Using the new ASTM slip standard

Assessing with SATRA’s STM 603 Slip Resistance Test machine.

by Peter Allen

Slip resistance testing is a complex process, and an effective slip test machine needs to control and measure a number of key criteria reproducing the critical factors relating to slip when walking. The SATRA TM144 test method has established a test protocol for slip testing. It is widely accepted within the footwear industry, and also forms the basis of the subsequent European standard EN ISO 13287 and now ASTM F2913-11. SATRA TM144 continues to provide a comprehensive basis for the development and approval of footwear, with respect to slip, within the global footwear industry.

In Europe, the US and in many other countries around the world, there are a growing number of legal obligations requiring retailers to only place safe products on the market. Reducing the risk of footwear slip is a critical safety aspect to be considered. The introduction of a new ASTM slip resistance standard (F2913-11 – ‘Standard test method for measuring the coefficient of friction for evaluation of slip performance of footwear and test surfaces/flooring using a whole shoe tester’) provides a quantitative assessment of the safety of footwear for the US market.

This new ASTM test can be conducted using SATRA’s STM 603 Slip Resistance Test machine. This extends the scope of the STM 603 machine, which also allows tests to be carried out in line with the SATRA TM144 test method, the European and International standard EN ISO 13287 and Canadian standard CSA Z195-09.

As indicated in the title of the new ASTM standard, it is not only applicable to assessing footwear slip resistance, but is also intended (as defined within the scope of the standard), to allow the assessment of ‘most types of indoor floorings, including matting and stair nosing, and surface contaminates on the flooring surface, including – but not limited to – liquid water, ice, oil and grease’. The scope also makes reference to surfaces ‘such as block pavers, pavers, turf and gravel’, as well as ‘special-purpose footwear or fittings containing spikes, metal studs or similar’, which ‘may be tested on appropriate surfaces’.

SATRA has over 30 years’ research experience investigating slip between footwear and a wide range of floorings and naturally occurring surfaces. Over this period, fundamental principles of slip have been identified, as well as the characteristics of footwear required to reduce the risks of slip.

The SATRA STM 603 test machine

A slip test machine can be used as a development tool to verify the slip resistance of new footwear products. It can also validate these products against a footwear specification in which a required coefficient of friction has been specified. Testing against industry-accepted slip resistance standards is a proven method to validate products, and to demonstrate due diligence in assessing products’ slip resistance.

The SATRA STM 603 slip test machine accepts a wide range of ground surfaces against which footwear can be tested for their resistance to slip. It is common to test footwear against a dry floor and wet floor and, in some cases, a surface with a defined lubricant. The standard tests (SATRA TM144, EN ISO 13287 and ASTM F2913-11) specify closely controlled, calibrated standard flooring surfaces, designed to give reproducible footwear slip test results.

To simulate cold weather conditions, an optional piece of SATRA equipment allows a temperature-controlled block of ice to be produced and used in the STM 603 slip test machine.

Conducting a slip test with STM 603

A section of calibrated standard flooring, an alternative floor surface, or a special surface (such as ice) is placed onto the floor carriage. The footwear is mounted on a foot form which, in turn is mounted onto the loading frame. The frame is adjustable to allow the inclination of the footwear to be set relative to the flooring. This allows the conditions of slip to be determined in different stages of the walking gait – for example, heel strike, forepart lift-off, or shoe flat to floor.

Software, supplied with the machine, includes pre-set parameters for SATRA TM144, EN ISO 13287 and ASTM F2913-11. The machine console incorporates a data acquisition computer, which gives graphical output and full numerical results. Additional information can be entered through the machine keyboard, allowing test criteria and other relevant data to be included. Once initiated, the program brings the footwear into contact with the test surface and applies a pre-set vertical load before translating the floor horizontally at a controlled speed. The horizontal and vertical forces are measured during the test.

The output from the test is a determination of the coefficient of friction between the shoe and the test surface. The coefficient of friction is defined as the ratio of the horizontal force to the vertical force as the shoe slips. Hence, a low coefficient of friction indicates that only a low horizontal load would be needed to cause the shoe to slip against the flooring type used in the test. By using a standard test surface, and with reference to acceptable required minimum and maximum coefficients of friction, the footwear can be assessed for slip resistance. In addition to the coefficient of friction result, the loads, speeds, horizontal distance covered and a continuous calculation of coefficient of friction are recorded graphically for the duration of the test.

The SATRA STM 603 has been developed with the benefit of extensive research into slip and slip testing methods, together with the experience gained from the daily practical use of the machine in the SATRA footwear testing laboratories. The machine and associated test methods have gained wide acceptance in the global footwear industry, with sales made to brands, manufacturers, test laboratories and institutes around the world. SATRA’s research team continues its research into slip and slip testing. This team can offer consultancy advice, as well as customer specific contract research. In addition to the sale of the STM 603 slip test machine and all associated accessories, SATRA also offers a footwear slip testing service with customers’ products supplied to our laboratories in the UK or China.

The STM 603 Slip Resistance Test machine offers a powerful tool for use in both product development and safety validation, with regard to footwear slip resistance.

Click here for comprehensive information on SATRA's range of test equipment.

Publishing Data

This article was originally published on page 30 of the March 2012 issue of SATRA Bulletin.

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