Metro ventilation system

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Metro ventilation system

Khlystova E.V.

INTRODUCTION

Underground transport and rail systems become more and more frequent as they allow rapid transit times while transporting a large number of users. The network of high speed trains and also standard rails are more and more transferred to underground tunnels in order to mitigate the environmental impact.

Both applications need ventilation rates. In Metros the influx of a large number of people and the presence of moving trains generate a reduction of oxygen and an increase in heat and pollutant. Mechanical ventilation is then required to achieve the necessary air exchange and grant users of the underground train systems comfortable conditions.

Ventilation systems have a second and even more important purpose. That is to guarantee safety in case of fire emergency. In order to create a safe and clean environment for escaping mechanical ventilation both in tunnels and in the stations is activated. In rails the ventilation of tunnels is mainly dedicated to fire emergencies where it is vital to keep under control the smoke propagation and create safe areas and clear environment for the users.

VENTILATION SYSTEM OPERATION

Special vent shafts ensure natural, forced, supply and exhaust ventilation of undeground metro facilities. Construction of ventilation in metro due to three types of ventilation systems:

? permanent, it works on a regular basis;

? temporary;

? emergency, it works on emergency situations: fire, smoke, toxic substances in the air.

Metro ventilation system can operate in supply or exhaust mode.

When ventilation system works on the inflow mode, it pumps a clean air stream in the metro, at work on the hood mode, it exhaust polluted air from the metro tunnel

The vent shaft includes:

ventilation chamber

reversible fans

ventilation kiosk (located above the earth's surface)

ventilation trunk (connects the chamber and kiosk)

Metro vent shafts are located beside the green spaces and/or parklands, located nearby Metro stations. This placement prevents infiltration of toxic gases from outside air.

The location of the vent shafts must comply with the requirements:

Vent shaft must be located at a distance of not more than 300 m away from the tunnel. ventilation shaft transport tunnel

Door of the vent kiosk must be marked with the number of shaft.

Metro ventilation system should be equipped with protection of each facilities: network sensors respond when changing internal volume, Ray intersections. If the alarm is triggered, the control panel receives the signal "alarm", which instantly reacts to the Metro police. All vent shafts must be equipped with sensors that warn about toxic industrial emissions, chemical weapons. Upon the occurrence of such cases germinator closed.

According to the sanitary standards ventilation provides a triple air exchange for one working hour. For a full day the system is able to process up to 2 billion cubic metres of air. It's technically difficult to arrange the proper level of air conditioning.

Temperature metro premises intended for passengers is provided by the tunnel ventilation. The design of vent must comply with the existing building requirements.

In accordance with the standard requirements, tunnel ventilation design does not provide heating/cooling air equipment. The airflow entering the tunnel, has the parameters of the external environment. The heat storage features of the soil applied for heating/cooling in winter/summer period.

The temperature of the summer season in Moscow according to the design standards of ventilating metro is + 22,6°C.

Vent system is not equipped with air-cooling devices in case of higher operating temperatures. The metro stations air temperature is directly dependent on the temperature of the air outside mass supplied from the surface of the earth via the ventilation system shafts. The volume of outside air supply must to reduce due to the rising day temperatures, so as not to overheat the metro station, and ventilate it as much as possible at night.

Vent system in the metro can not do without such elements as the Exhaust. The main function of the Exhaust is airing of battery metro substations and service areas. Exhaust kiosks are smaller than ventilation kiosks and different from ones. They quite often are close by.

VENTILATION SYSTEM DESIGN

The provision of adequate ventilation is a key factor in the design of complex transport systems, road tunnels and rail tunnels. In general different criteria apply to different modes of operation; all the criteria for all the operational modes must be satisfied for the design to be acceptable. Fundamentally, the system has to control smoke propagation, provide a smoke-free evacuation path during a fire emergency and remove heat/emission generated by operation. All this in such a way that the equipment's life expectancy is not diminished and very importantly a suitable environment for passengers and maintenance personnel is provided.

While the direct cost of the ventilation equipment is small, the costs and constraints associated with ducting, plant rooms and ventilation shafts are considerable and can have a significant impact on a project. This is particularly true for longer tunnel options, where the ventilation requirements are more onerous.

Therefore a sound and viable ventilation design is of utter importance.

Design of the longitudinal ventilation:

Calculate the needed thrust inside the tunnel

Find suitable jet fans

Define the redundancy

Calculate the minimum distance between jet fans set

Calculate pressure efficiency

Verify smoke temperature values at which jet fans are subjected during a fire event.

