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Protective Coveralls

Published: 15th Mar 2012 in OSA Magazine

heat and flame covereallsHeat and flame testing of protective coveralls

Manufacturers producing garments protecting workers against heat and flame hazards have three ISO standards which can be utilised in the design of the garments: namely ISO 11611:2007 (protective clothing for use in welding and allied processes), ISO 11612:2008 (protective clothing for workers exposed to heat) and ISO 14116:2008 (protective clothing for workers exposed to flame).

Note that these are dual EN ISO standards so that garments compliant with the ISO versions should also be acceptable within the European Union, provided the manufacturer also adheres to the requirements of the European PPE Directive 89/686.

ISO 11611 and ISO 11612 are specifications for garments providing protection against heat transmission as well as against flame spread; however, ISO 14116 is a specification for resistance to flame spread garments only. Other standards for clothing protecting against heat and flame are available such as national standards, including those produced by ASTM for the USA, AS/NZS (for Australia and New Zealand); however, these are not being considered in this article.

In order to claim compliance with either ISO 11611 or ISO 14116, garments must be tested in full and meet the minimum requirements, including those for design, marking and user information. In order to claim compliance with ISO 11612, however, the minimum requirements specified in the design, marking, user information, ignition and physical tests must be achieved and it is necessary to also meet the minimum requirements for at least one of the five specific heat transmission tests. ISO 11612 also contains some specific options covering whole garment tests and tests for performance against water penetration.

The testing is described later on in this article.
General garment requirements not covered by ISO 11611 and ISO 11612 must be assessed according to ISO 13688; however, ISO 14116 requires that garments meet the general requirement in EN 340:2003.

All three ISO standards (11611, 11612, 14116) have been in use for between three and four years now, and in fact are themselves nearing the final stages of a revision process which may make further changes to the performance requirements for certain garment properties.

It is worth noting that these ISO standards include specifications for garment design and the performance of seams, fasteners and other garment features, not just the specifications for the performance of the fabric. Many manufacturers and suppliers of clothing for the protection of industrial workers against the effects of heat and flame have become used to the need to plan new protective clothing designs around the requirements of these latest ISO standards.

Cleaning according to label care

In order to be fully compliant with these standards, manufacturers need to have the garments tested after pre-treatment processes based on the care labels and user information the manufacturer intends to apply to the garment. The care label should specify the type of cleaning treatment, the temperature and the maximum number of cleaning cycles the garment may undergo before its protective performance no longer complies with the standard. For example, a care label for a protective garment might specify that the garment should be industrially laundered at 75° C and also that the garment should be discarded after ten cycles because it may no longer be adequately protective. A test house responsible for testing this garment would then carry out testing after ten cycles of industrial washing according to ISO 15797 at 75° C.

If the manufacturer has not specified a maximum number then these standards specify as a default, five cycles. In such cases, however, the manufacturer must refer to this number of laundry cycles on the information for use leaflet which should be supplied with each garment.

In the case of CE marked garments for the European market it is mandatory that this information for use leaflet accompanies each garment when sold. The manufacturer may decide that the garment should not be laundered, in which case the care label must display negative symbols only (e.g. symbols with crosses through them); for example, ‘do not launder’ or ‘do not dry clean’.

Inherently, flame retardant fabrics should not lose their limited flame spread properties provided a build-up of contamination is avoided. Similarly, correctly treated flame retardant fabrics will generally keep their limited flame spread properties until long after the garment itself has deteriorated through a combination of use, wear and tear and cleaning.

flame retardant clothingManufacturers may wish to emphasise this in their user information, but they should make it clear that any claims about the longevity of limited flame spread properties of the fabric apply only to the fabric and not to seams or logos. Also, other properties such as physical strength might deteriorate over time and as a result of repeated cleaning. Indeed, repeated cleaning might eventually result in shrinkage, making the garment gradually more and more un-wearable.

In terms of specific claims about limited flame spread properties and thermal protection properties, the manufacturer should only make claims which can be backed up by test data.

For example, when a manufacturer’s information leaflet for users states that a garment can be washed 25 times, he is stating that the garment will be adequately compliant with the standard up to this point. In essence, any testing of such products is simply testing the claims made by the manufacturer, on the label and in the user information. The label should state the maximum number of washes.

Ignition/limited flame spread

The ability of a fabric or garment to resist being set alight when it comes into contact with a naked flame is assessed using the limited flame spread test (ISO 15025). This test is carried out on samples of seams as well as on the fabric – see Table 1 for a detailed explanation of limited flame spread testing requirements.

Furthermore, ISO 11612 requires that hardware and materials which are applied to the outermost surface of a heat and flame garment should be tested according to ISO 15025 method A, before and after washing and that the closure system must remain operational after testing. Testing of closure systems, however, is not required by EN ISO 11611 which instead states that the closure must be covered with a flap in a material which conforms to the surface ignition requirements. EN ISO 14116 has no such recommendations for closure systems.
(Note that after the current revision, it is probable that limited flame spread testing will be required before pre-treatment on fabrics and seams and on garment closures for ISO 11611, effectively bringing this standard into line with what ISO 11612 currently requires).

