Investigation prompts SAFE fire system review 26 Mar 2015

The SAFE fixed fire-fighting system – retrofitted at a cost of €20 million to improve safety and reduce structural damage – played no role in January’s Channel Tunnel blaze, Eurotunnel has admitted to TunnelTalk.

The fire – which “completely consumed” two trucks on board the affected shuttle, and caused further damage to 12 rings of segmental lining and to the rolling stock itself – was fought only by French firefighters using fixed equipment in the service tunnel.

Detailed Channel Tunnel track layout with cross passages and Interval locations

A Eurotunnel spokesman confirmed the shuttle truck-train had been unable to stop in the SAFE station, and that when the CO₂ sensor alarm went off, the train was already in the process of exiting. It was finally stopped more than 1km farther on in the Interval 4 section of the North Running Tunnel, but now outside the range of the SAFE specialist fixed fire-fighting system. Safety protocols do not allow for trains to be reversed back to the SAFE stations.

Among the major contributing factors in containing the blaze so quickly were the fast decisions and actions of French firefighters inside the tunnel. On 17 January (2015), and working from two cross passages, the French team took immediate action using manual mobile systems linked directly back to pumping equipment in the service tunnel. No time was given over to a fire assessment, and instead immediate action was taken in line with operating protocols. By this time all three train crew and 38 passengers had been safely evacuated.

Channel Tunnel layout and SAFE station locations

Fewer than a dozen rings of the segmental lining required repairs as a result of the fire, said Eurotunnel, and even then only to shallow depths of surface concrete along the soffit segments. Since no structural damage was caused to the lining, the owner-operator has programmed the minor repairs required into scheduled maintenance works.

Damaged fixed electrical equipment was replaced in the days immediately following the incident and the tunnel was back at full operating capacity soon after – far more quickly, and with less structural and business impact, than that suffered during the previous major incidents in 1996 and 2008.

The SAFE system will now be the focus of reviews of emergency planning options and protocols, along with that of the capability and approach of the French firefighting systems. The reviews will also have to examine if the SAFE system should be extended to cover more of the running tunnels in order to minimise the risk to safety and infrastructure if trains find themselves unable to stop inside the current station zones.

A SAFE station can hold the entire length of a truck shuttle train. The tunnel has four such stations (two on each side) which are divided into 29 x 30m sections, each section fitted with nozzles to produce a high pressure micro-mist. Sections can be individually activated.

The 53km long Channel Tunnel has twin running tunnels – North and South – joined by crossovers caverns at points approximately one-third and two-thirds along the fixed link. Each running tunnel, therefore, has three Intervals, each approximately 17km long.

SAFE water-mist fire suppressions system demonstration

In 2010 Eurotunnel retrofitted four, standard-design SAFE stations, at a cost of approximately €20 million, into the running tunnels – placing each one a few kilometres from the ends of the central Intervals, and back from the crossover caverns. In the North Running Tunnel the two SAFE stations are located at either end of its central Interval – Interval 4. One is in the UK zone, the other in the French zone. There are two SAFE stations similarly positioned in the South Running Tunnel at either end of its central Interval – Interval 3.

Since the fire was on the French side, the latest incident is being investigated by the French Government’s Bureau d’Enquetes sur les Accidents de Transport Terrestre (BEA-TT). The UK’s Rail Accident Investigation Branch (RAIB) is working alongside BEA-TT.

In early March, RAIB issued a statement of facts that included a brief note that the SAFE system had not been deployed. This contradicted information given out at the time by Eurotunnel. A spokesman said the mistaken details had emerged as a result of confusion in briefing meetings held during and immediately after the incident.

As investigations continue, RAIB’s recent statement also discussed arcing from the catenary in relation to the fire. It said electric arcing occurred between the overhead power line and the train as it entered the UK portal to go underground. This tripped the power supply and stopped the train, which was then given clearance to restart, but at reduced speed. Further into the journey, and as the train was passing through the French SAFE station – the last in the North Running Tunnel, and some 35km beyond the UK portal – both the tunnel and on-board alarms were activated. RAIB notes that the power supply to the overhead line tripped, and as the train was already leaving the SAFE station the driver had to make a controlled stop in the tunnel.

Noting RAIB’s comment that it was “probable” the initial arcing event might be related to the subsequent fire, Eurotunnel stressed that the exact cause is still under investigation. A spokesman said: “At this stage there is no information to fix the cause of the fire, and we can only say there was arcing in the sequence of events and that we will await the outcome of further investigations.”