Showing papers in "Journal of Loss Prevention in The Process Industries in 2008"

A correlation among safety leadership, safety climate and safety performance

Abstract: There has not been much consensus on the causality of safety climates in the past 25 years. Moreover, there is an overall lack of models specifying the relationship among safety leadership, safety climate and safety performance. On the grounds of social system theory, this study has investigated the potential correlation among them. Self-administered questionnaires that included a safety leadership scale, a safety climate scale and a safety performance scale were used to collect data in four universities in central Taiwan. The survey was conducted among 754 subjects selected via simple random sampling. The number of returned valid questionnaires was 465, and the response rate was 61.67%. Path analysis showed that safety climate partially mediated the relationship between safety leadership and safety performance. Canonical correlation analysis showed that safety controlling, one factor of safety leadership, had main influence on CEOs and managers’ safety commitment and action in safety climate, and on safety organization and management, safety equipment and measures, and accident investigations in safety performance. The results of the statistical analysis indicated that organizational leaders would do well to develop a strategy by which they improve the safety climates within their organizations, which will then have a positive effect on safety performance.

Self-ignition and explosion during discharge of high-pressure hydrogen

Abstract: The phenomenon of self-ignition and explosion during discharge of high-pressure hydrogen was investigated. To clarify the ignition conditions of high-pressure hydrogen jets, rapid discharge of the high-pressure hydrogen was examined experimentally. A diaphragm was used to allow rapid discharge of the high-pressure hydrogen. The burst pressure was varied from 4 to 30 MPa. The downstream geometry of the diaphragm was a flange and extension pipes, with the pipe length varying from 3 to 300 mm. The diameter of the nozzle was 5 or 10 mm. When short pipes were used, the hydrogen jet did not ignite. However, the hydrogen jet showed an increasing tendency to ignite in the pipe as the length of the pipe became longer. At higher burst pressures, a diffusion jet flame was formed from the pipe. The blast wave from the fireball formed on self-ignition of the hydrogen jet resulted in an extremely rapid pressure rise.

Damage to Offshore Oil and Gas Facilities Following Hurricanes Katrina and Rita: An Overview

Abstract: Hurricanes Katrina and Rita hit the centre of the American petrochemical industry, shutting down eight refineries, hundreds of oil-drilling and production platforms, and many other industrial facilities. Furthermore, it triggered unprecedented numbers of hazardous-materials releases from industrial facilities and storage terminals onshore, as well as from oil and gas production facilities offshore in the Gulf of Mexico (GoM). In this paper, we analyse the damage caused by the two hurricanes on the offshore oil and gas industry. Hurricanes Katrina and Rita caused the largest number of destroyed and damaged platforms and pipelines, and the highest number of mobile offshore drilling units set adrift in the history of GoM operations. Following the hurricanes, changes have been proposed to operating and emergency procedures, maintenance requirements, and design practices including mooring practices for mobile offshore drilling units.

Comments on explosion problems for hydrogen safety

Abstract: The future widespread use of hydrogen as an energy carrier brings in safety issues that have to be addressed before public acceptance can be achieved. The prediction of the consequences of a major accident release of hydrogen into the atmosphere or the contamination of high-pressure hydrogen storage facilities by air entrainment requires a good knowledge of the explosion parameters of hydrogen–air mixtures. The present paper reviews and comments on the current knowledge of dynamic parameters of hydrogen detonation for hazard assessment. The major problem that remains to be resolved involves the understanding of the effect of turbulence on the cellular detonation structure, the propagation of high-speed deflagrations and the transition from deflagration to detonations. It is recommended that future research should be aimed towards experiments that permit the quantitative understanding of the mechanisms of high-speed turbulent combustion rather towards large-scale tests in complex geometries where minimal quantitative information of fundamental significance could be extracted. In spite of its wide flammability and sensitivity to ignition and detonation initiation, it is felt that hydrogen can be produced, stored and handled safely with the appropriate considerations in the design of the hydrogen facilities.

