Dispersion modeling of LNG-Vapor on land – A CFD-Model evaluation study

Based on methane from renewable resources, LNG is an alternative fuel for heavy and long-distance traffic in land transport. Contrary to its positive properties, the fuel contains risks from an explosion and extremely low temperatures for personal and infrastructure safety. CFD-models are suitable for doing risk analyses for arbitrary scenarios. For examining how to model for risk research the dispersion of LNG-vapor, this paper contains a model variant study, with an evaluation by experiments.This paper describes the use of the CFD-code ANSYS Fluent for simulating experiments of the ‘LNG Safety Program Phase II‘. The content of the well-documented experiments was the research of the vaporization rate of LNG on land and the dispersion of LNG-vapor in the air. Based on the comparison to two experiments, overall 12 CFD-model variants with varying thermal and turbulence parameters were examined how they affect the transient LNG-vapor dispersion in air.The definition of turbulence-boundary-condition at the domain borders had the biggest impact on modeling, followed by the turbulence model. The most accurate model variant had been applied for observing the spreading behavior of LNG-vapor in the air after evaporation on land and analyzing the influence of the LNG-composition to the dispersion. The results show that the mixture of LNG-vapor and the air in the free field is cooler than the ambient air and spreads like a heavy gas on the ground.     

A new-generation safety contest in the construction industry – A long-term evaluation of a real-life intervention

A new-generation safety campaign has been taking place in southern Finland since 1997. The Finnish Construction Employer’s Association together with trade unions, safety inspectorates, and other institutions have been organising a safety contest based on the standardised TR-observation method. Safety inspectors conduct evaluation visits without previous notice to the sites, and best performing companies and sites are rewarded at annually held public seminars. Even though participation is voluntary, more than 70% of the total number of construction sites in the target area have participated in the contest, and the results have been successful. Deficiencies in protection against falling have decreased by 63%, in order and tidiness by 69%, and in working habits by 51%. The effectiveness is also evident in the accident figures. An estimated 4000 accidents and three fatalities are prevented each year, while other parts of the country during the same period show no improvement in accident risk. A key success factor may be the adoption among firms of a new, standardised safety monitoring method which has been used effectively by senior management teams. The method employs a combination of penalties and incentives in order to set and enforce new safety targets. Another success factor is the close co-operation between the construction industry, labour organisations and safety authorities.     

Building Safety indicators: Part 1 – Theoretical foundation

Development of early warning indicators to prevent major accidents – to ‘build safety’ – should rest on a sound theoretical foundation, including basic concepts, main perspectives and past developments, as well as an overview of the present status and ongoing research. In this paper we have established the theoretical basis for development of indicators used as early warnings of major accidents. Extensive work on indicators have been carried out in the past, and this could and should have been better utilized by industry, e.g., by focusing more on major hazard indicators, and less on personal safety indicators. Recent discussions about safety indicators have focused on the distinction between leading and lagging indicators; however, a discussion on terms should not impede the development of useful indicators that can provide (early) warnings about potential major accidents.     

Scaling of dust explosion violence from laboratory scale to full industrial scale – A challenging case history from the past

The standardized K_St parameter still seems to be widely used as a universal criterion for ranking explosion violence to be expected from various dusts in given industrial situations. However, this may not be a generally valid approach. In the case of dust explosion venting, the maximum pressure P_max generated in a given vented industrial enclosure is not only influenced by inherent dust parameters (dust chemistry including moisture, and sizes and shapes of individual dust particles). Process-related parameters (degree of dust dispersion, cloud turbulence, and dust concentration) also play key roles. This view seems to be confirmed by some results from a series of large scale vented dust explosion experiments in a 500 m³ silo conducted in Norway by CMI, (now GexCon AS) during 1980–1982. Therefore, these results have been brought forward again in the present paper. The original purpose of the 500 m³ silo experiments was to obtain correlations between P_max in the vented silo and the vent area in the silo top surface, for two different dusts, viz. a wheat grain dust collected in a Norwegian grain import silo facility, and a soya meal used for production of fish farming food. Both dusts were tested in the standard 20-L-sphere in two independent laboratories, and also in the Hartmann bomb in two independent laboratories. P_max and (dP/dt)_max were significantly lower for the soya meal than for the wheat grain dust in all laboratory tests. Because the available amount of wheat grain dust was much larger than the quite limited amount of available soya meal, a complete series of 16 vented silo experiments was first performed with the wheat grain dust, starting with the largest vent area and ending with the smallest one. Then, to avoid unnecessary laborious changes of vent areas, the first experiment with soya dust was performed with the smallest area. The dust cloud in the silo was produced in exactly the same way as with the wheat grain dust. However, contrary to expectations based on the laboratory-scale tests, the soya meal exploded more violently in the large silo than the wheat grain dust, and the silo was blown apart in the very first experiment with this material. The probable reason is that the two dusts responded differently to the dust cloud formation process in the silo on the one hand and in the laboratory-scale apparatuses on the other. This re-confirms that a differentiated philosophy for design of dust explosion vents is indeed needed. Appropriate attention must be paid to the influence of the actual dust cloud generation process on the required vent area. The location and type of the ignition source also play important roles. It may seem that tailored design has to become the future solution for tackling this complex reality, not least for large storage silos. It is the view of the present author that the ongoing development of CFD-based computer codes offers the most promising line of attack. This also applies to design of systems for dust explosion isolation and suppression.     

