Fire & Safety
Going underground Secure cable management in the spotlight
Richard Rands, UK Product Manager, Fastenings & Fixings from HellermannTyton, explains why secure cable fixings are essential for tunnel safety.
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n April, an underground fire in London’s West End led to 5,000 people being evacuated from the Holborn
area, with businesses and homes leſt in darkness and the city’s theatres closed as thick black smoke billowed from a manhole cover. The cause of the fire, in one of London’s busiest areas, was determined as being ‘faulty electrical cabling underground’, with London Fire Brigade investigators ruling that the electrical fault damaged an eight-inch gas main, which caused the 36-hour blaze. Starting in a large service duct which carries
electrical cables, gas and water pipes beneath the street, the electrical fire proved difficult to tackle and although not directly linked with the London Underground, nearby stations were also closed as a preventative measure. Although the age of the tunnel and power installation were also a factor in this incident, faulty cabling was pinpointed as one of the main causes and so it is essential that when addressing tunnel maintenance, cable management is a high priority.
Fastenings and fixings Loose cabling and unsafe wiring can lead to a multitude of serious risks including damage to underground utilities piping, as demonstrated by the London fire, as well as tangled installations and complications if cabling is exposed to extreme temperatures or unstable environments. With all the above in mind, fixings, mounts and fastenings play an essential role in keeping cabling systems secure and safe and installers must assess the environment thoroughly before even specifying accessories. Within underground installations extreme heats and tight spaces are all problems faced by those implementing a cabling system. Therefore, it is essential that there is no loose bundling and that the fixings
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and ties are highly fire resistant and not liable to premature collapse in the event of a fire. Stainless steel cable ties are recommended as they are designed for fixing loads and cables securely in environments including underground installations, railway carriages and jet engines where exposure to extreme environments and risk is common. VO flame retardant, self-extinguishing materials can also meet the required standards for such installations.
Another point to consider is escape routes and exits, which need to meet the electrical regulations set out in the new BS7671
Stainless steel ties
ATEX M6 earth connection
Underground enclosures such as ATEX help guarantee system integrity
standard. These outline the need for cabling near escape routes to be supported by fire- resistant fastenings and fixings which are not liable to collapse in extreme heat. Cabling should therefore be supported in such a way that in the event of a fire the system should not collapse, with the emphasis on wiring systems near escape routes – in particular, along walkways and near stairways. Stainless steel products are ideal for applications that require high strength, reliability and fire resistance. Capable of withstanding temperatures of over 500°C, stainless steel cable ties and fixings comply with the new regulations and can significantly reduce the risk of loose wiring and melting trunking. However, the fixing embedded into the structure also needs addressing, so as well as the actual fastening, the installation of cable mounts and supportive elements also need to be considered. There are a wide range of options that
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