“Vybuchovy trojuhelnik”: A software tool for evaluation of explosibility of coal mine atmosphere

Rescue operations during mine fires or methane explosions are highly dangerous for rescue workers. The knowledge of the composition of the coal mine atmosphere and the calculations of its explosibility may help to increase the safety of the rescuers. In the Czech Republic, a system called “Mine Gas Laboratory” (DPL) has been used for these purposes. The DPL allows measurement of the composition of the mine atmosphere and transmits the data necessary for evaluation to the surface. Up to now the explosibility evaluation of the coal mine atmosphere has depended either on the rescuers’ experience or on software code calculation. The code called “Vybuchovy trojuhelnik” (explosion triangle) is a graphical computing system intended for fast assessment of explosibility of fuel–air mixture. This article introduces the code and describes two simple methods of explosibility evaluation. The first method is “explosion triangle analysis”—a graphical method based on empirical graphs transformed into equations. The second method uses thermodynamic calculation based on chemical balance dynamics and Gibbs and Helmholtz energy. According to the requirements of the Czech Bureau of Mining (CBU) and Central Mine Rescue Service (HBZS), the code solves the problems of explosion triangle for both standard and non-standard coal mine atmosphere compositions. Unfortunately, the atmosphere composition must be introduced manually due to the unknown format of the data transmitted from the old DPL model. On 1 September 2005, a project started to develop a new system for on-line monitoring and atmosphere explosibility evaluation. The system should be able to measure CO₂, O₂, CH₄, H₂ and CO concentrations as well as the wind speed, temperature and humidity. The “Vybuchovy trojuhelnik” code will be used as a basis for explosibility evaluation, and an on-line connection with the new model of DPL will be established.     

“Slippery” work surfaces: Towards a performance definition and quantitative coefficient of friction criteria

There have been 50 years of research in walking/working surface slipperiness and coefficient of friction (COF) measurements. Nevertheless, numerous standards address slip/fall accidents only in terms of requiring surfaces to be qualitatively “nonslippery.” The literature useful for establishing quantitative criteria for “slippery” vs. “slip-resistant” have been summarized here. A performance definition for “slippery work surfaces” is proposed. Recommendations applicable to standards-making organizations are made, including changing terms such as “non-slip” to “slip-resistant” and defining “slippery” in terms of quantitative COF values. For persons walking unloaded on level surfaces, a COF standard of 0.5 would be reasonable. Research is recommended to determine if “slip-resistance” requirements and accident prevention could be achieved more easily be controlling the type of shoe, type of task, or amount of surface contaminant rather than controlling only the COF of the basic surface and its coating.     

A risk-estimation methodological framework using quantitative assessment techniques and real accidents’ data: Application in an aluminum extrusion industry

The risk estimation presumably is the most crucial part of the entire procedure of assessing hazards/unsafe situations in the work, and especially in the industries’ and constructions’ worksites, where the working conditions are unstable. We can consider the risk as a quantity, which can be estimated and expressed by a mathematical relation, under the help of real accidents’ data. The aim of this work is quadruplicate: (a) the development, elaboration and explanation of two new quantitative risk-assessment techniques, (b) the improvement of specific points of other scientific works, as far as concerns quantitative risk estimation, (c) the application of these techniques on an industrial productive procedure (as a case study) and (d) the comparison of their outcome risk-estimation results. Particularly, we develop and analyze the theoretical background of the two techniques, which we call as “proportional technique” and “decision matrix technique”, and apply them on an aluminum extrusion industry's worksite, which is situated in Greece, by using real data of potential sources of hazards, recorded by safety managers, during the 5.5-year time period of 1999–2004. Comparing the results of the two quantitative risk-assessment techniques, we infer that they are compatible. Therefore, the most important hazard source in the aluminum industry is the “squeezing and hits by dropping objects (transported by derricks)”, and imposes that immediate suppressive measures must be taken place to abolish the danger source.     