The effectiveness of U.S. OSHA process safety management inspection – A preliminary quantitative evaluation

This study attempted to evaluate the inspection effectiveness of the U.S. OSHA process safety management (PSM) standard using statistical correlation test. A total of 6578 citations of past 1277 OSHA PSM inspections from 1992 to 2006 were quantitatively compared with the findings of the U.S. Chemical Safety and Hazard Investigation Board (CSB) investigations on root and contributing causes of 19 major chemical accidents. Nonparametric Spearman's coefficient of rank correlation tests showed a moderately strong agreement between OSHA PSM inspection citations and CSB findings at p < .01 significant level, and the degree of agreement increased with time. These results suggested that past OSHA PSM inspections had cited the problems that were the accident root causes, and the effectiveness of PSM citations has been improved as more inspections were conducted since the standard promulgation. However, factors such as standard coverage, inspection frequency, inspection resources allocation, and inspection strategy, were critical for effective PSM standard enforcement and implementation. Future studies should include more aspects of PSM citations and CSB accident investigation data for better evaluation of inspection effectiveness. The results may be valuable to the PSM enforcement policy makers.     

Quantifying reputation loss of pipeline operator from various stakeholders’ perspectives – Part 1: Prioritization

Quantifying reputation loss (RL) due to pipeline damage is commonly generalized based on the owner's definition. This one-way perspective of portraying RL is unfair and unrealistic and consequently miscalculates the impact assessment of pipeline damage; hence, inaccurate risk prediction. It is crucial to develop a model to quantify qualitative RL to avoid unpredicted risk. Thus, this article provides a framework for a procedure to calculate RL by utilizing the factors identified in a previous study. In this paper (Part 1), the prioritization of factors based on the stakeholders' perspectives is presented. The factors were grouped into stakeholder-influenced categories and prioritized by a fuzzy analytic hierarchy process based on the feedback gained from the stakeholders, i.e., investors, customers, employees and the public. The result shows that factor D3, “Accident severity”, was ranked highest by all stakeholders. The priority vector for each factor obtained was assigned as a weight of the factor. The pipeline owner's reputation loss model (RLM) is developed by applying the obtained priority vectors in the subsequent paper (Part 2). The developed model was verified by experts as a comprehensive, clear, objective, practical and moderately reliable model. The model was applied to a case study and eventually produced a lower risk value when compared with the currently used model. It is proven that RL factors can be quantitatively measured and can simultaneously improve pipeline damage impact assessment. Thus, a risk-based inspection schedule can be managed comprehensively.     

Measurement of minimum ignition energies (MIEs) of dust clouds – History,present, future

