The Influence of Anchor Devices on the Performance of Retractable Type Fall Arresters Protecting Against Falls From a Height

Retractable type fall arresters are part of the equipment used for protecting people against falls from a height. They are an intermediate part between full body harness worn by a man and the structural anchor at the worksite. The most important task of retractable type fall arresters is to arrest people’s falls and to reduce their harmful consequences. Information received from users as well as laboratories testing protective equipment indicates that the performance of such equipment is incorrect under specific conditions. The paper is concerned with an analysis of the conditions in which retractable type fall arresters demonstrate intermittent performance and with an explanation of that phenomenon. The results of tests investigating anchor devices and the performance of retractable type fall arresters are presented. External and internal factors contributing to intermittent performance have been determined and guidelines for safer use of these devices have been developed.     

Locking of retractable type fall arresters--test method and stand.

Retractable type fall arresters are very effective personal equipment protecting against falls from a height. These devices are used under different atmospheric conditions and in the presence of various types of industrial pollution. For this reason appropriate locking after conditioning simulating extreme conditions of a worksite is one of the essential characteristics of retractable type fall arresters. This article presents the requirements for locking of the devices. A previously used locking test method and its disadvantages are discussed. The article suggests an improved test method and test equipment. Measurement of the test mass acceleration is the most important improvement introduced into the test method. The article shows laboratory tests used to verify the method, which turned out to be a valuable source of information concerning the performance of retractable type fall arresters.     

Locking of Retractable Type Fall Arresters—Test Method and Stand

Retractable type fall arresters are very effective personal equipment protecting against falls from a height. These devices are used under different atmospheric conditions and in the presence of various types of industrial pollution. For this reason appropriate locking after conditioning simulating extreme conditions of a worksite is one of the essential characteristics of retractable type fall arresters. This article presents the requirements for locking of the devices. A previously used locking test method and its disadvantages are discussed. The article suggests an improved test method and test equipment. Measurement of the test mass acceleration is the most important improvement introduced into the test method. The article shows laboratory tests used to verify the method, which turned out to be a valuable source of information concerning the performance of retractable type fall arresters.     

Test Method for Retractable Type Fall Arresters Designed for Horizontal Use

Retractable type fall arresters are designed to protect against falls from a height of people who need freedom of vertical movement. The practice of fall protection shows that the devices are also used to protect people who work on flat roofs. This application creates quite different operating conditions for the devices. In some situations those conditions can be dangerous for users. The article presents a theoretical analysis of phenomena occurring during a fall arrest with retractable type fall arresters arranged horizontally. The analysis was verified with laboratory tests. The article presents a proposal for the construction of a test stand and a test method for estimating retractable type fall arresters intended for horizontal use.     

Influence of weather conditions on the performance of energy absorbers and guided type fall arresters on a flexible anchorage line during fall arresting

Energy absorbers and guided type fall arresters on a flexible anchorage line belong to very popular group of equipment protecting against falls from a height. This equipment is used in different weather conditions (different temperature, humidity, precipitation, etc.), which influence its parameters. Fibre ropes and webbing, made from polyamide fibres, used in energy absorbers and guided type fall arresters, are sensitive to weather conditions. Laboratory tests proved that the changes in temperature, humidity, etc., especially influence dynamic elongation of this equipment and the force acting on anchor point during fall arresting. These phenomena decide directly about the fall arresting process and can influence safety of people working on a height.     

速差自控器动态性能试验方法的改进

为施工人员选择和配置安全可靠的个人防坠器,每年送到具有相应资质的检测单位进行强制检定,是防止高处坠落事故的重要手段。某型速差自控器在冲击试验中发生了钢丝绳断裂事故,为了查找和分析事故的真正原因,对不同厂家的速差自控器抽样,在相同试验方法和检测条件下进行冲击试验,并根据相关的标准对试验结果进行力学性能对比分析研究,找到了造成钢丝绳断裂事故的主要原因是该类型速差自控器使用的钢丝绳直径偏细以及缺少内部或外部缓冲器,研究中还发现部分国内标准技术要求不够明确,制造、检测和使用方对速差自控器相关标准理解存在偏差,是造成本次事故的间接原因。针对现有的部分速差自控器产品存在的质量问题,并根据现行最新标准和实际工作条件,提出改进了的检测方法和防范措施,从源头上防范坠落事故。     

