Showing papers in "Journal of Loss Prevention in The Process Industries in 2006"

A study of storage tank accidents

Abstract: This paper reviews 242 accidents of storage tanks that occurred in industrial facilities over last 40 years. Fishbone Diagram is applied to analyze the causes that lead to accidents. Corrective actions are also provided to help operating engineers handling similar situations in the future. The results show that 74% of accidents occurred in petroleum refineries, oil terminals or storage. Fire and explosion account for 85% of the accidents. There were 80 accidents (33%) caused by lightning and 72 (30%) caused by human errors including poor operations and maintenance. Other causes were equipment failure, sabotage, crack and rupture, leak and line rupture, static electricity, open flames etc. Most of those accidents would have been avoided if good engineering have been practiced.

Safety barriers: Definition, classification, and performance

Abstract: In spite of the fact that the concept of safety barriers is applied in practice, discussed in the literature, and even required in legislation and standards, no common terminology that is applicable across sectors have been developed of the concept of safety barriers. This paper focuses on safety barriers and addresses the following aspects; definitions and understanding of what is a safety barrier, classification of safety barriers, and attributes of importance for the performance of safety barriers. Safety barriers are physical or non-physical means planned to prevent, control, or mitigate undesired events or accidents. Barrier systems may be classified according to several dimensions, for example as passive or active barrier systems, and as physical, technical, or human/operational barrier systems. Several attributes are necessary to include in order to characterize the performance of safety barriers; functionality/effectiveness, reliability/availability, response time, robustness, and finally a description of the triggering event or condition. For some types of barriers, not all the attributes are relevant or necessary in order to describe the barrier performance.

Solid inertants and their use in dust explosion prevention and mitigation

Abstract: This paper is a review of the use of inert dusts to reduce the risk of dust explosions through both prevention and mitigation schemes. The review is conducted by referring primarily to the research results of the author and his colleagues in this area, with appropriate reference to the work of other researchers. A functional distinction is first made between inerting and suppression by explaining each term within the contexts of explosion prevention and explosion mitigation, respectively. The use of solid inertants is then described in terms of the various inhibitor and situation-specific parameters that can influence their effectiveness. Finally, application examples of the research results are given for research laboratories, test facilities, design engineers, and industrial practitioners.

A few fundamental aspects about ignition and flame propagation in dust clouds

Abstract: The history of the development of the process industry has been punctuated by a number of hazardous explosions, sometimes very severe. A few of them are still in the memory and certainly contributed to the birth of safety engineering. It has been known for more than one century than combustible dusts suspended in air are responsible for a part of those explosions but contrariwise to gas explosions, the available knowledge and practise seems still contain a significant part of empirism. The work summarised into this paper is an attempt to contribute to a better understanding of the explosion mechanisms of dust clouds. Hopefully, such additional information may help to refine the safety analysis exercise in the future. A specific effort has been devoted to combustion processes in the flame and the results indicate similarities with premixed gaseous flames. Several fundamental questions are addressed such as the incidence of thermal radiation, turbulence,… This information is important to treat ignition aspects. For spark type of ignition, it is shown that an absolute minimum ignition energy should exist for some dust clouds with a similar meaning than for premixed gaseous flames. For hot surface ignition, the standard ignition temperature (Godbert–Greenwald) seems to be reasonably correlated to the size and critical ignition temperature of the heating body. The possible implications of this new information within the scope of industrial safety are addressed in conclusion.