Nearly 130 years ago Holtzwart and von Meyer (1891) demonstrated by experiments that explosible dust clouds could be ignited by inductive electric sparks. Then more than half a century passed before the publication of the important quantitative research of Boyle and Llewellyn (1950) and Line et al. (1959). They worked with capacitive electric sparks and found that the minimum capacitor energies ½CU² required for ignition of various dust clouds in air decreased substantially when a large series resistance, in the range 10⁴–10⁷ Ω, was introduced in the discharge circuit. When considering that the net energies of the sparks themselves were only of the order of 10% of the ½CU² discharged, the minimum net spark energies required for ignition with a large series resistance were only a few per cent of the net energies required without such a resistance.Line et al. observed that the essential effect of increasing the series resistance, and hence increasing the discharge time of the sparks, was to reduce the disturbance of the dust cloud by the blast wave from the spark. This phenomenon was explored further by Eckhoff (1970, 2017), and subsequently by some simple experiments by Eckhoff and Enstad (1976). Franke (1974, 1977) and Laar (1980) confirmed the additional finding of Line et al. (1959) that the minimum ½CU² for ignition is also substantially reduced by including a series inductance in the discharge circuit, rather than a series resistance. The basic reason is the same as with a large series resistance, viz. increased spark discharge time and hence decreased disturbance of the dust cloud by blast wave from the spark. For this reason inclusion of an appreciable series inductance in the spark discharge circuit is an essential element in current standard MIE test methods.In experiments with spark ignition of transient dust clouds produced by a blast of air in a closed vessel, it is necessary to synchronize the occurrence of the spark with the formation of the dust cloud. The precision required from this type of synchronization is typically of the order of 10 ms, which can be obtained even by mechanical arrangements, such as rapid change of spark gap length, or of the distance between two capacitor plates. The present paper reviews some methods that have been/are being used for achieving adequate synchronization of dust cloud appearance and spark discharge. Some current standard experimental methods for determining MIEs of dust clouds experimentally have also been reviewed. The same applies to some theories of electric-spark ignition of dust clouds.At the end of paper some suggestions for possible future modifications of current standard methods for measuring MIEs of explosible dust clouds are presented. With regard to justifying significant modifications of existing standard methods, the “bottom line” is, as quite often in many connections, that any modifications should be based on realistic cost/benefit evaluations.     

Mathematical methods for application of experimental adiabatic data – An update and extension

The paper represents some results of comparative analysis of the methods used for processing and interpreting data of adiabatic calorimetry as well as applying it to practical situations. Specifically two approaches are compared – approximate method based on evaluation of simplified kinetics and a more comprehensive, simulation-based method that utilizes the evaluation of more detailed kinetic models.The analysis is focused on two important types of data processing – correction of experimental results on thermal inertia (phi-factor correction) and estimation of adiabatic time to maximum rate (TMR).The most widely cited method for phi-factor correction is considered and its improvement is proposed to enable more precise prediction of the adiabatic time scale. A procedure for phi-factor correction of pressure response is also proposed. The limitations of this enhanced Fisher's method are discussed by comparison with simulation-based method. All the illustrative materials are based on real examples.As an example of application, the simplified method will be used to predict TMR and its limitations will be discussed.     

Making work environment auditable – A ‘critical case’ study of certified occupational health and safety management systems in Denmark

This paper discusses the impact of certification on occupational health and safety management (OHSM) systems. Most research in the field has focused on how well such systems comply with voluntary standards such as OHSAS 18001 or with national and international legislation. However, this paper shows that even in cases of compliance, the certified systems have problems dealing with a range of contemporary complex work environment issues. Furthermore, certification also transforms the kinds of topics addressed and the procedures and activities applied in the system. Using the (in many ways successful) development of certified OHSM system in a manufacturing company in Denmark as a critical case, we demonstrate how certified OHSM systems unintentionally yet actively create an environment of ‘measurable and auditable facts’ shaped not only in response to legal and market demands for a safe work environment, but also as a consequence of the external demands for a visible and accountable work environment standard. We show how certified OHSM systems function like a hinge between internal operations and an external audience in a globalized market, thus giving priority to work environment issues that may later become demonstrable guarantees for a safe and healthy work environment. Thus the certified management system does not necessarily tackle the most urgent work environment issues and may exclude important aspects of the work environment such as psychosocial factors.     

A societal risk study for transportation of class-3 hazmats – A case of Indian state highways

United Nations Class-3 hazardous materials (hazmats) are basically liquid products and transported in road tankers under ambient temperature and atmospheric pressure. They are mostly flammables and some of them are toxic (e.g. benzene) as well. The spillages due to collision related incidents involving the road tankers, carrying such hazmats through highways, pose not only flammability hazards due to pool fire, flash fire and vapor cloud explosion (VCE), but create substantial toxic hazards also. The paper presents the risk-based study of route evaluation of two state highways and one urban city road in western India on account of transportation of class-3 hazmats, namely benzene, toluene, p-xylene, methanol, cyclohexane and acetone. A comparative evaluation of study routes was undertaken based on their societal risks presented in terms of F–N curves and assessed against HSE, UK as well as VROM, The Netherlands risk acceptance criteria. Societal risks contribution of cyclohexane to the overall flammability risk mainly VCE is found to be the highest followed by acetone and benzene compared to other study hazmats. This is due to highly explosive nature of cyclohexane resulting into vapor cloud explosion. While acetone and methanol pool fires are likely to cause larger area of damage compared to others, benzene supersedes others as far as toxicity risk is concerned and larger evacuation area is encountered, as it poses greater Immediately Dangerous to Life or Health (IDLH) distance than others. Besides, study of initial isolation distance following an accident in case of benzene tanker found that benzene spillage requires larger initial isolation distance than others and so are the day and night protective action zone distances.     

