High-performance cable manufactured by Draka UK is ensuring that essential power is reliably supplied to the tens of thousands of fire detection and emergency lighting devices that are safeguarding the rejuvenated St Pancras International station in London and the northern extension of the new high-speed rail link between London and Paris.  Here, Kevin Morris, Draka’s Business Development Executive, describes what he says is an installation that truly defines fire safety cabling.

By any standards, the completion of the HS1 – High Speed 1 – rail link from Folkstone to London, the revitalisation of St Pancras International station and the construction of new stations at Ebbsfleet and Stratford is a major feat of engineering.   It undoubtedly pushed rail engineering science to its limits.  The final part of this £5.8 billion scheme was the northern extension, or Section Two, which completes the new HS1 – known as the Channel Tunnel Rail Link until November 2007 – from Ebbsfleet near Dartford in north Kent to St Pancras.

The project was designed and managed by RLE [Rail Link Engineering], a consortium of Arup, Bechtel, Halcrow and Systra.  CORBER – a consortium of Costain, O’Rourke Bachy and EMCOR Rail – was responsible for the construction. EMCOR Rail, a part of EMCOR Drake & Scull, was the M & E contractor for the entire project with responsibility for the design, procurement, installation, testing and commissioning of engineering services throughout Section Two.  This included the mechanical, electrical, public health, communications, fire detection and alarm, voice alarm, public address, security and fire protection installations.

The extensive fire safety solution was undertaken by the Infrastructure and Rail Services division of EMCOR.  This covered St Pancras International station, where the world famous “Barlow Shed”, in its time the largest enclosed structure in the world, was extended to more than double its length to accommodate the 18-carriage Eurostar trains, each of which is 400 metres long.  It also included the new Ebbsfleet International Station, south of the Thames, and the new Stratford International Station near the City and Canary Wharf that is central to the 2012 London Olympics transport strategy.  It also took in three new twin-bore tunnels, 29 ventilation shafts at approximately 3km intervals along the tunnels, and a number of technical buildings. 

The division’s Safety Critical Systems team was led by Peter Patrick, head of EMCOR’s fire division and a widely acknowledged expert at undertaking major infrastructure capital projects.  On this contract he managed four project managers, five commissioning engineers and more than 50 electricians, and was responsible for system design and product selection, installation, testing and commissioning.

His demands were uncompromising.  He says: “The most sophisticated fire detection and alarm system will count for nothing if it is not provided with continuous and reliable power. So, potentially, thousands of lives and £millions of assets are put at risk by specifying anything other
than the best available fire-rated cables.”  He continues: “By specifying Draka cable we took chance out of the equation.  The company’s manufacturing and quality control, and its rigorous testing regimes are backed-up by third-party approvals.  I would settle for nothing less.”

In total, Draka supplied in excess of three-quarters of a million metres of cable, utilising Firetuf Connecta, Firetuf Standard and Firetufplus Enhanced cables.  These fire-rated 0HLS – Zero Halogen, Low Smoke – cables are collectively being used to supply dependable power to the fire detection and alarm, voice alarm and public address systems at St. Pancras, Ebbsfleet and Stratford stations, fire detection and alarm systems in the three new tunnels, the ventilation shafts and portals, and lighting throughout the tunnels.

The decision to specify 0HLS cables is significant, particularly bearing in mind the huge number of passengers that use Eurostar every day.  A key feature of 0HLS cables is that they do not emit halogen gases and burn without producing large amounts of dense smoke.  By comparison, under fire conditions, the standard PVC cables used widely in the construction industry emit hydrogen chloride gas, which has a suffocating odour that is detectable in even very low concentrations.  Burning PVC cables also generate hazardous volumes of debilitating or disorientating smoke that can easily increase the likelihood of panic and make safe evacuation much more difficult to achieve.

TUNNEL CABLE SOLUTION.

