Effect of initial pressure on explosion characteristics of 2, 3, 3, 3–tetrafluoropropene

With the popularity of refrigerants in the process industries, the potential safety problems caused by the use of refrigerants have attracted worldwide attention as people have realized their inherent explosion characteristics of refrigerants. This paper studied the explosion characteristics of refrigerant 2, 3, 3, 3–tetrafluoropropene (R1234yf) at different concentrations and initial pressures based on a 20 L experimental apparatus. The experimental results illustrated the peak overpressure of R1234yf increased with the rise of initial pressure. At a constant ambient temperature of 25 °C, the maximum rate of pressure rise and deflagration index showed an N-shaped trend with the increase of the refrigerant concentration from 6.8% to 10%. The maximum rate of pressure rise and deflagration index increased first and then decreased with the increase of the refrigerant concentration at atmospheric pressure, while they presented an M-shaped trend at pressurization condition. The peak overpressure, the maximum rate of pressure rise, and deflagration index reached 0.742 MPa, 4.04 MPa s⁻¹, and 1.1 MPa.m.s⁻¹ with a refrigerant concentration of 7.6%, respectively, which were less than those of refrigerant propane and difluoromethane (R32) at the optimal concentration. Furthermore, R1234yf exhibited better safety performance compared with refrigerant R32 in the same flammability classification.     

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.     

Synergism of Ergonomics,Safety, and Quality—A Behavioral Cybernetic Analysis

Abstract

This report extends a control systems or cybernetic model of behavior to the behavior of groups of many individuals—organizations and institutions—operating together with technology as complex sociotechnical (ST) systems. The premise is that the level of quality in performance of a complex ST system is predicated upon the degree to which its organizational design incorporates elements of a closed-loop behavioral control system: control goals and objectives, sensory receptors, sensory feedback, learning and memory, effectors, and sensory feedback control. From a control systems perspective, ergonomics is essential to effective organizational self-regulation. If working conditions are poorly designed, work performance and safety and quality outcomes cannot be closely controlled. Conversely, as shown by field evidence, good design promotes synergism between ergonomics, safety, and quality as a closed-loop consequence of effective employee and organizational self-control of system performance, safety, and quality.     

Influence of Exercise-Focused Group Activities on the Physical Activity,Functional Capacity,and Work Ability of Female Farmers—A Three-Year Follow-Up

Abstract

The objective of this randomised study was to evaluate the influence of exercise-focused group activities on female farmers’ physical activity, functional capacity, and work ability over a period of 3 years. Physical activity increased more in the intervention group (n = 62) than in the control group (n = 64) during the first year. By the third year physical activity had almost returned to the pre-intervention level. In the 3-year follow-up examination muscular endurance and cardio-respiratory fitness had improved in the intervention group, and musculoskeletal symptoms had decreased more often in the intervention group than in the control group. The index used to measure perceived work ability showed no changes over the 3-year period. It can be concluded that group activities focused on leisure-time physical activity and work habits can be recommended as health promotion measures for farmers’ occupational health services.     

Safety climate dimensions,leader–member exchange,and organizational support as predictors of upward safety communication in a sample of rail industry workers

The freedom employees feel to communicate safety concerns with their supervisors, termed upward safety communication, has been shown to be related to adverse safety events (Hofmann and Morgeson, 1999). Research to date has demonstrated that good supervisor–employee relationships (leader–member exchange), a sense that the organization values an employee (perceived organizational support) and safety climate (including perceived management attitudes toward safety, job demands interfering with safety, and pressure from coworkers to behave safely) all contribute to employees’ comfort in bringing up safety issues with their supervisors. However, little is known about which specific dimensions of safety climate are most predictive of upward safety communication. Using a sample of 548 railway workers, we found that when all factors were considered simultaneously using dominance analysis, the dominant factor predicting upward safety communication was perceived management attitudes toward safety, followed by job demands interfering with safety and then leader–member exchange. Implications for research and practice are discussed.     

The role of drug and alcohol use and the risk of motor vehicle crashes in Shiraz,Iran, 2014: A case–crossover study

Background: Traffic accidents and traffic-related injuries and mortality have become a major public health concern in Iran. This study aimed to examine the role of drug and alcohol use in motor vehicle accidents in Iran.

Methods: This case–crossover study was conducted on 441 drivers who survived a road traffic crash and were taken to the emergency department of Shahid Rajaee trauma hospital in Shiraz, southern Iran. Data were collected using checklists that included demographic characteristics and drug and alcohol use prior to driving. Alcohol and drug use was identified through self-report, and cannabis, morphine, and methamphetamine urine tests were used to confirm drug abuse among drivers.

Results: In total 17.9% of drivers reported using drugs (cannabis, opium, or metamphetamine) and 8.84% of drivers reported consuming alcohol prior to the collision. The crude odds ratios (ORs) for having a crash for opium, cannabis, and metamphetamine were 1.94 (95% interval confidence [CI], 1.11–3.38), 2.37 (95% CI, 1.03–5.42), 5.5 (95% CI, 1.21–24.81), respectively, and for all drugs was 3.83 (95% CI, 2.28–6.43). The OR for alcohol was 3.5 (95% CI, 1.73–7.06) based on self-report.

