Hazard Distance Research Articles

Methods for estimating fragment hazard in gas explosion

Fragmention is a principal factor for casualties in an indoor fuel gas explosion. This paper presents a predictive method for the spatial distribution of hazardous fragments and areas. The motion parameters of fragments in indoor explosions were obtained by a combination of fluid and structural dynamic analysis. Then the spatial distribution of falling points was obtained by solving the motion equation of fragments. Indoor obstacle is an important factor affecting the hazard of indoor explosions. In the case of a vented brick room measuring 4.6 m × 4.6 m × 3 m, with the ratio of obstacle volume to gas volume increasing from 0.24 to 0.36, the maximum launch distance increased from 6.18 m to 18.78 m, expanded to 3.04 times. The fragment hazards in indoor explosions of methane, hydrogen and LPG (Liquefied Petroleum Gas) with the same condition were compared. The hazard distance of hydrogen explosion is the largest, which is 3.11 times as wide as that of methane.

Toxic Chemical Release Hazard Distance Determination Using Chemical Exposure Index (CEI) in a Gas Refinery

Events leading up to the release of toxic chemicals in the processing plants are one of the main hazards of chemical industries that can endanger employees and also people in neighborhood. In this study, DOW's Chemical Exposure Index (CEI) is used to determine hazard distances of possible toxic chemical releases in one of the South Pars gas refineries. To do this, 318 considerable release scenarios were identified and by process parameters and CEI equations, airborne quantity, chemical exposure index and hazard distances were calculated. In the worst case of a toxic chemical release, hazard distance of the studied refinery is 10000 meters. The Sludge Catcher unit is the most dangerous unit in terms of toxic chemical release. In addition to the advantages of the CEI observed in this study also some limitations were observed including sensitivity to process parameters, no consideration of the material inventory and the concentration in the CEI calculations

Evaluation of hazard distances related to toxic releases in a gas refinery: comparison of chemical exposure index and consequence modeling approaches

The release of toxic chemicals is an important hazard of chemical plants. The purpose of this study is to compare the chemical exposure index (CEI) and consequence modeling to determine the hazard distance of toxic chemical release, utilizing a gas refinery as the case study. The CEI was utilized and considerable release scenarios were determined. The process hazard analysis software tool model was performed for consequence modeling of the scenarios with the highest airborne quantity. In the case of toxic chemical release based on both the CEI and consequence modeling, the sludge catcher unit was identified as the most dangerous unit. Hazard distances calculated by the CEI are significantly greater than those using consequence modeling. This is acceptable in terms of safety, but may not be applicable in reality. The results of the study showed a procedure for selecting an appropriate method in order to reduce costs and time.

Quantitative risk analysis of life safety and financial loss for road accident of fuel cell vehicle

Vehicular use of hydrogen is the first attempt to apply hydrogen energy in consumers’ environment in large scale and has raised safety concerns in both public authorities and private bodies such as fire services and insurance companies. This paper analyzes typical accident progressions of hydrogen fuel cell vehicles in a road collision accident. Major hydrogen consequences including impinging jet fires and catastrophic tank ruptures are evaluated separately in terms of accident duration and hazard distances. Results show that in a 70 MPa fuel cell car accident, the hazards associated with hydrogen releases would normally last for no more than 1.5 min due to the empty of the tank. For the safety of general public, a perimeter of 100 m is suggested in the accident scene if no hissing sound is heard. However, the perimeter can be reduced to 10 m once the hissing sound of hydrogen release is heard. Furthermore, risks of fatalities, injuries, and damages are all quantified in financial terms to assess the impacts of the accident. Results show that costs of fatalities and injuries contribute most to the overall financial loss, indicating that the insurance premium of fatalities and injuries should be set higher than that of property loss.

A consequences-based approach for the selection of relevant accident scenarios in emerging technologies

The rapid progress of innovative biorefinery technologies raises the issue of emerging risk and major accident hazard in biorefineries, as process safety aspects of such technologies are not developing at the same pace with respect to their dissemination and scale-up.To address such problem, in the present work a consequence-based approach was integrated in the framework of a consolidated QRA methodology (ARAMIS), formerly developed in the context of Seveso Directive in the process industries (mainly oil&gas). Among all the possible scenarios identified using ARAMIS, Relevant Accident Scenarios (RAS) were selected by calculating hazard distances using threshold values for the evaluation of damages on human target derived from existing regulations on the control of major accident hazards.The method has been described and used to quantify the risk associated to a biorefinery process: the conversion of lignocellulosic biomass materials to levulinic acid and gamma-valerolactone, where the use of hazardous substances and severe process conditions are required.Using the proposed approach allowed to reduce the number of scenarios to be retained for further analysis. The RAS resulted 1/3 of the scenarios initially identified, simplifying the rest of the risk assessment procedure.The integrated methodology enabled to depict a risk figure for the plant analysed which is not over-conservative, being beneficial during the risk management phase, when risk reduction measures have to be selected and implemented in order to achieve risk tolerance.

