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007HT switch boxes manufactured by K Controls have been selected by London Transport in a bid to improve ventilation in London Underground tube tunnels.

The temperature in parts of the London Underground has become unbearable in the summer months.

During the heat wave in 2006, temperatures underground were recorded as high as 47C.

It is estimated that 80 per cent of the heat generated in the tube is contributed by the trains; passengers only contribute about five per cent of the heat.

The high temperatures cause passenger discomfort and also threaten to damage the structure of the surrounding clay as it dries.

To provide a solution, London Transport invested in a combination of technologies, which include improving the ventilation in the tunnels.

The design concept is to cool down the tube by introducing more outdoor air during the winter at the midpoint between underground stations.

This will reduce the ground temperature surrounding the tube.

Dampers will regulate the flow of cool air into the tube.

The piston effect of the trains will then purge the warm air, which will be vented out through the pedestrian routes at each station.

The same fans and dampers that control temperature and pollution levels will play a key role in controlling the direction of airflow and smoke should there be a fire.

Emergency ventilation allows rapid removal of smoke and heat so that the tunnel can be evacuated and fire fighters can gain access as quickly as possible.

The ventilation dampers will be fitted with pneumatic or electric actuators that must be able to operate at elevated temperatures for a given time.

They have a safety feature that allows them to assume a predefined fail-safe position should the power fail.

The dampers and their actuation devices are tested to appropriate standards.

K Controls manufactures the 007HT switch boxes that will monitor the position of the dampers on this project from a remote control room.

They will be directly mounted to the damper shafts.

The 007HT has passed a formal fire test at 300C for one hour.

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