Most underground cable installations are found in tunnels which are usually either roadways or railway. These tunnels carry significant cable services where the highest standard of safety is demanded. In tunnels or any application where access is restricted or limited cables must not only function, they must not aid the spread of the flame or add to the dense and often toxic smoke already being emitted from the fire. This may be a fire alarm alerting the public, emergency light to show the way out or a smoke extraction system that can continue to function and reduce the risk of overwhelming smoke & fumes. This even extends a fire monitoring system tracking the spread of a fire allowing emergency teams to plan their strategy on tackling the scenario.
It is essential that the cable specified for critical applications have ‘fire survival’ capability. That is, the ability to survive in an emergency situation to provide the power to the vital services such as alarms, emergency lighting, smoke extraction to name a few. Critical circuits must perform in a true fire scenario and may be subjected to extreme heat, direct impacts, structural movements and exposure to high pressure jets of water.
A Fire survival cable must also not increase the risk of smoke inhalation or acidic gases. MICC cables are the ONLY type of FP cable that does not require any plastics or polymers to aid fire protection. Nothing to burn means the greenest, smoke free cable can increase visibility and reduce the risk of inhalation of smoke or acidic gases in places such as railways stations, underground tunnels and even rolling stock.
This may be a fire alarm alerting the public, emergency light to show the way out or a smoke extraction system that can continue to function and reduce the risk of overwhelming smoke & fumes. This even extends a fire monitoring system tracking the spread of a fire allowing emergency teams to plan their strategy on tackling the scenario.
British Standards are used to identify a cable that is fit for purpose. This would include ENHANCED fire performance, exposure to scenarios such as water and mechanical impact must be considered. As these cables are usually low voltage they would fall under the category of 20mm and under.
It’s not commonly known that typical standards such as BS 50200, BS 8434 & BS 6387:2013 C, W Z do not perform any direct impact on the cables during testing. The water tests is often referred to as a spray and the flow of water pressure can be less than 0.4 litres per minute ( a standard fire hose is generally greater than 650 litres per minute).
The standards also allow a new length of cable to be used for each category of testing. Therefore, for a cable to pass categories C, W and Z of BS6387, three separate lengths of cable are used. This brings an element of uncertainty as the questions are often asked how do we know the cable will survive all three in the unlikely event of a real fire?
On the evening of 18 November 1987 More than 150 firefighters and 30 fire engines were called to a blaze at King's Cross underground railway station in London. The tragic event saw 31 people lose their lives where exposure to smoke and fumes were found to be the main contributor to the high death toll. The disaster drew global attention to the risks involved to people and equipment exposed to fire in an underground environment.
The investigation that followed emphasised the importance of fire survival cable that satisfies vital safety criteria in underground installations built for the transportation of people.
THE CRITERIA COVERED THE NEED:
• To guarantee resistance to extreme destructive temperatures.
• To include fire-resistant materials that minimise the emission of toxic fumes and smoke.
• To allow people more time to escape.
• To enable the operation of emergency systems which facilitate safe and rapid evacuation.
LONDON UNDERGROUND LIMITED TEST FOR FIRE SURVIVAL CABLES.
In a true fire scenario, cables have to survive not only the extremes of high temperature, but also the impact from falling debris together with water and foam exposure. In the resulting aftermath of a fire, a cable may be required to withstand bending, impact and water immersion whilst remaining operational for several hours. In order to satisfy one of the most globally recognised standards, London Underground devised a test for fire survival cables. The aim of the tests was to extend the conditions of BS 6387 to recreate a realistic fire scenario. This test involved fire, thermal shock and DIRECT impact on the cable sample. ONE WMC sample underwent all the following tests continuing to maintain circuit integrity throughout the true fire scenario test.
The unique fire survival capabilities of Wrexham Mineral Cables are demonstrated by the fact that we actually tested our cable for all three test scenarios on one single cable sample.
Mineral insulated cable is unique in construction and does not need to be placed in expensive conduit for additional protection. In many cases MIC cables can be up to a third in size compared to a SWA cable - the only other type of fire performance cable that may not require conduit for added mechanical protection.
Mineral Cable can be surfaced mounted or buried and will not degrade over time. The life span of a mineral insulated cable when installed correctly can pass 50 years. In some cases, TEN times that of a polymeric fire resistant cable.
The quality and reliability of Wrexham Mineral Cables is recognised worldwide and throughout the electrical industry. Our cables are manufactured to meet British and European standards, achieving endorsements & certifications from many regulatory bodies including BRE - LPCB, the world renowned approvals body for fire performance products. Our LPCB product approval register has been maintained for over 25 years, one of the longest in Europe for any fire performance cable manufacturer. Our Quality system is also approved to ISO9001 through LPCB and our entire facility is run in accordance of ISO9001 Quality system standards.
BS5839-1:2017 Enhanced to Clause 26.2 BS EN 50200:2015
BS 8434-2:2003 + A2:2009 BS 8591 & BS 8491 CAT C BS6387:2013 C,W & Z BS 60331
The termination glands are ATEX EExd & IECEx approved to EN 60079 for use in potentially explosive atmospheres under the ATEX Directive 2014/34/EU.
For over 30 years we have manufactured in the UK, more than 180 million meters of MICC with ZERO failures in the field. With this impeccable record you can have complete confidence in our 30 year warranty cable system.
WMC project portfolio extends to many rail and underground rail sites. The WMC fire survival cable system will neither be obtrusive nor disfigure the appearance of a railway station/tunnel. In recent years WMC have worked with consultants and created bespoke colours of our MICC Cables to aid cosmetic appearances of railway lines and stations.
For further information on how WMC can help with your electric and data cables, please contact us