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Live test for Channel Tunnel fire system 20 Jan 2015

Patrick Reynolds for TunnelTalk

A live incident inside the Channel Tunnel has tested for the very first time the patented SAFE water-mist fire suppression system. Smoke from a truck travelling by train through the North Tunnel briefly brought all services in the UK-France twin-tube fixed link to a halt.

Water-mist demonstration in Channel Tunnel, 2011
Water-mist demonstration in Channel Tunnel, 2011

A spokesman for Eurotunnel said investigators were checking for damage to the tunnel infrastructure to assess any repairs or cleaning that will be needed. Further details of the investigation are not yet available, but in 2010 Eurotunnel retrofitted the Channel Tunnel with its new “SAFE” (Station Attaque FEu – fire attack station) system as a way to minimise infrastructure damage following previous fires in 1996 and again in 2008.

The incident occurred shortly before midday on 17 January, when a France-bound freight train set off CO2 detectors soon after passing the first of two speciallly installed SAFE stations in the North Tunnel. Safety procedures called for the train to be run to the next SAFE station, where it was stopped to enable truck drivers to evacuate their vehicles and escape via the service tunnel which sits between the North and South running tunnels.

An emergency services team based in the service tunnel carried out a visual inspection of the halted train at the SAFE station. The first appraisal found no fire, but evidence of smoke was discovered. Searching truck by truck, the team found a cargo load smouldering on one goods vehicle, and a section of the SAFE station’s water-mist system was activated to douse it.

Meanwhile, supplementary ventilation evacuated smoke and CO2 to a ventilation shaft. Other trains were prevented from entering the 53km long Channel Tunnel, while those already running inside were run to the nearest portal.

Damage caused by the 1996 freight shuttle train fire
Damage caused by the 1996 freight shuttle train fire

Late on 17 January safety inspectors entered Interval 4 to study the train. Overnight, the South Tunnel was gradually brought back into service, and then part of the North Tunnel – Interval 2. The following day a convoy removed the damaged train out through Interval 6 – to France – and then that section was also brought back into service.

Details of the investigation of Interval 4 and remedial works required have yet to be released.

The two SAFE stations in the North Tunnel are located near the ends of its 17km long central section – Interval 4. The South Tunnel has two SAFE stations similarly positioned on the opposite side.

Eurotunnel retro-fitted the four SAFE stations in 2010 to its own patented design, at a design and construction cost of about €20 million. Each station is a self-contained “fixed fire fighting system” (FFFS), and comprises 29 smaller sub-sections that can be individually activated to douse the problem part of a train. Each section is 30m long and equipped with Fogtec patented nozzles to produce a high pressure micro-mist from both sides of the tunnel and from above.

The system works by suspending small droplets of water in the air so that a two-dimensional fire-fighting system effectively becomes a three-dimensional one. As soon as the droplets hit the fire they vaporise, absorbing a lot of heat and energy in the process. As the mist continues to be absorbed, the fire is suppressed.

The last fire – in 2008 – also affected the North Tunnel, but in Interval 6 about 11km from the French portal. After a four-year insurance claim process that only ended in 2012, Eurotunnel settled on losses of €253 million for the 2008 fire. In 1996, the first fire in the Channel Tunnel damaged part of the South Tunnel. Severe damage to tunnel concrete in each case involved major repair works.

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