Secure cable management in the spotlight

Richard Rands (pictured), UK Product Manager, Fastenings & Fixings from HellermannTyton, explains why secure cable fixings are essential for tunnel safety.

In April, an underground fire in London’s West End led to 5,000 people being evacuated from the Holborn area, with businesses and homes left 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 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.

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 decision makers can specify and seeking out products that are, for example, London Underground (LUL) approved for fire safety is one way to ensure safety and reliability.

Enclosures

Enclosures housing electronic switchgear ensure the safety of third parties, often pedestrians, as well as the protection of utility works and equipment. When an underground enclosure fails, for example, due to a broken cover or cracked sidewall, a utility is exposed to potential liability in addition to any repair and replacement costs and in extreme cases can pose a risk to the public. To minimise these issues and to ensure the reliability of the system, specified underground enclosures, such as ATEX, will help guarantee system integrity over the long run.

Most suppliers offer a choice of materials including mild and stainless steel which can provide flexibility of choice according to the environment conditions, with self-extinguishing materials also a consideration. In each case a risk assessment should identify what hazard exists and the next steps in managing these conditions. The use of ATEX compliant products within such environments is one of the ways of reducing the likelihood of ignition and the danger of an explosion. Protecting cabling systems and high risk installations via enclosures is crucial.

Identification

Using cable management solutions to identify wiring, long-running cables and components is vital. Clear identification aids future maintenance and reconfigurations, as well as providing reassurance to those responsible for health and safety. Without the correct identification on the cabling systems, risk is increased to those handling installations, readability can be affected and health and safety regulations may not be met. Choosing the right material to withstand extreme environments is therefore crucial.

A Thermal Identification Printing System, or TIPS, makes it possible to have multiple lines of text with images and even bar and QR codes, and with the accompanying software, creating data tables that consist of hundreds of automatically sequenced idents takes just seconds. A system such as this is ideal for utilities companies that have large scale, regular cable or component identification projects that would benefit from having their own on-site printing capability due to the complexity and variety of their identification needs, including underground cabling. TIPTAGs are ideal for easy and convenient identification as they are clearly visible, resilient and can be fastened with cable ties with ease. This type of identification provides resistance to chemical, fire and other potential risks.

For those seeking to mark a variety of cable sizes and find an even simpler way to apply information, heat shrink tubing is an option to consider. Essentially printable sleevings, the tubing significantly reduces costs by eliminating the need to make up legends using individual cable markers and the tubing shrinks to fit around cables and wires to become a permanent marking. This once again ensures no tampering or removal and provides a safe way to avoid human error. It is advisable to use a product that has a good resistance against solvents and chemicals, as this will ensure cables and wires remain properly identified in a range of environments.

Insulation and protection

Heat shrink tubing offers unique and specific properties that provide essential protection against mechanical, environmental or electrical effects within a multitude of applications. Used in sensitive sectors such as rail, utilities and aerospace, the development of high performance cross linked polymers from polyolefin, polyesters to elastomers can produce heat shrink tubing and shapes to meet a whole spectrum of specifications and cable management needs.

Heat shrink products can be found in most applications where there are cables and wires, with the tubing providing insulation, protection and, in some cases, cosmetic enhancement. However, when talking about protection it doesn’t just mean against the elements; heat shrink tubing can insulate in extreme environments in aircraft, boats and military vehicles, and can also provide a barrier between cables and corrosive chemicals, as well as providing easy identification.

Used in a variety of applications, heat shrink tubing is, in most cases, easy to apply and work with, particularly as it can be used across a spectrum of industries, unifying cables and wires and can even be flame-retardant and halogen free depending on the type of tubing. Unlike other traditional methods, the tubing also retains its shape and does not falter with age or use. The maximum diameter of a cable bundle and the temperature range required for the application are both important factors to consider when choosing heat shrink tubing.

An additional benefit of heat shrink tubing is its ability to work in extreme temperatures between -55°C and +225°C, which again is ideal for arduous and unpredictable environments. Halogen free tubing is an essential requirement when assessing and installing underground cabling, heat shrink tubing offers other benefits include being waterproof, durable, protective against impact and able to withstand exposure to environmental elements resulting in all components being highly secured.

There are many important considerations to think about when it comes to underground cable management. Some of these include understanding failure when it comes to conditions and stress factors, the physical limitations of cable fixings and mounts, the environmental conditions that installations are exposed to and the initial design of a cable system. When these concepts are understood, installers will have a good base knowledge for underground cable management.

www.hellermanntyton.co.uk