Tunnel fans

During normal operation and especially during critical events e.g. fire, ventilation is of great importance for the safety of road users in road and railway tunnels.

Tunnel ventilation

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In normal operation the ventilation ensures the removal of exhaust gases, or damp hot air (danger of condensation) or mist. The very corrosive environmental conditions due to exhaust gases, moisture and salt place high demands on material quality and processing.

In case of fire, the tunnel ventilation has to carry away toxic, hot fire gases and smoke in a controlled manner in order to allow the affected traffic to escape from the tunnel.

in general three concepts are used: 

- Smoke exhaust through a false ceiling
- Longitudinal ventilation via the portals
- High-pressure ventilation of safety tunnels

 

False ceiling extraction:

Heat sensors located in the ceiling detect the fire location in the tunnel and open 2-3 suction flaps in that area. Large axial fans pull the smoke into the false ceiling and upwards to a chimney. Flaps and fans are designed redundantly and can withstand fire gases of 400°C and more for extended periods of time.

Longitudinal ventilation via the portals: 

Jet fans mounted on the ceiling of the tunnel create a thrust directing smoke to the portals or to the exhaust openings. Depending on the location of the fire, the jet fans can also be operated in a reversed manner. The jet fans must also be able to withstand hot fire gases for a certain time during full operation.

High-pressure ventilation of safety tunnels:

Longer tunnels are usually equipped with a parallel safety tunnel. Escape doors to these safety tunnels are positioned at regular intervals. In order to prevent the penetration of exhaust gases or smoke through the escape doors, fresh air is always fed into the safely tunnels via a high-pressure vent.