Estimation of safety distances in the vicinity of fuel gas pipelines

Abstract: In this paper, safety distances around pipelines transmitting liquefied petroleum gas and pressurized natural gas are determined considering the possible outcomes of an accidental event associated with fuel gas release from pressurized transmission systems. Possible outcomes of an accidental fuel gas release were determined by performing the Event Tree Analysis approach. Safety distances were computed for two pipeline transmission systems of pressurized natural gas and liquefied petroleum gas existing in Greece using real data given by Greek Refineries and the Greek Public Gas Enterprise. The software packages chetah and breeze were used for thermochemical mixture properties estimation and quantitative consequence assessment, respectively. Safety distance determination was performed considering jet fire and gas dispersion to the lower flammable limit as the worst-case scenarios corresponding to immediate and delayed cloud ignition. The results showed that the jet fire scenario should be considered as the limiter for safety distances determination in the vicinity of natural and petroleum gas pipelines. Based on this conclusion, the obtained results were further treated to yield functional diagrams for prompt safety distance estimation. In addition, qualitative conclusions were made regarding the effect of atmospheric conditions on possible events. Thus, wind velocity was found to dominate during a jet fire event suppressing the thermal radiation effect, whereas gas dispersion was found to be affected mainly by solar radiation that favors the faster dissolution of fuel gas below the lower flammable limit.

Quantitative assessment of domino scenarios by a GIS-based software tool

Abstract: A software procedure was developed for the quantitative assessment of domino effect The procedure was based on a systematic methodology for the identification of domino scenarios and for the assessment of consequences and expected frequencies of the escalation events A geographical information system (GIS) platform was interfaced to the domino assessment software The implementation of plant lay-out data to the GIS allowed the automatic identification of the possible targets of escalation effects by the software procedure, and a straightforward calculation of the contribution to individual and societal risk indexes caused by the possible domino scenarios The procedure was applied to the analysis of several case-studies based on actual plant lay-outs The results evidenced that the approach allows the quantitative assessment of risk caused by escalation events with a limited additional effort with respect to that required by a conventional QRA The use of a GIS-based software was a key element in the limitation of the effort required for the quantitative assessment of domino scenarios Moreover, the results of the case-studies pointed out that the estimation of risk increase due to domino events is an important tool for an effective assessment and control of industrial risk in chemical and process plants

Determination of explosion parameters of methane-air mixtures in the chamber of 40 dm3 at normal and elevated temperature

Abstract: The experimental results of the measurements of the explosion pressure and rate of explosion pressure rise as a function of molar methane concentration in the mixture with air in the 40 dm3 explosion chamber are presented. The research was aimed at determination of the explosion limits, according to the EU Standard. The influence of initial temperature of the mixture (changing in the range of 293–473 K) on the fundamental explosion parameters was also investigated. The ignition source was an induction electrical spark of the power equal to approximately 10 W. It was stated, that the increase of initial temperature of the methane-air mixture causes a significant increase of the explosion range.

Inherent safety tool for explosion consequences study

Abstract: The lack of formal integration between process design stages with risk and consequence estimation is a hurdle to designing inherently safe process plants. Conventional risk assessment methodologies are often not carried out concurrently with process design. Therefore, process designers lack the information about risk levels and consequence that may result from the process conditions being considered in a particular process route until the design is completed. Hence, effects of changes in process conditions on risk levels and consequence cannot be studied in a time effective manner during the design stages. Few studies have been identified on the possibility and viability of integrating risk estimation with process design. But viable framework and methodology for doing so has not yet been reported. This paper presents a feasible framework in which risk and consequences estimation can be part of design stages. A demonstrative tool named as integrated risk estimation tool (iRET) was developed by using process simulation software, HYSYS and spreadsheet, MS Excel as the platforms. iRET estimates risk due to explosions by using TNT equivalence method and the TNO correlation method. iRET has a potential to be extended to include all forms of risk such as fire, explosion, toxic gas releases and boiling liquid expanding vapour explosion (BLEVE). The paper also presents case studies to demonstrate the functionality and viability of using iRET in conjunction with process design. The results of these case studies have successfully shown that the risk due to explosion can be assessed during the initial design stage ensuring a safer plant. The framework and iRET there by presented here provide systematic methodology and technology to design inherently safer plants.

Occupational accident models—Where have we been and where are we going?

