What is the Low Smoke Zero Halogen Cable?

by http://www.fiber-mart.com

Cables are predominant components in tree structure of a digital data center, ensuring the flow of vital information from one active device to another. In order to have products that have fire resistance properties in data center, it is important to focus on each LAN or WAN component to see the standard fire compliant standards that are present in such a catastrophic scenario.
A PVC cable (made of polyvinyl chloride) has a jacket that gives off heavy black smoke, hydrochloric acid, and other toxic gases when it burns. Low Smoke Zero Halogen (LSZH) cable has a flame-resistant jacket that doesn’t emit toxic fumes even if it burns.
On the cable industry market, there are two standards that are predominant for non-PVC cables in the fire conditions:
Historically, the European product safety standards have focused on cable designs that exclude halogens in their designs. The IEC 60332-1 governs the flame retardant
grade specifications for cables for LANs, WANs and other networking products. IEC 60332-1 applies to the majority of medium and large-scale installations in Europe. It requires LSZH jackets on cables installed near places where people congregate or anywhere there is exposed wire.
U.S. standards, on the other hand, have focused on the product’s fire resistance properties and its resistance to propagation of flame during fire conditions.
The current cost-effective compound technology available for the industrial wire and cable market forces engineers to choose either excellent flame performance or halogen-free, low-smoke performance without sacrificing electrical performance.
Wire and cable insulations are generally broken down into two distinct types, thermoplastic and thermoset.
The primary difference being that a thermoplastic material will melt when exposed to high heat or fire conditions, while a thermoset material will not melt when exposed to heat, will better resist softening and degrading, and will turn to a char under high heat or fire conditions.
As thermoset materials inherently provide better emergency performance at elevated temperatures, electrical overload conditions, and better flame propagation resistance than a thermoplastic material, they are generally preferred in industrial applications, as the conductor will have a greater propensity to see these types of operating temperatures during normal operation.
The properties of a thermosetting compound are created by an irreversible chemical reaction during processing which causes the molecules to link (cross-link), thereby “strengthening” their molecular structure. While these cross-linking properties are extremely beneficial to cable performance, they also make the development of thermosetting compounds with comparable properties to thermoplastic materials more difficult and have historically presented a greater challenge to the industry.
European standards tend to focus on cable designs generating low-smoke and containing zero-halogens (LSZH) and specific electrical requirements, while the North American standards primarily focus on a combination of fire retardancy and specific electrical performance, with a high degree of emphasis on wet electrical qualifications.
The term “low-smoke, zero-halogen” describes two distinct properties of a cable compound. The term “low- smoke” describes the amount of smoke which a compound emits when burned, while “zero-halogen” describes the amount of halogens used to make the compound. Designated halogen-free cables, hand, do not produce a dangerous gas/acid combination when exposed to flame.
In Data Center cabling and specially in patching, we may find the Cat5e UTP LSZH cable that  is performance optimized with 4 balanced twisted pairs on 24 AWG insulated solid bare copper conductors. SCP Cat5e UTP LSZH cables are constructed to create a round and flexible cable for easy pulling and stripping of the LSZH jacket.
How are cables tested or what are the main functional tests that have to be passed by the LSZH cables?
Electrical performance.
Flame propagation
Smoke measurement
Certified and listed by a nationally recognized independent testing laboratory Halogen content measurement. The thermoset insulations are rated for use at 90°C wet and dry conditions.

Author: Fiber-MART.COM

eShop of Fiber Optic Network, Fiber Cables & Tools

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