A further point is that both ISO 11611 and 11612 specify that either the surface ignition test or the edge ignition test – or both – should be used to test the garment according to the “risk during the foreseen use for the garment” to use the wording in the standards. It is not clear, however, when either the ‘surface’ or ‘edge’ ignition test should be used.?If the manufacturer has not specified whether one or the other or both should be used, then SATRA would discuss with the manufacturer what testing should be applied. The following points at least would be taken into account in any recommendation as to what testing should be carried out:

• Whether the garment is loose or tight fitting

• Whether pocket flaps can be fastened or remain loose

• Whether a specific work environment is free from naked flame hazards

The cautious approach would be to conduct both edge and surface ignition testing and this is what SATRA would advise. In the specific case where a garment is being tested with a view to obtain CE marking allowing export to the European Union, the EU notified body appointed for conducting the type examination will be able to advise the safest approach.

Both standards (ISO 11611 and ISO 11612) require as a minimum, that either the surface ignition or the edge ignition must be carried out. It has been SATRA’s experience, however, that the surface ignition test is always necessary.

If the ignition testing of a garment edge is required then specimens should be cut from a garment. If a garment is not available, however, a simulated garment edge can be formed by folding the edge of a piece of fabric and securing the fold with suitable fastenings such as paper clips. A garment is required in order to prepare specimens for edge ignition testing of seams. Garments are also required in order to ignition test closure systems and logos.

The specific requirements for the performance of materials and assemblies according to ISO 11611 and 11612 can be summarised as follows: no flaming to the top or either side edge of the test specimens, no holing of the specimens, no molten or flaming debris, after-flame times and after-glow times to be no more than two seconds. The ISO 14116 requirements for limited flame spread are a bit more exacting and also they permit three different levels of performance referred to as Index 1, Index 2 and Index 3.

In summary, to achieve Index 1, each individual test specimen must not allow any part of the lowest boundary of flame to reach the top or either side of the specimen, there shall be no flaming debris and any afterglow must not spread from damaged areas of the specimen to undamaged areas after the flame has extinguished. In addition to these requirements Index 2 allows no hole formation and Index 3 allows neither hole formation and it also specifies that each individual specimens after-flame time shall not exceed two seconds.

Heat transmission rates

Heat transmission tests are concerned with measuring how hot the inside surface of a garment gets when a heat source is applied to the outer surface of the garment.

ISO 11611 includes two heat transmission tests, both of which should be carried out on the test garment e.g. impact of molten metal droplets and resistance to the transfer of radiant heat. The test results are classified according to the performance achieved into either class 1 (providing the minimum requirements for class 1 are achieved) or class 2 (providing the minimum requirements for class 2 are achieved).

The introduction of this classification allows some flexibility in designing and specifying welders’ garments. It allows manufacturers to produce lighter weight garments where heat loads are relatively low and heavier duty garments with greater protection against thermal hazards for use in areas exposed to higher levels of spatter or higher heat loads. The standard includes an informative annex in which appropriate welding operations are suggested as suitable for each class of garment.

ISO 11612 includes five heat transmission tests and assigns a letter of the alphabet to each one. In order for a garment to comply with ISO 11612 it is necessary that it complies with the minimum requirements of at least one of the heat transmission tests described below:

• Heat transmission on contact with flame (also called the convective heat test) which is assigned the code letter B

• Heat transmission to radiant heat source which is assigned code letter C

• Heat transmission to contact with molten aluminium which is assigned code letter D

• Heat transmission to contact with molten iron which is assigned code letter E

• Heat transmission to contact with a hot object which is assigned code letter F

The test for heat transmission from a radiant heat source has four levels, but the others have three levels.

ISO 11612 includes two optional physical tests which the manufacturer may request to be carried out in order to demonstrate extra protection for wearers or to provide further information on the garment performance. These are resistance to water penetration and water vapour resistance. Both tests are drawn from European standard EN 343. If the manufacturer wishes to claim that his garment is resistant to the ingress of water then both of these tests must be carried out and the garment assessed according to EN 343. Resistance to water penetration is required on the seams of the garment and on the fabric after a range of pre-treatments including exposure to fuel and oil, laundering, abrasion and flexing.

The two optional thermal tests include whole garment testing for prediction of burns, using a thermal manikin such as the SATRA manikin SID, and resistance to the thermal effects of an electric arc. The manikin testing should be carried out according to ISO 13506 at a heat flux over the manikin surface of 84 kW/sqm. When required, garments intended to protect against the thermal hazards of an electric arc should be assessed according to IEC 61482-2, which includes specific design requirements plus performance requirements and test procedures for the assessment of fabrics and garments against an electric arc.

