INTRO: Richard Hope explains why enclosure of open-sided wagons has been ruled out
RESTORATION of freight shuttle services by mid-June was announced by Eurotunnel on April 3, subject to the Channel Tunnel Safety Authority approving a package of additional safety measures. No lorries have been carried since the major fire of November 18 1996, which has necessitated two-way working in the middle section while repairs to the south running tunnel are completed (RG 1.97 p21).
The damaged lining has been repaired, and electrical and mechanical systems are being installed, putting Eurotunnel on course to restore normal working from May 16. At present, passenger shuttle and Eurostar trains are limited to two an hour in each direction. Despite this constraint, most of the demand for road and rail passengers, and for rail freight, is being met.
A summary of Eurotunnel’s internal inquiry report stresses the absence of serious injury to 31 passengers and 3 crew aboard the freight shuttle, on which a lorry of cornflakes caught fire. However, Co-Chairman Patrick Ponsolle said there had been ’avoidable delays’ in getting them into the service tunnel; as a result of changes recommended in the report ’evacuation should be completed within 5min’ of a train stopping. The Safety Authority is expected to produce its own report later this month, and a French judicial inquiry into the cause of the fire is proceeding; sabotage has not been ruled out.
The train stopped at 21.58 with the club car opposite the door of a cross-passage into the service tunnel, but the passengers could not escape for 25min because the loco and club car were enveloped in dense smoke. This entered the club car through small openings, and when the Chef de Train opened an external door briefly.
The reasons for the delay were failure by the Railway Control Centre at Cheriton to interpret complex smoke management rules correctly, and the inability of the train crew to identify precisely which cross-passage door the club car was opposite so that the RCC could open it. When it was finally opened at 22.21, a ’bubble’ of fresh air cleared smoke from around the door exactly as intended.
On receiving a confirmed fire alarm, Piston Relief Ducts connecting the two running tunnels were closed by the RCC. The massive longitudinal doors which isolate the two running tunnels at the crossover caverns were also commanded to close, but one door in the French cavern stopped short leaving a gap of up to 20 mm.
The door failed because PRDs in the area which should have been left open were closed, and trains in the north running tunnel were instructed to drive out at 100 km/h instead of slowing to 30 km/h near the crossover. The door drive mechanism is not strong enough to overcome forces exerted by a difference in pressure in the two running tunnels. The ’closure not confirmed’ door indication in the RCC was a key factor in delaying the full use of the Supplementary Ventilation System to blow smoke away from the club car until 22.30.
The obvious conflict between equalising pressure across the doors and closing PRDs quickly to isolate the two running tunnels has been largely resolved by a decision to keep the doors closed when the crossovers are not being used.
Once evacuation was complete, and the French team of back-up firemen had arrived, they remained in the service tunnel and took no action to fight the fire for more than an hour. By now the SVS was fully operational, as formally required, blowing fresh air towards the rear of the train to enable firemen to attack the blaze from the front.
It was during this time that most of the damage to the train and the tunnel lining seems to have occurred, with the fire being supplied by the SVS with oxygen for combustion. Not until the belated arrival of the British ’second line of response’ fire fighting team, 2h after the train stopped, was any attempt made to suppress the fire. No water was drawn from the fire main until just after midnight, and the fire was reported as largely extinguished at 05.00.
The major decision facing Eurotunnel has been whether to enclose the lorry carrier wagons, or stick with the semi-open design finally approved by the Safety Authority in 1993 after a six year struggle to demonstrate that they were not unsafe. This serious fire demonstrated dramatically that, in Ponsolle’s words, ’the Channel Tunnel is one of the safest transport systems in the world.’ As Co-Chairman Robert Malpas pointed out, this is due to the ’unique pressurised service tunnel costing £1bn’ which ’functioned perfectly’.
Eurotunnel has therefore reached the firm conclusion that no structural change to the wagons is necessary, given the extra measures proposed which will cost £20m to implement and add £1m to £2m per year to operating costs.
However, the policy of stopping a freight shuttle instead of driving out does increase the risk of damage to the tunnel and consequential loss of revenue - the total insurance bill is expected to exceed £200m. The decision of the firemen to let the train burn for over an hour has deeply alarmed Eurotunnel and its insurers. The main benefit of enclosure would be reinstatement of the ’drive-out’ policy, but detailed technical analysis has confirmed earlier conclusions that it is not viable.
Enclosure of the existing wagons would be ineffective without drastic restrictions on the weight and height of lorries. While it might be technically feasible to build new six-axle enclosed wagons with on-board fire suppression capable of carrying 44 tonne lorries, extra internal height would be required for roller shutter end doors. Even more vertical clearance would be necessary to avoid damage from over-height trailers that hit the existing wagon portals occasionally.
In all, the floor must be lowered by as much as 300mm. Reducing the wheel diameter by this amount has serious implications for maximum speed, axleload and maintenance. Buying 300 such wagons could cost £400m, but losing freight shuttle revenue for three years while they are developed makes the price tag for enclosure nearer £1bn, far in excess of any conceivable safety benefit.
Instead, Eurotunnel proposes to install six fire suppression stations within each running tunnel where a burning freight shuttle will stop, if possible, for immediate evacuation. The idea is that water sprays controlled by the RCC will cool the fire and stop it developing long enough for fire fighters to arrive. o
’The Channel Tunnel is one of the safest transport systems in the world’
TABLE: Table I. Changes made or proposed by Eurotunnel because of the shuttle fire
TABLE: Fire detection and suppression: