What are halogens?
Elements such as fluorine, chlorine, bromine, iodine, and astatine are halogens and are in the seventh main group in the periodic table of the elements. They are found in many chemical compounds, chlorine for example in polyvinyl chloride. PVC, as it is abbreviated, is very durable, which is why it is used in many technical products, including as an insulation and sheathing materials in cables. Chlorine and other halogens are often added as additives to improve flame retardancy. However, this comes at 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?
Halogen-free cables, as the name suggests, are free of halogens in the composition of the plastics. Halogen-containing plastics give themselves away by the chemical elements in their names, such as the aforementioned polyvinyl chloride, chloroprene rubber, fluoroethylene propylene, fluoropolymer rubber, and a few more.
If you want or need to use halogen-free cables, make sure they are made of plastics such as silicone rubber, polyurethane, polyethylene, polyamide, polypropylene, thermoplastic elastomers (TPE), or ethylene propylene diene rubber, among others. They do not contain any health-hazardous stabilizers made from heavy metals or plasticizers, and the additives for flame retardancy are ecologically safe.
What are halogen-free cables called?
A cable is halogen-free if no halogens such as chlorine, fluorine, or bromine are used in the insulation and sheathing material of the cable or even in the heat shrink tubes, such as the PROTECT HF shrinking tube from LAPP. Cable glands, protective cable conduit systems, or connectors can also be made of plastics without halogens and are therefore halogen-free. If you need halogen-free cables and cables for direct burial, for example, you should therefore lookout for the following designations on the products:
- Chloroprene rubber
- Fluoroethylene propylene
- Fluoropolymer rubber
- Polyvinyl chloride
- Silicone rubber
- Thermoplastic elastomers
Over time, several marketable designations have emerged in the cable industry concerning the labeling of halogen-free cables. Depending on the manufacturer, you will therefore encounter designations for halogen-free cables such as:
- HFFR I Halogen-free, flame-retardant
- LSZH (oder auch LS0H) I Low smoke, zero halogen
- FRNC I Flame retardant, non-corrosive
- HF I Halogen-free
LAPP products can be identified by the letters H in the product name. This is the case, for example, with our control cable ÖLFLEX CLASSIC 110 H or, more generally, 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 manufactured to be flame retardant and self-extinguishing, halogen-free and offer high functional safety.
Why are halogen-free cables important for fire protection?
Halogens can be harmful to health. This is particularly the case when plastics containing halogens - above all PVC - burn. If a fire breaks out, halogenated hydrogens are released from the plastic. With water, such as the firefighting water used by the fire department, but also with the moisture of mucous membranes, halogens combine to form acids, chlorine becomes hydrochloric acid, fluorine becomes the highly corrosive hydrofluoric acid. Also, a mix of dioxin and other highly toxic chemicals can be formed. If they get into the respiratory tract, they can corrode it and lead to death by asphyxiation. Even those who survive the fire can suffer permanent health damage. This is not the case with halogen-free cables.
For holistic fire protection, cables should also have flame retardancy and low smoke emission. Flame protection delays catching fire and the spread of flame and promote self-extinction. Here, manufacturers are in a dilemma because chlorine and bromine are very good flame retardants and are therefore often added to plastics for cables. However, because of the health hazards mentioned above, this is controversial and only permitted where no persons are endangered. LAPP, therefore, uses materials that have a high flame retardancy but still manage without halogens.
What is the advantage of halogen-free cables?
If halogen-free cables are strongly heated or burn, they form considerably fewer corrosive acids or gases that are hazardous to health. ÖLFLEX® control cables or data cables of the UNITRONIC® and ETHERLINE® brands are particularly suitable for use in public buildings, means of transport, or generally in places where high personal / animal or property damage can occur in the event of a fire. They have a low smoke density, so they develop less smoke and make it easier for trapped persons to find escape routes.
If you need a halogen-free NYM cable, rely on our NHXMH sheathed cables, the halogen-free alternatives to commercially available, non-halogen-free NYM cables. For our control cable ÖLFLEX® Classic 110, there is, the halogen-free alternative ÖLFLEX CLASSIC 110 H.
It makes particular sense to use halogen-free cables if the longest possible functional integrity is to be guaranteed in the event of a fire. This is important, for example, in buildings where surveillance cameras are to provide images of the source of the fire. The high-speed data cable ETHERLINE® FIRE from LAPP transmits data at a full transmission rate even after two hours in the flames.
Long functional integrity even in the event of a fire
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. To designate a cable as halogen-free in the sense of the normative requirements, it is rather a matter of not exceeding certain values.
Briefly summarized, this part of the standard specifies the test equipment as well as the procedure for determining the amount of halogen acid gas generated during the combustion of the materials of cables and insulations.
LAPP cables designated as halogen-free according to IEC 60754-1, therefore, provide the user with the assurance that the tested material does not exceed a halogen acid content of 5 mg/g.
The standard DIN EN 60754 describes in part 2 the determination of acidity by measuring the pH value as well as the conductivity.
For you as a user, this means that our halogen-free cables conform to IEC 60754-2 and do not fall below a pH value of 4.3. Furthermore, the determined conductivity value of our cables does not exceed the limit value of 10 µS/mm.
As already mentioned in the advantages of halogen-free cables, the long functional integrity, as well as the unobstructed view, are often very important aspects in the event of a fire. The latter is decisive, for example, for the evacuation of people in buildings, accessibility for the fire department, or, for the monitoring systems in the case of downstream analyses of the cause of the fire.
The DIN EN 61034 standard specifies the procedure for measuring the smoke density of burning cables under defined conditions.
The smoke density of cables is expressed in minimum values for light permeability. In Annex A of the standard, calculations for fire safety can be taken from this.
In Annex B, the standard DIN EN 61034-2 makes recommendations for cases where there are no requirements in other standards. In this appendix, a value of 60% for light transmissibility is recommended as the smallest value.
LAPP products that comply with the standard DIN EN 61034, therefore, guarantee a light permeability of at least 60 % according to the described test method.