Comparisons of hazard distances and accident durations between hydrogen vehicles and CNG vehicles

A comparison study is conducted to reveal the differences of hazard distances and accident durations between hydrogen vehicles and CNG vehicles during a representative accident in an open environment, i.e gas release from thermally-activated pressure relief device (TPRD). The analysis is performed for the scenario of impinging jet fires released from 4.2 mm TPRD diameter, with release inventory assumption on the basis of similar driving range: 4 kg hydrogen storage at 35 MPa and 20 kg methane storage at 25 MPa. Results show that the release duration for CNG vehicle is over two times longer than that for hydrogen vehicle, indicating that CNG vehicle jet fire accident is more time-consuming and firefighters have to wait a longer time before they can safely approach the vehicle. For both hydrogen vehicle and CNG vehicle, the longest hazard distance near the ground occur at a few seconds after the initiation of the TPRD. Afterwards the flames will shrink and the hazard distances will decrease. For firefighters with bunker gear, they must stand at least 6 m and 14 m away from the hydrogen vehicle and CNG vehicle, respectively. For general public, a perimeter of 12 m and 29 m should be set around the accident scene for hydrogen vehicle and CNG vehicle, respectively.

Consequence Analysis of Fire and Release of Mercaptan Spills in Pressure Reducing Station of a Provincial Gas Company

Background: Mercaptans are the highly flammable and malodorous natural gas odorants in the urban gas distribution network and are used to detect gas leakage. Exposure to high concentrations of this substance has deleterious impacts on human health. Objectives: The purpose of this study was to determine the hazard distance and to examine the consequences of fire and the distribution of Mercaptans spills in its containing station in a specific provincial gas company. Methods: Modeling scenarios were defined based on the valid existing events and related consequences with respect to the gas pressure reducing station. To determine the safe distances of hazardous areas, applicable data and criteria were used in accordance with total GS SF 253. These criteria include the amount of flammable radiation in the event of Mercaptan fire, the amount of LFL (low flammable level) Mercaptan distribution, and the distribution rate of various concentrations of Mercaptan (0.5, 10 and 100 ppm). Subsequently, modeling was performed using input parameters and via Process hazard analysis software Tools (PHAS) software. Finally, the consequence evaluation of scenario occurrence and hazard distance were identified through the modeling results. Results: The distribution and pool fire caused by Mercaptan spill from containers were considered as the worst scenario at the respective gas station. Results from the modeling indicated a large distance distribution (3997 m) from the concentration of 0.5 ppm of Mercaptan (concentration of respiratory tract burning threshold) in case of a spill. Furthermore, according to the results of modeling in the event of a fire, the maximum radiation distance is 4.7 kW/m2 in the 10/D climate class, which extends up to 28 meters. Conclusions: Given the distribution of Mercaptan at long distances and the proximity of gas pressure reduction stations of the respective gas company to the residential and medical facilities, it is strongly recommended that the location of these barrels be moved away from residential areas.

Risk assessment methodology for onboard hydrogen storage

A quantitative risk assessment of onboard hydrogen-powered vehicle storage, exposed to a fire, is performed. The risk is defined twofold as a cost of human life per vehicle fire, and annual fatality rate per vehicle. The increase of fire resistance rating of the storage tank is demonstrated to drastically reduce the risk to acceptable level. Hazard distances are calculated by validated engineering tools for blast wave and fireball, which follow catastrophic tank rupture in a fire, act in all directions and have larger hazard distances compared to jet fire. The fatality cash value, probabilities of vehicle fire and failure of thermally activated pressure relief device are taken from published sources. A vulnerability probit function is employed to calculate probability of emergency operations' failure to control fire and prevent tank rupture. The risk is presented as a function of fire resistance rating of onboard storage.