Mechanisms of high-pressure hydrogen gas self-ignition in tubes

Abstract: This paper describes a numerical and experimental investigation of hydrogen self-ignition occurring as a result of the formation of a shock wave. The shock wave is formed in front of high-pressure hydrogen gas propagating in a tube. The ignition of the hydrogen–air mixture occurs at the contact surface of the hydrogen and oxidant mixture and is due to the temperature increase produced as a result of the shock wave. The required condition for self-ignition is to maintain the high temperature in the mixture for a time long enough for inflammation to take place. The experimental technique employed was based on a high-pressure chamber pressurized with hydrogen, to the point of a burst disk operating to discharge pressurized hydrogen into a tube of cylindrical or rectangular cross section containing air. A physicochemical model involving gas-dynamic transport of a viscous gas, detailed kinetics of hydrogen oxidation and heat exchange in the laminar approach was used for calculations of high-pressure hydrogen self-ignition. The reservoir pressure range, when a shock wave is formed in the air that has sufficient intensity to produce self-ignition of the hydrogen–air mixture, is found. An analysis of governing physical phenomena based on the experimental and numerical results of the initial conditions (the hydrogen pressure inside the vessel, and the shape of the tube in which the hydrogen was discharged) and physical mechanisms that lead to combustion is presented.

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

Abstract: 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.

Study of the human evacuation simulation of metro fire safety analysis in China

Abstract: Metro construction in China enjoyed and will continue to enjoy unprecedented development in the tenth 5 Year Plan period and the upcoming eleventh 5 Year Plan period. In China, cities are densely populated, and as a modernized urban rail transit means, metros have been undertaking increasingly important tasks of large passenger flow transportation, under which circumstance the injury and casualty will be enormous if an accident occurs. China's work safe laws and regulations have stipulated that safety evaluation must be carried out during planning, design, construction and operation of metros. As a part of the metro safety evaluation, occupant safe evacuation is a critical aspect to be assessed. This paper will first introduce the occupants evacuation design in the construction of metros in China based on Code for design of metro (CFDOM) (GB 50157-2003), including evacuation passage design, evacuation time and evacuation safe area as well as fire-engineering-based occupants evacuation design philosophy and calculation method. Finally, a computer simulation of the process of evacuation of occupants from deep buried metro station (DBMS) by using occupants evacuation dynamic model will be conducted on the example of DBMS of Guangzhou Metro Line 6, so as to study whether the occupants can be safely evacuated from DBMS in case of fire.

Individual risk analysis of high-pressure natural gas pipelines

Abstract: Transmission pipelines carrying natural gas are not typically within secure industrial sites, but are routed across land out of the ownership of the pipeline company. If the natural gas is accidentally released and ignited, the hazard distance associated with these pipelines to people and property is known to range from under 20 m for a smaller pipeline at lower pressure to up to over 300 m for a larger pipeline at higher pressure. Therefore, pipeline operators and regulators must address the associated public safety issues. This paper focuses on a method to explicitly calculate the individual risk of a transmission pipeline carrying natural gas. The method is based on reasonable accident scenarios for route planning related to the pipeline's proximity to the surrounding buildings. The minimum proximity distances between the pipeline and buildings are based on the rupture of the pipeline, with the distances chosen to correspond to a radiation level of approximately 32 kW/m2. In the design criteria for steel pipelines for high-pressure gas transmission (IGE/TD/1), the minimum building proximity distances for rural areas are located between individual risk values of 10−5 and 10−6. Therefore, the risk from a natural gas transmission pipeline is low compared with risk at the building separated minimum distance from chemical industries.

Flame acceleration and DDT run-up distance for smooth and obstacles filled tubes

Abstract: The process of flame acceleration inside the tubes and channels depends on several parameters such as nature of the fuel involved, composition of the mixture and configuration of the enclosure itself. The wall roughness and the presence of obstacles in the flame path act as a turbulence generator causing continuous flame acceleration. In some situations the flame can reach a sufficiently high speed to allow the transition of the deflagration into a detonation. A considerably large amount of experimental data on flame speed and DDT run-up distance for several mixtures have been accumulated. Nevertheless simple relationships, based on the most relevant parameters governing the phenomenon, could be useful for design purpose and safety assessment. The present paper suggests some simplified formulas for the evaluation of flame speed and DDT run-up distance of flammable mixtures for both smooth and obstacles filled tubes.

