VOSI V41.21-98

December 7, 1999

UNIVERSAL SPECIFICATION / TEST METHOD
FOR
SLIP RESISTANT (*) WALKWAYS, IN THE FIELD & LABORATORY
AS MEASURED BY A DRAG TYPE FRICTION TESTER

1. SCOPE

2. REFERENCED DOCUMENTS

3. TERMINOLOGY

3.1 Definitions

3.1.1 Friction - The resisting force that arises when a surface of one substance slides, or tends to slide, over an adjoining surface of itself or another substance.

3.1.2 Static Coefficient of Friction (SCOF) - The ratio of the horizontal component of force (parallel to the walkway surface, passing through the tester center of gravity and aligned with the tester's major axis) required to overcome the resistance to begin movement to the normal component of the vertical force (weight) of the object. Sensor contact time is 3 seconds maximum. See 5.7.4 for Kinetic Coefficient of Friction (KCOF) measurement.

3.1.3 Kinetic (dynamic) coefficient of friction (KCOF) - The COF under conditions of macroscopic relative motion between two bodies. (ref 2.9)

3.1.4 Pedestrian Slip Resistance (Appendix Ref. 12) - That property of a walkway surface which significantly reduces the probability of a person slipping thereon when wearing any slip resistant footwear. (See. "Slip Resistant Walkway " & "Slip Resistant Footwear")

3.1.5 Slip Resistant Walkway (Appendix Ref. 12) (Primary Criteria) - A walkway surface wherein the average SCOF between standardized leather and a clean, dry, level surface is 0.45 minimum when using a sensor pressure similar to walking sole pressure [(69 - 173 KPa (l0 - 25 PSI)].

3.1.6 Slip Resistant Walkway (Outdoors or Indoors with Walkways Normally Subjected to Water Contamination) - A walkway surface wherein the SCOF between Standardized Monarch EVA (Appendix Ref. 17) and a level, dry or wet (water) surface is 0.50 and 0.35 minimum, respectively, when using a sensor pressure similar to walking sole pressure [(69 - 173 KPa (l0-25 PSI)]. The wet kinetic coefficient of friction (KCOF) shall be 0.30 minimum at 5 cm / sec (2" / sec) (Appendix Ref. 14,15). Dry SCOF/Wet SCOF = 1.50 max (Ref 2.7)

3.1.7 Slip Resistant Footwear (Appendix Ref. 12) (Primary Criteria)- Any smooth shoe sole or heel material having a 0.35 minimum dry SCOF against the "Primary Standard Polypropylene (leather) Test Panel" (Definition of "Standard Leather") when using a sensor pressure similar to walking sole pressure [(69 - 173 Kpa (l0 - 25 PSI)]. Running sports footwear and work boot materials shall have a 0.60 minimum SCOF when tested as previously stated. (Ref. Ref. 2.8) (Appendix Ref. 12). See Note 3.

3.1.8 Slip Resistant Footwear (Footwear normally subjected to water contamination) - Any smooth shoe sole or heel material having a minimum SCOF of 0.50 dry and 0.35 wet on the Primary Standard Florida Ceramic Tile specified in paragraph 2.7 (Appendix Ref. 16) when using a sensor pressure similar to walking sole pressure. The wet kinetic (dynamic) coefficient of friction (KCOF or DCOF) shall be 0.30 minimum at 5 cm/sec. (2"/sec) see Note 3 (Ref. 2.8)

3.2 Test Method Terms

3.2.1. "Standardized Leather "(Appendix Ref. 5, 8) - Leather which has been tested against the "Primary Standard Polypropylene Test Panel" per paragraph 5.5. The average SCOF obtained has been shown to maintain its original 0.35 value over time.

3.2.2. "Secondary Standard Polypropylene Test Panel"(Appendix Ref. 8) - A test panel which is marked with a "Standard SCOF" , based on simultaneously testing with the "Primary Standard Polypropylene Test Panel," and used when standardizing the leather sensor prior to SCOF testing (see 5.3.3.5 and 5.5.3)

3.2.3. "Sensor" - The "Standardized Leather ", affixed to the bottom of the tester, which contacts the walkway surface when measuring dry SCOF. The "Standardized Monarch EVA" when testing dry and wet.

