Journal of Health and Safety at Work

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Introduction: Process industries, often work with hazardous and operational chemical units with high temperature and pressure conditions, such as reactors and storage tanks. Thus, probabilities of incidence such as explosions, and fire are extremely high, The purpose of this study was to present a comprehensive and efficient method for the quantitative risk assessment of fire and explosion in the process units.

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Material and Method: The proposed method in this study is known as the QRA and includes seven steps. After determination of study objectives and perfect identification of study process, first, qualitative methods are used to screen and identify hazard points and the possible scenarios appropriate are identified and prioritized. Then, estimation of frequency rate are done using past records and statistics or Fault Tree Analysis along whit Event Tree. PAHST professional software and probit equations are used in order to consequence modeling and consequence evaluation, respectively. In the last step by combination of consequence and frequency of each scenario, individual and social risk and overall risk of process or under study unit was calculated.

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Result: Applying the proposed method showed that the jet fire, flash fire and explosion are most dangerous consequence of hydrogen generation unit. Results showed that social risk of the both fire and explosion caused by full bore rupture in Desulphrizing reactor (Scenari3), Reformer (scenario 9) and Hydrogen purification absorbers are unacceptable. All of the hydrogen generation unit fall in ARARP zone of fire individual risk (FIR) and FIR up to 160 m of boundary limit unit is unacceptable. This distance is not only beyond of hydrogen generation unit boundary limit, but also beyond of complex boundary limit. Desulphurization Reactor (75%) and Reformer (34%) had the highest role in explosion individual risk in the control room and their risks are unacceptable.

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Conclusion: Since the proposed method is applicable in all phases of process or system design, and estimates the risk of fire and explosion by a quantitative, comprehensive and mathematical-based equations approach. It can be used as an alternative method instead of qualitative and semi quantitative methods.

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Introduction: Occupational exposure to crystalline silica increases the risk of lung cancer and restrictive lung disease with extensive fibrosis. Silica dust is a major health hazard in foundry factories. The aim of this study was to determine core making workers’ exposure to respirable crystalline silica dust in a foundry factory.

Material and Method: This cross-sectional study was conducted in core-making unit of a foundry factory in 2015. Occupational exposure of 55 workers to respirable crystalline silica aerosols was evaluated by using the improved NIOSH7602 method in core-making unit. Risk assessments for silicosis and excess lifetime risk of mortality from lung cancer were done according to Manettej and Rice models, respectively. Data was analyzed with Spss19 software.

Result: The mean of respirable crystalline silica dust was 0.246 ± 0.351 (mg/m3). All  workers’ exposure to respirable crystalline silica was higher than recommended occupational exposure limits. Silicosis mortality risk and excess lifetime risk of mortality from lung cancer were estimated in the range of 6-63 and 65 per thousand people, respectively.

Conclusion: The mean of workers’ exposure to respirable crystalline silica was higher than recommended occupational exposure standards in core making unit. The risk assessment of silicosis mortality and excess lifetime risk of mortality from lung cancer were higher than acceptable levels of risk.

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Introduction: Failure modes and effects analysis (FMEA) method is used in industries to identify, assess and prioritize risks. Multi-criteria decision-making methods (MCDM) select the best option from different criteria. Therefore, this study aims to identify, assess and prioritize risks using FMEA based on SWARA-VIKOR multi-criteria decision-making methods in a gas pressure reduction station.
Material and Methods: In this descriptive and analytical study, stepwise weight assessment ratio analysis (SWARA) and decision-making optimization and compromise solution (VIKOR) methods were used to rank the risks of failure modes identified in FMEA. SWARA method was employed to determine the severity, probability and discovery weights, and VIKOR technique was applied to rank the failure modes of the system equipment. Finally, an operational example of the pressure reduction station was presented to show the application and feasibility of the proposed model. A comparative study was conducted to confirm the practicality and effectiveness of the proposed model.
Results: In total, 35 main failure modes were identified in the pressure reduction station. Failure of regulator sleeve and safety valve and regulator diaphragm rupture were assigned the first, second and third ranks of risk priority, respectively. The sensitivity analysis results showed the proposed approach had desirable stability and only the failure mode of increasing the heater flame temperature was very sensitive to changes in the weight of the criteria. Results of ranking the failure modes of the station indicated there were many changes in the ranking of failure modes based on the proposed approach.
Conclusion: The proposed approach could provide more reasonable and accurate results for ranking risks because the criteria were weighed step by step based on the experts’ opinion.

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Introduction: Reliability is always of particular importance in system design and planning; thus, improving reliability is among the approaches for achieving a safe system. Simulation methods are widely used in system reliability assessment. Therefore, this study aims to assess the reliability of the City Gate Gas Station (CGS) using Monte Carlo Simulation (MCS).
Material and Methods: This descriptive and analytical study was conducted in one of the CGSs of North Khorasan Province in 2021. The CGS process was carefully examined and its block diagram was plotted. Then, failure time data of CGS equipment were collected over 11 years and time between failures of subsystems was calculated. The failure probability distribution function of subsystems was determined using Easy Fit software and Kolmogorov-Smirnov test. Moreover, subsystems’ reliability was estimated by MCS. Finally, station reliability was calculated considering the series-parallel structure of the CGS.
Results: The results revealed that the failure probability density distribution function of CGS subsystems was based on gamma and normal functions. The reliabilities of filtration, heater, pressure reduction system, and odorize were calculated as 0.97, 0.987, 0.98, and 0.992 respectively, and their failure rates were 0.000003477, 0.0000014937, 0.0000023062, and 0.0000009169 failures per hour respectively. The station reliability was calculated as 0.93.
Conclusion: The failure probability distribution function and reliability assessment of subsystems were determined by data modeling and MCS respectively. Filtration and pressure reduction systems had the highest failure rate and required a proper maintenance program.

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Introduction: Iran has the most extensive maritime transport fleet in the Middle East, with 2700 km of water border with other countries in the region. However, the complex and hazardous marine environment has turned this advantage into a disadvantage. On the other hand, technological advancement has added to the complexity. Thus, new accident analysis tools should be developed to bring unity to marine casualty analysis and improve the analyst’s power of discovery from incident information. The current project aims to develop a specialized AcciMap-based marine accident investigation method.
Material and Methods: The primary stages of this applied descriptive study include data collection, method development, and validation. The necessary information about the factors leading to marine accidents was initially gathered through a review of previous studies, expert interviews, and analysis of actual cases. The AcciMap technique was then partially developed, and marine experts approved the designed model.
Results: This study’s results included an AcciMap model established on three levels: external influences (national and international), intra-organizational factors, and environmental/individual conditions and individual activities. Whereas external factors (international and national) are categorized into three main layers, two sublayers, and 13 secondary sublayers, intra-organizational factors are categorized into two main layers, 11 sublayers, and 35 secondary sublayers, and environmental/individual conditions and individual activities are organized in one main layer, three sublayers, and 11 secondary sublayers.
Conclusion: The developed approach can identify flawed levels and determine who is responsible for implementing corrective action. Because it includes emerging components that are effective in accidents, the method used in this study can better examine data from marine accidents.