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D1.1 Field Evaluation of Two Commonly Used Slipmeters-Chang WR, Cotnam JP

A variety of slipmeters have been used to assess the slipperiness between shoe and floor surfaces. The operations of these slipmeters were outlined in their respective international standards for single measurements. However, these standards usually do not cover some critical elements in floor assessment such as how to select measurement locations and how many repeated measurements are necessary at each location. Furthermore, most slipmeters were evaluated in the laboratory setting with new floor surfaces and artificial contaminants. In this experiment, two commonly used slipmeters, the Brungraber Mark II and English XL, were evaluated in the kitchens of eighteen fast food restaurants. At each restaurant, four floor tiles in each of four different work areas were selected for repeated measurements with these two slipmeters. The work areas included the fryer, grill, sink and back door, where the potential for accidents in slips and falls was high. Measurements were taken during business hours. The floor conditions were not altered except that water was applied to the floor surface around the sink to simulate conditions when washing tasks were being performed. The typical contaminants on the tiles were grease near the fryer and grill, and water, dirt and food debris near the back door. At each location, 12 measurements were taken with each slipmeter. The Neolite shoe pads were sanded with 400 grit silicon carbide abrasive paper right before the first and seventh measurements.

The results of an ANOVA analysis showed statistically significant differences in friction among different tiles in some areas. Since the appearance of these tiles was very similar, a significant difference in friction coefficient could increase the potential of a slip and fall accident when employees fail to anticipate the floor conditions and respond accordingly.

 

D1.2 The Impact of Neoliter Test-Foot Variability and Tribometer Type on Slip Resistance Measurements-Sapienza MA

To determine if either the Neolite test foot material used for friction measurement, or the tribometers themselves were in any way contributing to the measured results, we utilized a series of single factor designed experiments. The protocol involved three different types of pedestrian surfaces, official solid vinyl tile and official vinyl composition tile, obtained from the Chemical Specialties Manufacturers Association (CSMA), and official ceramic tile, obtained from the Tile Council of America (TCA). All materials were used for the Niolite determination while just the official ceramic tile was used for the tribometer evaluation that included the James Machine, the Mark I PAST, the Mark II PIAST, and the VIT. The experimental design came from Box, Hunter, and Hunter, Statistics for Experimenters, John Wiley & Sons, Inc., 1978. The protocol consisted of a series of runs with each machine using different test-feet with one sample of each type of pedestrian surface. To minimize any inherent testing bias, the run series were randomized. Test results were analyzed using standard analysis of variance techniques. The between sample variances were compared to the within sample variances and a determination was made regarding the significance of the test-feet. This particular type of experiment assumes a null hypothesis. That is, the different test-feet will not have any significant effect on the test results. The results indicated clearly that 1) the null hypothesis must be rejected and that Neolite does, in fact, have a statistically significant effect on the test results and 2) friction is also dependant on what tribometer is used to measure it.

 

D1.3 The Evaluation of Two Commonly Used Slipmeters: The Repeatability and the Effect of Slip Criteria- Chang WR

A variety of slipmeters have been used to assess the slipperiness between footwear and floor surfaces. Although the operations of these slipmeters were outlined in their respective international standards, some of the critical elements in the measurement protocols were ambiguous. Two commonly used slipmeters, the Brungraber Mark II and English XL, were evaluated in this experiment. A systematic approach was established to obtain friction coefficients. Since the operators need to determine if a slip occurs in arriving at a friction coefficient, they often must develop their own criteria without proper instruction from the manufacturers of these slipmeters. Two criteria of slip conditions at the interface were used to cover all possible slip criteria that the operators might use. One criterion was that any movement at the interface was considered a slip. The second criterion was that only fast movement was considered a slip and, therefore, any slow movement, any finite dwell time at the impact or any partial stroke were considered as a non-slip. A total of 15 shoe materials and 3 floor materials were used in this experiment. The surface conditions included dry, wet, oily and oily wet. Three samples were used for each material combination and surface condition. Three measurements were taken from each sample. All the friction measurements were performed at a temperature of 70 ± 3 degrees F and a relative humidity of 50 ± 5%.

The results of an ANOVA analysis indicated that the differences in friction coefficient among the three samples and between the two slip criteria were statistically significant for some material combinations and surface conditions. These differences could contribute to the discrepancy in the results reported among different institutions due to different samples and different slip criteria used.

 

D1.4 Precision and Bias Testing of the English XL Variable Incidence Tribometer and the Brungraber Mark II Portable Inclinable Articulated Strut Slip Tester- Flynn JE, Underwood DC

Precision and bias testing was conducted on both the English XL and Brungraber Mark II tribometers. Six independent laboratories were involved with the English XL while ten independent laboratories participated in the study of the MK II. Each laboratory used their own tribometer to perform the measurements.

Three types of ceramic tile were selected to minimize changes in surface characteristics resulting from repeated testing. To minimize the effect of variability in the test surfaces, the same surfaces were sent to each of the study participants. In each case, the tiles were marked to specify the exact placement of the VIT and the MK II. In an attempt to minimize the differences between test feet, each participant used the same test foot. The test foot for each type of tribometer was fitted with Neolitẻ from Smithers Scientific. All of the surfaces were tested under both wet and dry conditions.

The results of the study were analyzed statistically according to ASTM Practice E691. When looking at the VIT, it was found that the average value of the repeatability standard deviation was 0.02. The average value of the 95% repeatability limit was 0.05. The average value of the reproducibility standard deviation was 0.03 and the average value of the 95% reproducibility limit was 0.09.

When looking at the MK II, it was found that the average value of the repeatability standard deviation was 0.04. The average value of the 95% repeatability limit was 0.05. The average value of the reproducibility standard deviation was 0.07 and the average value of the 95% reproducibility limit 0.19.

Bias was not established as there currently are no accepted standard surfaces to allow such comparison.

 

    

 

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Page last updated: March 2001
Page last reviewed: March 2001
Content Source: National Institute for Occupational Safety and Health (NIOSH) Division of Safety Research