The effect of habit as a behavioural response in risk reduction programmes

A company's decision to implement a risk reduction programme must take account of employees' behavioural responses to the target risk. Hazard reporting by train drivers is examined in semi-structured interviews and a questionnaire study. It is suggested that the behavioural response of drivers, in terms of writing a report, depends on how the hazard is perceived. The response to “trivial” and “routine” hazards is habitual non-reporting, being characterized by a lack of risk evaluation. However, hazards that are evaluated as posing a significant risk are reported. Possible ways of breaking habitual responses to hazards, using behavioural change programmes, are discussed, and it is argued that management commitment is essential for their success.     

Application of domino effect quantitative risk assessment to an extended industrial area

Escalation of primary accidental scenarios triggering a “domino effect” have caused extremely severe accidental events in the chemical and process industry. The identification of possible escalation events is required in the safety assessment of sites where relevant quantities of hazardous substances are stored or handled. In the European Union, “Seveso-II” Directive requires the assessment of on-site and off-site possible escalation scenarios in sites falling under the obligations of the Directive. In the present study, a methodology developed for the quantitative assessment of risk due to domino effect was applied to the analysis of an extended industrial area. Recently developed equipment damage probability models were applied for the identification of the final scenarios and for escalation probability assessment. The domino package of the Aripar-GIS software was used for risk recomposition. The results evidence that quantitative risk assessment of escalation hazard is of fundamental importance in order to identify critical equipment and to address prevention and protection actions.     

Development of a method for predicting the ignition of explosive atmospheres by mechanical friction and impacts (MECHEX)

Mechanical friction and impacts is still today a main cause of ignition of explosive atmospheres (ATEX) in the industry and this trend seems to be stable in time. This situation certainly results from a significant gap of knowledge in the underlying mechanisms so that the parameters to play on are not precisely identified. In this programme of European dimensions, the process of degradation of the mechanical energy into heat during friction and impacts have been studied.

An extensive experimental programme is presented to this end. The mechanisms of dissipation of the mechanical energy into heat during friction has been studied with rubbing machines in which a slider equipped with temperature sensors rubs against a rotating wheel. For impacts, a new device has been developed using a special “air driven cannon” to propel a projectile accurately up to 50 m/s onto an inclined target. A very significant effort has been reserved to the investigation of the ignition mechanisms, not only for ATEX but also for dust accumulations.

Some “simple” modelling is proposed on purpose of practical applications. For frictional situations, a critical rubbing power is calculated without any limitations about any lower boundary concerning the rubbing velocity. For “impacts”, the relevant parameter for ignition is not the kinetic energy of the projectile but its velocity and the nature of the materials.     

Slip and fall accident prevention: A review of research, practice, and regulations

This paper summarizes current research, practices, and regulations regarding walking/working surface slipperiness and coefficient of friction (COF) measurements. The literature and data are reviewed from three aspects:

1. (a) the biomechanics of walking and psychophysiological factors involved in slips and falls studied by the scientific community,

2. (b) various measuring devices and methods developed in an attempt to quantify the “slipperiness” of walking/working surfaces, and

3. (c) an acceptable quantitative standard for the “slipperiness” of surfaces and the impact of the Americans with Disabilities Act (ADA) on such a standard.

Unresolved issues related to slip-resistance are identified. A multifaceted approach and synergy from researchers, the building industries, standards organizations, and government are needed to obtain concensus on such issues.     

Unified correlations for vent sizing of enclosures at atmospheric and elevated pressures

Innovative vent sizing technology is presented for explosion safety design of equipment at atmospheric and elevated initial pressures. Unified correlations for vent sizing are suggested. They are modifications of previously reported correlations verified thoroughly for experimental data on vented gaseous deflagrations under different conditions but only at initial atmospheric pressure. Suggested correlations are based on experimental data on vented deflagrations of quiescent and turbulent propane–air mixtures at initial pressures up to 0.7 MPa. Typical values of turbulence factor and deflagration–outflow interaction number are obtained for experimental vented deflagrations at initial pressures higher than atmospheric.

