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How does ANSI DCOF compare with Pendulum Test Value?

The most recent American National Standards Institute (ANSI) dynamic coefficient of friction (DCOF) test method, A326.3 (April 2017), states that “hard surface flooring materials suitable for level interior spaces expected to be walked upon when wet with water shall have a wet DCOF of 0.42 or greater when tested … as per this standard.” The older ANSI A137.1 AcuTest is essentially the same test as A326.3 and includes a similar statement. (Both tests use the BOT-3000E digital tribometer.)

Many people understandably see this statement and quickly assume that at 0.42 or greater, the floor is safe to use in wet conditions. Not true. Later in the same paragraph ANSI says, “The specifier shall determine materials appropriate for specific project conditions, considering by way of example, but not in limitation, type of use, traffic, expected contaminants, expected maintenance, expected wear, and manufacturers’ guidelines and recommendations.” Furthermore, for exterior applications, “a single DCOF limit value [such as 0.42]… is not provided.”

How should the flooring buyer or specifier deal with this conundrum? Our recommendation is to use safety standards for more than 40 specific situations (supermarket aisles, stairs, external ramps, bathrooms, pool decks, commercial kitchens, etc.) that have been in effect with only minor adjustments since 1999. This requires a pendulum DCOF test, which Safety Direct America can conduct (We also conduct the ANSI A137.1 and A326.3 tests.)

ANSI DCOF vs. Pendulum Test Value, both for wet conditions

A 49-point comparison of  ANSI A326.3/A137.1 with the Pendulum Test Value PTV (using a hard rubber slider) is shown in the graph at right. Many different types of flooring are included. The horizontal axis shows wet PTV and the vertical axis wet ANSI DCOF. A least-squares curve with correlation coefficient of 0.73 is fitted to the data. The graph shows the following:

  1. If we use the common pendulum safety standard of 36 as a minimum for “low slip potential,” the curve suggests a DCOF value of 0.62 or higher — considerably greater than the 0.42 minimum in the ANSI standards. But the DCOF could range from around 0.40 to 0.75 and still give a PTV of 36.
  2. If we want a DCOF of 0.42 or higher, the Pendulum Test Value the curve suggests is 15 — in the range of “high slip potential.” But the PTV could range from around 15 to 50 for that same DCOF.

Variation with time. Slip resistance of a floor is not a constant as time goes on, but can change substantially with wear. Very slippery floors can get slightly better, but slip-resistant flooring can lose its wet slip resistance, in some cases in a matter of weeks. That’s why McDonalds Restaurants spent years developing a test for “Sustainable Slip Resistance.” Their specification requires a wet Pendulum Test Value of 35 or higher after a specified amount of abrasion. This is equivalent to one or two years of traffic in a busy customer area.

Safety Direct America’s “Recommended Slip Test Package plus Wear Test” includes all three tests (pendulum DCOF test, ANSI A326.3, and Sustainable Slip Resistance), allowing a client to assess slip risk initially and after some time in use. This can avoid an expensive mistake of installing and maintaining a floor that is an injury and lawsuit waiting to happen. Almost all buyers would like their flooring to have an economically reasonable lifetime.

The ANSI A326.3 standard, using the BOT-3000E, is becoming popular in the USA. Among its disclaimers: that this test “can provide a useful comparison of surfaces, but does not predict the likelihood a person will or will not slip on a hard surface flooring material.” The pendulum’s initial safety standards were based on 3,500 real-world tests on all types of flooring, with and without falls, over a 25-year period. The pendulum continues to be the preferred method of assessing real-world slip resistance in 49 nations, and has been in continuous use for 50 years.

Discussions with Carl Strautins of SafeEnvironments in Australia were helpful in preparing this post.

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