Downwind chlorine hazard estimates for the 2015-2016 Jack Rabbit II campaign

We present estimates of the downwind inhalation health hazard to humans arising from large-scale releases of pressurised liquefied chlorine based on data from the Jack Rabbit II chlorine dispersion field campaign. For chlorine releases in the range of 7 to 9 metric tons, lethal, severe, and mild health effects are expected up to 1 km, between 2 and 5 km, and more than 11 km downwind from the release, respectively. The AEGL-3, AEGL-2, and AEGL-1 acute inhalation hazard thresholds are expected to be exceeded between 2 and 5 km, up to 11 km, and beyond 11 km downwind from the release, respectively. Since these hazard distance estimates are based on chlorine concentrations that were directly measured (i.e., not modelled), their accuracy depends only on the quality of the health effects models, and not on the quality of any atmospheric transport and dispersion model or container release (chemical source term) model.

Don’t Turn a Blind Eye to Safety

While lasers have many useful purposes for both commercial and military applications, they can also be hazardous if not operated safely. This paper discusses the safety precautions that must be taken to adequately protect personnel when operating and/or testing lasers in a free-space environment. First, a brief overview of lasers and associated terminology are introduced. Second, the properties of one of the two most common beam profiles, Gaussian, are discussed. An understanding of the beam profile is important in correctly identifying the safe operating environment for the laser. Exposure to laser energy can result in damage to the eye and skin. Therefore, the concepts of Optical Density, Nominal Ocular Hazard Distance and Skin Hazard Distance are discussed. These parameters help ensure that the correct Personal Protective Equipment (PPE) is used and help identify the hazard zone. Finally, recommendations for selecting the appropriate PPE are discussed. The concepts presented in this paper can be applied to any hazardous laser system.

Image-based construction hazard avoidance system using augmented reality in wearable device

Abstract Construction sites are inherently dynamic due to continuous resource changes. As construction projects become bigger and more complex, this dynamism can lead to more frequent incidents on jobsites. Safety training, personal protective equipment, and regulations have been applied to improve the safety of construction sites. However, because of the dynamic and congested nature of construction sites, these practices still cannot guarantee safety. This paper proposes a vision-based hazard avoidance system that proactively informs workers of potentially dangerous situations. The system enables workers to recognize and consequently avoid dangers before accidents occur by displaying augmented hazard information on a wearable device. The system comprises of three modules; a vision-based site monitoring module that utilizes image capture device and wearable devices to identify site hazards, a safety assessment module that uses captured image data and fuzzy-based reasoning to evaluate the safety level of each object, and a visualization module that provides actionable information such as hazard orientation, distance, and safety level. The safety information provided by the proposed system can mitigate hazards and improve construction site safety.

Monte Carlo method for the analysis of laser safety for a high-powered lidar system under different atmospheric conditions

A major concern of high-powered atmospheric lidar systems is eye safety. Atmospheric lidars are often run unattended in adverse weather conditions where scattering redirects laser energy from the main beam. These naturally varying “soft targets” (such as fog and precipitation) are not accounted for in American National Standards Institute (ANSI) standards but, through multiple scattering events, can potentially create adverse viewing conditions. This paper introduces a Monte Carlo method that uses scattering phase functions for fog and snow and applies multiple scattering analysis to map the energy density within a scattering volume around the primary beam. Careful attention is given to accurately describing the forward scattering portion of the phase function as it scatters a significant amount of the beam energy. This method is compared to ANSI standard hazard zone calculations to determine what effect scattering has on the size of the hazard zone. For direct beam viewing, hazard zone size estimates are within about 3% of the ANSI defined Nominal Ocular Hazard Distance (NOHD) for clear air but are approximately 56% smaller than the NOHD as optical density increases for scattering in fog and approximately 33% smaller for scattering in blowing snow. For indirect beam exposure, clear air gives the worst approximation to the ANSI defined Nominal Hazard Zone (NHZ), in error by approximately 93%; fog approaches the ANSI results, within 30% error, whereas blowing snow shows 70% error. Finally, scattering enhancement mechanisms are considered which relate to the definition of the scattering layer of interest and increase scattered energy density observed by approximately 4%. In all cases, the ANSI calculated NOHD and NHZ are larger than the hazard zones that include scattering but the size of the zones is inextricably linked to the type of scattering ignored in the standard NOHD and NHZ calculations.