Physical tests

Physical tests common to all three standards include dimensional stability to washing, tensile strength, tear strength and seam strength. Within EN ISO 11611 and 11612 there are also requirements for the burst strength of knitted fabrics although strangely there is no requirement given in EN ISO 14116 for burst performance. Table 2 shows the various test methods and minimum strength requirements for textile and leather materials.

Experience has shown that the most challenging test in Table 2 is the tear test. Some fabrics fail to achieve the minimum 20 N required for ISO 11611 welding garments or sometimes even the 15 N requirements in EN ISO 11612. One possible reason is the greater number of cleaning cycles sometimes used now during the pre-treatment for these garments and fabrics. All of the physical tests in Table 2 must be carried out after the pre-treatment specified by the manufacturer. For example, Table 3 shows the tear strength results for one fabric after five and then after 50 washes. Note that these physical tests, whether on leather or woven fabrics, are tested? in the two principal directions (e.g. warp and weft for woven fabrics and two directions at right angles to each other for leather).

The fabric in Table 3 meets the tear strength requirements for EN ISO 11611 after five washes but fails to meet the tear strength requirements for EN ISO 11611 after 50 washes. Clearly not all fabrics used in garments intended to protect against heat and flame are susceptible to such a drop in tear strength due to laundering but it is clearly a risk for some. For fabrics at risk of this effect (mainly those with a cellulosic content) some initial screening of tear test properties before the laundering process begins is advisable to determine that the tear strength exceeds 20 N by a comfortable margin (or 15 N for ISO 11612 garments and 7.5 N for ISO 14116 garments).

Note that the current standards’ revision may result in a modification (e.g. lowering) of the requirements for tear strength for textiles and may include a burst test requirement in EN ISO 14116 for knitted fabrics.

All three standards (ISO 11611, ISO 11612 and ISO 14116) also require that fabrics are dimensionally stable to washing and in addition ISO 11612 requires that fabrics, seams and components are dimensionally stable when exposed to a temperature in an oven of 180° C for five minutes. In addition, no fabric nor any component must melt or ignite. Optionally this test may be carried out at 260° C.

Finally, ISO 11611 includes a test to measure the electrical resistance of the garment fabric in order that the wearer is protected from the risk of electrical shock, a risk inherent when using certain types of welding equipment.

Garment design

Both ISO 11611 and 11612 require that the coverage provided by protective suits, either one piece or two piece, covers the upper and lower torso from the neck to the wrists and to the ankles. Other standards cover PPE for the hands, feet and face. Additional protective items such as aprons or sleeves can be tested and certified to these standards but should only be used as additional protection on top of a compliant coverall or two piece suit.

For welders’ clothing according to ISO 11611 and for ISO 11612 clothing designed to protect against splashes from molten metal, specific design features are required; for example, cover pockets with flaps except for vertical side pockets below the waist and behind the side seam, and ensure no upward facing seams are present.

The coverage and design requirements in EN ISO 14116 are somewhat less onerous. Perhaps the most important requirement is that Index 1 materials (e.g. basically those materials which sustain holing in the flame ignition test) must be positioned so that they cannot come into contact with the bare skin of the wearer or a non-compliant undergarment. If a garment consists completely of index 1 material then it must be worn on top of index 2 or index 3 material.

Similarly, a multilayer garment may consist of an outer shell of index 1 material but the innermost lining, which would be in contact with the wearer, must be in index 2 or 3 material.

Testing to these standards may present a challenge to manufacturers but SATRA will be able to advise which tests are required. For manufacturers intending to supply into Europe, the products covered by the three standards discussed herein at least fall into the intermediate category of PPE as detailed inDirective 89/686. This means that before they can be placed on the EU market they must be subjected to a type examination by a notified body and CE marked.

Where the garment offers protection against certain hazards such as very high levels of radiant or convective heat, the thermal effects of an electric arc, or resistance to large splashes of molten metal they would be regarded as complex category PPE. In this case, in addition to a type examination they also require on-going testing or regular audits according to either article 11A or 11B of the PPE Directive. As a Notified Body SATRA is also able to certify such products to the European PPE directive and in the case of complex design products SATRA is able to carry out the on-going production monitoring for such garments in accordance with EC Directive Article 11. 

Published: 15th Mar 2012 in OSA Magazine

Author


David McKeown


David McKeown graduated in Natural Sciences and gained a PhD in Metallurgy at Cambridge University. After more than 40 years in welding and joining, during which time he has been responsible for research and development, marketing, quality control, customer technical service, training and examination, he is now Manager, Corporate Projects at TWI Ltd, the Research and Technology Organisation specialising in materials joining.

TWI Ltd

Granta Park

Great Abington

Cambridge CB1 6AL

Good advice on the approach to be made can be obtained from the web sites of TWI, www.twi.co.uk, and the Health and Safety Executive, www.hse.gov.uk.


David McKeown

Website:
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Phone:
+44 (0) 1223 899000


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