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Last month’s fire in the Channel Tunnel was severe by all accounts, but the speed at which the operators are returning services to normal has surprised many observers. Ron Alalouff investigates the background to the incident.
On the face of it and subject to the findings of continuing investigations, emergency procedures seem to have operated satisfactorily as far as getting people out is concerned, in spite of the fact that several lorry drivers had to be treated for the effects of smoke inhalation. Whether the operators of the tunnel, however, can continue with the cost, damage, disruption and impact to their reputation caused by such fires is another matter.
What do we know so far? A 10km section of one of the two main running tunnels remains closed, as investigators examined the damage caused by a fire said to be in excess of 1000 degrees C at its peak. The fire took hundreds of firefighters 16 hours to extinguish and resulted in the hospitalisation of 14 lorry drivers, some of whom were suffering the effects of smoke inhalation. So what were the fire safety measures in place at the time of the fire?
Well, the Channel Tunnel actually consists of three tunnels: two running rail tunnels, and a service tunnel which is linked to them at crossover points at around 350m intervals. In the event of an evacuation, the train stops at one of these points and staff undertake what is known as a “safety exchange”. This involves staff and passengers donning smoke hoods and waiting until the a fire resistant door is opened remotely by the control centre to enable them to cross into the service tunnel. As the door opens, positive pressure created by an emergency ventilation system in the service tunnel creates a ‘bubble’ of clean air through which people can cross into the safety of the service tunnel.
‘Airline’ procedures
In the case of trains carrying lorries, the lorry drivers sit in an amenity coach or club car during the journey through the tunnel. As such, there is only one coach to evacuate in the event of an emergency. Air inlet dampers fitted to the air conditioning are designed to close on actuation of an alarm. Detection in the tunnel comes in the form of smoke, flame and gas sensors located along its length. There is no suppression system as such, though a water main runs along the length of the service tunnel for firefighters to use. There are also unspecified detectors fitted on the trains themselves.
An investigation into the 1996 fire by the Channel Tunnel Safety Authority found, among other things, that:
– The fire had grown from around 1.5MW before the train entered the tunnel to 10MW by the time it came to a halt, producing large quantities of smoke.
– When the train stopped, the smoke moved forward engulfing the amenity or club coach and the fire may have grown to as large as 50MW. Conditions in the coach were then untenable and immediate evacuation was essential.
– A supplementary ventilation system, which should have been holding back the heat and smoke by this stage, operated too late. By the time it did, the fire could have been as large as 350MW for a short time.
– As well as filling the tunnel in its wake, the smoke spread across the open crossover and through the pressure relief ducts to affect the opposite running tunnel, causing problems during evacuation.
Remedial action
The recommendations of the report were all addressed, mostly in the form of operational and procedural changes, although some technical developments were implemented. As for last month’s fire, a spokesman for Eurotunnel, the operators of the Channel Tunnel, told FSE there were robust procedures in place and staff were highly trained to deal with such incidents, having gained experience in blackout conditions in a smoke simulator, so they “can do it with their eyes shut”. Responding to reports of some of the lorry drivers complaining about the evacuation process, he said there would have been “airline-style emergency response instructions to prepare to evacuate and to put on smoke hoods”.
He went on to say that safety measures were regulated by an intergovernmental commission made up of representatives from the French and UK governments. “They regulate us – they are absolutely happy that we have the best safety systems for our type of operation. Cost has never been an issue when Channel Tunnel safety has been concerned.”
But when we spoke to the Channel Tunnel Safety Authority, which is charged by the intergovernmental commission to regulate safety, they put a different perspective on the fire safety measures that are required. A spokesman told us that under UK and French law, safety systems could only be required if they were “reasonably practicable”, so the cost to the operator was a factor in such decisions. “It’s a question of proportionality,” he said.
He confirmed that after the 1996 fire, there was a feasibility study of on-board watermist suppression systems, but it was judged to be unreliable in service, expensive to maintain and delivered few benefits. After last month’s fire, however, there was little doubt that such a system would be re-examined.
One of the difficulties with something like the Channel Tunnel is that it is truly unique, and there are no well established published standards to follow. The fire safety system has been engineered, based on a probabilistic risk analysis of different scenarios and reactions. Undoubtedly, the authorities will be using data being gathered from last month’s fire to re-test some assumptions and to take appropriate action where necessary.
