Development of an objective determination of a slip with a portable inclineable articulated strut slip tester (PIAST)

A portable inclineable articulated strut slip tester (PIAST) is a slipmeter that is widely used in the USA to measure coefficient of friction (COF) at the shoe sole and floor interface. A determination of a slip at the measurement interface, which is currently judged subjectively by operators, plays a crucial role in deciding the outcomes of a PIAST measurement. The goal of this study was to develop an objective determination of a slip based on the movement of the weight used by the slipmeter. The displacement of the weight and the time duration of consecutive strikes in a measurement were used to derive the objective slip criterion. Various footwear materials, floor materials and surface conditions were used to cover a wide range of COF values. The results of the regression analysis indicated that the objective COF predicted by the method developed in the current study was significant (R² = 0.997, β = 0.991, p < 0.001) in predicting the subjective COF determined by the operator.     

Evaluation of two models of a slipmeter

The aim of the study was to compare the performances of the Brungraber Mark II (BM II) and Mark III (BM III) slipmeters. Friction measurements with the two slipmeters were conducted in a laboratory using four footwear materials, four floor types, and three surface conditions. Both the coefficient of friction (COF) values obtained with the slipmeters and the force platform-based COF values were measured. The COF measured with the BM II was slightly higher than that measured with the BM III with a R² of 0.83. A comparison of the averaged normal force between the two slipmeters showed that the BM II generated a significantly higher normal force than the BM III at a low COF and the difference of the normal force between the two slipmeters decreased when the COF value was increased. The regression analysis results in this study showed that the force platform-based COF values were closer to the COF values obtained with the BM III than with the BM II. The R² values for the regression model between the COF values obtained from the slipmeter and the force platform were 0.90 and 0.79 for the BM II and BM III, respectively.     

Slip Resistance of Industrial Floor Surfaces: Development of an Elastomer Suited to In-Situ Measurement

Slips contribute to 12% of occupational accidents. A slip resistant floor is a mean to prevent slipping accidents occurring in workshops. Floor slip resistance is often evaluated by measuring a friction index, proportional to the force opposing slipping of a reference elastomer on the floor surface under test. When implementing a portable appliance, slip resistance measurements carried out on lubricated floors were not stabilized. The authors advanced the hypothesis of oil impregnating the elastomer. A new elastomer suited to in-situ measurement has been developed to achieve stable measuring conditions. This study highlights the fact that the nature and characteristics of a reference elastomer must be specified when slip resistance measurements are carried out.     

“Slippery” work surfaces: Towards a performance definition and quantitative coefficient of friction criteria

There have been 50 years of research in walking/working surface slipperiness and coefficient of friction (COF) measurements. Nevertheless, numerous standards address slip/fall accidents only in terms of requiring surfaces to be qualitatively “nonslippery.” The literature useful for establishing quantitative criteria for “slippery” vs. “slip-resistant” have been summarized here. A performance definition for “slippery work surfaces” is proposed. Recommendations applicable to standards-making organizations are made, including changing terms such as “non-slip” to “slip-resistant” and defining “slippery” in terms of quantitative COF values. For persons walking unloaded on level surfaces, a COF standard of 0.5 would be reasonable. Research is recommended to determine if “slip-resistance” requirements and accident prevention could be achieved more easily be controlling the type of shoe, type of task, or amount of surface contaminant rather than controlling only the COF of the basic surface and its coating.     

Subjective assessments of floor slipperiness before and after walk under two lighting conditions

A gait experiment was performed. The participants were tested under shoes, floors, surface and lighting conditions. They gave floor slipperiness ratings before and after a gait trial. The perceived sense of slip (PSOS) was collected. It was found that the perceived floor slipperiness (PFS) before walking was affected significantly by the lighting, floor and surface conditions. Relative low PFS values were recorded under wet and detergent-contaminated conditions in the normal daylight condition as compared with those in the dimmed condition. The PFS after the gait was significantly affected by the floor and surface conditions. The PSOS was highly correlated with the PFS after trial. The regression analyses results indicated that both the coefficient of friction (COF) of the floor and lighting were primary predictors of the PFS before a gait. The COF and walking speed were the primary predictors of the PFS after a gait.     