Preparation and performance of novel APP/NaY–Fe suppressant for coal dust explosion

Coal dust explosion occurs easily in the coal chemical industry. To ensure safety in industrial production, NaY zeolite was used as carrier modified with Fe ions and combined with ammonium polyphosphate (APP) to prepare a novel composite suppressant for coal dust explosion. The explosion suppression performance of novel APP/NaY–Fe suppressant was investigated by flame propagation inhibition experiments. The results show that Fe ion modification can effectively improve the explosion suppression performance. By increasing content, the explosion suppression performance of the explosion suppressant increases. The maximum explosion pressure P_max of coal dust drops to 0.13 MPa when 50 wt% explosion suppressants were added, and the coal dust explosion cannot continue to expand. Complete suppression of explosion could be achieved by adding 66 wt% explosion suppressants. Combined with XRD, SEM and TG results, the explosion suppression mechanism was proposed. The novel explosion suppressant has high thermal stability, good dispersity and its explosion suppression components distribute uniformly. It shows good explosion suppression performance by the synergistic effect among explosion-suppression components.     

Readability of OHS documents – A comparison of surface characteristics of OHS text between some languages

Readability of documents, including occupational health and safety (OHS) documents, is a key factor in their adoption and application. The author uses two measures of English readability favoured by the US for health communication, and in defense communications respectively. Also included is the use of measures for Chinese, Japanese, Malay/Indonesian, and Spanish. One measure, McLaughlin’s (1969) SMOG formula, was also trialed on documents in five languages other than English. The tests included parallel texts from China, Europe, Malaysia and the US, and also parallel texts in English, Chinese and Spanish, and on like topics (except for Turkish where available choices were limited). On the data obtained, it is suggested that the SMOG test with modified criteria may be applicable to Finnish, Hungarian, Malay, Spanish and possibly Turkish. Readability of the OHS documents on the measures used varied quite widely, both within and between languages. To put this in context, some internationally comparable literacy results for mid high school students are presented.     

Protective clothing for pesticide operators: part I – selection of a reference test chemical for penetration testing

A systematic approach was taken to develop a database for protective clothing for pesticide operators; results are reported as a two-part series. Part I describes the research studies that led to identification of a pesticide formulation that could serve as a reference test chemical for further testing. Measurement of pesticide penetration was conducted using different types of pesticide formulations. Six fabrics were tested using 10 formulations at different concentrations. Three formulations were subsequently selected for further testing. Analysis of the data indicated that, when compared with other formulations, mean percent penetration of 5% Prowl 3.3 EC [emulsifiable concentrate diluted to 5% active ingredient (pendimethalin)] is either similar to or higher than most test chemicals. Those results led to choosing 5% Prowl 3.3 EC as a reference test liquid. Part II of the study, published as a separate paper, includes data on a wide range of textile materials.     

Challenges in performing technical safety reviews of modifications – A case study

The aim of the present study, is to identify strengths and weaknesses of the technical safety review process at a Swedish Nuclear Power Plant (NPP). In this context, the function of safety reviews are understood as expert judgements on proposals for design modifications¹ and redesign of technical systems (i.e. commercial nuclear reactors), supported by formalised safety review processes. The chosen methodology is using two complementary methods: interviews of personnel performing safety reviews, and analysis of safety review reports from 2005 to 2009.The study shows that personal integrity is a trademark of the review staff and there are sufficient support systems to ensure high quality. The partition between primary and independent review is positive, having different focus and staff with different skills and perspectives making the reviews, which implies supplementary roles. The process contributes to “getting the right things done the right way”. The study also shows that though efficient communication, feedback, processes for continuous improvement, and “learning organizations” are well known success factors in academia, it is not that simple to implement and accomplish in real life.It is argued that future applications of safety review processes should focus more on communicating and clarifying the process and its adherent requirements, and improve the feedback system within the process.     

