BASEC News

The Importance of Cable Certification

02/06/14
The British Approval Service for Cables (BASEC) is working with organisations across the region to raise awareness of cable safety. Dr Jeremy Hodge, chief executive at BASEC, discusses who provides advice to specifiers and fire engineers on cables used in emergency evacuation systems and why cable certification is so important, especially when lives are at risk.

To ensure the safe evacuation of a building in the event of a fire, there are a combination of active fire systems such as emergency lighting, smoke control and extraction, gaseous fire extinguishing and firefighter support systems that need to be factored in. Many of these systems require electrical power supplies and control circuitry to remain fully functional throughout a potentially serious fire that could last many hours. In a high rise building, in particular it is vital that power supplies for fire-fighting lifts, smoke extract systems and emergency lighting remain intact for a prolonged period to ensure everyone can make it out of the building safely.

There have been a number of fire-related incidents across the region- Doha Mall, a high rise building in Jumeriah Lake Towers and numerous villa fires in Sharjah – which further highlights the need for fire performance cables that are fit for use. Another problem seen is fires during the construction process, before all protection is fitted and active. These can be much more serious and special care needs to be taken during the construction phase.

At the same time, architects, engineers and designers are taking advantage of new technologies to produce more elaborate layouts, which need more effective fire performance systems.

As high prestige buildings become more complex in this way, the need for higher performance cables has been identified by a number of manufacturers. Public buildings such as hospitals, shopping centres, office buildings with atriums, sports stadiums and even some high specification residential premises all need to be using advanced fire safety engineering design approaches.

Traditional fire protection approaches rely primarily on materials choice and passive compartmentation to provide limitations to fire growth and spread. Fire safety engineering techniques allow a more open building structure, but they ensure safe evacuation in the event of a fire by a combination of traditional approaches and modern, active fire systems such as smoke control and extraction, phased evacuation, gaseous fire extinguishing and firefighter support systems. Many of these systems require electrical power supplies and control circuitry to remain fully functional throughout a potentially serious fire lasting many hours. Examples include power supplies for fire-fighting lifts and smoke extract systems. Robust fire resistant cables are needed in order to satisfy these needs, cables that have been tested under quasi-real conditions and with proven performance.

There are two main types of cable on the market. Those that, when subjected to fire, have low smoke emissions and are flame retardant, and those that are fire resistant, which will continue to provide circuit integrity for a certain period of time. While basic low smoke cables will contribute less to the growth of a fire, only those cables with circuit integrity fire resistance will provide the assurance of continuing operation.

Testing fire performance cables

Fire tests for cables vary considerably. Almost all cables, whether designed for fire performance or not, undergo a simple flame propagation test using a gas flame. Cables with special fire performance characteristics undergo one or more tests from a range of possible tests including possible severity or survival time. For example, BS 7629-1 / BS 5839-1 cables may be tested to either BS EN 50200 Annex E or BS 8434-2, and classified as standard or enhanced grade respectively, offering 30 minute or 2 hour circuit integrity.

Recently more severe fire tests have been developed to assist architects and fire engineers in achieving higher levels of safety in buildings using active fire protection such as smoke extraction systems, which rely on continuity of power supply during a fire. An example is the test method specified in BS 8491, which is referred to in BS 7346-6 (Components for smoke and heat control systems -specifications for cable systems).

BASEC is also frequently asked about ‘low smoke halogen free’ (LSHF) type cables, and the requirements for this categorisation. Again, relevant cable standards specify that two tests are used – smoke emission in a 3m cube, and corrosive and acid gas emissions in a tube furnace. LSHF does not in itself mean that there is any circuit integrity performance.

When specifying fire performance cables it is not usually necessary to specify the individual tests a cable must pass. These are listed and specified in the cable standards, so simply specifying that a cable must fully comply with, for example, BS 7846 F120, means that all the relevant fire tests included in this standard must have been passed. A BASEC approval for this cable means that all such tests have been passed and are being regularly re-checked.

This is an important fact – the third party certification of a cable means it has been independently checked!

While the cable industry has safety standards, the fact that anyone can self-declare means safety and quality are interpreted differently. For example, even if a cable is marked with only a standard number, the probability that nobody other than the manufacturer has examined that cable is high.

In the Middle East, BASEC and top cable manufacturers are working to support the work of the utilities, civil defence authorities and the Emirates Authority for Standardisation & Metrology (ESMA) to ensure that only approved cables are used in the country.

Unfortunately there have been cases where the ‘entire chain’ from manufacturer through trader to contractor has been known to cut corners. Problems commonly encountered in faulty cables include undersized copper conductors with low conductivity, non fire-resistant sheathing, and insufficient or poor quality armouring. This is then sold through unscrupulous traders at the cheapest prices. The problem is everyone is trying to save their five or 10%. When you get the end product in your hands, you may be actually looking at a serious problem without realising it.

For further information about BASEC and its work in the Middle East visit www.basec.org.uk or you can contact BASEC’s technical team directly on +44 (0) 1908 267300

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