About Slip Meters

Learn more about static and dynamic coefficient of friction measuring devices and why they are used.

Everyday tools for monitoring floor safety and maintenance.

Static Coefficient of Friction Testing

American Slip Meter, Inc. has been involved in floor safety and manufacturing drag sled type slip meters since 1993. We are actively involved in the ASTM, ANSI and NFSI committees that develop and maintain walkway testing standards. Craig Stephenson, Vice President, is a Walkway Auditor Certificate Holder through the ANSI/NFSI Accredited Program.

There has been a lot of discussion and opinions published on the internet concerning drag sled testers and static coefficient of friction testers. One item that surfaces frequently is the opinion that drag sled testers cannot be used on wet surfaces. This is an opinion, mostly made up of manufacturers of strut type testers and dynamic testers. the truth is that drag sled testers have been around for many years and have been used for both dry and wet testing since day one.

The ANSI/NFSI B101.1 Test Method for Wet SCOF of Common Hard Floor Surfaces is a consensus standard for wet static coefficient of friction. Our ASM 825A tests to this standard.
The Scope of previous ASTM C1028 paragraph 1.1 “This test method covers the measurement of static coefficient of friction of ceramic tile or other surfaces under both wet and dry conditions while utilizing Neolite heel assemblies. This test method can be used in the laboratory or in the field.”
These are two of the world’s largest standards origination writing and maintaining a standard for DRAG SLED WET TESTING.

The other opinion that seems to surface a lot is that static coefficient of friction testing is being replaced with dynamic coefficient of friction testing. There is a company that has published on their website about the “New Gold Standard” that was published on dynamic testing is going to obsolete static testing. This is something that they would like to see, in their opinion, because they perform dynamic testing. The truth in this matter is that both static and dynamic testing have been around for years and neither are going away. The new standards that ANSI and NFSI published for dynamic testing is a very much needed document in the testing field but it IS NOT AND WAS NEVER INTENDED TO BE WRITTEN TO REPLACE STATIC TESTING.

I did ask the question from a fellow NFSI B101 committee member at the April 2011 meeting as to why he thought that with the addition of the dynamic test method, the static test method should be obsoleted. The reply was that static testing clouds the issue with their customers. It seems as though there is quite a bit of work being done to try to eliminate static testing because they cannot sell and explain why their customers should use and rely on dynamic testing.
This does seem like the way of a lot of businesses though, when you cannot sell and justify your business, try, try and try to eliminate competition. You will not hear us sell you a static tester by telling you dynamic is no good. Both test methods have a place in the industry. I will ask each of you to look at the definitions of static and dynamic coefficient of friction, look at your normal step when you walk and decide for yourself which type of test you need.

Static coefficient of friction (SCOF): The amount of horizontal force required to initiate movement of a body in horizontal motion.
Dynamic coefficient of friction (DCOF): The amount of force required to maintain a body in horizontal motion.

Now, watch your own foot when you walk. Are you contacting the surface, your foot remaining in the location while you build up force to propel your body forward(SCOF) or are you gliding or sliding across the floor to see how far you will move(DCOF)?

There is a need to know how much force to maintain a body in motion but if you do not initiate the slip first, a low SCOF, does DCOF, or how far you will continue to slide, come into play? When a slip does occur, you want to see a high DCOF number. With this, your chance of recovery is far greater than a surface with a low DCOF.

To sum this up, Drag sled testers CAN be used for WET testing. STATIC COEFFICIENT OF FRICTION (SCOF) is how much force is required to initiate horizontal movement, or a slip. SCOF IS AND WILL BE A VALUABLE TEST.