Determination of the performance limits of flame arresters at increased oxygen concentrations

This investigation shows how an increased oxygen concentration influences the performance limits of crimped ribbon deflagration flame arresters at elevated pressures. An evaluation of the maximum experimental safe gap (MESG) as reliable criterion for describing the performance limits under non-atmospheric conditions is given. Measurements of MESGs and flame arrester performance tests were performed. Various fuel/oxygen/air mixtures containing ethylene and propane were used as testing gases. Former studies on the pressure dependence and the influence of oxygen on the MESG were initially confirmed. Furthermore, performance tests using a commercial deflagration flame arrester revealed that such a flame arrester may prevent flame transmission also at non-atmospheric conditions within a limited range. For various oxygen concentrations the performance limits were reached at the same MESG. Hence, it can be assumed that a flame arrester possesses a device- and fuel-specific maximum experimental safe gap for a specific gas mixture in different concentrations and at different pressures. This performance-related maximum safe gap can be used as a parameter for estimating and describing the performance limits of a flame arrester. It offers an attempt to simplify the testing and qualification of deflagration flame arresters for non-atmospheric conditions.     

Dynamic Performance of Horizontal Flexible Anchor Lines During Fall Arrest— A Numerical Method of Simulation

Designing fall arrest systems, which contain horizontal flexible anchor lines is an important technical problem related to the safety of people who work at a height and need horizontal freedom of movement. The article presents a numerical simulation of the dynamic performance of horizontal flexible anchor lines during fall arrest. The model of a 2-component system—a horizontal flexible anchor line and a falling rigid mass, described with a second order non-linear differential equation—is the main element of this method. This method of simulation is realised by a computer program, which allows obtaining the most important data characterising a fall arrest. The article shows laboratory tests used for the verification of this method, which turned out to be a valuable source of information and which can be used for designing fall arrest systems.     

CDC's research portfolio in older adult fall prevention: a review of progress, 1985-2005, and future research directions

PROBLEM: Falls are a leading cause of mortality and morbidity among adults age 65 and older. Population models predict steep increases in the 65 and older population bands in the next 10-15 years and in turn, public health is bracing for increased fall rates and the strain they place on health care systems and society. To assess progress in fall prevention, the Centers for Disease Control and Prevention conducted a research portfolio review to examine the quality, relevance, outcomes and successes of the CDC fall prevention program and its impact on public health. METHODS: A peer review panel was charged with reviewing 20 years of funded research and conducting a SWOT (strengths, weaknesses, opportunities, and threats) analysis for extramural and intramural research activities. Information was collected from grantees (via a survey instrument), staff were interviewed, and progress reports and products were reviewed and analyzed. RESULTS: CDC has invested over $24,900,000 in fall-related research and programs over 20 years. The portfolio has had positive impacts on research, policies and programs, increasing the public health injury prevention workforce, and delivering effective fall prevention programs. DISCUSSION: Public health agencies, practitioners, and policy makers recognize that while there are some evidence-based older adult fall prevention interventions available, many remain unused or are infeasible to implement. Specific recommendations across the public health model, include: additional research in gathering robust epidemiologic data on trends and patterns of fall-related injuries at all levels; researching risk factors by setting or sub-population; developing and testing innovative interventions; and engaging in translation and dissemination research on best practices to increase uptake and adoption of fall prevention strategies. CDC has responded to a number of suggestions from the portfolio review including: funding translation research of a proven Tai Chi fall intervention; beginning to address gaps in gender, ethnic, and racial differences in falls; and collaborating with partner organizations who share in CDC's mission to improve public health by preventing falls and reducing fall-related injuries. IMPACT ON INDUSTRY: Industry has an opportunity to develop more accessible and usable devices to reduce injury from falls (for example, hip protectors and force reducing flooring). By implementing effective, evidence-based interventions to prevent falls and reduce injuries from falls, significant decreases in health care costs can be expected.     