“Blind” examination of new vent sizing technology on another set of experiments with methane–air and propane–air mixtures has shown that predictions by suggested vent sizing technology are better than by the NFPA 68 guide for “Venting of Deflagrations”.

In the development of recently reported results for initial atmospheric pressure it has been concluded that the innovative vent sizing technology is more reliable compared to the NFPA 68 guide at elevated initial pressures as well. Moreover it is crucial that the calculation procedure remains the same for arbitrary deflagration conditions.     

Combating interference by unauthorised persons

Under the new threat situation it is necessary to impede and if necessary detect ingress by unauthorised persons into the relevant establishment. It may be necessary to take additional measures to protect installations or parts thereof that are especially hazardous or at risk from terrorist attacks from interference by unauthorised persons.

It is the duty of the state to take precautionary and preventive measures to impede or prevent external terrorist attacks or entry by force into establishments. The necessary resources for this purpose must be made available even in times of limited budgets.

Since total protection can never be guaranteed, external emergency measures have a particularly important role to play. The competent authorities in this sector must receive the necessary information from the operators and must take the measures within their sphere of responsibility without delay.

Much of the information necessary for assessment of the risk situation by the operators and the authorities is already available under the provisions on the safety report and the external alarm and emergency plans according to European Seveso II Directive (96/82/EC).

It is recommended that a restriction of disclosure of information on the grounds of public safety should only be permitted for establishments/installations which are to be regarded as security-relevant on the basis of the hazard and the risk analysis.

The outline of the systematic approach of a security analysis like it is proposed in Germany is described separately.     

Accidents and risk control

A framework for transformation of knowledge and experience from risk analysis to emergency education is presented. An accident model was developed built on the concept “uncontrolled flow of energy (UFOE)”, where essential elements are the state, location and movement of the energy. A UFOE can be considered as the driving force of an accident, e.g. an explosion, a release of heavy gases. A domain model has been developed for representing emergencies occurring in society. A domain is a group of activities with allied goals and elements, and the domain model uses three main categories: status, context and objectives. Ten specific domains have been investigated including process plant, energy production and distribution, natural disasters and different sorts of transport. Totally 25 accident cases were consulted and information was extracted for filling into the schematic representations with two to four cases pr. specific domain.     

Risky, aggressive, or emotional driving: addressing the need for consistent communication in research

Problem. Researchers agree that a consistent definition for aggressive driving is lacking. Such definitional ambiguity in the literature impedes the accumulation of accurate and precise information, and prevents researchers from communicating clearly about findings and implications for future research directions. This dramatically slows progress in understanding the causes and maintenance factors of aggressive driving. Summary. This article critiques prevailing definitions of driver aggression and generates a definition that, if used consistently, can improve the utility of future research. Pertinent driving behaviors have been variably labeled in the literature as risky, aggressive, or road rage. The authors suggest that the term “road rage” be eliminated from research because it has been used inconsistently and has little probability of being clarified and applied consistently. Instead, driving behaviors that endanger or have the potential to endanger others should be considered as lying on a behavioral spectrum of dangerous driving. Three dimensions of dangerous driving are delineated: (a) intentional acts of aggression toward others, (b) negative emotions experienced while driving, and (c) risk-taking. Impact on Industry. The adoption of a standardized definition for aggressive driving should spark researchers to use more explicit operational definitions that are consistent with theoretical foundations. The use of consistent and unambiguous operational definitions will increase the precision of measurement in research and enhance authors' ability to communicate clearly about findings and conclusions. As this occurs over time, industry will reap benefits from more carefully conducted research. Such benefits may include the development of more valid and reliable means of selecting safe professional drivers, conducting accurate risk assessments, and creating preventative and remedial dangerous driving safety programs.     

Important meteorological data for use in risk assessment

This paper presents a methodology for the calculation of atmospheric stability classes in correlation with wind velocities for six sites of the Greek territory, namely Ellinikon (Athens), Elefsis, Megara, Heraklion, Chania and Patras, based on real data obtained from meteorological observations in these sites and on computations related with their geographic position. In addition to that, a comparison is presented of the atmospheric stability classes produced with online measurements for the Ellinikon (Athens) site with significant coincidence in the results.

