data from two samples of personnel distributed across three installations on the UKCS and nine on the NCS with a response rate of 67%: N = 170 (UKCS) and N = 621 (NCS). In addition, two focus group interviews were held in each country, with 15 participants in each. The results show that our model makes sense. Shelf shows a significant influence on safety performance in all but the final stage in our five-step logistic regression model, indicating that the effect may be mediated by safety compliance and safety participation. Installations and different work teams have different exposure and structural work factors matter significantly. Somewhat counter-intuitively, employees who have a “nomadic” status and who hold the least regular shift rotations appear to have a lower risk of being involved in incidents. High trust in workmates buffers against incident involvement and the same applies for high safety compliance. The results, challenges and implications for research and safety practitioners are discussed.     

Analyzing injury severity of bus passengers with different movements

Objective: Though public transport vehicles are rarely involved in mass casualty accidents, when they are, the number of injuries and fatalities is usually high due to the high passenger capacity. Of the few studies that have been conducted on bus safety, the majority focused on vehicle safety features, road environmental factors, as well as driver characteristics. Nevertheless, few studies have attempted to investigate the underlying risk factors related to bus occupants. This article presents an investigation aimed at identifying the risk factors affecting injury severity of bus passengers with different movements.

Method: Three different passenger movement types including standing, seated, and boarding/alighting were analyzed individually using classification and regression tree (CART) method based on publicly available accident database of Great Britain.

Results: According to the results of exploratory analyses, passenger age and vehicle maneuver are associated with passenger injury severity in all 3 types of accidents. Moreover, the variable “skidding and overturning” is associated with injury severity of seated passengers and driver age is correlated with injury severity of standing and boarding/alighting passengers.

Conclusions: The CART method shows its ability to identify and easily explain the complicated patterns affecting passenger injury severity. Several countermeasures to reduce bus passenger injury severity are recommended.     

Response to commentary on “The Driver Behaviour Questionnaire as a predictor of accidents: A meta-analysis”

A commentary on our previously published meta-analysis about the predictive validity of the Driver Behaviour Questionnaire (DBQ) raised a number of points. These points do not dispute the quantitative results as such, but suggest that our introduction and discussion overly favor the DBQ and are incomplete in a number of ways. The commentary targeted the following topics: common method variance, intercorrelations of different instruments, accident data validity, correcting for measurement error,

Common method variance

Our meta-analysis provided an extensive discussion of validity threats, including ones not treated before in the DBQ literature, such as common scale anchors and publication bias. We see little added value in the commentary when it informs the readership of common method variance (CMV), as we clearly did this in our article. It is widely understood that CMV can account for a large share of the variance when self-reported data are intercorrelated (see Podsakoff, MacKenzie, Lee, & Podsakoff, 2003

Intercorrelations of different instruments

The commentary reacts to an introductory sentence in which we stated that the DBQ is strongly situated in a network of other questionnaires and tests (such as Trait Anxiety, Cognitive Failures Questionnaire, and Sensation Seeking Scale), by asserting that we seem to interpret such correlations as a positive feature of the DBQ and by pointing out that correlations between the DBQ and other self-reports may have arisen spuriously because of CMV.We dispute the assertion that we regard correlations

Accident data validity

The commentary rejects our position that not only self-reported accident data are susceptible to biases, but recorded data too. Note that our remark applied to all types of recorded accidents, including police reports, hospital data, insurance data, as well as fleet data from professional drivers, and not just company data as in the work by af Wåhlberg, Dorn, and Kline (2011), which is mentioned in the commentary. The literature discusses several sources of bias for recorded accidents that are

Correcting for unreliability

The commentary pointed out that our correction for attenuation is unusual, a surprising claim considering the established importance of correction for measurement error in theory testing (Liu and Salvendy, 2009, Schmidt and Hunter, 1999). The available DBQ research provided almost no information on measurement error, so we did not apply a correction as part of the meta-analysis. Instead, we applied one afterwards, based on the raw data of the largest DBQ study available, and illustrated that

Exposure

The commentary points out that our results were not corrected for exposure in any way. First of all, this statement is false, because our meta-analysis did include effect sizes corrected for exposure. We used a special moderator category for effect sizes other than zero-order correlations. These effect sizes were derived from regression analysis, often with mileage as one of the predictors.Second, it may be noted that af Wåhlberg himself reported that the association between exposure and

Further references

The commentary attended us to 11 studies supposedly not included in our meta-analysis. We appreciate af Wåhlberg and Dorn's close scrutiny of our reference list for potential omissions on the DBQ-accident relationship. It may be noted that missing a small fraction of studies in a meta-analysis of this scope is almost inevitable.The samples of four of the studies (Dobson et al., 1999, Elliott et al., 2007, Parker, 1999, Stradling et al., 2005) identified in the commentary were already included

Discussion

The purpose of a meta-analysis is to provide a quantitative summary of a metric of interest, correlations between the DBQ, and external criteria in our case. af Wåhlberg and Dorn's commentary does not dispute the quantitative results in themselves (except with regard to the correction for exposure), but targets the qualitative introduction and discussion of our article.The commentary raises some valid points, albeit points already discussed in our article. We too believe that common method