Measuring the slip resistance of floorings and footwear

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Detlef Mewes, Institute for Occupational Safety and Health of the German Social Accident Insurance, Germany


Introduction

Testing and assessment of anti-slip characteristics is of major importance for the prevention of slipping accidents. Numerous different methods and devices have been developed over the years to measure the slip resistance of floorings and footwear. Different European countries have adopted various test methods and rating systems. Because these test methods are based on different principles and are used under different conditions there is no correlation between them. No single test currently in use is perfect. All have their advantages, but also their own particular flaws and disadvantages.


Floorings

The most common test methods for floorings are ramp tests, tribometer tests and pendulum tests.

Ramp test

Picture 1a: Ramp test
Picture 1b: Ramp test


Source: Mewes Detlef

A widely used test is the ramp test according to the German norm DIN 51130. This test requires an operator who is protected by a fall restraint harness. The operator, wearing standard footwear, walks backwards and forwards over a sample of a flooring material that has been evenly coated with oil. Beginning with the ramp in a horizontal position, he gradually increases the angle of inclination until the limit of safe walking is reached and the test person slips. The acceptance angle obtained is used to express the degree of slip resistance.

Table 1: Resistance classes of floorings according to the German legislation Berufsgenossenschaften Regeln BGR 181 Source: [1]
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Table 2: Classification of floorings according to German norm DGUV-I 8687 Source: [2]

Five resistance classes (R9 to R13, see Table 1) are used for this purpose. Floor coverings with the resistance class R9 satisfy the lowest requirements for slip resistance; those with class R13 the highest.

The ramp test is also carried out barefoot with the use of soapy water as a contaminant (DIN 51097)[3]. The angle at which slipping occurs is used to establish an A, B or C rating for the barefoot test (Table 2)[2]. Barefoot ramp tests are useful in wet areas, such as swimming pools and saunas.

The ramp test allows testing of all types of floorings, such as ceramics, granite, natural stone, timber, steel gratings and flexible materials. The ramp test can also be used to determine the slip resistance of profiled surfaces. To a certain degree this test method takes into account the human walk. However, ramp test work requires well-trained operators in order for reliable and reproducible results to be obtained. This test is not suitable for on-site tests. The ramp test is the preferred test method for instance in Germany, France and the Benelux countries.

Tribometer test

This test method is based upon a friction force measurement. A body equipped with sliders is pulled at a constant speed over the flooring surface. The force required to pull the body is determined over the length of the measuring distance.

Picture 2: The GMG 200, an example of a tribometer tester


Source: Mewes Detlef

In order to determine the sliding friction coefficient, this force is divided by the vertically acting force. This test can be carried out in wet and in dry conditions both in a laboratory and on-site. DIN 51131 states provisions governing tribometers. Figure 2 shows as an example the GMG 200 test device. This device is predominantly used in Germany, Poland and Austria.

The coefficients of dynamic friction measured with the GMG 200 or with its predecessor, the GMG 100, are evaluated as follows. At coefficients lower than 0.30, the floor is classified as being insufficiently slip resistant. An acute risk of slipping exists. The slip resistance of the floor must be improved. If necessary, a new floor must be installed. If coefficients of friction of between 0.30 and 0.45 are measured, the floor may be classified as slip resistant, but risk-oriented measures such as those described in the section on the prevention of slip accidents must be taken, in consideration of operational requirements. Where the coefficient of friction exceeds 0.45, the floor is deemed to be serviceable without qualification. It exhibits an adequate slip resistance potential, and the risk of slipping is low even under unfavourable conditions, such as moisture.

Other tribometers are the FSC 2000 and BCRA Tortus. These devices are not covered by a standard at present. In Italy, Ministerial decree 236/89 requires slip resistant floorings to have a friction coefficient greater than 0.4 in the dry and wet state, as measured with the BCRA Tortus. Some such devices are considered to give over-optimistic slip resistance readings on wet, polished or glazed surfaces.

Pendulum test

Picture 3: Example of a pendulum tester


Source: Mewes Detlef

The pendulum test measures the loss of energy due to friction as the standard rubber-coated slider assembly slides across the test surface. It provides a standardized value of slip resistance[4]. This is the PTV (pendulum test value). PTVs can be obtained for dry surfaces and surfaces contaminated with water. Pendulum tests can be performed both in a lab and on-site. The pendulum does not always accurately measure heavily profiled surfaces. The pendulum is the preferred test method in the United Kingdom and Spain.