Conclusion: Drug and alcohol use are increasing the risk of traffic crashes in Iran. Risk-reducing programs must be designed and implemented.     

A survey of forest workers in New Zealand. Do hours of work, rest, and recovery play a role in accidents and injury?

PROBLEM: A number of structural and organizational changes have occurred recently within the New Zealand Forestry Industry, with concerns being raised about the impact of these changes on the forestry worker in terms of fatigue, sleepiness, and compromised safety. This study explored the relationship of fatigue, and some of its key determinants, with accidents and injuries in a group of forestry industry workers in New Zealand. METHOD: A total of 367 forestry workers responded to a self-administered questionnaire. RESULTS: Fatigue was found to be commonly experienced at work in the forest, with 78% of workers reporting that they experienced fatigue at least "sometimes." This study found that certain groups of workers reported long working hours, reduced sleep, compromised recovery time, and intensely paced work. The results of logistic regression analysis showed that recent sleep, number of breaks taken during the workday, and specific job/tasks were independently associated with reporting of high fatigue levels at work. Near-miss injury events were significantly more common among those reporting a high level of fatigue at work. Accidents and lost-time injury were associated with length of time at work, ethnicity, and having had near-miss injury events. DISCUSSION: Together, these results suggest that fatigue and aspects of work organization, which are likely to be fatiguing, may be associated with compromised safety for forest workers. IMPACT ON INDUSTRY: With an already slim margin of error present in forest operations, an impairment due to increased fatigue may constitute a significant risk factor for accidents and injuries in this workforce. The results indicate the need for further examination of shift and workload management among forestry workers, as well as a role for improving industry awareness about the causes and consequences of fatigue.     

The missing link? Implications of internal,external, and relational attribution combinations for leader–member exchange,relationship work,self‐work,and conflict

Attributions are causal explanations made by individuals in response to important, novel, and/or unexpected events. Numerous attribution theories have examined how people use information to make attributions and how attributions impact an individual's subsequent emotions and outcomes. However, this research has only recently considered the implications of dyadic‐level attributions (i.e., relational attributions), particularly in the context of leader–follower relationships in organizations. Therefore, the purpose of this theoretical paper is threefold. First, we integrate research on attributional biases into the research on relational attributions. Second, we integrate and extend attribution theory to consider the implications of convergent and divergent internal, external‐person, external‐situational, and relational attributions for leader–member exchange (LMX) quality, relationship work, self‐work, and conflict. Third, we make the implicit ranking of attribution combinations and the resultant levels of relationship work explicit. In doing so, we contribute to attribution theory and research by proposing how attribution combinations produce positive and negative outcomes that are both intrapersonal and interpersonal. Further, we contribute to the LMX literature by explicating how leader–follower attribution combinations influence relationship quality.     

Spatial patterns of off-the-system traffic crashes in Miami–Dade County,Florida, during 2005–2010

Objective: The objective of this study is to analyze the spatial distribution of the vehicles involved in crashes in Miami–Dade County. In addition, we analyzed the role of time of day, day of the week, seasonality, drivers’ age in the distribution of traffic crashes.

Method: Off-the-system crash data acquired from the Florida Department of Transportation during 2005–2010 were divided into subcategories according to the risk factors age, time of day, day of the week, and travel season. Various spatial statistics methods, including nearest neighbor analysis, Getis-Ord hot spot analysis, and kernel density analysis revealed substantial spatial variations, depending on the subcategory in question.

Results: Downtown Miami and South Beach showed up consistently as hotspots of traffic crashes in all subcategories except fatal crashes. However, fatal crashes were concentrated in residential areas in inland areas.

Conclusion: This understanding of patterns can help the county target high-risk areas and help to reduce crash fatalities to create a safer environment for motorists and pedestrians.     

Interview with Mr. Djankou Ndjonkou, Director of ILO Beijing Office and Vice-Chairman of the Organizing Committee of China International Forum on Work Safety

Question 1: Why does the ILO co-sponsor the Forum with the SAWS? Answers: OSH is an important issue in China with rapid industrialization and economic restructuring. There are many major accidents happening in China. The Forum is one of the initiatives of the SAWS for improving the situation, As you know, OSH is     

One,two or three dimensions of work engagement? Testing the factorial validity of the Utrecht Work Engagement Scale on a sample of Polish employees

Work engagement, as conceptualized by the Utrecht Work Engagement Scale (UWES), is a work-related positive state of mind that is characterized by vigour, dedication and absorption; however, it still remains unclear how many dimensions work engagement comprises. This study tested the factorial validity of 11 different UWES factorial models that are available in the literature using a confirmatory factor analysis approach on a large sample of multi-occupational Polish employees (N?=?1420). The two-factor UWES-6, comprising vigour and dedication, was found to be reliable and remained invariant across samples drawn from four different organizational positions. It also presented a better fit than the three-factor UWES-9, which is a scale used as a standard in contemporary research on work engagement. The findings suggest that the three-factor UWES-9 might not be an optimal measure of work engagement in Poland.