The Firetuf Connecta system is specifically designed for tunnel lighting and power applications, and more than 100km of Connecta cable, incorporating no fewer than 5,000 factory-fitted sockets, was used throughout the three tunnels.  This was the largest single Firetuf Connecta installation to date.  

These tunnels comprise 22km of 7.15-metre diameter twin-bored tunnels, the 3km Thames Tunnel under the River, and the 19km London Tunnels deep beneath East London from Islington to Dagenham.   They pass through some of the most densely populated, heavily- developed land in the world; beneath 2,600 properties, seven miles of surface railway, 12 existing tunnels – including four London Underground stations – and 600 gas, water and sewage pipelines.

The Connecta cable was supplied via Custom Design Group in Cwmbran, Draka’s Connecta partner, in a variety of precise predetermined lengths between factory-fitted moulded Connecta socket outlets.  Secondary outlets to individual appliances were taken from the primary cables via moulded Connecta plugs.  This ensured the fastest possible cable installation on the project; it minimised the site labour requirement, and helped to reduce the overall project timescale.  As Connecta installations require minimal maintenance, the solution is also confidently expected to make a significant contribution towards reducing Network Rail’s ongoing maintenance and servicing costs.

The decision to select Connecta for the project was also motivated by EMCOR’s commitment to fire safety, and its determination to install only the finest quality, third-party approved cable, to ensure circuit integrity under fire conditions.  Thanks to Firetuf Connecta’s superb fire performance, lighting in the HS1 tunnels will continue to function if any section of the circuit is involved in a fire.  Firetuf Connecta is fully approved to BS 6387: 1994, in particular the C, W and Z test that is used to determine if a cable is capable of maintaining circuit integrity under different fire conditions.

ENHANCED PROTECTION.

The tunnel ventilation shafts – some as deep as 54 metres – also serve as emergency access and escape routes, and their fire detection and alarm equipment is fed by Draka’s Firetufplus cable.  This is a BS 5839: 2002 compliant Enhanced-grade cable that offers superior pliability, robustness and flame retardancy, and provides 60 minutes of fire and mechanical protection, followed by 60 minutes of fire, mechanical impact and water protection, exceeding the requirements of Clause 26.2e of BS 5839.  This ensures that the electrical circuit’s integrity is maintained, even in the event of a fire.  The BASEC [British Approvals Service for Cables] and LPCB [loss Prevention Certification Board] approved Firetufplus cable also satisfies the requirements of BS 7629,

The same superior performance cable is used throughout St Pancras, Ebbsfleet and Stratford stations for the fire detection and alarm systems and the stations’ public address systems. 

At St Pancras, now one of the largest transport hubs in Europe, Firetufplus links the station’s 14 Kentec Electronics’ Syncro control panels and repeaters controlling a total of 5,000 Hochiki analogue addressable optical smoke sensors, multi-sensors, heat detectors, audio visual devices and base sounder beacons.  The installation takes in the world-famous “Barlow Shed” train shed arch that spans 73 metres and is over 30 metres high at its apex.  It covers every one of the 13 platforms, six of which are around one kilometre long and are devoted to international Eurostar services.

The cable features a pressure-extruded sheath construction that provides greater protection than Standard-grade cable in the event of fire.  It incorporates spark-free cores and a 100 percent cover electrostatic screen.  Cable termination and installation is quick and easy, using 0HLS nylon or brass stuffing glands.  The cable’s pliability also makes life easier for the installer, as does the fact that it is available in long lengths.

However, selecting Draka cable turned out to offer the project more than technical excellence, as Peter Patrick explains: “At one stage in the contract, three days before a planned Easter holiday weekend opening of the temporary station accommodation, we suddenly found ourselves in urgent need of an extra 1000 metres of a particular cable.   Draka pulled out all of the stops and had the cable manufactured and delivered to site within 48 hours, which enabled us to complete the planned installation before the system came back on line.”   He concludes:  “That was typical of the service we received from Draka throughout the contract.”