Numerical study on the spontaneous ignition of pressurized hydrogen release through a tube into air

Abstract: Spontaneous ignition of pressurized hydrogen release through a tube into air is investigated using a modified version of the KIVA-3V CFD code. A mixture-averaged multi-component approach is used for accurate calculation of molecular transport. Autoignition and combustion chemistry is accounted for using a 21 step kinetic scheme. Ultra fine meshes are employed along with the Arbitrary Lagrangia–Eulerian (ALE) method to reduce false numerical diffusion. The study has demonstrated a possible mechanism for spontaneous ignition through molecular diffusion. In the simulated scenario, the tube provided additional time to achieve a combustible mixture at the hydrogen–air contact surface. When the tube was sufficiently long under certain release pressure, autoignition would initiate inside the tube at the contact surface due to mass and energy exchange between low temperature hydrogen and shock-heated air through molecular diffusion. Following further development of the hydrogen jet downstream, the contact surface became distorted. Turbulence plays an important role for hydrogen/air mixing in the immediate vicinity of this distorted contact surface and led the initial laminar flame to transit into a stable turbulent flame.

Runaway reaction and thermal hazards simulation of cumene hydroperoxide by DSC

Abstract: A simplified self-heating rate equation was developed to simulate the adiabatic thermal hazards of 88 mass% cumene hydroperoxide (CHP) in cumene. CHP has been predominantly used in producing phenol and acetone by catalytic cleavage and as initiator in the acrylonitrile–butadiene–styrene (ABS) copolymer polymerization process. In this study, we acquired experimental data, such as the heat of decomposition (Δ H d ) and exothermic onset temperature ( T 0 ) by differential scanning calorimetry (DSC). The data were, in turn, used to simulate a runaway reaction and thermal analysis on 88 mass% CHP under various scenarios. The thermal safety software (TSS) series was employed to evaluate reaction kinetics, to simulate the runaway excursion of interest and to allow determination of critical conditions or thermal explosion of the tank. The liquid thermal explosion (LTE) model to simulate thermal explosion of CHP is aimed at ensuring safe storage or transportation. The reliability of both model simulations was assessed by experimentally comparing the thermal hazards with DSC. This simplified methodology is a sound, efficient tool for thermal hazards assessment of energetic chemicals.

CFD modelling of hydrogen release, dispersion and combustion for automotive scenarios

Abstract: The paper describes the analysis of the potential effects of releases from compressed gaseous hydrogen systems on commercial vehicles in urban and tunnel environments using computational fluid dynamics (CFD). Comparative releases from compressed natural gas systems are also included in the analysis. This study is restricted to typical non-articulated single deck city buses. Hydrogen releases are considered from storage systems with nominal working pressures of 20, 35 and 70 MPa, and a comparative natural gas release (20 MPa). The cases investigated are based on the assumptions that either fire causes a release via a thermally activated pressure relief device(s) (PRD) and that the released gas vents without immediately igniting, or that a PRD fails. Various release strategies were taken into account. For each configuration some worst-case scenarios are considered. By far the most critical case investigated in the urban environment, is a rapid release of the entire hydrogen or natural gas storage system such as the simultaneous opening of all PRDs. If ignition occurs, the effects could be expected to be similar to the 1983 Stockholm hydrogen accident [Venetsanos, A. G., Huld, T., Adams, P., & Bartzis, J. G. (2003). Source, dispersion and combustion modelling of an accidental release of hydrogen in an urban environment. Journal of Hazardous Materials, A105, 1–25]. In the cases where the hydrogen release is restricted, for example, by venting through a single PRD, the effects are relatively minor and localised close to the area of the flammable cloud. With increasing hydrogen storage pressure, the maximum energy available in a flammable cloud after a release increases, as do the predicted overpressures resulting from combustion. Even in the relatively confined environment considered, the effects on the combustion regime are closer to what would be expected in a more open environment, i.e. a slow deflagration should be expected. Among the cases studied the most severe one was a rapid release of the entire hydrogen (40 kg) or natural gas (168 kg) storage system within the confines of a tunnel. In this case there was minimal difference between a release from a 20 MPa natural gas system or a 20 MPa hydrogen system, however, a similar release from a 35 MPa hydrogen system was significantly more severe and particularly in terms of predicted overpressures. The present study has also highlighted that the ignition point significantly affects the combustion regime in confined environments. The results have indicated that critical cases in tunnels may tend towards a fast deflagration, or where there are turbulence generating features, e.g. multiple obstacles, there is the possibility that the combustion regime could progress to a detonation. When comparing the urban and tunnel environments, a similar release of hydrogen is significantly more severe in a tunnel, and the energy available in the flammable cloud is greater and remains for a longer period in tunnels. When comparing hydrogen and natural gas releases, for the cases and environments investigated and within the limits of the assumptions, it appears that hydrogen requires different mitigation measures in order that the potential effects are similar to those of natural gas in case of an accident. With respect to a PRD opening strategy, hydrogen storage systems should be designed to avoid simultaneous opening of all PRD, and that for the consequences of the released energy to be mitigated, either the number of PRDs opening should be limited or their vents to atmosphere should be restricted (the latter point would require validation by a comprehensive risk assessment).