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Last month’s fire in the Channel Tunnel was severe by all accounts, but the speed at which the operators are returning services to normal has surprised many observers. Ron Alalouff investigates the background to the incident.
On the face of it and subject to the findings of continuing investigations, emergency procedures seem to have operated satisfactorily as far as getting people out is concerned, in spite of the fact that several lorry drivers had to be treated for the effects of smoke inhalation. Whether the operators of the tunnel, however, can continue with the cost, damage, disruption and impact to their reputation caused by such fires is another matter.
What do we know so far? A 10km section of one of the two main running tunnels remains closed, as investigators examined the damage caused by a fire said to be in excess of 1000 degrees C at its peak. The fire took hundreds of firefighters 16 hours to extinguish and resulted in the hospitalisation of 14 lorry drivers, some of whom were suffering the effects of smoke inhalation. So what were the fire safety measures in place at the time of the fire?
Well, the Channel Tunnel actually consists of three tunnels: two running rail tunnels, and a service tunnel which is linked to them at crossover points at around 350m intervals. In the event of an evacuation, the train stops at one of these points and staff undertake what is known as a "safety exchange". This involves staff and passengers donning smoke hoods and waiting until the a fire resistant door is opened remotely by the control centre to enable them to cross into the service tunnel. As the door opens, positive pressure created by an emergency ventilation system in the service tunnel creates a ‘bubble’ of clean air through which people can cross into the safety of the service tunnel.
‘Airline’ procedures
In the case of trains carrying lorries, the lorry drivers sit in an amenity coach or club car during the journey through the tunnel. As such, there is only one coach to evacuate in the event of an emergency. Air inlet dampers fitted to the air conditioning are designed to close on actuation of an alarm. Detection in the tunnel comes in the form of smoke, flame and gas sensors located along its length. There is no suppression system as such, though a water main runs along the length of the service tunnel for firefighters to use. There are also unspecified detectors fitted on the trains themselves.
An investigation into the 1996 fire by the Channel Tunnel Safety Authority found, among other things, that:
•The fire had grown from around 1.5MW before the train entered the tunnel to 10MW by the time it came to a halt, producing large quantities of smoke.
•When the train stopped, the smoke moved forward engulfing the amenity or club coach and the fire may have grown to as large as 50MW. Conditions in the coach were then untenable and immediate evacuation was essential.
•A supplementary ventilation system, which should have been holding back the heat and smoke by this stage, operated too late. By the time it did, the fire could have been as large as 350MW for a short time.
•As well as filling the tunnel in its wake, the smoke spread across the open crossover and through the pressure relief ducts to affect the opposite running tunnel, causing problems during evacuation.
Remedial action
The recommendations of the report were all addressed, mostly in the form of operational and procedural changes, although some technical developments were implemented. As for last month’s fire, a spokesman for Eurotunnel, the operators of the Channel Tunnel, told FSE there were robust procedures in place and staff were highly trained to deal with such incidents, having gained experience in blackout conditions in a smoke simulator, so they "can do it with their eyes shut". Responding to reports of some of the lorry drivers complaining about the evacuation process, he said there would have been "airline-style emergency response instructions to prepare to evacuate and to put on smoke hoods".
He went on to say that safety measures were regulated by an intergovernmental commission made up of representatives from the French and UK governments. "They regulate us – they are absolutely happy that we have the best safety systems for our type of operation. Cost has never been an issue when Channel Tunnel safety has been concerned."
But when we spoke to the Channel Tunnel Safety Authority, which is charged by the intergovernmental commission to regulate safety, they put a different perspective on the fire safety measures that are required. A spokesman told us that under UK and French law, safety systems could only be required if they were "reasonably practicable", so the cost to the operator was a factor in such decisions. "It’s a question of proportionality," he said.
He confirmed that after the 1996 fire, there was a feasibility study of on-board watermist suppression systems, but it was judged to be unreliable in service, expensive to maintain and delivered few benefits. After last month’s fire, however, there was little doubt that such a system would be re-examined.
One of the difficulties with something like the Channel Tunnel is that it is truly unique, and there are no well established published standards to follow. The fire safety system has been engineered, based on a probabilistic risk analysis of different scenarios and reactions. Undoubtedly, the authorities will be using data being gathered from last month’s fire to re-test some assumptions and to take appropriate action where necessary.