There are several types of tests for slip resistance, this post explains what they are, how they are executed and how to understand what the results mean for the average person.
Last time we addressed 3 questions surrounding slip resistance and slip resistance testing:
- What Does “Slip Resistant” Mean?
- How Is Slip Resistance Measured?
- What Slip Resistance Standards Exist?
Hopefully you learned a little more about why slip resistance testing is so vital when choosing a workplace safety program and specific pair of slip resistant footwear. This time I want to dive more deeply into the actual mechanics of slip resistance testing, including what implements are used in the process of testing and what variables are accounted for. Once again, this is heavy stuff and can get rather technical, so feel free to email or leave a comment if you find yourself lost.
What Methods Exist For Testing Slip Resistance?
The first slip resistance measurement device was invented in the 1930’s and there have been nearly 100 such devices invented since. However, there are currently only two devices which have received the ASTM F-13 standard for testing: the portable inclineable articulated strut tribometer (PIAST, aka Brungraber Mark II) and the variable incidence tribometer (VIT, aka English XL). These devices have been certified to produce repeatable, reproducible, measurable results.
- English XL – Developed by William English, which is powered by a small carbon dioxide cartridge set at a specific pressure. This cartridge pushes a test foot across a walking surface at continually higher pressures until a slip occurs.
- Brungraber Mark II – This testing device uses a 10 lb. weight on an inclineable frame and a “test foot” suspended over the test walking surface. The foot is released at increasing angles, dragged over the walking surface by the weight, until a slip occurs. This is the most commonly accepted testing method in the United States, so this is the method that SR Max uses to test.
In relation to these two tests are the ASTM F-1677 (Mark II) and ASTM F-1679 (English) standards. Both of these standards for measurement have been withdrawn by the ASTM, leaving no official national standard for measuring the slip resistance of safety footwear. (One point to consider, however, is that standards for slip resistant flooring require a 0.50 COF to be considered safe, which is why SR Max requires all of our shoes to test at a minimum of 0.40 in order for us to sell them.)
What Does HS Oily/Wet Mean?
There are several floor variables that are tested for when utilizing the English and Brungraber tests. Most often you will see results from three: Dry, Wet and HS Oily/Wet. By testing for all these conditions, it gives an idea of how a slip resistant outsole will perform under those various stressful conditions in the workplace. All of these tests are performed on a square of clean Red American Olean Quarry tile.
– “Dry” means that a square of dry tile is used as the walking surface.
– “Wet” means that a square of tile is covered with 25 ml of distilled water
– “Hi Soil Oily/Wet” means that a square of tile is covered with 25 ml of distilled water and 0.2 grams of vegetable oil
The most important condition to consider is HS Oily/Wet, because this is akin to the toughest work environments you will face. How a shoe performs under these conditions is the true judge of a shoe’s slip resistance rating. A shoe can have a perfect 1.0 on Dry conditions and be absolutely useless to you as a work shoe if it won’t protect you in greasy, oily and wet conditions.
All of this technical information is helpful, but can also be overwhelming. The best thing to remember when picking out a slip resistant shoe or safety shoe vendor is to do research. Companies should be able to provide information about the performance of their products. Just like a car maker should be able to tell you the MPGs, engine size, passenger limit and 0-60 mph of a vehicle, a shoe provider should be able to tell you how their shoe performs in HS Oily/Wet conditions. If it’s not explicitly available, ask. If they can’t tell you, find a company who can.