Dust/vapour explosions : Hybrid behaviours?

Abstract: This article underlines the peculiar behaviour of hybrid mixtures towards explosions. It should notably be noticed that there are more than additive effects on explosions severity, especially on the maximum rate of pressure rise. Moreover, the evolution of the maximum explosion pressure as a function of combustibles concentrations shows that the impact of hybrid mixtures is perceptible even for vapour amounts or dust concentrations lower than the explosion limits of the pure compounds.

The evaluation of safety behaviors in a gas treatment company in Iran

Abstract: The study aims to evaluate the workers’ safety behavior in an Iranian gas treatment company. The methodology was based on the safety behavior sampling (SBS) technique. After specifying the unsafe behaviors and with reference to the results of a pilot study, a sample of 3248 was determined, with a sampling accuracy of 5% and confidence level of 95%. The results indicated that 26.7% of workers’ behaviors were unsafe. The most important unsafe behaviors were awkward postures in working hours with 13.1% of total unsafe behaviors. The results also notified a significant relationship between age and job experience on unsafe behaviors (p<0.001). The relationship between unsafe behaviors and previous accidents records was also significant (p<0.005). The ultimate findings of the study showed that a considerable number of workers’ behaviors were unsafe, which is one of the main antecedents of industrial accidents. Considering catastrophic consequences of accidents in gas treatment industry, the results emphasize on diminishing unsafe behaviors and recommend applying behavior-based safety principles.

Micro incident analysis framework to assess safety and resilience in the operation of safe critical systems: A case study in a nuclear power plant

Abstract: Safety in modern organizations, comprised of many nested levels with different types of coupling between them, must be managed by a control structure embedded in this adaptive sociotechnical system. The resilience of sociotechnical critical systems still relies on human ability to handle unexpected events adequately. In this study, based on a schematic view of a nuclear power plant control system composed of three structural system layers, planning, operation, and hardware, we present a framework to analyze micro incidents during nuclear power plant operation. The analysis show operators’ control actions used to solve small conflicts that arose at the operational layer, and how they marshaled the resources required for their action/cognition, i.e. the material, social, and cultural characteristics of the environment. The micro incident framework enables an anticipated view of operators’ control actions, providing processes for systemic analysis and critical thinking about the possibility that relatively small problematic situations in the loosely coupled system layers may lead to negative outcomes at some future time.

Combination of safety integrity levels (SILs): A study of IEC61508 merging rules

Abstract: The role of a safety system is to provide a safety-related function in order to monitor and maintain the safety of any equipment under its control. The safety analysis of such systems is of prime importance to avoid catastrophic consequences or even the loss of human life. In general, the various hazards that any equipment may encounter are considered without any safety functions. Later on, each hazard is studied using methods such as the risk matrix to quantify the associated risk. These methods determine which safety integrity level (SIL) needs to be implemented in order to reduce this risk to a tolerable one. Once this safety target is evaluated, an architecture is chosen during the design phase of the safety system. The standard IEC61508 states the requirements for safety systems to verify if the implemented functions reach these targets. For instance, Part 2 suggests a non-prescriptive method to merge different safety subsystems in order to achieve one with a higher SIL than those supplied by these subsystems. During the design of a SIS, the SIL selection is a very critical phase because often this system is the last line of protection against hazardous events. Even if this method is just informative, using it as a guide to follow may be an easy shortcut to label products with a dedicated safety degree. This merging method seems not to be based on an analytical method and for this reason the present paper investigates its robustness by starting from a multiphase Markovian approach. It consists in dividing the study window time of a system in phases in which a Markovian modelling is available. This method is then applied to two tudy cases given in the standard to illustrate the use of this merging method.