Hazard analysis of failure of natural gas and petroleum gas pipelines

This paper deals with the analysis of hazards associated with accidental release of high pressure from gas-pipeline transportation system. Simplified equations which are related to the fluid properties, operating pressure, the diameter of pipeline, hole or rupture diameter and the length of the pipeline have been used for the hazard analysis due to pipeline failure. The kind of release (i.e. leak) through a hole or the complete rupture was found not to affect the effective release rate because of an increase in the operating pressure. Among various gases, the release rate of butane with lower value of specific heat ratio (γ) is found to be always higher than that of propane and methane which have higher value of γ. Decay coefficient, defined as the ratio of release rate at any instant and to the initial maximum release rate, decreases with an increase in the leak (or hole) size. The accident affected distance increases with an increase in the hole size. During the leakage of natural gas and petroleum gas pipeline, affected distance of hazard is slightly higher for fire as compared to other events. The simplified models can be used with confidence to estimate the hazard distance or hazard area. The procedure developed will be helpful for safety management or emergency response planning for the pipeline transportation of the natural gas and petroleum gas.

Lidar Measurements Supporting the Ocular Hazard Distance Calculation Using Atmospheric Attenuation

A series of lidar measurements has been performed at the Vidsel Test Range, Vidsel, situated in the inland of the very northern part of Sweden, as a part of an assessment of reducing the laser hazard distance using atmospheric attenuation within the calculations of nominal ocular hazard distance (NOHD). The question was “How low is the atmospheric attenuation as function of height in this area, using a wavelength of 1064 nm?” The work included building a ground based backscatter lidar, performing a series of measurements and analyzing the results. The measurements were performed during June to November, 2014, with the objective to measure at clear air and good weather situations.The lidar measurements at 1064 nm showed a very low atmospheric attenuation as a function of height to altitudes of at least 10 km at several occasions. The lowest limit of backscatter coefficient possible to measure with this instrument is 0.3·10-7 m-1 sr-1 . Assuming a lidar ratio varying between 30 – 100 sr, this was leading to an extinction coefficient of about 0.9 - 3·10-6 m-1 . The atmospheric attenuation reduces the laser hazard distance with about 50 – 56 % depending on the lidar ratio. A recommendation is to monitor the atmospheric attenuation at the occasions when the method to the reduced laser hazard distance using atmospheric attenuation is used.

Modeling long distance dispersal of airborne foot-and-mouth disease virus as a polydisperse aerosol – Application to the emergence of a new strain from Egypt to Israel

Long distance dispersal (LDD) of airborne aerosol of foot-and-mouth disease (FMD) virus was extensively modeled in the literature. Most studies modeled this aerosol in simplistic approach as a passive tracer, neglecting physical and biological mechanisms that affect bio-aerosols such as the FMD aerosol. This approach was justified either because under persistent wind these mechanisms lower the extant of downwind hazard or on the grounds that the effect of some of the physical mechanisms on particles as small as the FMD particles (0.015–20 μm) is supposed to be negligible compared to the effect of atmospheric turbulence. Even when the FMD aerosol was treated as aerosol, it was assumed that it is monodisperse, i.e., all its particles are of the same size. The aim of the study is to examine whether these simplistic approaches are indeed justified when dealing with LDD of a bio-aerosol under actual atmospheric conditions. In order to do so, the influence of a more realistic modeling of the FMD aerosol as a polydisperse aerosol was compared to passive tracer and to monodisperse aerosol. The comparison refers to a case of a widespread FMD outbreak that occurred in 2012 in Egypt. This outbreak involved the emergence of a new serotype in Egypt, SAT2 and concern was raised that this serotype will advance further to Asia and Europe. Israel is located on the land bridge between Africa, Asia and Europe, and shares a long desert border with Egypt as well as a long Mediterranean shore adjacent to Egypt's shore. This unique location as well as the fact that Israel does not have any cattle trade with its neighboring countries make Israel an interesting test case for the examination of the necessary conditions for the long distance dispersal (LDD) of a new FMD strains from Africa to Europe. The analysis in this study shows that under quasi-stationary wind conditions modeling FMD dispersal as a passive tracer results in a significantly longer hazard distance. Under non-stationary conditions this modeling assumption results in an under-estimation of the hazard distance in comparison to the results of polydisperse aerosol. In these conditions modeling the FMD dispersal as a monodisperse aerosol results in similar under-estimation. The implications of such under-estimation may be severe because it may lead authorities in a threatened area to refrain from taking the necessary protective measures. Therefore, the modeling of the FMD aerosol as a polydisperse aerosol is preferable, leading to realistic estimation both under non-stationary and stationary wind conditions.