Abstract: Oil and gas accident statistics reveal that workers’ potential for injury or death from occupational accidents is at least as high as that associated with explosions, fires, and other major incidents. The authors’ contribution to the ongoing efforts to improve the situation is a holistic, quantitative model capable of predicting occupational accident frequency. Model inputs include external, corporate and direct factors, and the approach includes methods often favoured by professionals from the safety, engineering, and psychology disciplines. As a precursor to model development, a comprehensive literature review was conducted. One objective of the review was to understand the previous approaches taken by other researchers and thereby identify any gaps in the knowledge. The lack of a holistic, quantitative model addressing occupational accidents in the oil and gas industry was established. A second objective was to select and categorise the factors most influential in the accident process and thereby provide a foundation for the present model. Optimal choices required a systematic study of the factors proposed by other researchers. The literature studied has been summarised in this paper, subdivided into two primary groups: (i) descriptions of existing accident models, and (ii) analyses of existing data. In addition, descriptions of literature specifically concerned with two key elements in the occupational accident process, human factors and safety culture, have been included. Based on the literature reviewed, the novelty of the present model has been discussed. The systematic approach taken to choose the factors thought most influential in the occupational accident process, and which were therefore included in the model, has been described. Some details of the proposed model have been included.

Aspects of risk analysis associated with major failures of fuel pipelines

Abstract: This paper presents a methodology of risk assessment for hazards associated with transportation of dangerous substances in long pipelines. The proposed methodology comprises a sequence of analyses and calculations used to determine basic reasons of pipeline failures and their probable consequences, taking individual and societal risk into account. A specific feature of this methodology is a combination of qualitative (historical data analysis, conformance test and scoring system of hazard assessment) and quantitative techniques of pipeline safety assessment. This enables a detailed analysis of risk associated with selected hazard sources by means of quantitative techniques. On the ground of this methodology typical problems that usually pose serious threat and constitute part of risk analysis for long fuel pipelines are also presented. To verify above methodology, complete risk analysis was performed for the long distance fuel pipeline in Poland.

Flame propagation and combustion in some dust-air mixtures

Abstract: Some results of measurements of laminar burning velocities and of maximum flame temperatures for combustible dust-air mixtures (starch dust-air mixtures, lycopodium-air mixtures and sulphur flour-air mixtures) are presented. Thin (25 and 50 μm) thermocouples have been used to measure maximum flame temperatures. The results are compared with those obtained with other devices such as resistors, pyrometers and are compared to the theoretical values. It appears that the observed discrepancies seem principally to come from the relatively poor efficiency of the burning processes inside the flame front than to heat losses by radiation as suggested before. Two methods for determining laminar burning velocities have been used: the classical ‘tube method’ and a ‘direct method’ based on the simultaneous determination of the flame speed and of the mixture velocity ahead of the flame front using a tomographic technique. Two different tube diameters are considered as well as additional results obtained with a small burner. The validity of these techniques is firstly assessed by comparing the results obtained with CH4-air mixtures and secondly by considering their relevancy for combustible dust-air mixtures (influence of the size of the apparatus). In particular, the influences of heat flame by radiation and of flame stretching are considered.

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

Abstract: 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.

Micro calorimeter study on the thermal stability of lithium-ion battery electrolytes

Abstract: With the extensive applications of lithium-ion batteries, many batteries explosion accidents were reported. The thermal stability of lithium-ion battery electrolyte could substantially affect the safety of lithium-ion battery. The C80 micro calorimeter was used to study the thermal stability of several commonly used organic solvents and electrolytes. The samples were heated in argon atmosphere and air atmosphere, respectively. The chemical reaction kinetics was supposed to fit by an Arrhenius law, then the self-accelerating decomposition temperature was calculated. It is found that most of the samples are stable in argon atmosphere while decomposing in air atmosphere, and the single organic solvent is more stable than the electrolyte generally.

