UNI EN ISO 14116
PROTECTIVE CLOTHING AGAINST THE LIMITED FLAME SPREAD
The UNI EN ISO 14116 standard specifies the performance requirements that must have the materials and the assembly of materials and limited spread protective workwear. The aim is to reduce the possibility of a garment burning when it comes into occasional and brief contact with small flames in locations where there is no significant flame hazard or the presence of other heat types. Additional requirements for garments are also specified.
What fireproof clothing protects from
Speaking of fire protection, we refer to all the measures aimed to control as much as possible the harm to people and things and to limit its consequences.
When working with open flames or the potential flame presence, it is crucial to use workwear that protects against these risks. Fireproof clothing is made of non-flammable or retardant materials that reduce the possibility of the fabric or material burning. This type of fabric is designed to resist very high temperatures, providing excellent protection from flames and slowing burning times.
Scope of application
Flame resistant clothing is primarily designed to protect the body from heat and flames.
Different types of fireproof clothing have specific characteristics depending on the risks to which the operator may be subjected. Each type is regulated by additional standards that further specify their performance characteristics. They are:
- Aluminized heat-resistant work clothing;
- Work clothing for forest and/or vegetation fires;
- Protective clothing for welding and related processes;
- Workwear for firefighters;
- Workwear for Oil & Gas operators.
General Requirements for Flameproof Clothing
According to the UNI EN ISO 14116:2015 standard, the protective clothing related to this standard must be flame retardant, therefore non-flammable or delaying or reducing the possibility of combustion so that it burns and can become dangerous for the operator.
This standard divides garments into three different categories based on specific tests:
- Category 1, the flame should not spread, should not generate flaming residue, and there should be no residual glow;
- Category 2, the flame must not spread, must not generate flaming residues, there must be no residual glow and the fabric must be free of holes;
- Category 3, the flame must not spread, must not generate flaming residues, there must be no residual glow, the fabric must be free of holes and must not show deterioration for at least the first two seconds of exposure to the flame.
A category 1 garment must be worn over category 2 or 3 clothing and cannot come into contact with the skin.
More on the EN 14116 standard
The flame-retardant textile sector has undergone significant technical-scientific developments in recent decades.
In the past, to make a fabric fireproof, especially cotton, a chromium or titanium compound was spread over it. These products act as Flame Retardant (FR), preventing the formation of tarry substances and instead favouring the carbonaceous ones which burn with more difficulty, avoiding the spread of combustion.
With time and proper analysis, it emerged that Chromium has a toxic and carcinogenic action, while Titanium and Zirconium are not very resistant to washing. The use of these elements was soon abandoned and replaced with organobromine compounds.
In the 1960s, the flame-retardant characteristics of heat-resistant synthetic textile fibres were discovered, which replaced the materials used previously. The heat-resistant properties of these fibres derive from the chemical structures of the polymers that compose them.
The Flame Retardant chemicals have the purpose of creating chemical processes capable of interfering with the combustion process of the fabric, favouring:
- The release of water or gas and diluting the gases that fuel combustion;
- The absorption of thermal energy to bring cooling to the burning material;
- The production of a resistant, non-flammable layer on the surface of the material.
Before applying the protection to the fabric, the flame retardant must be tested on a small area, just to make sure it is compatible and that will not cause any harm. The fabric under test must be thoroughly cleaned and dry before applying any flame retardant treatment.
A big disadvantage of flame retardants is that they lose their flame retardant properties with washing, in addition to the fact that it produces toxic fumes when exposed to flames.
Limit Oxygen Index
The flame retardant qualities of Flame Retardants are indicated by a number, accompanied by the abbreviation L.O.I., i.e. Limit Oxygen Index: the minimum concentration of oxygen expressed as a percentage that supports the combustion of a polymer. This is the main parameter for differentiating or evaluating the flammability of a fibre.
Considering that under normal conditions the oxygen concentration in the air is 21%, according to the L.O.I. the fibres can be divided into three groups:
- The first group includes both natural and man-made fibres, easily flammable, characterized by an L.O.I. of around 18 (cotton, acrylic, polypropylene, cellulosic fibres). Other synthetic fibres have an L.O.I. of around 22 (polyamide, polyester), and guarantee acceptable behaviour only in less critical applications (flooring, wall coverings, etc.).
- The second group includes man-made fibres, characterized by L.O.I. values between 28 and 31, which present a flame retardant behaviour. These fibres have the advantage of giving the fabrics permanent flame retardant properties, acting as flame retardants flame inhibitors. The most widespread and developed flame-retardant textiles on the market are made with these modified fibres because, with adequate reaction to fire properties, they combine costs, processability and textile and aesthetic qualities suitable for most market requirements.
