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Technical Textiles

Published: 28th Jan 2014

ARTICLE CONTINUES BELOW

Protecting users against hazardous risks has historically been a challenging goal. Beginning with the first harnesses made of leather over a knight’s armour in the 12th Century, up to modern, high tech fabrics and textiles, we see the enormous potential protective equipment has for many industrial sectors.

It’s therefore not surprising that today – and probably in the future too – all different kinds of protective textiles are of huge importance for the European textile and clothing industries, as well as the end users. These products are technical textiles with real high tech character and they are used in numerous industrial contexts, public facilities, in the field of law and order and the military.

The European market

In 2014 we will enter the 22nd year of the European home market founded on January 1, 1993. It is definitely not an overstatement to say that this may be one of the most important milestones for the development of protective textiles and clothing.

Besides the grown economic benefits of the European home market and driven by the different European Directives and legislation for the protection of people in their workplace, a new economic sector arose: heat and flame protective clothing; chemical protective clothing; garments for high visibility; foul weather protection; protective gloves; as well as many other kinds of protective textile equipment all changed to products where there is a duty for certification.

The CE mark has been used millions of times since protective clothing came into being. At the same time, this was also the starting point for the development of European standards. Until this time, individual rules and norms with sometimes country-specific peculiarities regulated the safety and performance of protective clothing in every country, but since July 1, 1995, all kinds of protective clothing has to correspond with the new harmonised standards, especially developed to conform with the European Directive 89/868/EEC for personal protective equipment (PPE).

Today there exist a huge number of new or revised testing and evaluation procedures. Revisions of standards for heat and welders’ protective clothing changed the requirements for these kinds of garments to a complete flame protection for the user – from the seams up to the embroidered company logo.

High visibility warning clothing, according to the newly published EN ISO 20471, has to prove the performance of its fluorescent colour as a new product and one aged by artificial Xenon-light, and also after a defined number of care cycles. Protective clothing against the enormous thermal risks of an electrical arc fault, not really widely used at the beginning of the CE certification process, is now not only internationally standardised but also part of many national and international guidelines for the selection of such kinds of protective clothing.

In addition, protective clothing especially developed for use via textile rental companies will no longer be tested in domestic washing machines. Instead, the ready garment test happens in standardised washing and drying machines suitable for industrial care.

These few examples are only the tip of the iceberg and demonstrate how challenging and ambitious the market of protective textiles and clothing is. At the beginning the business was dominated by more simple products with just a few, well defined protective functions, but today more and more multifunctional protective clothing dominates the markets.

This can be seen as proof that European fabric manufacturers form the basis for creating novel protective clothing by implementing innovative ideas for new fibre blends, an intelligent fabric construction and customised functionality in their fabrics. Developments like these, brought into a qualified and fashionable design by experienced garment manufacturers, convince a wide range of industrial sectors.

Influence of harmonised standards

As mentioned before, the European Directives for the protection of individuals, relevant throughout the EU, have changed the meaning of protective clothing – it is now a legally regulated product. To fulfil the requirements, the existence of qualified standards is appreciated by manufacturers, as well as test and certification authorities.

For hundreds of test procedures such as burning behaviour, tensile strength, or penetration resistance against chemicals, it is necessary to qualify the protection performance of the main materials of a garment. Here, the existence of standards is understandable, otherwise there would be no chance to qualify and quantify the performance parameters of the fabrics on a commonly agreed basis.

Besides the technical issues of a harmonised standard, the presumption of conformity with the European Directive 89/686/EEC as the legal-oriented aspect of a harmonised standard published in the Official Journal of the European Union (OJE) probably has the same level of importance. For the development of appropriate protective clothing, revisions of the so called PPE product standards have to be taken into consideration too.

What this means in practise is explained in the norm EN 531:1995, ‘Protective clothing for workers exposed to heat’, which was one of the most popular protective clothing standards from 1995 to 2008.