Table 3 from the UKSRG Guidelines 2006 compares the relative risk of slipping with PTVs.

Table 3: Rating of pendulum test results Source: [5]

SlipSTD PAS

Co-financed by the European Commission, the SlipSTD project had the objective to define common 'European' minimum slip resistance requirements for ceramic tiles based on defined and measurable surface properties in preference to traditional slip resistance testing. It was conceived as a joint approach to overcome the objections to and shortcomings of the various approaches outlined above. The SlipSTD PAS (Publically Available Standard) is the outcome from that[6]. It suggests a new approach for testing the surface of a hard floor covering, to determine an acceptable slip resistance performance levels appropriate to the floor covering’s installed usage and foreseeable contamination. It envisages three classes for hard floor coverings:

  • Class 1: Hard floor coverings for internal pedestrian areas that are foreseeably clean and dry and are routinely maintained as such.  
  • Class 2A: Hard floor coverings for internal pedestrian areas foreseeably contaminated with water and/or dry contaminants. 
  • Class 2B: Hard floor coverings for internal pedestrian areas foreseeably contaminated with other liquid contaminants with viscosity higher than water, such as oil and grease. 

Coverings are classified through the measurement of surface characteristics of the material (primary surface parameters) measured using optical topography techniques.

Footwear

Picture 4: Measuring the slip resistance of footwear


Source: Mewes Detlef

The method for measurement of the slip resistance of shoes is described in EN 13287[7]. The item of footwear to be tested is placed on a ceramic tile or steel floor, subjected to a given normal force, and moved horizontally relative to the surface.

Glycerine or sodium lauryl sulphate solution acts as contaminant on the surface. The frictional force is measured and the dynamic coefficient of friction is calculated. Depending on the test conditions, the friction coefficients must fulfil certain requirements given in EN 20345 (Table 4)[8].

Table 4: Requirements for slip resistant footwear according to EN 20345 Source: [8]


References

  1. DGUV – Deutsche Gesetzliche Unfallversicherung, BGR 181, Fußböden in Arbeitsräumen und Arbeitsbereichen mit Rutschgefahr, Sankt Augustin, 2003
  2. 2.0 2.1 DGUV – Deutsche Gesetzliche Unfallvwersicherung; DGUV-I 8687, Bewertung der Rutschgefahr unter Betriebsbedingungen, Sankt Augustin, 2011.
  3. DIN 51097, Testing of floor coverings – Determination of the anti-slip properties – Wet-loaded barefoot areas, walking method – Ramp test, DIN, Berlin, 1992.
  4. BS 7976, Pendulum testers, BSI, London, 2002.
  5. UKSRG – UK Slip Resistance Group, ‘The Uk Slip Resisistance Group Guidelines’, The assessments of floor slip resistance, Coventry, 2006.
  6. SlipSTD PAS http://www.ceramgroup.com/projects/slipstd/
  7. EN ISO 13287, Personel protective equipment – Footwear – Test method for slip resistance, Brussels, 2007.
  8. 8.0 8.1 EN ISO 20345, Personel protective equipment – Safety footwear, Brussels, 2007.


Links for further reading

Bergische Universität Wuppertal – Fachgebiets Sicherheitstechnik/Arbeitssicherheit. Retrieved 9 June 2011, from: [1]

Decreto ministeriale14/06/1989 n. 236, Prescrizioni tecniche necessarie a garantire l’accessibilita, l’adattabilita e la visibilita degle edifici privati e di edilizia residenziale pubblica sovvenzionata e agevolata, ai fini del superamento e dell’eliminazione delle bariere architettoniche, Rome, 1989.

DGUV – Deutsche Gesetzliche Unfallversicherung - Fußböden, Rampen, Treppen. Retrieved 9 June 2011, from: [2]

DIN 51530, Testing of floor coverings– Determination of the anti-slip property – Workrooms and fields of activities with slip danger, walking method – Ramp test, DIN, Berlin, 2010.

DIN 51531, Testing of floor coverings – Determination of the anti-slip property – Method for measurement of the sliding friction coefficient, DIN, Berlin, 2008.

HSE – Health and Safety Executive. Slips and Trips. Retrieved 9 June 2011, from: [3]

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