What are the materials used to create Prysmian fire resistant cables?

Previously, we discussed how Prysmian fire performance cables are critical in helping to protect lives and property. The requirements of FP cables make them an essential component in public buildings, but which materials are essential in the creation of fire resistant cables?

British Standards for cable construction

British Standards for cable construction tell manufacturers what materials to use. They are specific to each cable type and serve as the construction manual for cable makers.

The Standards provide detail about conductors, insulation, wire armour or metallic protection, and the final sheath, and specify a range of parameters. These include what conductor resistance is required, the low smoke and zero halogen performance required, and dimensions.

British Standards for cable construction also provide a detailed checklist for test and certification bodies, such as the British Approvals Service for Cables (BASEC) and Loss Prevention Certification Board (LPCB).

BS 7629-1

British Standard 7629-1 ‘Electric cables – specification for 300/500 V fire resistant screened cables having low emission of smoke and corrosive gases when affected by fire. Multicore and multipair cables’, is the construction manual for the cable manufacturers of small cables that need low fire hazard performance and fire resistance.

Prysmian FP200 Gold and FP PLUS cables have been designed and tested to meet the requirements of BS 7629-1. Having third party certification provides confidence to engineers, building owners and insurers that the cables used in emergency systems meets all the necessary requirements.

BS 7846

British Standard BS 7846 ‘Electric cables – thermosetting insulated, armoured, fire-resistant cables of rated voltage 600/1000 V, having low emission of smoke and corrosive gases when affected by fire specification’, is the design, manufacture, and test manual for cable makers to provide fire resistant power cables for use in emergency building services.

This standard, just like BS 7629-1 details all material types, the physical dimensions such as conductor material and sizes, minimum insulation, sheath thickness and all the other electrical and physical tests required.

BS 7846 compliant cables are fire resistant power cables featuring Steel Wire Armour (SWA) to increase resistance to mechanical stress. Prysmian FP600s cables meet the requirements BS 7846 F120 fire test, the highest grade, making it the ultimate fire resistant, armoured cable for use on critical circuits. This means equipment associated with fire fighting or safe evacuation such as smoke ventilation, fire curtains and fire-fighters lifts can continue to work in the event of a fire.

Similarly, to FP200 Gold and FP PLUS, FP600s is BASEC and LPCB certified.

Enhanced Insudite and Insudite

Standard building cables such as Prysmian “twin & earth” cable are insulated and sheathed with Polyvinyl Chloride (PVC), which is a very effective general material for electrical and physical protection, and has a maximum working temperature of 70°C.

However, no PVC is used in any Prysmian FP cables. This is because PVC burns readily and produces toxic acid gas and thick black smoke. So, what is used for Prysmian FP cables?

Prysmian devised the original insulation materials for extruded fire resistant cables in the 1970s then in the 1990s upgraded to Insudite. This improved damage resistance of FP200 making the replacement, FP200 Gold, the market leading fire resistant choice ever since. In 2002, Prysmian launched FP PLUS to meet new fire alarm requirements for ‘enhanced’ fire resistant cables. The longer, hotter requirements allowed Prysmian to develop ‘enhanced Insudite’ and today FP PLUS is the go-to choice for large and complex buildings.

Insudite is a rugged insulation system providing the best combination of fire resistance, electrical performance and physical strength. This means it can survive the harsh environment of an active building site and also perform as expected in the event of fire long into the future.

Insudite has a tough, durable hard skin designed to be highly resistant to damage, which makes it ideal for all installations, such as in applications where there’s potential for third party damage to the cable after first fix e.g., exposed fire alarm cables prior to the installation of suspended ceilings.

Arguably, the most important component of fire resistant cables is the insulation and sheathing. It is essential that fire resistant cables are able to maintain circuit integrity in the event of a fire to keep critical systems such as fire alarms, emergency lighting, life safety and fire fighting systems going.

More information , including datasheets on FP200 Gold, FP PLUS and FP600s is available to download from the Prysmian UK website. Third party certificates on all three cables can be found in the Technical Area online.

Discover how FP cables are rigorously tested in our next blog…