Managing the condition-based maintenance of a combined-cycle power plant : An approach using soft computing techniques

Abstract: This paper describes how a condition-based maintenance plan was developed for a combined-cycle power plant at a medium-sized Italian refinery. Including forecasting activities in the maintenance cycle achieved the dual goal of identifying any need for measures ahead of the deadlines established for routine preventive maintenance in the event of alarm conditions being detected, and of postponing any scheduled measures in the event of the components in question still being in good condition. Soft computing tools were experimentally used to achieve these objectives. Recurrent neural nets and neuro-fuzzy systems were used to ensure that the assessment of the trends of the global values was effective in determining the time remaining before the next outage period was needed. Using these tools enabled an accurate prediction of the values of the vibrations on rotating machinery based on the values of the operating parameters given as input. The plan was part of a maintenance management scheme seen as a container of inspection activities providing the foundations for systematically organizing certain servicing measures (e.g. the replacement of bearings, or alignments on rotating machinery, etc.), and to prevent sudden breakdown situations.

Explosibility of cork dust in methane/air mixtures

Abstract: Explosibility studies of hybrid methane/air/cork dust mixtures were carried out in a near-spherical 22.7 L explosibility test chamber, using 2500 J pyrotechnic ignitors. The suspension dust burned as methane/air/dust clouds and the uniformity of the cork dust dispersion inside the chamber was evaluated through optical dust probes and during the explosion the pressure and the temperature evolution inside the reactor were measured. Tested dust particles had mass median diameter of 71.3 mm and the covered dust cloud concentration was up to 550 g/m 3 . Measured explosions parameters included minimum explosion concentration, maximum explosion pressures and maximum rate of pressure rise. The cork dust explosion behavior in hybrid methane/air mixtures was studied for atmospheres with 1.98 and 3.5% (v/v) of methane. The effect of methane content on the explosions characteristic parameters was evaluated. The conclusion is that the risk and explosion danger rises with the increase of methane concentration characterized by the reduction of the minimum dust explosion concentration, as methane content increases in the atmosphere. The maximum explosion pressure is not very much sensitive to the methane content and only for the system with 3.5% (v/v) of methane it was observed an increase of maximum rate of pressure rise, when compared with the value obtained for the air/dust system. q 2005 Elsevier Ltd. All rights reserved.

The nature and large eddy simulation of coherent deflagrations in a vented enclosure-atmosphere system

Abstract: The nature of coherent deflagration phenomena in a vented enclosure-atmosphere system is analysed. The study is based on experimental observations of SOLVEX programme in the empty 547-m3 vented enclosure and consequent analysis of the same test by large eddy simulations (LES). A comparison between simulated and experimental pressure transients and dynamics of flame front propagation inside and outside the enclosure gave an insight into the nature of the complex simultaneous interactions between flow, turbulence and combustion inside the enclosure and in the atmosphere. It is revealed through LES processing of experimental data that the substantial intensification of premixed combustion occurs only outside the empty SOLVEX enclosure and this leads to steep coherent pressure rise in both internal and external deflagrations. The external explosion does not affect burning rate inside the enclosure. There is only one ad hoc parameter in the LES model, which is used to account for unresolved subgrid scale increase of flame surface density outside the enclosure. The model allows reaching an excellent match between theory and experiment for coherent deflagrations in the empty SOLVEX facility. The mechanism of combustion intensification in the atmosphere is discussed and the quantitative estimation of the model ad hoc parameter is given.

Combining HAZOP with dynamic simulation—Applications for safety education

Abstract: A quantitative variation of the hazard and operability analysis (HAZOP) procedure is demonstrated. The process is divided into sections and dynamic models of the separate sections are prepared. Those models are used in the framework of the HAZOP procedure to determine the magnitude of the deviations from normal operation conditions that may lead to serious accidents and to test design modification to improve the safety characteristic of the process. A process involving an exothermic reaction conducted in a semi-batch reactor is used to demonstrate the advantages of the proposed procedure and its application for safety education and operator training. The programs used for simulating the reactor are available at: ftp://ftp.bgu.ac.il/shacham/OctanoneProd/ . It is shown that the use of those programs can enhance considerably the safety education by providing tools for systematic screening of process deviation associated with possible hazardous events, determining the threshold values that may lead to such events and enabling the examination of a particular design for the adequate safe range of operation.