A hazmat multi-commodity routing model satisfying risk criteria: a case study

Abstract: The risk caused by transportation of hazardous materials can be reduced by routing, that is by the choice of alternative less risky paths than those usually preferred by truck drivers. In order to solve the routing problem a new model named OptiPath has been developed, offering a wide set of different optimisation strategies, optionally including compliance with risk acceptability criteria. The OptiPath methodology has been integrated in the Trat4-GIS software for transportation risk analysis. In this paper the application of OptiPath to a complex Italian real-life scenario is outlined. The main aim of the work is to show the capability of the methodology in highlighting the trade-offs among strategies for the selection of the preferred solution and the importance of Trat4-GIS in offering help to administrators involved in the decision-making process which characterises land-use and transportation planning activities.

Detailed and reduced chemistry for hydrogen autoignition

Abstract: Reaction-rate parameters are given for the detailed chemistry of gas-phase hydrogen combustion, involving 21 reversible elementary steps. It is indicated that, when attention is restricted to specific combustion processes and particular conditions of interest, fewer elementary steps are needed. In particular, for calculating autoignition times over a wide range of pressures for temperatures between about 1000 and 2000 K, five irreversible elementary steps suffice, yielding a remarkable reduction in complexity. It is explained that, from a mathematical viewpoint, in terms of global reaction-kinetic mechanisms, the hydrogen–oxygen system in principle comprises only six overall steps. Rational reduced chemical mechanisms for hydrogen combustion therefore necessarily must have fewer than six overall steps. For autoignition over the range of conditions specified above, ignition times can be determined accurately by considering, in addition to an elementary initiation step and an elementary termination step, at most three overall steps for reaction intermediaries, which reduce to two for very fuel-lean conditions and to one for stoichiometric or fuel-rich conditions. The resulting reductions can simplify computations that need to be performed in risk analyses for hydrogen storage and utilization.

Managing domino effect-related security of industrial areas

Abstract: In chemical enterprises, security managers are interested in easy-to-handle and user-friendly decision-support tools, providing them with straightforward information ready for implementation. Therefore, a theoretical conceptualization on how to manage-in a relatively simple way-the prevention and the mitigation of intentionally induced domino effects in a possibly very complex industrial cluster is described in this paper. The theoretical concepts for treating different chemical companies as single industrial area, and how security experts can deal with high-consequence security matters is explained. A case study illustrates a real application of the novel computer-automated tool designed for enhancing security measures at a cluster level.

The use of a simulator to include human factors issues in the interface design of a nuclear power plant control room

Abstract: Technology plays an important role in advanced control rooms that relies on complex technical equipment and interfaces. Human error has many causes such as performance shaping factors, organizational factors and interface design. In the safe operation of nuclear power plant, the performance of the control room crew plays an important role. In this respect, a well-designed control room and human–system interfaces (HSIs) are crucial for safe and efficient operation of the plant, reducing the occurrence of incidents, accidents and the risks of human error. Therefore, it is essential that the interfaces design must be conducted in a well-structured way, applying human factors principles in all phases of the control room life cycle. The aim of this paper is to present an approach to design the interfaces for a nuclear reactor control room. The methodological framework includes human factors guidelines and standards, checklists and ergonomics as an aid tool, based on the operator activity analysis. In this paper, we describe the application of the proposed methodology in an advanced control room of a nuclear power plant simulator.

Correlations for flame speed and explosion overpressure of dust clouds inside industrial enclosures

Abstract: Explosion relief vents on enclosures in powder-handling plants are currently designed according to technical standards that in some situations may overestimate the required vent area significantly. These technical standards sometimes do not take into account the real work conditions of industrial plants (e.g. turbulence intensity) and therefore explosion worst cases are not always foreseeable. The availability of methods either for the evaluation of explosion overpressure or sizing of relief vents, with involvement of the pre-ignition turbulence, could be very useful for a better estimate of these quantities. In this work two empirical correlations are presented: the first one allows the calculation of the flame speed and the burning velocity starting from the explosion indices K St and P max of the standardized 20-l sphere test. The second allows either the calculation of the explosion overpressure or the sizing of relief vents of an enclosure.