A study of this standard in detail shows different inconsistencies:

• The starting point of a certification according to EN 531 was the test of the flame retardant performance of the used outer material. For this, the material was washed five times in a household washing machine according to EN ISO 6330 and finally dried once before the burning behaviour according to EN 532/ISO 15025 was tested. If the material fulfilled the requirements specified in the standard, it was generally suitable for the intended use (code A)

• All the other important heat transfer tests, such as convective (code B) and radiant (code C) heat resistance, or protection against liquid aluminium (code D) or iron splashes (code E) were carried out on material without any pre-treatment by washing. This seems to be an inhomogeneous and less practise-oriented approach

• Surprisingly, there were also no textile-physical requirements such as tensile or tear strength, although these parameters were at the same time necessary for protective clothing used in welding and allied processes (EN 470-1:1995)

Fortunately, product standards for PPE, like other technical documents, are subject to continuous revisions and maintenance cycles. The EN ISO 11612, for example, is a new revision of EN 531 and should bring substantial improvements. I’m convinced this goal was reached in 2008 where EN ISO 11612 was published for the first time in the OJE.

From both a technical and safety point of view the EN ISO 11612 represents an obvious evolutionary step compared to the former standard. Now the norm defines flame retardant requirements for all material layers, all accessories present on the outside of the garment, as well as for the pocket lining. It also fixes limit values for the mechanical strength and overcomes the inconsistencies regarding the pre-treatment.

Without a doubt, this is a significant increase in safety for the user. It can, however, only be realised by significantly higher testing costs and less flexibility in using accessories, logos, embroidery, or badges.

Some other points remain open. Although used 10,000 times in the industry, EN ISO 11612 doesn’t offer a standardised test procedure or appropriate protection level either for grinding or for cutting-off machines. This fact still leads to complaints from users who obviously overstrain their heat or welders’ protective clothing, believing it’s completely tested and CE certified.

One of the best examples of how new standards influence the market of protective textiles and clothing is the testing and evaluation procedures for arc thermal resistance according to IEC 61482 series. While working under live conditions, there is a general hazard and potential risk of injury due to electric arcs, particularly in case of arc faults, which may internally occur with short-circuits in electric installations.

The protection against electric arc faults is of great importance at or near to electric power installations. Electricians mounting, repairing, maintaining or operating electrical equipment and installations should feel safely protected in this situation. An essential contribution to this protection, in particular against the thermal arc effects, can be made by clothing made of suitable textiles.

To be in accordance with all the guidelines and regulations for PPE and workers’ safety, a reliable test procedure is necessary to confirm the clothing is arc resistant, and guaranteeing the required level of protection. Test method, procedure, set-up and parameters have to meet the practical needs. The test conditions have to be selected and conducted in accordance with the relevant power network and installation, as well as practical exposure scenarios.

From the international point of view, today only two harmonised test standards exist to attain this goal. Since 2002 a fabric could be tested under the standard IEC 61482-1. The result was the Arc Thermal Performance Value (ATPV), the so called ‘Arc-Rating’ which represents an incident energy value expressed in cal/cm² on a fabric, or fabric assembly, that results in a 50% probability that sufficient heat transfer through the tested specimen is predicted to cause the onset of a second degree skin burn injury based on the Stoll curve.

This test procedure is based on the American Standard ASTM F1959, first published in 1999 and revised as the first edition of IEC 61482-1-1 in 2009. The use of the ATPV always requires the understanding and proper use of different American guidelines for the determination of the arc risk, like IEEE 1584 (Guide for performing arc flash hazard calculation) or NFPA 70E (Electrical safety in the workplace as the heart of US arc flash regulations).

At this early stage in Europe no equivalent test procedure existed and the business of arc protection textiles and garments was not really present, or was still in its infancy. At the beginning of 2002, however, this changed dramatically as a team of experts started the work on a European approach to arc testing.

