Halogen-free cables – how, what, when and why?
What are halogens?
Elements such as fluorine, chlorine, bromine, iodine and astate are halogens and appear in the seventh main group in the periodic table of the elements. They are found in many chemical compounds, for example in polyvinylchloride. PVC, as it is known for short, is very durable, which is why it is used in many technical products, as well as for insulation and sheath material in cables. Chlorine and other halogens are often included as additives to improve flame protection. But that comes with a price. Halogens are harmful to health. For this reason, plastics that do not contain halogens are increasingly being used for cables.
What is a halogen-free cable?
As their name suggests, halogen-free cables are halogen-free in the composition of the plastics. Plastics containing halogens can be identified by the chemical elements in their names, such as the previously mentioned polyvinyl chloride, chloroprene rubber, fluoroethylene propylene, fluoro polymer rubber, etc.
If you want to or have to use halogen-free cables, make sure that these consist of plastics such as silicone rubber, polyurethane, polyethylene, polyamide, polypropylene, thermoplastic elastomers (TPE) or ethylene propylene diene rubber. They do not contain any heavy metal based stabilisers or softeners, and the additives for flame protection are environmentally safe.
How are halogen-free cables designated?
A cable is halogen-free if no halogens such as chlorine, fluorine or bromine are used in the cable’s insulation and sheath material. Cable glands, hose systems, connectors or shrink hoses, such as the PROTECT HF shrinking tube from LAPP, can also be made of halogen-free plastics and are thus halogen free. If you need halogen-free cables, for example, please note the following product designations:
|Halogenated plastics||Halogen-free plastics|
Over time, a number of common market designations have emerged in the cable industry with regard to the marking of halogen-free cables. Depending on the manufacturer, you can thus find designations for halogen-free cables such as:
|LSZH (or LS0H)||Low smoke, zero halogen|
|FRNC||Flame Retardant Non Corrosive|
LAPP products are identified by the letters H in the product designation. For example, our control cable ÖLFLEX CLASSIC 110 H or, in general, the NHXMH sheated cables as a halogen-free alternative to the PVC installation cable NYM. Halogen-free cable glands are identified by the letters HF. The SKINTOP® ST-HF-M cable gland and the SILVYN® heat-shrinkable tubes are flame-retardant and self-extinguishing, as well as being halogen free, and offer a high level of functional reliability.
Why are halogen-free cables important for fire protection?
Halogens can damage health. This is particularly the case when halogenated plastics, particularly PVC, burn. If a fire breaks out, hydrogen halides are released from the plastic. Halogens combine with water, such as the extinguishing water used by the fire brigade or fluid from the mucous membranes, to form acids - chlorine becomes hydrochloric acid, fluorine the highly corrosive hydrofluoric acid. In addition, a mixture of dioxins and other highly toxic chemicals can be formed. If they get into the airways, they can cause damage and cause suffocation. Even if someone survives the fire, their health can be permanently damaged. This is much less the case for halogen-free cables.
For integrated fire protection, cables should also have flame protection and low smoke generation. The flame protection slows down combustion and propagation of the flame and promotes self-extinguishing. Manufacturers face a dilemma here, as chlorine and bromine are excellent flame retardants, which is why they are often mixed in with plastics for cables. However, because of the health hazards mentioned, this is controversial and is only permitted where no people are in danger. As a result, LAPP uses materials with a high level of flame protection but without halogens.
What is the advantage of halogen-free cables?
If halogen-free cables are heavily heated or burned, they form considerably less corrosive acids or gases that are harmful to health. ÖLFLEX® control cables or data cables from the UNITRONIC and ETHERLINE® brands are particularly suitable for use in public buildings, transport or in general where fires can severely injure people or animals or damage property. They have a low smoke gas density, so they produce less fumes and make it easier for trapped people to find escape routes.
If you require a “halogen-free NYM cable”, rely on our NHXMH sheath cables - the halogen-free alternatives to the standard, halogen-free NYM cables. Our ÖLFLEX® Classic 110 control cable is available in the halogen-free ÖLFLEX CLASSIC 110 H or ÖLFLEX® CLASSIC 130 H variants.
Halogen-free cables are particularly useful if you want to guarantee the maximum possible functional retention in the event of a fire. This can be important in buildings where surveillance cameras provide pictures of the source of the fire. The ETHERLINE® FIRE high-speed data cable from LAPP transmits data at full transmission rate even after two hours in the flames.
Normative requirements for halogen-free cables and connectors
A halogen-free cable that complies with the relevant norms and standards is not necessarily completely free of halogens. For a cable to qualify as halogen free within the meaning of the normative requirements, certain values must not be exceeded.
Halogen-free cables according to IEC 60754-1 or DIN EN 60754-1
In short, this part of the standard defines the test equipment and the procedure for determining the amount of halogen acid gas that is formed when the materials are burned in cables and insulated wires.
LAPP cables, which are designated as halogen free according to IEC 60754-1, therefore give the user the assurance that the material tested does not exceed a halogen acid content of 5 mg/g.
Halogen-free cables according to IEC 60754-2 or DIN EN 60754-2
Part 2 of DIN EN 60754 describes the determination of acidity by measuring the pH value and conductivity.
For you as a user, this means that our halogen-free cables in accordance with IEC 60754-2 do not fall below a pH value of 4.3. The determined conductivity value of our cables and lines is also not above the limit of 10 μS/mm.
Halogen-free cables according to DIN EN 61034-2
As already mentioned in the section advantages of halogen-free cables, long functional integrity and an unobstructed view are often very important aspects in the event of a fire. The latter is crucial for the evacuation of people in buildings, the accessibility of the fire brigade or for monitoring systems, for example in the event of secondary analyses of the cause of fire.
DIN EN 61034 defines the method for measuring the smoke density of burning cables under defined conditions.
The smoke density of cables and wires is expressed in minimum values for the light permeability. Fire safety calculations can be derived from this in Annex A of the standard.
In Annex B, DIN EN 61034-2 standard makes recommendations for the event that there are no requirements in other standards. In this annex, a light permeability value of 60% is recommended as the minimum value.
LAPP products that comply with the DIN EN 61034 standard therefore guarantee a light permeability of at least 60% according to the test method described.