3.2.4. "Standardized Monarch EVA" (Appendix Ref. 17, 8) - A synthetic rubber-like material used for dry and wet testing of SCOF which has been tested against the "Secondary Standard Florida Ceramic Tile".

3.2.5. "Secondary Standard Florida Ceramic Tile" (Appendix Ref. 16,8) - Used for dry and wet testing. A test panel which is marked with a "Standard dry and Wet SCOF" based on simultaneously testing with the "Primary Standard Florida Ceramic Tile".

3.2.6. "Walkway (leather / rubber) Traction Index"(TI) The ratio of the actual SCOF to the minimum required SCOF under dry and wet (water) conditions. Leather / polypropylene dry and rubber / Florida Ceramic Tile dry and wet. T.I. must be greater than or equal to 1.00 for a "slip resistant walkway".

4. REQUIREMENTS

5. TEST METHOD

5.1 Scope

5.1.1 This test method covers the measurement of the static coefficient of friction (SCOF) of clean, dry and wet level walkway surfaces in the field and laboratory by a horizontal pull (drag type) slip tester. This test method is not suitable for rough or corrugated surfaces, surfaces with contaminants other than water, or surfaces that are not a plane within the area of contact and travel of the testing sensor. SCOF on ramps is determined by vector summation.

5.1.2 This standard does not purport to address all of the safety problems, if any associated with its use. It is the responsibility of the user of this standard to establish appropriate safety practices and determine the applicability of regulatory limitations prior to use.

5.2 Significance and Use

5.2.1 This test method must be used for measuring SCOF between walkway surfaces and user contact materials such as shoe sole and heel material. The measurements made by this type of apparatus are related to the slip resistance of clean dry surfaces to leather type shoe materials and wet surfaces to Monarch EVA type (rubber) shoe materials.

5.2.2 The test results using this test method for SCOF are comparable to this type of equipment only.

5.2.3 BOCA (ref. 2.3) recommends a 0.50 minimum SCOF between leather and the walkway surface. An OSHA proposed guideline states that 0.50 minimum SCOF is recommended as a guide to achieve proper slip resistance. This is the same value as the ASTM D2047 definition of a "slip resistant" polish; which is the same approximate SCOF required by a fast walking young male.12 Official publications (building codes, consensus standards, ASTM Standard Practice Guidelines, government publications, etc.) should reference VOSI V41.21 and V41.22 for slip resistant walkway and footwear requirements

5.3 Apparatus

5.3.1 By the horizontal pull slip tester. A typical apparatus consists of a) a force gauge or load cell/sled assembly b) a standard calibration weight c) three mounting locations for attaching "sensor" material (see 5.3.2) and d) a means to pull the apparatus across the surface being tested. The horizontal force must be applied manually, by attaching the hook on the force gage to the hook on the sled, and pulling (Figure 1) (Appendix Ref. 3). A power actuated device uses a tension cord to "reel" in the sled across the surface being tested (Appendix Ref. 4). The vertical loads shall result in a contact pressure of not less than 69 KPa (l0 PSI) and not more than l73 KPa (25-PSI).

5.3.1.1 The standard calibration weight has a mass equal to one half the weight of the sled assembly (2.2 +/- 0.00454 Kg (5.0 + / - 0.01 lb. for the Technical Products tester)) (Appendix Ref. 3).

5.3.2 Sensor Material (Appendix Ref. 5). The sensor material shall conform to Type 1,Class 6 leather cut from a bend with the long dimension perpendicular to the backbone as specified in KK-L-165C as amended. Cut the leather to the size required by the specific apparatus. Monarch EVA (Appendix Ref. 17) is used for dry and wet testing of walkways.

5.4 Test Surfaces

5.4.1 Test surfaces must be any flat surface that is in a continuous plane for at least the area covered by the test sensor. The area adjacent to the test surface must be sufficiently continuous to accommodate the tester and traveling limits of the apparatus.

5.4.1.1 Substrate- The in situ or the laboratory test surface being measured. Viscoelastic properties of the substrates as well as surface contaminants like oil; water or dirt will affect the SCOF of any coatings or flooring materials.