Risk management of road and rail transport of hazardous materials in Sicily

Abstract: A Transportation Risk Analysis (TRA) tool has been used to accurately assess the risk associated to a variety of road and rail transportation cases representative of hazardous materials transport by land in Sicily. Due to the high risk level, some risk mitigation options have been investigated: the possibility of changing route and/or transport modalities have been examined for each transportation activity, all the combinations of road, rail and intermodal (road+rail) transport have been calculated and that minimising the risk has been identified with the aid of the TRA tool.

Hydrocarbon releases on oil and gas production platforms: Release scenarios and safety barriers

Abstract: The main objective of this paper is to present and discuss a set of scenarios that may lead to hydrocarbon releases on offshore oil and gas production platforms. Each release scenario is described by an initiating event (i.e., a deviation), the barrier functions introduced to prevent the initiating event from developing into a release, and how the barrier functions are implemented in terms of barrier systems. Both technical and human/operational safety barriers are considered. The initiating events are divided into five main categories: (1) human and operational errors, (2) technical failures, (3) process upsets, (4) external events or loads, and (5) latent failures from design. The release scenarios may be used as basis for analyses of: (a) the performance of safety barriers introduced to prevent hydrocarbon releases on specific platforms, (b) the platform specific hydrocarbon release frequencies in future quantitative risk analyses, (c) the effect on the total hydrocarbon release frequency of the safety barriers and risk reducing measures (or risk increasing changes).

Simulation of dust explosions in complex geometries with experimental input from standardized tests

Abstract: The present paper describes the development of a new CFD-code (DESC) for the assessment of accidental hazards arising from dust explosions in complex geometries. The approach followed entails the estimation of the laminar burning velocity of dust clouds from standardized laboratory-scale tests, and its subsequent use as input to the combustion model incorporated in DESC. The methodology used to obtain the laminar burning velocities is demonstrated by igniting turbulent propane-air mixtures to deflagration in a standard 20-litre USBM-vessel, and extracting the laminar burning velocity from the pressure–time curves; the results are compared with literature data. Laminar burning velocities for clouds of maize starch dust in air were estimated following the same procedure, and the resulting empirical model was used to simulate dust explosions in a 236-m3 silo.

On the response of 500 gal propane tanks to a 25% engulfing fire

Abstract: This paper presents detailed data on the thermal response of two 500 gal ASME code propane tanks that were 25% engulfed in a hydrocarbon fire. These tests were done as part of an overall test programme to study thermal protection systems for propane-filled railway tank-cars. The fire was generated using an array of 25 liquid propane-fuelled burners. This provided a luminous fire that engulfed 25% of the tank surface on one side. The intent of these tests was to model a severe partially engulfing fire situation. The paper presents data on the tank wall and lading temperatures and tank internal pressure. In the first test the wind reduced the fire heating and resulted in a late failure of the tank at 46 min. This tank failed catastrophically with a powerful boiling liquid expanding vapour explosion (BLEVE). In the other test, the fire heating was very severe and steady and this tank failed very quickly in 8 min as a finite rupture with massive two-phase jet release. The reasons for these different outcomes are discussed. The different failures provide a range of realistic outcomes for the subject tank and fire condition.

Structure of flames propagating through aluminum particles cloud and combustion process of particles

Abstract: Structure of flames propagating through aluminum particles clouds and combustion processes of the particles have been examined experimentally to understand the fundamental behavior of a metal dust explosion. The combustion process of individual aluminum particles in a flame propagating through the aluminum particles cloud has been recorded by using a high-speed video camera with a microscopic optical system, and analyzed. The flame is shown to be consisted of a preheat zone of about 3 mm thick, followed by a combustion zone of 5–7 mm thick. In the combustion zone, discrete gas phase flames are observed around each aluminum particle. Also an asymmetric flame around a particle is observed, which might be caused by an ejection of aluminum vapor from a crack of oxide shell surrounding the particle.

Accidents in the chemical industry: are they foreseeable?