Objective and subjective measurements of slipperiness in fast-food restaurants in the USA and their comparison with the previous results obtained in Taiwan

Floor slipperiness is a critical issue in slip and fall incidents which are a major source of occupational injuries. The objectives of the current study were to investigate if the protocols used in a field study conducted in Taiwan could be used in similar environments in the USA and whether consistent results could be obtained. Protocols used in the field study to investigate floor slipperiness in western-style fast-food restaurants in Taiwan included both objective and subjective measurements. Using the same methods as in Taiwan, friction was measured on tiles in six major working areas of 10 fast-food kitchens in the USA as an objective measurement of slipperiness, while the subjective measurement was employees’ ratings of floor slipperiness over the same areas. The Pearson’s and Spearman’s correlation coefficients in the USA between the averaged friction coefficients and subjective ratings for all 60 evaluated areas across 10 restaurants were 0.33 (p = 0.01) and 0.36 (p = 0.005), respectively, which were lower than the correlations of 0.49 and 0.45, respectively, obtained in Taiwan. Cultural differences, the amount of water on the floors in the sink areas and the existence of a slip resistant shoe program in one country might be contributors to the lower correlation coefficients in the USA. However, the current study confirmed the results obtained in Taiwan that average friction coefficient and perception values are in fair agreement, suggesting that both might be reasonably good indicators of slipperiness.     

Performance of slippery and slip-resistant footwear in different wintry weather conditions measured in situ

In Finland about 70,000 people are annually injured in pedestrian and bicycle falling accidents occurred at the street, walkways and courtyards. Around 2/3 of these occur when the walking surface is covered by ice or snow. In general, slipping is caused by both environmental and human factors. The primary environmental factor behind slipping accidents is slip resistance characteristics of underfoot surface. Especially in winter slipping accidents are mainly due to inadequate friction between footwear and underfoot surfaces. Portable devices measuring friction, i.e. slipmeters, may be used for assessing slipperiness on different walking surfaces in situ. During winter seasons 2003 and 2004 a study was performed to evaluate the usability of portable slip simulator for measuring slipperiness of walkways on varying weather conditions and to assess slip resistance of different footwear. The Portable Slip Simulator proved to be applicable for measuring in situ the slipperiness of wintry walking surfaces and evaluating quality of winter maintenance. Significant differences in traction between footwear were found especially in normal Finnish climate winter days when friction provided by slip-resistant footwear was multifold compared to a poorer one. On very slippery icy surfaces no footwear provided enough grip and, therefore, in such conditions anti-slip devices should be used.     

Friction measurements on ramps using the Brungraber Mark II slipmeter

It is a common belief that a person is more likely to slip when walking on an inclined surface than when walking on a level surface. Reports of friction measurements were common on horizontal surfaces but were rare on inclined surfaces. A slip measurement device reports different readings on the same surface with different inclined angles if the effect of gravity comes into play. In this study, friction measurements were conducted on the same surface with 0°, 10° and 20° inclined angles under different footwear materials, floors, and surface conditions, using a Brungraber Mark II slipmeter. Statistically significant results were obtained for the measurement results under the inclined angle, footwear material, floor, and surface conditions. A regression model was established to describe the coefficients of friction on ramp floors under footwear material/floor/surface conditions. This model is significant at p < 0.0001 with an R² of 0.87. The cosine function of ramp angle, as suggested in the regression model, was recommended to be used as a correcting factor for friction measurement results using the Brungraber Mark II on ramps to report the corrected friction coefficient of the surfaces.     

Coefficient of friction,walking speed and cadence on slippery and dry surfaces: shoes with different groove depths

Objective. The present study aimed to determine the coefficient of friction (COF), walking speed (WS) and cadence while walking on slippery and dry surfaces using shoes with different sole groove depths to predict likelihood of fall. Background. Design of shoe sole groove is crucial to prevent slipping during walking. Methods. 22 healthy young men (mean age 24.5, body mass index 22.5) volunteered for this semi-experimental study. Six different conditions of the test (combination of three shoes and two surfaces) were defined and the condition was repeated three times. In total, 396 trials (22 subjects?×?3 groove depths?×?2 surfaces?×?3 times) were obtained for data analysis. COF was recorded by force platform at 1000?Hz and walking parameters recorded using 3D motion analysis with six infrared cameras at 200?Hz. Results. The highest COF was obtained from the deepest groove depth (5.0?mm) on both dry and slippery surfaces. The COF on slippery surfaces was significantly lower in comparison with dry surfaces. WS and cadence were not significantly different on dry and slippery surfaces. Conclusion. The deeper groove is better to prevent slipping because the COF increases by increasing the shoe sole groove depth. WS did not change on dry and slippery surfaces.     

Slip safety risk analysis of surface properties using the coefficients of friction of rocks

This study was conducted to determine the most appropriate surface processing techniques (SPT), environmental conditions (EC) and surface roughness (SR) to minimize the risk of slipping when pedestrians walk on a floor covering of rocks barefoot and with shoes. Coefficients of friction (COFs) and values of SR were found using five different types of rocks, four SPT and two (ramp and pendulum) tests. Results indicate that the parameters which affect the COF values of rocks include SR, EC and SPT. Simple linear regression was performed to examine the relationship between the values of the COF and the SR. The value of the COF was identified as R²?≥?0.864. Statistical results, which are based on experimental measurements, show that rocks are classified according to their safe use areas depending on their COF and SR values.     

