SUBWAY VENTILATION ARRANGEMENT
As a rule, in vehicular tunnel ventilation systems, jet ventilation units (VSA, VSB types) provide ventilation in normal mode.
In case of fire or an essential excess of harmful impurities` concentration in a tunnel, fan units' automatic control systems (AV type) are activated, starting the units at maximum capacity.
The ventilation system switches to emergency operation mode and removes harmful impurities from the tunnel.
Control systems operate in automatic mode and control ventilation systems and other equipment in the tunnel as the concentration of harmful substances increases or decreases. Gas pollution detectors, which transmit the readings of the current concentration of the pollutants to the ACS, are located on the upper parts of the tunnel walls.
The tunnel ventilation system comprises:
1 fan control cabinet, designed for the functioning of the logic of the whole system and parameters` control; when the frequency converter operates.
2 power cabinets, which receive control signals from the control panel and contain the power part of the system, designed for direct start-up and regulation of the tunnel and tunnel complex operation.
The number of power cabinets depends on the amount of devices in the system (fans, gates, tubular electric heaters).Ventilation scheme of subway constructions is based on the geometry and depth of the tunnel location, the characteristics of the traffic flow, and external wind pressure. Moreover, the control systems simulate scenarios of the most likely emergencies, assess the degree of risk to people, and develop an algorithm of the ventilation system in case of emergencies.