Towards more detailed determination of third party impact on risk on natural gas pipelines: Influence of population density

The paper presents a refined way to quantify the effects of third party interference on risk that is posed on people by transmission pipelines for natural gas. The main focus is set on the influence of population density on risk. Using the interdisciplinary approach, the presented study combines the knowledge from relevant risk assessment recommendations, physical consequences of hazardous events, existing history databases of hazardous event frequencies and urban planning. A quantitative boundary between two most populated types of area was established. A flexible risk coefficient was determined for a suburban type of populated area that is dependent on average population density. Consequently, a new approach for determination of a hazard distance from the pipeline and area boundaries for calculation of average population density was presented. This differs from the established methods described in some guidelines, but is based on results of applied quantitative risk assessment. The final result is more accurate determination of risk levels in suburban areas. Described methods may serve as a supplement to the existing models for quantitative risk assessment on pipelines used in natural gas transportation and may be used by pipeline operators as well as policy- and decision makers.

Consequence Analysis of Jet Fire Accidents Occurred in Salt Cavern Natural Gas Storage: Hazard Distance and its Influence Factors

Natural gas storages in salt caverns are receiving an increasingly important role in energy storage system of many countries. This study focuses on analyzing the consequence of jet fire associated with natural gas storages in salt caverns. A widely used software, ALOHA, was adopted as simulation tool. The reliability of ALOHA was validated by comparing the simulated results with the field data observed in real accidents and the values calculated by a simple model presented in a previous study. The China's first natural gas storage in salt cavern, Jintan natural gas storage, was selected for case study. The case study reveals that the hazard distance of jet fire decreased with the increase of pipeline length, as well as the decrease of pipeline diameter and operating pressure.

Fuzzy logic approach to calculation of thermal hazard distances in process industries

In this paper, a general procedure to deal with uncertainties in each stage of consequence modeling is presented. In the first part of the procedure, the sources of uncertainty are identified and confirmed by sensitivity analysis for the source term, dispersion, physical effects and consequence analysis. While the second part comprises an application of the fuzzy logic system to each step of the consequence modeling. The proposed procedure is verified by the case study for a pool fire liquefied natural gas (LNG) on water. The results in terms of thermal radiation distances are compared with calculations obtained using the Monte Carlo method and with experimental data. The consequence model based on fuzzy logic approach provides less uncertain and more precise results in comparison to the deterministic consequence model.

Housing Density and Ecosystem Function: Comparing the Impacts of Rural, Exurban, and Suburban Densities on Fire Hazard, Water Availability, and House and Road Distance Effects

Many amenity-rich regions are experiencing rapid land-use change through low-density residential development or exurbanization. Those same natural-resource amenities that attracted migration are often degraded by housing growth and associated development. This study examines the impacts of exurbanization on three ecosystem indicators (fire hazard, water availability, and generalized distance effects of houses and roads) and compares them to areas with rural and suburban housing densities in the Sonoita Plain, southeastern Arizona. We found that although they support significantly lower population densities, exurban areas have impacts on ecosystem function comparable to suburban areas. Exurban areas had the highest potential for fire, suggesting that it is the presence of people rather than the density that increases fire hazard. The increase in the number of wells in exurban areas far exceeded suburban areas and matched increases for agricultural use in rural areas. When the impacts of houses and roads on ecosystem function were considered, 98% of exurban areas were “highly” or “very highly” impacted, compared to 100% for suburban areas and 35% for rural areas. Since development in the area is not readily visible, assessing the spatial extent of impacts is important for understanding the vulnerability of systems and guiding decisions about development.

Laser Safety Standards and Measurements of Hazard Parameters for Medical Lasers

Laser sources are nowadays largely adopted in medicine and hence they are widespread in medical environment, where patients are present and the users are not always highly specialized in managing laser sources. This has greatly boosted the attention towards safety issues related to exposure to laser beams and to strictly assess the values of well defined laser radiation standard parameters characterizing the level of hazard of laser sources. In this framework, we measured two of the most important parameters, Maximum Permissible Exposure (MPE) and Nominal Ocular Hazard Distance (NOHD), for some of the laser sources mostly employed in medicine. Additionally, we compared our results with data elaborated from standards in order to single out safe and comfortable working conditions. The results here reported have shown that information provided by manufacturers is often not enough to define the hazard level of the laser source and measurements of the main safety parameters are mandatory.