These calculated values of the meteorological parameters (particularly of atmospheric stability) are most appropriate for uncertainty calculations in quantified risk assessments (QRAs) of hazardous installations sited in the above-mentioned areas, especially when risk and safety-related decisions need to be taken. Consequent results obtained with these parameters are more realistic compared to the “classical” assumption of D5/F2, which leads to significant diversification in the estimation of risk.     

Prevention and suppression of explosions in gas-air and dust-air mixtures using powder aerosol-inhibitor

The prevention and suppression of explosions is a very topical field of research because annually hundreds of coal mine workers became their victims. In this research a very effective powder “powder for suppression of explosions” (“PSE”) for the suppression of explosions has been developed and tested. The experiments on suppression of explosions of a methane–air mixture (MAM) at a laboratory conditions using “PSE”-powder have been carried out. The possibility of lowering the power of coal-dust explosion with the help of a “PSE”-powder has been investigated. The feasibility of almost instantaneous disperse of powders using intentionally created mini-explosions (ammonal) was investigated. The barrel-suppressor of explosion in the experimental adit (tunnel) was studied and the large-scale tests for suppression of MAM-explosions in experimental adit were also subjects of study.     

Strategies for controlling hazards at work

This paper presents an heuristic framework for analyzing hazards (potential for loss or harm) and strategies that may be developed to control their realization. Two basic forms of intervention for hazard control (anticipation and reaction) are identified. Three broad anticipative strategies are discussed: (1) elimination of the source of the hazard, (2) containment of the risk of its realization, and (3) mitigation of likely consequences. The communication and judgmental processes involved in decisions about strategies are shown to be embedded in the organizational “political” context, in which a variety of interests backed by varying sources of power and influence are represented. The development, implementation, and monitoring of any strategies that are decided upon are then discussed, including the fact that such actions and events may not produce the intended results. Comments are also made on the need for data provided by monitoring to be evaluated and appropriate adaptations made. Finally, a brief section of the paper discusses reactive strategies.     

Electrostatic spark ignition of sensitive dust clouds of MIE<1 mJ

Accidental electrostatic sparks in industrial plant producing/handling powders/dusts occur whenever a non-earthed electrically conducting object has been charged tribo-electrically to a high voltage and suddenly discharges its energy to earth via an air gap of appropriate length. When assessing the electrostatic spark ignition hazard in an industrial plant, the parameters of prime concern are the capacitances C of electrically conducting plant items that may become charged tribo-electrically, the voltages U to which they may become charged, and the minimum electric spark ignition energies (MIE) of the dust clouds of concern. Whenever , there is a possibility of accidental electrostatic spark ignition.

Current standard apparatuses for determining MIE of dust clouds have a lower spark energy limit of 2–3 mJ. In an investigation by the present authors, discussed in detail elsewhere, a new spark generator capable of producing synchronized capacitive sparks of energies down to the order of 0.01 mJ was developed and used for testing a selection of ignition-sensitive powders for MIE. Several of the MIEs found were 1–2 orders of magnitude lower than the lower energy limit of current standard test apparatus. Other experiments by the present authors, also reported elsewhere, have shown that quite low MIEs can be found for some dusts even with a less optimal synchronization mechanism, which may occur accidentally in practice.

The main object of the present paper is to discuss possible practical concerns arising from the finding that clouds in air of some dusts can have very low MIEs. In such cases, one may have to pay attention to even minor C values, i.e. minor plant items. Alternatively, with larger C values, even quite low voltages may give rise to hazardous spark discharges.

However, some types of fine metal powders of low MIEs will quite readily form electrically conductive layers on the solid surfaces with which they make contact. Hence, electrostatic spark ignition inside process equipment containing such dusts may be less probable than in the case of process equipment containing non-conducting dusts of correspondingly low MIEs.

There may be a need for a new standard test method for determination of MIEs of dust clouds in the <1 mJ range.     

