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Re: What prevents moderrn locomotives from overheating in long tunnels?
Author: Max Wyss
Date: 09-08-2018 - 01:08
There are thermal issues with electric locomotives in long (alpine) tunnels.
It has not that much to do with the heat generated by the locomotives (although the armatures may get pretty hot; the material (insulation) used in current locomotives must stand 220 °C).
The issue is natural heat; in the Gotthard base tunnel, it can get up to 55°C or so, and pretty humid. This tunnel has one of the biggest rock coverages (more than 2000 m), which causes the heat. This is also the reason why the Gotthard Base Tunnel has a ventilation system; if there were not as high temperatures in the tunnel, it would not be needed at all. The Simplon tunnel (for many years the longest tunnel of all) gets to about 50°C, and has a coverage of some 1800 m.
One of the consequences is condensation, and the armatures do not really like condensation… It gets worse in the winter, when snow melts, and the water does not get off properly, when leaving the tunnel, it freezes again, and can block suspension spring coils, for example. And with an ambient temperature 10 to 15% higher than normal, the cooling capacity of the system gets lower. Fortunately, these very long tunnels do not have steep grades (usually less than 1%).
Of course, it is much easier to insulate an electric engine (theoretically, it could be completely sealed). In any case, the Swiss locomotive builders were aware of the issues, and the design of the high performance locomotives since the 1960s at least takes care of them.
It has not that much to do with the heat generated by the locomotives (although the armatures may get pretty hot; the material (insulation) used in current locomotives must stand 220 °C).
The issue is natural heat; in the Gotthard base tunnel, it can get up to 55°C or so, and pretty humid. This tunnel has one of the biggest rock coverages (more than 2000 m), which causes the heat. This is also the reason why the Gotthard Base Tunnel has a ventilation system; if there were not as high temperatures in the tunnel, it would not be needed at all. The Simplon tunnel (for many years the longest tunnel of all) gets to about 50°C, and has a coverage of some 1800 m.
One of the consequences is condensation, and the armatures do not really like condensation… It gets worse in the winter, when snow melts, and the water does not get off properly, when leaving the tunnel, it freezes again, and can block suspension spring coils, for example. And with an ambient temperature 10 to 15% higher than normal, the cooling capacity of the system gets lower. Fortunately, these very long tunnels do not have steep grades (usually less than 1%).
Of course, it is much easier to insulate an electric engine (theoretically, it could be completely sealed). In any case, the Swiss locomotive builders were aware of the issues, and the design of the high performance locomotives since the 1960s at least takes care of them.
