A fire at any of the five thousand plus telephone exchanges in the UK not only poses a risk to human life, but means potentially expensive telephone and internet disconnection for local companies and loss of business for the service provider. Meirion Buck, Senior Design and Technical Manager for Adaptaflex discusses the dangers of poor cable protection at telephone exchanges across the country.

With exchange facilities in every major UK city, featuring hundreds of high voltage cables, each containing an estimated two to three thousand wires, the potential for damage, faults, or the outbreak of fire, is clear.  A number of high-profile cases are easy to find through a quick online search, including the tens of thousands impacted when the Derby telephone exchange caught fire in late 2014. Fortunately, the early morning outbreak meant that there was no loss of life, although substantial costs to refurbish the facility and to re-establish services to 32,000 local homes and 4,000 businesses were incurred.

The threat of fire is always present in environments where a large amount of cabling is in constant use, with telephone exchanges being at particular risk due to the heat of computer equipment being operated nearby and the fact that many cable management solutions in these facilities are outdated.

Cable fires can start for a number of reasons, but an ever growing threat, especially in underground environments, comes from rodents. A chewed cable can easily impact the effectiveness of the wiring and, at worst, generate electrical short circuits and sparks that can ignite. Many telephone exchanges are located within enclosed environments that are also the natural habitat of mice and rats. The Manchester exchange for instance, is situated 115 feet underground, making the proximity of rodents unavoidable.

Preventing the ingress of dust and liquids, through conduit and fittings that are Ingress Protection (IP) rated, is also a key consideration. The impact of foreign bodies making contact with internal wiring could be another cause of electrical faults and fires, whilst water damage can cause loss of connection for landlines, as seen at the start of this year in Chester.

Taking all of these risks into account, a solid and reliable solution must now be applied; arguably to all telephone exchanges in the country. An infrastructure upgrade not only protects life and finances, but meets the on-going demand for broadband with continued advances in fibre cabling that will allow the handling of more data than ever before.

With each major city having its own telephone exchange, ensuring complete protection is a large scale operation. Our Adaptaflex team is currently assisting on an established programme of upgrades at the exchanges of a major UK telecoms provider, with a number of quick and effective solutions are being installed over the next three to five years.

The major change is to introduce new systems that prioritise the use of enclosed wiring looms. A key area of the upgrade naturally related to fire safety, where a UL94 V-0 fire rating was specified for the equipment provided. Additionally, with the large amount of exchanges that need upgrading across the country, efficiency of installation needed to be addressed.

Using the specification and other criteria, we recommended a combination of non-metallic PRCS conduit and Adaptalok ATS™ fittings, specifically the blue elastomer version as it achieves the V0 fire rating. We’ve seen a positive response to Adaptalok ATS™ non-metallic fittings due to the particular environmental constraints of a telephone exchange. For example, it has a simple ‘push to lock’ action which makes it easy to use in the tight and often dark workspaces found in telephone exchanges, particularly when they are located underground. Again paying attention to the particular environmental constraints of an exchange, the PRCS conduit was an ideal choice because of its suitability for use in confined areas, due to its Enhanced Low Fire Hazard (LFH), self-extinguishing, low smoke and zero halogen properties, as well as its good compression and tensile strength.

As access to these types of cables is often limited, in-situ checks are unlikely and monitoring of the strong threat of exposure to dirt and water could be limited. As a result, ingress protection is vital and remained a key consideration for the exchanges and the final solution. Together the PRCS conduit with ATS fittings are able to provide an IP rating up to IP69K. As a complete non-metallic solution, there is inherent resistance from corrosion, which helps reduce the risk of failure and can provide savings in the cost of maintenance.

Ultimately, changing to an internet cloud-based service, where information is stored remotely, may remove the need for outdated telephone exchanges that are situated across multiple locations. However, this would be an expensive operation which despite removing the need for wire routing, would still have its own requirements for protection via conduit and fittings. The best solution at present is to maximise the use of effective and compliant conduit and fittings that are readily available on the market.