Expert opinions, fuzzy probabilities, and warnings: toward a mathematical method for evaluating warning “read and heed” effectiveness

In many situations, and particularly in legal matters, decisions may be based on whether some possibility is judged to be “more probable than not”, as for example, whether a warning, had it been present, would “more probably than not” have prevented an injury. The probability of a warning accomplishing its purpose of preventing injury can, in principle, be computed based on probability calculus. However, this paper proposes that: (1) such computations must use “fuzzy” probability statements which as a result produce a range of weighted possibilities for the final outcome and, moreover; (2) the critical statistic for determining whether the outcome is “more probable than not” is the median rather than the mean of the possible outcomes. This paper briefly outlines the mathematics for such computations and provides several examples. The paper basically treats fuzzy probabilities as standard “random variables” restricted to the range of [0,1].For brevity, this paper only treats the multiplication of two or more fuzzy probabilities. However, this is adequate for evaluation of a two stage “read and heed”, or of longer multiple step linear sequences and is indicative of the general approach. Treatment of the additive and general case will be found in later publications.     

A quantitative risk assessment tool for the external safety of industrial plants with a dust explosion hazard

A quantitative risk assessment (QRA) tool has been developed by TNO for the external safety of industrial plants with a dust explosion hazard. As a first step an industrial plant is divided into groups of modules, defined by their size, shape, and constructional properties. Then the relevant explosion scenarios are determined, together with their frequency of occurrence. These include scenarios in which one module participates, as well as domino scenarios. The frequency is partly based on casuistry.

A typical burning velocity is determined depending on the ignition type, the dust properties and the local conditions for flame acceleration. The resulting pressure development is predicted with the ‘thin flame model’. Module failure occurs when the explosion load exceeds thresholds, which are derived from single degree of freedom (SDOF) calculations for various types of modules. A model has been developed to predict the process of pressure venting after module failure and the related motion of launched module parts.

The blast effects of the primary explosion are based on results from calculations with BLAST3D. The blast and flame effects of the secondary external explosion due to venting are calculated using existing models. The throw of fragments and debris is quantified with a recently developed model. This model is based on trajectory calculations and gives the impact densities, velocities, and angles as output. Furthermore the outflow of bulk material is taken into account. The consequences for external objects and human beings are calculated using existing models. Finally the risk contours and the Societal risk (FN curve) are calculated, which can be compared to regulations.     

Some experiences in hazard identification and risk shortlisting

‘Rapid ranking’ has been used for many years as a method of determining the priority which should be given to formal investigation of the wide range of hazards and risks present on major process industry sites. Such methods tend to evolve to meet the needs of specific applications. Some historical and recent applications are outlined, and the nature of the developments which they led to are discussed. Particular topics discussed include: development of the method such that it is usable by operating managers rather than specialists; use to raise risk consciousness; adaptation for use as an aid to hazard identification; use to define both which risks should be studied and which risks, even if low, should be incorporated in routine monitoring and periodic auditing programmes; use as a basis for comparison of the relative risks presented by a variety of different industrial installations; use for a range of different types of risk; and extension beyond ranking to include ‘shortlisting’ i.e. deciding which risks to include in a study programme and which to leave out. Philosophical difficulties with the approach are discussed, including the danger of omitting from detailed study a risk which is erroneously shown as low, and the uncertainty of the absolute level of the ranked risks. Approaches to minimizing these problems are discussed.     

风险管理在船舶保安中的应用研究

对一艘船舶而言,由于其货物、人员、贸易航线具有流动性、危险性和隐蔽性等特点,存在着不同程度被恐怖主义利用和攻击的威胁风险,并且一旦发生保安事件所带来的后果非常严重,包括人命伤害、财产损失、环境破坏,甚至引起社会恐慌等,因此,船舶保安已成为国际航运界关注的焦点。本文根据风险管理原理,结合ISPS规则要求,确定船舶保安风险管理流程,并对船舶面临的保安威胁进行辩识分析,提出旨在降低船舶可能遭受恐怖威胁的保安措施,以指导航运企业保安工作的开展。