Factors to Guide You in Selection of Right Fire Cable for Successful Operations

                            If a fire breaks out, fire cable play a critical role in supporting the emergency and building critical systems, allowing for the safe passage of occupants out of the building and allowing for shutdown procedures to take place. Emergency lighting, sprinkler systems, extraction systems, smoke dampers and shutters, emergency generators, pressurisation fans, emergency voice communications, and fire alarms are all applications where a fire cable would be specified.

Depending on the cable's construction, insulation such as magnesium oxide (Mgo), MICA tapes, and polymers are used to protect the solid or stranded conductors. The insulation is then shielded by an outer sheath, which is typically made of copper, steel wire armoured wire, or a fire-resistant polymeric sheath, each of which performs differently under fire conditions.

To meet the requirements of a fire  cable, the construction must adhere to the Australian Standard applicable to the type of fire cable.

All standards differ in terms of the time and temperature at which the cables are tested under fire conditions. These can range from a 30 minute cable tested at 830oC  to a three hour cable tested at 940oC.   All of these standards should reassure specifiers that the chosen cable will continue to function in the event of a fire.

How to choose best Australian Cable

We all know that fire is a dynamic force that moves, expands, and changes the shape, size, and properties of everything it touches. Testing for a true fire scenario would include the risk of flashover, falling debris during the fire (including directly onto the cable), and water exposure from a sprinkler system or fire hose.

The Australian Standards contain good examples of test scenarios. For example, tests on cables larger than 20mm requires direct impact testing as well as jet water pressure testing on a single sample. Another example is,  tests on cables under 20mm, which requires a three-hour fire test that could simulate trapped residents in a tall building or petrochemical leaks in a refinery. In these scenarios, safety-critical equipment may be required to operate for several hours.

Znergy cables, on the other hand, believes that there should be a single test for better fire-resistant cables. If a cable is required to function in the event of a fire, regardless of size or construction, each single cable sample must pass a true fire scenario test.

Changes that recognise polymeric fire  cable may not survive direct impact during a fire have been welcomed. It states that all non-armoured fire-resistant cables must be installed inside fire-resistant conduit, which adds complications and costs. For example, the conduit facilitates the movement of smoke from the source fire to other parts of the building – this smoke is toxic, making it much more dangerous when inhaled, and explosive around even the smallest spark, easily resulting in fire spread rather than containment. This has huge implications within hazardous areas, especially when building zones are segregated as non-explosive and explosive, in some cases simply by a fire wall.

Most fire cables use polymers or tapes to increase their fire resistance, but these materials can burn away at temperatures as low as 80oC, exposing the critical conductors. In order to give some soft skinned polymer cables flame retardant properties, halogens such as chlorine, bromine, and fluorine are added to the outer sheath. When these halogenated polymers are exposed to fire, they emit extremely toxic halides. This smoke not only restricts breathing, but it also increases the risk of inhaling it when following the standard rules during a fire. During a fire, it's best to get low and crawl along the ground until you find the nearest available exit. According to our own investigations, which are documented on our website, the smoke emitted by some of these cables is so dense that it falls to the ground. Our in-house testing is done on a single cable sample; imagine an installation with dozens of cables running in parallel. We also discovered that this smoke is flammable in addition to being dense.

Australian Cable Manufacturers have advocated for more stringent testing standards, as well as the introduction of a higher classification of fire survival cable, for those that can continue to power critical circuits in the event of a fire and withstand the rigours of safety systems such as falling debris, collapsing walls, fire hoses, or even the activation of high-pressure sprinklers and smoke extraction.

Australian Cables with Mineral Insulation

Mineral insulated cable (MIC) has been used commercially. It has many inherent safety and fire-resistant advantages in terms of fire performance.

It is created by wrapping magnesium oxide around copper rods inside a circular copper tube known as the copper sheath for protection, resulting in its own fire-proof conduit. And, unlike any other type of fire-resistant cable, there are no polymers, tapes, or armouring used, so this cable can operate directly in the heart of a fire and remain safe. The copper sheath has a melting point of over 1080oC, while the high-density magnesium oxide has a melting point of over 2000oC. The continuous operating temperatures of cables are frequently a deciding factor in selection. A bare mineral insulated cable can operate continuously at temperatures of up to 250oC, far exceeding the capabilities of any other polymeric fire-resistant cable. Mineral Insulated Cables can operate directly in the heart of a fire for more than three hours at temperatures in excess of 1050°C, while enduring direct impact and exposure to water pressures in excess of any current Australian Standard.

Because of its unique design, it does not require a conduit for mechanical or vermin protection and prevents liquids and gases from flowing through the cable. Because of its extreme tolerances, it is an ideal candidate for creating a water, air, and dust-tight seal with a fully approved mineral cable gland.

As a result, Mineral Insulated Cable is regarded not only as a fire-resistant cable but also as the ultimate fire survival cable, as it offers the greatest resistance to fire, heat, and impact damage. As a result, this type of cable is trusted to operate in the most extreme and demanding conditions, and has been installed in some of the world's most famous historic buildings and iconic structures.

With a strong emphasis on building safety all over the world, there is a growing push for more stringent inspections of buildings and the systems that serve them. According to our findings, inspecting cables that are either buried in walls or placed in conduits can be extremely difficult. Mineral Insulated Cable can be surface mounted, has its own "built-in conduit," does not degrade like polymeric cables, and can be inspected in seconds.

Throughout the construction industry, there has been a real push to make everyone in the supply chain more accountable throughout the various stages of the building's existence. How can specifiers and designers, who are responsible for product specification, be held accountable if products cannot be relied on and do not perform as advertised?

Fire Cable are an essential component of building safety, but due to a lack of understanding about their importance, inferior cables are all too often installed. We are working hard to educate the market on the advantages of specifying fire survival cables like Mineral Insulated Cables. In an era of increased accountability, there should be no wiggle room, and as an industry, we can no longer settle for bare-bones compliance to get the job done.

Please email us at sales@znergycable.com. Visit the contact page of Australian cable manufacturers if you have any questions about fire cable.