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In Step with Standards

What tests are used for making sure standards are followed

Well engineered safety footwear offers wearers protection from a variety of hazards in a range of working environments. Comprehensive laboratory testing allows a manufacturer and supplier to demonstrate that its footwear offers the necessary level of protection from hazards such as accidental impacts and crushing, and meets legislative requirements.

In the first of a two part series, Simon Courtney takes a look at the main standards and the tests and requirements they contain. In this edition he specifically covers testing methods for impact resistance and compression resistance, while in January’s edition he’ll discuss slip resistance, nail penetration resistance, metatarsal protection and electrical resistance properties.

Introduction

The main series of testing standards for footwear which has been adopted by the EU and elsewhere is the EN ISO 20344 series. These standards were produced by technical committees working under instruction from the European Committee for Standardisation (CEN) and the International Standards Organisation (ISO) and have been adopted by many countries internationally.

Canada and America have produced their own standards. The American Society for Testing and Materials (ASTM) and Canadian Standards Association (CSA) have both produced safety footwear standards.

The ASTM and CSA standards are not the same but do share similarities as they use many of the same testing methods, which will be discussed later in this article. Although other standards do exist these are usually derived from one of these three series. There are a number of differences between these standards, but all of them contain requirements for toe protection, penetration resistant inserts and electrical resistance.

EN ISO standards

The EN ISO 20344 series of standards takes a more comprehensive approach than other standards, with tests not only for the key safety features of the footwear, but also performance tests for the whole footwear and its components.

The series comprises four standards with the first, EN ISO 20344:2011: Personal protective equipment - Test methods for footwear, as the title suggests, containing details of the test methods.

In some cases these details consist of a reference to another standard. For example, the determination of the corrosion resistance of metallic toecaps and penetration resistance of inserts are tested in accordance with EN 12568:2010 and hence the details and parameters of the test are not detailed within EN ISO 20344. In other cases full details necessary to enable the test to be carried out are provided.

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The remaining three standards, EN ISO 20345:2011: Personal protective equipment - Safety footwear; EN ISO 20346:2004: Personal protective equipment - Protective footwear; and EN ISO 20347:2012: Personal protective equipment - Occupational footwear, contain specification requirements for the three categories of footwear.

Safety and protective footwear is defined as footwear which incorporates protective features to protect the wearer from injuries which could arise through accidents and are fitted with toecaps.

The main difference between these two categories is the level of protection offered by the toecap. The third category, occupational footwear, is defined as footwear incorporating safety features to protect the wearer from injures which could arise through accidents but does not incorporate a toecap.

EN ISO 20346 is the only standard which has not had a recent update (currently on-going) and is designed to cover footwear for industries where the level of protection does not need to be so great. EN ISO 20344, 20345 and 20347 have been recently updated but EN ISO 20346 has not. This has resulted in the standards becoming out of step, although EN ISO 20346 is less commonly used.

The standards cover two classes of footwear: class I is footwear made from leather and other materials, and class II is all rubber or all polymeric footwear. All three standards contain a core of mandatory tests, but also contain additional optional testing which allows manufacturers to make additional performance claims by using marking categories which demonstrate that products meet the requirements associated with these selected additional properties. Footwear meeting only the mandatory requirements is labelled SB for safety footwear, PB for protective footwear and OB for occupational footwear.

For ease of marking, the most widely used combinations of basic and additional requirements have been put together into group categories as shown in Table 2. Individual codes also exist and these are often used in conjunction with the group marking categories, as shown in Table 3. For example, footwear labelled as code SB P indicates the item meets the mandatory requirements and provides penetration resistance as an addition.

American and Canadian standards

The ASTM and CSA standards are less comprehensive than the EN ISO series and only contain requirements for the safety features of the footwear, and do not include requirements for non-safety properties, such as the thickness and tear strength of upper materials.

The ASTM standards, which have also seen recent new publications in 2011, comprise two parts, again separating the test methods from the performance requirements. These standards are ASTM F2412-11: Standard Test Methods for Foot Protection and F2413-11: Standard Specification for Performance for Protection (Safety) Toe Cap Footwear. The Canadian standard CSA Z195:09 contains test methods and performance requirements in a single document.

Impact resistance

All toecap protection works on the ‘defended space’ principle where the cap provides a shell in which the toes are protected from damage. It is a requirement of EN ISO 20345 and 20346 that toecaps also meet the requirements for their dimensions and corrosion resistance contained within EN 12568: Foot and leg protectors - Requirements and test methods for toecaps and penetration resistant inserts.

Although toecaps may be tested alone, it is important that the whole footwear is assessed as the effectiveness of the caps will greatly depend on satisfactory positioning and inclusion in the footwear. Toecaps require sufficient support by the sole unit: poor soling material and pattern design and/or poor footwear manufacture can greatly reduce the effectiveness of even the strongest of toecaps.

The EN ISO, ASTM and CSA standards all contain methods and requirements for impact resistance of footwear incorporating toecap protection, which may be metallic or composite materials. The principle of these tests is the same where toe section test samples of complete footwear are assessed for their resistance to impact by a falling mass. Many toecaps will demonstrate a degree of recovery immediately after the impact and hence the final shape of the toecap will not necessarily reflect the lowest position the cap was deformed to at the point of impact.

The test methods use soft modelling clay formed into cylinders which are placed under the toecap close to the back edge and are deformed on impact and show no recovery after testing. When the toecap is deformed during impact the clay cylinder is also deformed and the lowest position of the toecap is recorded in the deformed clay, and its minimum height is measurable.

In the EN ISO standard a wedge shaped striker of 20kg is used, where the ASTM and CSA standards use a cylindrical bar shaped striker of 22.7kg with the circular face of the striker impacting vertically down on to the toecap. The striker is referred to as the impactor in the ASTM standard.

As with the EN ISO standard, the CSA standard contains two tests with different energy levels to allow for two grades of toecap; the ASTM method contains only a single impact energy level. During testing, the striker is dropped from sufficient height to produce the required impact energy as described in Table 4.

The ASTM method requires that only single sizes of footwear are tested to represent the whole footwear range, which is a size US 9 for men’s footwear and size US 8 for women’s footwear, and hence only contains requirements for these sizes. The EN ISO and CSA standards take a more comprehensive range and contain a series of clearance requirements which are grouped together into size ranges.

Compression resistance

The EN ISO and the ASTM standards, contain test methods to assess the compression resistance of footwear containing toecaps against accidental compression damage, unlike the CSA standard which contains no test for this property. As with the impact resistance test, the ASTM standard only contains requirements for men’s size US 9 and women’s size US 8, while the EN ISO standards again require a wider range of sizes to be assessed, and hence specify a series of size related clearance requirements.

In this test a section of the whole footwear which contains the toe region of the boot, is cut from the rest of the footwear just behind the cap, and is compressed between two flat horizontal plates until a pre-set load is reached. Once the required load has been reached the load is removed and the degree of maximum deformation is measured from the minimum height of deformed clay cylinders. The compressive loads used in testing are given in Table 4 on page 110.

Summary

The most appropriate series of standards for a manufacturer to test and be in accordance with will depend on where in the world the footwear is intended to be sold, and the range of requirements the footwear needs to meet will depend on the claims being made about them.

Published: 19th Nov 2012 in Health and Safety International

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Simon Courtney is a footwear technologist at SATRA Technology. He has a wide knowledge of testing and supports customers with technical reports, advice and in the preparation of company-own specifications.
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