The boiling liquid expanding vapour explosion (BLEVE) is fifty ... and lives on

Abstract: The boiling liquid expanding vapour explosion (BLEVE) is among the most fearsome of accidents that can occur wherever a pressure liquefied gas (PLG) exists. If a container with a PLG suffers structural failure—be it due to creep, fatigue, or fire-induced or other forms of accidental jeopardy—it may lead to a sudden depressurization of the container. As a result, the PLG will suddenly be transformed into a liquid which is ‘superheated’ in respect of the precipitously lowered pressure. Depending on the nature of the chemical, its quantity, and the mechanism of the container failure, such a situation can lead to instantaneous and violent vaporization of the contents, causing a ‘boiling liquid expanding vapour explosion’—a BLEVE. Even though BLEVEs have been occurring ever since the use of pressure liquified gases began, they were not recognized or studied as a clearly distinct form of explosion that they are, until 1957. In that year, three engineers working in USA coined the term BLEVE when they witnessed an explosion which could not be categorized by any of the explosion types known till then. Even though, as described in this paper, the acronym took time to gain wide currency, it has served the very important purpose of giving the BLEVE phenomenon a distinct identity. This, in turn, has stimulated considerable work towards the understanding and control of BLEVEs. In this commemorative piece, which marks the 50th year of the coinage of the BLEVE acronym, we recall the event which led to the coinage, and the pioneering work of the three who introduced BLEVE to the world—J.B. Smith, W.S. Marsh, and W.L. Walls.

Importance of human contribution within the human reliability analysis (IJS-HRA)

Abstract: The human reliability analysis (HRA) was investigated intensively in the last decades and many methods have been developed. The most important feature of HRA is a good data, which can be obtained from full scope plant simulators. The objective of this study is to investigate how importance factors of human failure events obtained from results of probabilistic safety assessment (PSA) can be used in sense to improve human reliability. The study considers recently developed method: Institute Jožef Stefan (IJS)-HRA, which integrates some features of existing methods and some new features, and its application in a large PSA model. Two ways for quantification and application of importance factors are presented. The results show that only few human failure events dominate in the HRA analysis. The results show that only few parameters from human reliability database contribute significantly to the risk. Identification of dominating human failure events and identification of the significant parameters are a valuable input for determining the priorities of simulator training.

Partial stroke testing of process shutdown valves: How to determine the test coverage

Abstract: Partial stroke testing (PST) has recently been introduced as a semi-automatic means to test process shutdown valves. Normally, this type of testing does not disturb the process and can detect many of the failures that traditionally have been revealed only by functional testing. The fraction of all dangerous failures that are detected by PST is called the PST coverage and is decisive for the effectiveness of the PST. So far, limited guidance on how to determine the PST coverage has been given. This paper discusses the application and limitations of PST and suggests a new procedure for how to determine the PST coverage factor.

Scale effects on hydrogen-air fast deflagrations and detonations in small obstructed channels

Abstract: An experimental study of flame propagation, acceleration and transition to detonation in hydrogen–air mixture in 2-m-long rectangular cross-section channel filled with obstacles located at the bottom wall was performed. The initial conditions of the hydrogen–air mixture were 0.1 MPa and 293 K and stoichiometric composition (29.6% H 2 in air). The channel width was 0.11 m and blockage ratio was 0.5 in all experiments. The effect of channel geometrical scale on flame propagation was studied by using four channel heights H of 0.01, 0.02, 0.04, and 0.08 m. In each case, the obstacle height was equal to H /2 and the obstacle spacing was 2 H . The propagation of flame and pressure waves was monitored by four pressure transducers and four ion probes. The pairs of transducers and probes were placed at various locations along the channel in order to get information about the progress of the phenomena along the channel. As a result of the experiments, the deflagration and detonation regimes and velocities of flame propagation in the obstructed channel were established.

Experiment-based fire and explosion risk analysis for powdered magnesium production methods

Abstract: More than 100,000 tons of powdered or granular magnesium are produced annually in China in factories with high potential fire and explosion risk. The primary methods for magnesium powder production are reviewed in this paper. Fire risk analyses, based on minimum ignition energy (MIE) and minimum ignition temperature (MIT) test results for magnesium powder of different diameters, are provided for each method. Sparks caused by static electricity, mechanical friction, or impact are the most likely ignition sources for fine magnesium powder fires and explosions. However, MIT of powdered magnesium was much higher than that of organic or coal dust even for very fine magnesium powder. Magnesium powder fires and explosion were not readily caused by hot surfaces. A two-stage combustion model was experimentally determined for a magnesium dust layer.