5.4.2 For testing of walkway surfaces in the field ( in situ ), the following conditions should be considered.

5.4.2.1 The area required for operation of the apparatus shall be smooth and continuous.

5.4.2.2 The test surface area that will be contacted by the apparatus sensor pads shall be smooth, flat and without discontinuities. The test surface must contain finite depressions that cover not more than 5% of the sensor area.

5.4.3 When determining the SCOF of walkway surfaces in their "as found" or unaltered condition, the test shall be performed per the following procedure.

5.4.3.1 Identify the surface to be tested by location relative to surroundings: i.e., type of walkway material, color, direction of walkway travel, extent of surface wear, type of floor coating or polish if used, method of application, and maintenance procedures. Record the temperature and humidity.

5.4.3.2 Surface Preparation - Prior to starting the tests, remove surface dirt from the test area by lightly brushing with a paper towel. Be careful not to alter the substrate surface during the process of removing the loose surface dirt. The surface is now ready for testing.

5.4.3.3 In Situ tests shall be made on both a high traffic and no traffic (close to a wall) areas in order to evaluate the effect of wear on the SCOF of in situ surface finishes. The SCOF of any surface finish must be equal to or greater than the SCOF of the substrate without the applied finish.

5.5 Calibration

5.5.1 For the manually operated device, determine the force gage correction factor at 0.50 SCOF by using a standard calibration weight that is one-half the weight of the sled apparatus (vertical force). Lift the standard test weight slowly using the force gage provided with the sled apparatus (Fig. 1). The gage correction factor is determined by dividing the weight of the standard weight by the force gage reading. For power actuated devices and other types of manually operated devices, follow the manufacturer's suggested calibration procedures.

5.5.2 Allow the temperature/humidity gage to stabilize before testing.

5.5.3 Prepare the sensor pads per 5.6.1. Determine the leather correction factor at the test site by conducting a series of tests using the secondary standard polypropylene test panel placed on the high friction woven fabric panel retention mat. Rotate the panel through two revolutions in 90-degree increments (total of eight readings). Discard the initial reading if it is out of the range of the other readings (see Note 5). Repeat this reading for eight valid measurements. Calculate the average SCOF. Divide the marked SCOF value (see par. 5.3.3.5) of the secondary standard test panel by the average measured SCOF of the same test panel to determine the leather correction factor. (L.C.F.). Measure L.C.F. both before and after testing the walkway surface. Average both L.C.F.s for use in 5.8.

5.5.4 Prior to performing an on-site test , the performance of the test instrument and the operator must be verified against a secondary standard polypropylene test panel when initially received. The average of the eight successive readings taken per 5.5.3 must be within 0.02 of the value stated in the manufacturer's log (Appendix Ref.8). The range of readings must be within 0.05. The manufacturer of the apparatus shown in Fig. 1 will provide "Certificates of Operator Qualification".

5.6 Procedure - Dry for Determining Whether Walkway is Slip Resistant

5.6.1 Test the proper functioning of the force gage. Verify the instrument calibration per par. 5.5 or the manufacturer's instructions. Dress the leather sensor pads after affixing them to the tester with the hide side (hair follicle side) outside. Place the complete assembly on a sheet of wet/dry carborundum paper.9 Repeatedly pull the complete assembly in its normal direction of travel across the carborundum paper until a uniform bearing surface is achieved. This is accomplished by sanding the pads initially 30 times using a stroke about 102 mm (4 in.) long on 120 grit paper followed by 15 strokes on 400 grit. Sand pads five times on 400 grit wet/dry paper before each set of tests. Brush or wipe all foreign material from the tester pads using a paper towel. Use same sanding procedure for EVA (rubber) except sand 25 times / 80 grit and 25 times / 400 grit.

5.6.2 Place the apparatus on the test surface with sufficient distance for travel of the sled. Apply the load so as to minimize the duration of contact with the floor (2-sec. avg.). Record the maximum horizontal axial force needed to initiate movement. When movement is observed immediately stop the test. Beginning with the normal walking direction, repeat the operation through two revolutions in 90-degree increments for a total of eight readings by relocating the sled apparatus. Repeat the initial reading if out of the range of the other readings. Minimize the time the apparatus is in contact with the surface by pre-loading the horizontally positioned force gage. Remove sensor pad pressure when not testing.