可重组制造系统降级运作的可靠性分析

作为一种全新的制造系统类型,笔者对可重组制造系统的一种降级运作模式进行系统整体性能和可靠性的分析与研究。针对可重组制造系统中可能存在非关键设备失效的情况,在选取系统中存在单台关键设备的条件下,建立可重组制造系统在一定时期内降级运作的有效性模型。应用马尔可夫可靠性模型对系统不同的运行状态推导出转换方程,对系统的生产率和有效性两大指标进行计算和分析。通过对系统正常状态和降级状态的有效度和生产率的比较,得出了系统存在降级运行模式时,比系统全部由关键设备组合的运行模式具有更高的生产率和有效度,并在一定条件下,系统有效度比生产率增加更快的两大结论。     

Aging without injury in the United States requires action today

Introduction: In 2017, unintentional injuries were the seventh leading cause of death among older adults (age ≥ 65), resulting in over 55,000 deaths. Falls accounted for more than half of these deaths. Given that older adults are the fastest growing age group in the United States, we can anticipate that injuries will become an even greater health concern in the near future. Methods: Aging without injury is possible. There are evidence-based strategies that can reduce falls. However, older adults may not realize that falls can be prevented or they may be afraid to admit their fear of falling or difficulty with walking as these issues may signal their inability to live independently. Results: In this commentary, we will highlight what the Centers for Disease Control and Prevention is doing to prevent older adult falls. We also highlight the importance of broadening older adults' awareness about falls to successfully empower them to begin contemplating and preparing to adopt fall prevention strategies that can help them age in place. Conclusions: Older adult falls are common and can result in severe injury and death but they can be prevented. Broadening older adults' awareness about falls can empower them to take the actions necessary to reduce their fall risk. Practical applications: Increasing awareness about falls can help older adults, healthcare providers, and local and state health departments take steps to reduce fall risk.     

The National Falls Free™ Initiative, working collaboratively to affect change

Introduction

Since 2004 the National Council on Aging (NCOA) has been working in collaboration with a growing number of national, state, and local organizations through the Falls Free^© Initiative to address the growing public health issue of falls and fall-related injuries among older adults. Through collaborative leadership, evidence-based interventions, practical lifestyle adjustments, and community partnerships we are working to reduce the number of older adult falls.

Impact on industry

The many activities of the national and state coalitions have brought recognition to the issue of fall prevention, education, and training to providers and greater investment in programs and services resulting in tremendous momentum and community activism. While we have yet to realize an impact on rates of falls, this strategic investment in building the infrastructure needed to affect change is the first step toward reducing the growing number of falls among older adults.     

Explosions in closed pipes containing baffles and 90 degree bends

There is a general lack of information on the effects of full-bore obstacles on combustion in the literature, these obstacles are prevalent in many applications and knowledge of their effects on phenomena including burning rate, flame acceleration and DDT is important for the correct placing of explosion safety devices such as flame arresters and venting devices. In this work methane, propane, ethylene and hydrogen–air explosions were investigated in an 18 m long DN150 closed pipe with a 90 degree bend and various baffle obstacles placed at a short distance from the ignition source. After carrying out multiple experiments with the same configuration it was found that a relatively large variance existed in the measured flame speeds and overpressures, this was attributed to a stochastic element in how flames evolved and also how they caused and interacted with turbulence to produce flame acceleration. This led to several experiments being carried out for one configuration in order to obtain a meaningful average. It was shown that a 90 degree bend in a long tube had the ability to enhance flame speeds and overpressures, and shorten the run-up distance to DDT to a varying degree for a number of gases. In terms of the qualitative effects on these parameters they were comparable to baffle type obstacles with a blockage ratios of between 10 and 20%.     

Falls from buildings and other fixed structures in New Zealand

Epidemiologic studies of falls from buildings and other fixed structures have historically focused on the urban environment. In this study, national injury mortality and hospitalisation data, supplemented by Coroner's investigation reports, were used to describe the epidemiology of such falls across an entire nation, New Zealand. The overall death rate was 0.30 per 100,000 persons per year. Ninety-three percent of cases were older than 14 years of age. Sixty-nine percent of falls were from buildings, with 31% from other structures. Sixty-seven percent of fatal falls were from a height of 10 meters or less. The incidence rate of hospitalisations was 21.4, with the highest rates among those aged 0–9. Fifty-five percent of non-fatal falls were from buildings, with 45% from other structures. National measures to prevent falls from structures should extend to a wide variety of structures and environments. Data presented on the age distributions of falls from different types of structures and structural components (windows, etc.) provide indicators for fall prevention.     