A statistical model to estimate the probability of slip and fall incidents

A statistical model to estimate the probability of slip and fall incidents is presented. In estimating such an event, the available friction is usually compared with the required friction for the activities. In the models available in the literature, only mean values were compared or a minimum threshold was used to represent the required friction. In the current model, it is assumed that both the available and required friction coefficients have stochastic distributions. Formulations for a general distribution were developed and are presented. The results generated with the current model are compared with those based on other models using a normal distribution. The results indicate that there could be significant differences between the current model and the existing models in estimating the probability of a slip incident.     

A prediction model for the flash point of binary liquid mixtures

A prediction model based on the partial least squares of the multivariate statistical analysis methods was developed for the flash point (FP) of binary liquid mixtures. Estimation of the FP of flammable substances is important for safety measures in industrial processes. Since experimental FP data of liquid mixtures are scarce in the literature, there have been many researches to estimate the FP of liquid mixtures using physicochemical laws. In this study, the partial least squares (PLS) method using experimental data was used as a prediction model of the FP of binary liquid mixtures. The FPs predicted from the PLS method were also compared to results from the existing calculating methods using physicochemical laws such as Raoult's law and the Van Laar equation.     

Heel contact dynamics during slip events on level and inclined surfaces

This study describes heel contact dynamics during slip events, information that must be known to develop biomechanically relevant shoe-floor coefficient of friction measurement systems. Sixteen subjects walked on a level, 5 and 10° ramp with two possible contaminants (dry, oil). Foot motion was recorded at 350 Hz and compared among no-slip, slip-recovery and slip-fall events. For all trials, the foot rotated to foot-flat, even during slip and fall trials. Heel sliding patterns recorded upon and shortly after heel contact were similar for all conditions. Slip distances, sliding velocities and heel acceleration profiles varied across trials. During the fall trials, the slipping motion of the foot was found to decelerate approximately 200 to 300 ms into stance before accelerating again, eventually leading to the fall. This deceleration was believed to be an attempt by the subject to recover from the slip. Recovery attempts on inclined surfaces were less successful than on level floors. In general, the slip distance and peak forward sliding velocity associated with fall trials were greater than or equal to 10 cm and 0.8 m/s, respectively. These complex motions at the shoe-floor interface during slipping should be taken into account for improving slip resistance measurement systems.     

单侧接触埋置结构与瞬态SH波的动力相互作用——时域边界元分析

应用时域边界元法 ,研究了单侧接触埋置结构与瞬态SH液 (剪切横波 )的动力相互作用 ,当入射SH波足够强时 ,界面会出现局部滑移并假设摩擦遵守库仓定理。笔者从实际情况出发 ,提出了新的数学模型和计算方法 ,计算了埋置矩形结构与瞬态SH波的动力相互作用问题 ,由于对此类问题的深入研究 ,为评估和预测埋置结构在动荷载下的安全性及疲劳寿命提供了重要的理论价值     

Preferred surface microscopic geometric features on floors as potential interventions for slip and fall accidents on liquid contaminated surfaces

PROBLEM: Surface roughness affects friction, so selection of floor surfaces with certain roughness characteristics could potentially reduce slip and fall accidents. This article summarizes the preferred surface microscopic geometric features that could increase friction on surfaces covered with liquid contaminants. METHOD: Three types of surface features, represented by the average of the maximum height above the mean line in each cut-off length (R(pm)), the arithmetical average of surface slope (Delta(a)), and the kernel roughness depth (R(k)), are identified as preferred surface microscopic geometric features for a higher friction. The proper settings on the profilometers (instruments used to measure surface roughness) for optimizing these surface parameters are specified. The friction mechanisms involved reveal why these features are more desirable. RESULTS: Although surface roughness is important in determining slipperiness, there is still insufficient information to establish a safety criterion based on roughness; however, the method presented in this paper can readily provide a relative comparison. IMPACT ON INDUSTRY: The summary presented will help safety professionals properly select new floor surfaces or assess existing floors to reduce slip and fall accidents.     

Slip and fall accident prevention: A review of research, practice, and regulations

This paper summarizes current research, practices, and regulations regarding walking/working surface slipperiness and coefficient of friction (COF) measurements. The literature and data are reviewed from three aspects:

1. (a) the biomechanics of walking and psychophysiological factors involved in slips and falls studied by the scientific community,

2. (b) various measuring devices and methods developed in an attempt to quantify the “slipperiness” of walking/working surfaces, and

3. (c) an acceptable quantitative standard for the “slipperiness” of surfaces and the impact of the Americans with Disabilities Act (ADA) on such a standard.