Toxic release of chlorine and off-site emergency scenario – A case study

Release of chlorine gas causes deaths and injuries to workers and the public, resulting in the evacuation of communities and adversely affecting the environment as a whole. The off-site emergency plan is an integral part of any major hazard control system. This paper highlights some salient features of the emergency scenario from a chemical plant, which ultimately lead to fatal consequences all around upon releases of toxic chlorine gas. A typical scenario illustrating the dispersion model of chlorine (for three isopleths concentration) has been estimated by Complex Hazards Air Release Model (CHARM) software package. The enlarged form of this model diagram has been outlined on the area map of the study area for contingency planning. As a broad guide line to the district authorities for contingency planning, evacuation time has also been calculated with reference to a concentration level of 3 ppm chlorine.     

Development and evaluation of RAMP I – a practitioner’s tool for screening of musculoskeletal disorder risk factors in manual handling

RAMP I is a screening tool developed to support practitioners in screening for work-related musculoskeletal disorder risk factors related to manual handling. RAMP I, which is part of the RAMP tool, is based on research-based studies combined with expert group judgments. More than 80 practitioners participated in the development of RAMP I. The tool consists of dichotomous assessment items grouped into seven categories. Acceptable reliability was found for a majority of the assessment items for 15 practitioners who were given 1?h of training. The usability evaluation points to RAMP I being usable for screening for musculoskeletal disorder risk factors, i.e., usable for assessing risks, being usable as a decision base, having clear results and that the time needed for an assessment is acceptable. It is concluded that RAMP I is a usable tool for practitioners.     

Investigation of accidents involving powered two wheelers and bicycles – A European in-depth study

Introduction: The number of road fatalities have been falling throughout the European Union (EU) over the past 20 years and most Member States have achieved an overall reduction. Research has mainly focused on protecting car occupants, with car occupant fatalities reducing significantly. However, recently there has been a plateauing in fatalities amongst ‘Vulnerable Road Users’ (VRUs), and in 2016 accidents involving VRUs accounted for nearly half of all EU road deaths. Method: The SaferWheels study collected in-depth data on 500 accidents involving Powered Two-Wheelers (PTWs) and bicycles across six European countries. A standard in-depth accident investigation methodology was used by each team. The Driver Reliability and Error Analysis Method (DREAM) was used to systematically classify accident causation factors. Results: The most common causal factors related to errors in observation by the PTW/bicycle rider or the driver of the other vehicle, typically called ‘looked but failed to see’ accidents. Common scenarios involved the other vehicle turning or crossing in front of the PTW/bicycle. A quarter of serious or fatal injuries to PTW riders occurred in accidents where the rider lost control with no other vehicle involvement. Conclusions: Highly detailed data have been collected for 500 accidents involving PTWs or bicycles in the EU. These data can be further analyzed by researchers on a case-study basis to gain detailed insights on such accidents. Preliminary analysis suggests that ‘looked but failed to see’ remains a common cause, and in many cases the actions of the other vehicle were the critical factor, though PTW rider speed or inexperience played a role in some cases. Practical Applications: The collected data can be analyzed to better understand the characteristics and causes of accidents involving PTWs and bicycles in the EU. The results can be used to develop policies aimed at reducing road deaths and injuries to VRUs.     

Severity analysis of Indian coal mine accidents – A retrospective study for 100 years

A retrospective study on severity analysis of Indian coal mines accidents for 100 years was done considering fatal and serious accidents and the resulting causalities. The impact of recommendations based on safety conferences and committees over the years was studied. An event evaluation algorithm (EEA) was developed for this purpose. The hazard rate functions and cumulative risk functions for major hazards in Indian coal mines were developed. The study evaluated the status of safety level as well as the scope of improvement for Indian coal mines safety.     

Learning from incidents – A method for assessing the effectiveness of the learning cycle

This paper describes a method for assessing the effectiveness in the steps of the learning cycle: the 1st loop with reporting – analysis – decision – implementation – follow-up, and the 2nd loop on an aggregated basis. For each step, the dimensions considered the most relevant for the learning process (scope, quality, timing and information distribution) and for each dimension the most relevant aspects (e.g. completeness and detail) were defined. A method for a semi-quantitative assessment of the effectiveness of the learning cycle was developed using these dimensions and aspects and scales for rating. The method will give clear indications of areas for improvement when applied. The results of the method can also be used for correlation with other safety parameters, e.g. results from safety audits and safety climate inquiries. The method is intended to be used on a sample of the broad range of incidents normally seen in process industry companies. The method was tested on a two-year incident reporting material from six companies from various types of process industries. It was found that the method and the tools worked very well in practice. The results gave interesting insights into the effectiveness of learning from the incidents.