API standard 521 guidance on mixing of hot/cold liquids and prevention of superheat limit explosions

American Petroleum Institute (API) standards and recommended practices have identified inadvertent mixing of hot and cold liquids as a potential cause for equipment overpressure since 1955. The limited guidance has been informative but provides minimal if any details on conditions that could cause an overpressure and its potential severity. Therefore, the user must interpret how and when to prevent and/or mitigate the scenario. This guidance has changed little over the years. In June 2020, API published the 7th Edition of API Standard 521 which now provides specific guidance as to conditions whereby pressure relief devices can be considered for protection and conditions where prevention remains as the only recourse. This paper discusses the basis for the revised guidance in API Standard 521 and includes supplemental guidance.     

Pedestrian falls: A review of the literature and future research directions

IntroductionPedestrian falls (PFs) – falls in public spaces without collisions with other road users – are a significant cause of serious transport-related injuries, amounting to three-quarters of all pedestrians admitted to hospital.MethodsThis scoping review examined peer-reviewed research on PFs published between 1995 and 2015. Electronic databases (Scopus, SafetyLit, and PubMed) were used to find studies identifying PFs or outdoor falls (the latter also including falls in gardens).ResultsWe identified only 28 studies reporting relevant information on PFs (i.e., 15 prospective, 10 retrospective, and 3 intervention studies). The results show that more walking is related to a lower risk of PFs. Older people, especially older women, have a higher risk of (injurious) PFs. Outdoor fall victims have equally good or better health characteristics and scores on balance tests compared to those who have not experienced such falls. Road factors such as uneven surfaces, busy junctions, stairs, and slippery surfaces seem to play an important role in PFs, but much of the research on these factors is of a qualitative nature.ConclusionsPF victims are generally in good health (apart from normal age-related problems) but at risk due to road factors.Practical applicationsWe recommend to adopt a human factors approach. The road system should be adapted to human capabilities and limitations including those of pedestrians. Measures such as preventing uneven surfaces and good winter maintenance seem to be effective. However, we advise more quantitative research on road factors to inform design guidelines and standards for public space authorities given the qualitative nature of current research on road factors.     

Experimental analysis of gas explosions at non-atmospheric initial conditions in cylindrical vessel

Accidental gas explosions in industrial equipment are seldom initiated at atmospheric conditions. Furthermore, fuel–air mixtures are generally turbulent due to rotating parts or flows. Despite these considerations, few studies have been devoted to the analysis of explosion properties at conditions of temperature and pressure different from ambient and in the presence of turbulence; therefore, experiments are still needed, even at lab-scale, e.g. for the design of mitigation system as venting devices.In this work, experimental explosion tests have been performed in 5 l, cylindrical tank reactor with stoichiometric methane–air mixtures at initial pressure and temperature up to 600 kPa and 400 K, centrally ignited or top ignited, and with the effect of initial turbulence level by varying the velocity of the mechanical stirrer.     

Slips and falls on ice and snow in relation to experience in winter climate and winter sport

The objective of this paper was to investigate whether living experience in winter climate and winter sport helps to prevent slips and falls on ice and snow. A questionnaire survey was conducted among foreigners at Luleå University of Technology of Sweden, where winter season lasts for six months in a year. Seventy respondents replied. The results of ordinal regression showed that the slip frequency according to a 5-point rating scale decreased as the living experience in cold environments increased (B=−0.0113, p=0.019). A logistic regression was applied to model the probability of fall events occurrence based on the experience of living in cold climate. The results showed that the fall events reduced as living experience increased (B=−0.030, p=0.001). Chi-square test showed that fall events in those who took part in winter sport were significantly less than in those who did not participate in winter sport (χ²=10.745, p=0.001). The findings imply that experience of living in cold environments and training in gait balance on ice and snow can have positive effects in preventing slips and falls for inexperienced workers and pedestrians. This study also revealed that the majority of fall events happened on hard ice covered with snow while wearing ordinary winter footwear, indicating the need to improve slip resistance.     

基于流固耦合的充气滑梯安全稳定性研究

大型充气式滑梯的主要失效原因为风载作用下的倾覆。通过分析充气式滑梯在典型风载工况下的受力情况,应用ANSYS软件对充气式滑梯的几种锚固方案进行流固耦合仿真模拟。对仿真结果进行分析,得出该工况下的最佳锚固方案。提出一个校核锚固角度的公式,并计算出锚固绳与地面的角度须在30°~60°。依据分析结果,提出锚固点设置的具体措施,设施的整体高度超过3 m时,须在其主承风面高处位置增设辅助锚固点,以降低倾覆力矩和设施主体变形。