In contrast to the American way of arc rating, the European arc test procedure operates in defined protection classes in accordance with one of the basic rules of the PPE Directive 89/686/EEC. Over an intermediate stage, in 2007, the first edition of the so called ‘Box-Test’ was standardised in IEC 61482-1-2. This test procedure uses a directed and constrained electric arc in a low voltage circuit and operates in the two defined protection classes, 1 or 2. The conditions simulated by the Box-Test are worst case scenarios for switchgear assemblies and installations in LV power systems, in the appropriate short-circuit current range. Besides the enormous impact of radiation, convection and molten metal splashes, the special box design takes thermal arc consequences which may result from the amplifying effect of an installation’s back and side walls into account.

One of the major differences of IEC 61482-1-2 in comparison to the ATPV test is the two test classes for any kind of fabric or fabric assembly result in a clear PASS/FAIL.

During the first years of the standard development conventional fabrics and fabric assemblies used for heat, flame and welders’ protection were the dominant solutions. Together with the publication of the new European Box-Test standard the fabric manufacturers started enormous research activities for special arc protection fabrics and fabric assemblies.

For class 2 protection, traditional fabrics made either of FR cotton or aramid fibres were increasingly replaced by multi-fibre blends with five or more components, and woven in innovative constructions.

Besides extended possibilities to create multifunctional protective garments with only one material, a relevant decrease in weight of 25% and more are the major benefits for end users – without any exaggeration, a great example of the innovation power which new standards bring into the business of textile materials development.

Newly published guidelines from the International Social Security Association (ISSA) or the German Social Accident Insurance (DGUV) for the selection of PPE against the thermal risks of electrical fault arcs will also support such innovation in the future.

Safety first?

There are questions about whether a new or revised harmonised standard always improves the user’s safety.

Since October 2013 there has been much discussion in the field of high visibility warning clothing, where the new EN ISO 20471 superseded the former EN 471. Probably the major question is actually the validity of certificates based on EN 471 and therefore also the usability of garments tested and certified under use of the superseded standard.

In contrast to the new revisions of heat, flame or welders’ protection standards, like EN ISO 11612 EN ISO 14116 or EN ISO 11612, the changes in EN ISO 20471 are much less evolutionary. It’s probably not disrespectful to say that the requirement for an additional test of the background material regarding chromaticity coordinates and the luminance factors after at least five cycles of care represents the most important change.

Neither the three well known colours – red, orange-red and yellow – nor the minimum required areas of visible material, important for the classification of each garment, were changed. Also, the colour fastness grades are still more or less the same as before. The new standard contains requirements relating to risk assessment and risk analysis of high visibility garments which may help end users during the process of selecting the right garment – a garment manufacturer may be happy about this new feature if it helps make their business easier.

Irrespective of the enhanced content, there are still some important aspects which were more or less already valid in the former standard. For experts in the field it’s not really surprising to read that the selection and use of high visibility clothing can vary among user countries and may be subject to local regulations. Garment manufacturers and wholesalers selling the same high visibility garments in different European countries like UK, Netherlands or Germany, learned this truth many years ago.

In spite of the new paragraph ‘Ageing’, we see that the end user is responsible for the performance of his/her garment during its life cycle – this is on the same high level as before the revision. Although the notified bodies now have to measure chromaticity coordinates and luminance factors after care cycles, it’s still the user who has to decide whether to continue use or to change to a new garment. Every morning he/she is still the only party to see the garment marked with the effects of daily work.

Before the standard’s revision, any stain of dirt or blotched areas from contact with oil, lubricating grease or tar on the yellow or orange parts of the garment was recognised as minimising the high visibility functions. As far as we know, no objective tool or system exists to assess and recalculate the minimum visible area to determine the garment’s class.

Last but no least it’s the standard itself that clearly states that the number of cleaning cycles is not the only factor related to the lifetime of a high visibility garment, so it may be an advantage of EN ISO 20471 to test the colour after some care cycles. There are, however, some doubts that end users have any major benefits from this procedure.

Published: 28th Jan 2014 in Health and Safety International

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