Abstract: ‘Accidents recur,’ which is what Kletz [Kletz T. (1993). Lessons from disasters, how organisations have no memory and accidents recur . UK: Institution of Chemical Engineers] wrote in 1993. Indeed, despite all measures taken accidents may re-occur, but ‘disruptions’ in a process reoccur much more frequently. If a disruption occurs it may lead to an accident. If the same disruption reoccurs it is certainly suspect and should be considered as a potential precursor. In this paper, we concentrate on these disruptions and we will define them as precursors if they recur. Organizations somehow lack the ability to control such recurring disruptions that may escalate into serious accidents under certain circumstances. The presence of such precursors long before the occurrence of an accident raises doubts about how well organizations control safety. In this paper, the control mechanism inside organizations is examined, by means of several accident investigations. It will be shown that not only accidents recur, but also that disruptions recur in a period preceding the actual accident. The recurrence of these disruptions implies that the corresponding organizational control mechanism must be failing. Often, alternative circumstances prompt the escalation of such precursors and lead to actual accidents. It is demonstrated that the use of detailed accident information is of great importance for companies that are actually willing to prevent accidents through the elimination of disruptions preceding accidents.

The effectiveness of process safety management (PSM) regulation for chemical industry in Korea

Abstract: From the 1960s, Korean industries have been encouraged by the government to nurture heavy and chemical industry and to modernize the economics and industrial structures. The development of chemical industry particularly became the turning point in industrial development, and played a major role in the construction of a new industrialized country. However, the process systems in the chemical industry have become more complex and larger, and the inventories of dangerous chemicals that are produced or consumed have continuously increased. Therefore, the hazards from potential accidents such as fire and explosion or release of toxic chemicals have also increased. In fact, from the end of 1980s to the beginning of 1990s in Korea, a number of major industrial accidents such as ABS extruder explosion, TDI release and dryer explosion, etc. occurred and caused many fatalities. As the chemical companies recognized the importance of preventing major hazards, PSM system, the prevention of major industrial accidents, was introduced in January 1995 by amending Industrial Safety and Health Act, and it has been enforced from January 1, 1996. According to the law, the business owner of a workplace with hazardous or dangerous equipment shall submit a process safety report to the Government to prevent any accidents, which could inflict an immediate damage on workers or on areas in the vicinity of the workplaces. As a result of PSM implementation for 7 years, various kinds of effectiveness have been made. Accident rate including number of fatalities has been decreased, and productivity has been increased as well as product quality.

Suppression effects of powder suppressants on the explosions of oxyhydrogen gas

Abstract: Suppression tests of oxyhydrogen gas explosions were performed in an explosion tube with five types of dry powder used as the suppressants. The experimental results showed that the powder with large dust cloud density and small radius has better suppression effect, which agrees well with previous correlative results. Moreover, our results also showed that particles with chemical activity and light material density, their suppression effect are more prominent than that of the inert particles with heavy density. To discover the detailed suppression process of dust powder, governing equations were developed based on the homogeneous reactive two-phase flow. The TVD scheme and the Lax–Wendroff–Rubin scheme were adopted to solve the reactive gas phase and particle phase, respectively. The time splitting technique was employed to handle the stiffness of the coupled equations. Our calculated results showed that the dust cloud has the suppression effect on the explosion of oxyhydrogen gas, and with the increase of dust cloud density or the decrease of particle diameter, its suppression effect become more evident, which is in good agreement with our experimental results, in addition, the numerical results showed that with the same particle diameter, the suppression performance is enhanced with the reduction in particle material density.

A numerical model to simulate smouldering fires in bulk materials and dust deposits

Abstract: A numerical model is presented which consists of a set of partial differential equations for the transport of heat and mass fractions of eight chemical species to describe the onset of self-ignition and the propagation of smouldering fires in deposits of bulk materials or dust accumulations. The chemical reaction sub-model includes solid fuel decomposition and the combustion of char, carbon monoxide and hydrogen. The model has been validated against lab-scale self-ignition and smouldering propagation experiments and then applied to predictions of fire scenarios in a lignite coal silo. Predicted reaction temperatures of 550 K and propagation velocities of the smouldering front of about 6 mm/h are in good agreement with experimental values derived from lab-scale experiments.