Evaluation of the blast-wave overpressure and fragments initial velocity for a BLEVE event via empirical correlations derived by a simplified model of released energy

Abstract: When a pressure vessel filled with a liquid is involved in a fire, a variety of effects are to be expected. If the vessel is filled with LPG, a boiling liquid expanding vapour explosion (BLEVE) is one of the possible effects, although it does not always happen. Actually BLEVE is a complex phenomenon resulting from many factors which are hard to summarize into mathematical formulations or models. Nevertheless it could be useful in order to assess the consequences of a BLEVE, to have access to simplified models lying on physical basis. In this paper empirical correlations for blast-wave overpressure and fragments initial velocity are presented. The basic hypothesis that BLEVE is a phenomenon driven by the excess heat stored in the liquid (overheated liquid) is assumed and some thermodynamic approximations are introduced. Despite these approximations and the empirical formulation simplicity, the results accuracy is good.

A systemic approach to managing safety

Abstract: The existing approaches to safety management seem to put emphasis on management functions, guidelines, national and international standards, quality principles, to establish the safety management system (SMS) of organizations. These approaches may represent a step forward to managing safety but may not be enough to address the management of safety effectively. There is a need to adopt a systemic approach to safety management. Systemic may be defined as trying to see things as a whole and attempting to see events, including failure, as products of a working of a system and, within that, see fatality/injury/property loss, etc. as results of the working of systems. A systemic approach has been adopted to construct a systemic safety management system (SSMS) model. The model aims to maintain risk within an acceptable range in the operations of any organization. It is contended here that if the features of the model (i.e. the systems, their associated functions, and the channels of communication) are in place and working effectively then the probability of failure should be less than otherwise. In this way the SSMS has a fundamentally preventive potentiality. It is hoped that this approach will lead to more effective management of safety.

Evaluation of an intensified continuous heat-exchanger reactor for inherently safer characteristics

Abstract: The present paper deals with the establishment of a new methodology in order to evaluate the inherently safer characteristics of a continuous intensified reactor in the case of an exothermic reaction The transposition of the propionic anhydride esterification by 2-butanol into a new prototype of “heat-exchanger/reactor”, called open plate reactor (OPR), designed by Alfa Laval Vicarb has been chosen as a case study Previous studies have shown that this exothermic reaction is relatively simple to carry out in a homogeneous liquid phase, and a kinetic model is available A dedicated software model is then used not only to assess the feasibility of the reaction in the “heat-exchanger/reactor” but also to estimate the temperature and concentration profiles during synthesis and to determine optimal operating conditions for safe control Afterwards the reaction was performed in the reactor Good agreement between experimental results and the simulation validates the model to describe the behavior of the process during standard runs A hazard and operability study (HAZOP) was then applied to the intensified process in order to identify the potential hazards and to provide a number of runaway scenarios Three of them are highlighted as the most dangerous: no utility flow, no reactant flows, both stop at the same time The behavior of the process is simulated following the stoppage of both the process and utility fluid The consequence on the evolution of temperature profiles is then estimated for a different hypothesis taking into account the thermal inertia of the OPR This approach reveals an intrinsically safer behavior of the OPR

Reliability analysis of metallic targets under metallic rods impact: Towards a simplified probabilistic approach

Abstract: In this paper, the authors develop a probabilistic model in order to analyse the reliability of metallic targets impacted by cylindrical metallic projectiles (resulting from industrial facilities explosion, for instance). The random variables are the projectiles features (mass, velocity at impact, incidence angle between the projectile and the target plane, the diameter) and the target properties (ultimate strength and strain of the constitutive material as well as the target thickness). A simplified mechanical model is proposed. in the case of cylindrical projectiles and planar targets. It relies on the hypothesis of plastic behaviour of the target constitutive material whereas it assumes that the projectile behaves as a rigid body. The theoretical penetration depth into the target is compared with experimental data collected from existing references.