Unresolved issues related to slip-resistance are identified. A multifaceted approach and synergy from researchers, the building industries, standards organizations, and government are needed to obtain concensus on such issues.     

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.     

Flash points measurements and prediction for binary miscible mixtures

Flash point is one of the most important parameters used to characterize the potential fire and explosion hazards for flammable liquids. In this study, flash points of twenty eight binary miscible mixtures comprised eighteen flammable pure components with different compositions were measured by using the closed cup apparatus. The obtained experimental data are further employed to develop simple and accurate models for predicting the flash points of binary miscible mixtures. Based on the vapor–liquid equilibrium theory, the normal boiling point, the standard enthalpy of vaporization, the average number of carbon atoms, and the stoichiometric concentration of the gas phase were selected as the dominant physicochemical parameters that were relevant to the overall flash point property of liquids. With these parameters for pure components as well as the compositions of mixtures, the new form of characteristic physicochemical parameters for mixtures were developed and used as the input parameters for the flash point prediction of mixtures. Both the modeling methods of multiple linear regression (MLR) and multiple nonlinear regression (MNR) were employed to model the possible quantitative relationships between the parameters for mixtures and the flash points of binary miscible mixtures. The resulted models showed satisfactory prediction ability, with the average absolute error for the external test set being 2.506 K for the MLR model and 2.537 K for the MNR model, respectively, both of which were within the range of the experimental error of FP measurements. Model validation was also performed to check the stability and predictivity of the presented models, and the results showed that both models were valid and predictive. The models were further compared to other previously published models. The results indicated the superiority of the presented models and revealed which can be effectively used to predict the FP of binary miscible mixtures, requiring only some common physicochemical parameters for the pure components other than any experimental flash point or flammability limit data as well as the use of the Le Chatelier law. This study can provide a simple, yet accurate way for engineering to predict the flash points of binary miscible mixtures as applied in the assessment of fire and explosion hazards and the development of inherently safer designs for chemical processes.     

Process safety management lessons learned from a fire and explosion accident caused by a liquefied petroleum gas leak in an aromatics reforming unit in Taiwan

A severe fire and explosion accident was caused by a liquefied petroleum gas leak in Taiwan in 2019. This accident resulted in the loss of approximately US$3.5 billion in output value due to a one-and-a-half-year shutdown after the accident; however, no casualties were recorded at the accident scene. An analysis of the accident pipelines demonstrated that the pipeline leak had been caused by hydrochloric acid corrosion. Cause analysis based on the accident timeline, fault tree analysis, and causal factor charting indicated inadequacies in five elements of process safety management (PSM) namely mechanical integrity (MI), management of change, emergency planning and response, process hazard analysis (PHA), and process safety information (PSI) as the root causes of the accident. Furthermore, insufficient PSI (i.e., a lack of comprehensive understanding regarding corrosion mechanisms) was deemed to have been the core problem leading to the accident. This accident revealed common shortcomings that are often overlooked in PSM implementation in Taiwan; thus, the present research can serve as a vital reference for improving PSM programs in Taiwan.     

Process Safety Management (PSM) for managing contractors in process plant

Accidents involving contractors continue to occur with regular frequency. By using the standard set within the PSM 29 CFR 1910.119(h) regulations, it has been identified that certain aspects of the way contractors do work are not up to the stipulated regulatory requirements especially regarding matters like not providing mandatory personal protective equipment (PPE) to the workers, not discussing hazards related to handling procedures with the workforce and improper control of non-routine activities during changes in shifts. The PSM 29 CFR 1910.119(h) regulations promulgated in 1992 provides standards that covered processes to obtain and evaluate data regarding contractors' health and safety programs as well as the contractors' performance evaluation. Many of the accidents involving contractors are direct result of poor training of contractors and/or poor control of the contracted work. Even though most organizations have their own contractor management systems, there are issues in meeting the requirements of PSM. The PSM standard only state “what to do” not “how to do it”. This is known as self-regulatory policy which depends on the industries understanding to interpret the standard that also contribute to this problem. This paper presents a structured and easy technique to plan and implement a practical and comprehensive contractors' management system in process industries that will comply with OSHA CFR 1910.119. A model has been developed based on this technique and its application has been tested in a pilot plant for compliance to PSM regulation. The model is beneficial to the process industries as any deficiencies in the PSM contractors' management program will be highlighted by the model which will then easily correct the identified deficiency so as to minimize and prevent catastrophic accidents.