- The third group is composed of fibres, defined as “heat resistant” which have L.O.I. values from over 30 to 50 such as carbon fibres, meta and para-aramid fibres and other fibres made up of condensed aromatic or cyclic core polymers. Textile products made with them, in combustion, tend to carbonize and do not emit flammable gases.
These are the raw materials for high-cost technical products, which require special precautions for production and processing: consequently, their use, which is growing significantly, is reserved for specific sectors willing to pay the price for superior performance.
Summary table of Flame Retardant materials
L.O.I. LIMIT OXYGEN INDEX
|FR TREATED COTTON||28|
|FR VISCOSE RAYON||28|
This third group includes very heat-resistant fibres such as glass and aramid fibres.
Glass fibres are used to make a wide variety of “composite materials“. They consist of two or more materials such as glass fibres and a so-called matrix, generally of resin, plastic or metal, which serves to protect the fibres and maintain the shape of the resistant fibres so that they maintain the correct orientation in absorbing the efforts.
Glass fibre has several positive characteristics such as high mechanical strength, thermal insulation capacity, resistance to temperature variations, and the effect of chemical agents and good flame retardant properties.
Aramid fibres are polymeric fibres obtained by processing aromatic polyamides. Polyamides can contain a certain number of “aromatic rings”, which is a characteristic structure of the benzene molecule consisting of six carbon atoms placed at the top of a regular hexagon and an external hydrogen atom. When the content of aromatic rings is greater than 85%, they are called aramids.
Fabrics made of aramid fibres do not melt, drip and fuel combustion in the air.
Efficiency tests against heat
The DuPont Group has developed two test methods that measure the level of thermal protection offered by a fabric or garment: Thermal Protection Performance (TPP) and Thermo Man.
With a Thermal Protection Performance test, the fabric is subjected to a realistic fire condition with combined radiant and convective heat. The test consists of measuring the time and amount of thermal energy per surface area required for the temperature on the back (inner) surface of the fabric to reach a level that would cause a second-degree burn. Dividing the TPP value (cal/cm²) by the base weight of the fabric (in g/m²) we obtain the FFF factor (Fabric Failure Factor), which indicates the thermal insulation capacity of the fabric. A high FFF factor results in better thermal protection per kg of fabric. This test enables an objective comparison between materials under the same conditions, taking into account the protection/weight ratio.
The Thermo Man test is carried out on garments: the garment is worn by a dummy equipped with more than 100 thermal sensors. The garment is exposed to fire reaching temperatures up to 1000°C. This way, it is possible to simulate the fire conditions typically found in industrial accidents in order to verify the protective efficiency and integrity of the garments.
Washing and maintenance
Here are some tips to maintain the flame-retardant characteristics of this type of protective clothing:
- The garments can be washed or dry-cleaned using conventional methods without altering their flame-retardant characteristics;
- It is recommended to wash the garments at 60°C and always follow the washing recommendations provided by the garment manufacturer;
- The washing cycle must not last more than an hour;
- It is important to rinse the garment well to remove detergent residues;
- It is possible to use a dryer at a temperature of 60°C;
- It is recommended to use a liquid detergent with a neutral pH not higher than 9.0. If it is difficult to remove stains, they can be treated before putting the garment in the washing machine, by applying liquid stain-removing soap on the stain;
- Garments should never be bleached with chlorine or oxidizing agents and under no circumstances should they be washed with caustic agents such as ammonia or bleach.
The fibres of the future are mainly two: polyamide-imide fibres (P.A.I.) and polybenzimidazole fibres (PBI).
P.A.I. have high mechanical strength, good abrasion resistance and low thermal expansion (up to 250°C). They show dimensional stability to heat and resistance to extremely high temperatures.
They have excellent radiation resistance and are applied in high-tech equipment, electrical components, gaskets, etc.
PBI competes with Kevlar fibres and presents:
- High resistance to chemicals and solvents;
- It is incombustible;
- Excellent friction and wear behaviour;
- Good dielectric (electrostatic field) and electrical insulation properties.
These fibres are used to make suits for astronauts, firefighters and especially in gloves to protect against direct contact at high temperatures.
They have a high cost and in order to lower the price, without compromising performance, it is thought to use it together with other fibres with similar characteristics (e.g. Kevlar).
Generally, a flame-resistant garment (intrinsically or with a chemical process) is associated with carbon fibre, giving it anti-static properties.
Safety in welding
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