5.7 Procedure- Dry & Wet Testing with Monarch EVA

5.7.1 This procedure is performed only after determining whether the walkway is "slip resistant", i.e., 0.45 minimum SCOF when tested per 5.6 and correcting average SCOF per 5.8.

5.7.2 Remove leather pads and substitute Monarch EVA pads per manufacturer's instructions and repeat 5.6. Spray test surface with distilled water.

5.7.3 Multiply the average SCOF by the gage correction factor. Corrected average SCOF must be 0.50 minimum dry and 0.35 minimum wet. (Note ref. 2.4 specifies 0.60 minimum SCOF dry and wet using a Neolite sensor)

5.7.4 Measure kinetic COF (KCOF) simultaneously with SCOF test for 0.30 minimum requirement (Ref. 3.1.6) with sensors sliding on wet (5.7.2) walkway surfaces at an approximately constant velocity of approximately 5 cm/sec (2"/sec).

5.7.5 Measure kinetic COF (KCOF) simultaneously with SCOF test for 0.30 minimum requirement (Ref. 3.1.7) with sensors sliding on wet (5.7.2) Florida Ceramic Tile at an approximately constant velocity of 5 cm/sec (2"/sec).

5.8 Calculations

5.8.1 Divide the force gage scale reading (lbs.) by the weight of the assembly that is in contact with the surface. (On some devices the scale is calibrated directly in SCOF (Appendix Ref. 3)).

5.8.2 For each of the readings taken, estimate the SCOF to the nearest 0.01. Determine the average SCOF. Discard the initial reading if greater than all other readings and then repeat it (See Note 5). Example: Average horizontal axial force to start motion = 2.72 Kg (6.0 lbs.).

5.9 Report

5.9.1 The report shall include the following:

5.9.1.1 A description of the type and location of walkway surface tested, including any applied finishes.

5.9.1.2 The temperature and humidity of the surrounding air during the test.

5.9.1.3 The type of instrument used for SCOF measurements.

5.9.1.4 Report both the uncorrected and the corrected SCOF arithmetic averages and the plus/minus variations of the eight readings and the standard deviation (S.D.) (Note 6).

5.9.1.5 Report the leather and rubber Walkway Surface Traction Index.

5.9.1.6 State whether the surface is or is not slip-resistant based on a minimum 0.45 SCOF overall corrected average. ("Standardized Leather" Sensor). List the Leather Walkway Surface Traction Index.

5.9.1.7 Report the average SCOF, plus/minus variations and S.D. of the eight readings for dry and wet tests with Monarch EVA. List the dry and wet Rubber Walkway Surface Traction Index.

5.9.1.8 State whether the dry and wet surface is slip-resistant with a Monarch EVA sensor based on a minimum 0.50 dry SCOF and 0.35 wet SCOF. If dynamic test is performed, minimum 0.30 DCOF wet is required at 5cm/sec (2"/sec).

5.10 Precision and Bias (Appendix Ref. 10)

5.10.1 Table 1 is based on a round robin conducted in 1994 where six laboratories evaluated three test surfaces (one was a polypropylene surface, see Note 7) using two drag type SCOF testers. All laboratories tested the identical surfaces and leather sensor. Leather sensors for the drag type testers were cut from the same 3" square leather sensor used on articulated strut type testers. While the round robin was not conducted in accordance with Practice E691, the results are presented in accordance with its guidelines. Within lab standard deviations of each test result were estimated from range data {s(x) = R/d2 (n) }. Although each lab only reported one test result per material ( with n = 8, per this specification/test method), standard deviation of the means were estimated by dividing the standard deviation of a test result by ( 8 1/2). Table 1 shows the corrected SCOF averages for all three labs, surfaces, and testers (Appendix Ref. 3,4).

6. CERTIFICATION AND INSPECTION

7. KEYWORDS

APPENDIX REFERENCES