Comparison of Three Different Slip Meters under Various Contaminated Conditions

Abstract

ObjectivesTo challenge the problem of slipperiness, various slipmeters have been developed to assess slip hazard. The performance of in-situ slipmeter is, however, still unclear under the various floor conditions. The main objectives of this study were to evaluate the performance of three kinds of slipmeters under real conditions, and to find their dynamic and kinematic characteristics, which were compared with gait test results.MethodsFour common restaurant floor materials were tested under five contaminants. Slipmeters and human gaits were measured by high speed camera and force plate to find and compare their dynamic and kinematic characteristics.ResultsThe contact pressures and built-up ratio were below those of subjects. The sliding velocity of British Pendulum Tester was above those of subjects, while those of BOT-3000 and English XL were below those of subjects. From the three meters, the English XL showed the highest overall correlation coefficient (r = 0.964) between slip index and Ra, while the rest did not show statistical significance with surface roughness parameters (Ra, Rz). The English XL only showed statistical significance (p < 0.01) between slip index and contaminants. The static coefficient of friction obtained with the BOT-3000 showed good consistency and repeatability (CV < 0.1) as compared to the results for the BPT (CV > 0.2) and English XL (CV < 0.2).ConclusionIt is unclear whether surface roughness can be a reliable and objective indicator of the friction coefficient under real floor conditions, and the viscosity of contaminants can affect the friction coefficient of the same floors. Therefore, to evaluate slipperiness, the performance of the slipmeters needed to improve.

Contaminant film thickness affects walkway friction measurements

“…These differences were robust across film thicknesses, suggesting that the effect was due to contaminant type rather than secondary to a film thickness effect. The effect of different types of contaminants on tribometer-measured friction ( 11 , 32 ) and on the propensity for humans to slip ( 33 ) have both been studied separately, but these two phenomena have not been studied together. The contact pressures and geometries of a human foot striking the ground can be different from those created by tribometers ( 11 ), and therefore the initial film thickness effects observed here may not translate directly to human slip risk.…”

“…The effect of different types of contaminants on tribometer-measured friction ( 11 , 32 ) and on the propensity for humans to slip ( 33 ) have both been studied separately, but these two phenomena have not been studied together. The contact pressures and geometries of a human foot striking the ground can be different from those created by tribometers ( 11 ), and therefore the initial film thickness effects observed here may not translate directly to human slip risk. In some cases, the rank order of two surfaces changed between different contaminants (e.g., surfaces A and B contaminated with water and SLS as measured by the BOT 3000E, Figure 4 ).…”

“…In addition to these pressure-related effects, the presence of a liquid film on a surface can mask the surface texture and reduce the friction generated by adhesion. Adhesion is particularly sensitive to contaminant viscosity, with higher viscosity fluids causing a greater reduction in adhesion and lower friction ( 10 , 11 , 19 ). These physical phenomena affect the shoe–floor friction during walking (or other human gait-related activities) and likely also affect the friction measurements made using tribometers.…”

“…Tribometer measurements can vary depending on tribometer model, operator/user, time between tests, test foot, and the presence or absence of a contaminant (1,2,(7)(8)(9). For liquid contaminants, the type and concentration of the contaminant further affect surface slipperiness and slip risk (10)(11)(12). The amount of liquid contaminant-especially its thickness underfoot-may also affect surface slipperiness.…”

Friction Coefficient of Rubber Shoe Sole Sliding Against Different Rubber Floor Tiles

“…At a time, one specimen (rubber tile) was adhered to the test rig's base, (50 x 40 cm) and supported by two load cells. The friction force was measured while the normal load was applied to the rubber tile using footwear sliding manually against the tile at a constant sliding speed of 0.16 m/s, [12,14,15]. The outsole of the footwear was chosen as soft rubber, 65 Shore A hardness without grooves to resemble the worst sliding case.…”