Longitudinal ventilation is used to reach a required value of air velocity inside the tunnel.

In normal operation mode it can be used to provide the minimum fresh airflow to the passengers inside the tunnel.

In emergency operation mode it can be used to reach the critical air velocity value or to confine smoke toward an extraction point.

For metro and railway tunnels offers a wide range of axial fans, sound attenuators, dampers and grilles:

Axial fans AXC and AXR

Unidirectional (AXC) or truly reversible (AXR)

Diameters from 1.400 to 1.600 mm

Volume flows up to 150mі/s and 5.000 Pa of pressure using contra-rotating fans in series

Up to 400°C for 2h operation

Certified according to EN 12101-3 axial-mrt Sound attenuators

Cylindrical silencers with or without acoustic pod directly connected to the fan

Limited acoustic attenuation and low pressure losses

Should the system require higher attenuations a splitter silencer can be sized, the splitters can be fix or moveable types on special rails in order to allow the possibility of easy cleaning

Aerodynamic nose of the splitters (on request) to reduce the pressure losses even more

Acoustic material fire resistance classified ClassA1 in accordance to ISO EN13501-1

Standard finish in neoprene tissue or expanded metal sheet

Structure material can be pre-galvanized, hot dip galvanized or stainless stee Dampers

Multi leaf dampers with parallel or opposite blades specially designed for underground applications

Made of hot dip galvanized steel after manufacture or in stainless steel AISI

304L/316L equivalent to EN 1.4301/1.4404

Air leakage less than 0.1 mі/smІ at 1kPa

Blade deflection less than L/180 at 6 kPa

Operational cycling (open-close) up to 6 million cycling

Actuators pneumatic, electro-pneumatic, spring return, on/off, modulating

Supply 230 or 400V, 50 or 60 Hz, 1 or 3 ph

The entire damper including motor can operate with hot air or smoke up to 400°C for 2 h certified in accordance to CETU/PIARC.

Supply grilles

Wide range of supply grilles made of aluminium or stainless steel

AISI304/316 equivalent to EN1.4301/1.4404

Heavy construction suitable for underground applications

Control dampers to set up the volume flow through the grilles

LIFE SAFETY

Fires occuring in tunnels or stations are very different from other types of fires; their consequences can be larger due to their situation (underground). There are several problems that are directly related to the nature of the space.

The smoke and heat produced by the fire could affect a great part of the tunnel or the station; this will have consequences for the evacuation and also for the firefighting operations. The main issue is normally the production of smoke and its possibility to spread , for complex systems the smoke strategy is very important.

For large interchange/transfer stations the evacuation strategy tends to be very complex with several levels working together, in some cases there might be several types of transportation systems within the same building (bus, rail, metro). For the majority of the cases it is necessary to understand the people movement both from a pedestrian planning point of view and from an emergency movement point of view.

For stations the compartmentation strategy is generally an important issue, a normal approach is to use virtual compartmentation (due to construction practicability and architectural design restraints) and in that way keep clear views, smooth people flows and large open spaces.

Specifically for road tunnels an active measure, with different views around the world regarding the feasibility, is the use of suppression systems. A suppression system normally has a significant impact on the fire size and heat release rate but also on the behaviour of the smoke produced.

REFERENCES

1. Kaledina N.O., Kobylkin S.S., Kaledin O.S., Kobylkin A.S. Designing ventilation in the construction of underground structures - Moscow: The Mountain Book, 2016. - 80 p.

2. Fugenfirov AA, Rusakov V.E. Ventilation of transport tunnels - Omsk: Publishing House of SibADI, 2013. -56 p.

3. Dodek, P., Keenan, S., Cook, D. et al, Evidence-based clinical practice guideline for the prevention of ventilator-associated pneumonia. Ann Intern Med. 2014; 313 p.

4. Pinhu, L, Whitehead, T, Evans, T, and Griffiths, M. Ventilator-associated lung injury. Lancet. 2003; 361: 340 p.

5. Makovsky LV, Trofimenko Yu.V., Evstigneeva N.A. Ventilation of road tunnels Tutorial. - M .: MADI (GTU), 2009. - 148 p.

6. Fomichev V.I. Ventilation of tunnels and underground structures - St.

Petersburg: Stroiizdat, 1991. -200 p.

7. https://www.systemair.com Metro and Rail Ventilation

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