Functional safety concept for hazardous systems and new challenges

Abstract: Selected issues associated with the functional safety analysis according to the international standards IEC 61508 and IEC 61511 are presented. Determining the safety integrity level (SIL) of electric/electronic/programmable electronic (E/E/PE) safety-related systems is outlined. The importance of quantitative probabilistic modeling of these systems in verifying SIL is emphasized. Some aspects concerning the functional safety analysis of systems for detecting the combustible or toxic gases in relation to a CENELEC draft standard prEN 50402 are shortly discussed. Basic principles of methodology for the functional safety assessment of protective systems for potentially explosive atmospheres proposed in a CEN draft standard prEN 15233 are addressed.

A matrix-based risk assessment approach for addressing linear hazards such as pipelines

Abstract: Pipelines represent a linear risk source that can create unique challenges when assessing risks. In the past, risk has been managed by identifying construction requirements and setbacks based on population densities and types of land use. In the current risk assessment a matrix-based approach has been developed so as to determine the risks associated with high-vapor pressure liquids pipelines. The approach involved the development of a matrix representing each 100 m section of the reviewed pipeline along with approximately 30 risk factors that describe that section of the pipeline. Further, a receptor matrix was constructed to account for each hectare of land within 1 km of the reviewed pipeline system. This approach has allowed for the determination of risk as a function of location and separation from the pipeline and in turn has allowed for the determination of those areas where peak risks exist. In addition, this approach has ensured that the linear geometry related to pipeline risks has been accurately modeled. The resulting estimated risks have been evaluated against MIACC risk thresholds (geographic risk-based measures) and against proprietary internal corporate standards (societal risk-based measures). In this way the acceptability of the risk from the perspective of both the potentially impacted community and that of the pipeline operator can be measured. The net result is that the company has a clear picture of the risks associated with its pipeline and is better able to optimize its risk management and pipeline integrity programs.

Burning velocity evaluation from pressure evolution during the early stage of closed-vessel explosions

Abstract: In the present paper, a comprehensive set of data on explosions in a spherical and a cylindrical vessel with central ignition was examined in order to check the validity of the cubic law, empirically found by many authors for explosions in small- and medium-size closed vessels. Experiments were performed on propylene–oxygen mixtures, in the presence of various additives (Ar, N 2 , CO 2 , CH 2 BrCl or exhaust gases), at total initial pressures p 0 from 0.3 to 1.3 bar. For this pressure range, the cubic law was found valid for pressure rise Δ p≤p 0 and the cubic law constants were evaluated by a non-linear regression analysis. These constants were further used to compute the burning velocities of the examined systems according to the isothermal and adiabatic compression models. This simple and reliable method for burning velocity determination may find an useful application to complex systems, formed either by a composite fuel (landfill gas, gasoline, Diesel fuel) and air or by single fuel–air mixed with composite additives (i.e. their own exhaust gases).

BLEVE: A new approach to the superheat limit temperature

Abstract: Several methods proposed for calculating the value of the superheat limit temperature were analysed. The results obtained indicate that the procedures based on the thermodynamic stability approach introduce a significant uncertainty into the final values, depending on which equation of state is used. We propose a new approach based on the energy balance in the initial liquid mass just before the explosion. The temperature obtained using this method, Tsl−E, corresponds to the situation in which the energy transferred adiabatically between the cooling liquid and the vaporising liquid fractions is at its maximum. This leads to a minimum content of energy in the remaining liquid. Although these two approaches are equivalent—the procedures based on the thermodynamic stability approach use also the minimum energy state as a criterion—the new proposed method only uses the properties of the substance to obtain Tsl−E. Thus, Tsl−E represents the behaviour of each substance as a function of its molecular structure, while this influence is lost if a simple equation of state is used. Finally, some considerations are made on the limitations of the superheat limit temperature as a criterion for establishing whether an explosion is or is not a BLEVE.