Fire Fighting Design of Shanghai Metro Station

出　　自： CECS-TC24 and CCES-WWE-P United Annual Conference & Academic Exchange Between CP — IAPMO Technical Papers, May, 2001, Shanghai, p113-117.
发表时间： 2001-5

Gao Naiyun Peng Haiqing Fan Jinchu Deng yang
School of Environmental Science and Engineering,Tongji University,China
Add: 1239 Si Ping Rd.,Shanghai, Zip Code: 200092
Fax 021-65986786 Tel 021-65982691; 021-55057579

Abstract The purpose of this article introduces characteristics of fire fighting design of Shanghai Metro Station, such as, the principles of fire fighting design, hydrant system, water screen system, sprinkler system, full automation and submerge chemicals system, use of pipe material, meaning of leak current, measures of preventing it and otherwise in detail.

Keywords Subway station Fire Water Supply Subway fire fighting

A bid for design of Shanghai Metro Line One was invited in the summer of 1987. Then construction of Shanghai Metro reached a practical stage, including some works such as the feasible studies, etc. There are usually two floors in the subway station (the upper floor is the concourse and the blow one is the platform), which is as same as the stations of the other countries in the world. The station and the tunnel form a half - closed construction work. After the station put into operation, all kinds of electric equipment is serried and the passengers are crowded in the station. Once a fire disaster happens, the temperature in the tunnel will increase rapidly, the smoke becomes thicker and thicker, the passengers are too difficult to be evacuated, and fire fighters can‘t be easy to enter there for fire control. It will bring a great loss for the people‘s lives and property. Fire is the greatest disaster in the subway station according to the related reports. So fire-fighting design is viewed as a very vital work and fire control must be designed as an integrated system. There is no "Code for Subway Design " inland when Shanghai Metro Line One was in the stage of design. At that time, according to design experiences of subway stations in Beijing, Hongkong and foreign countries, it was decided that gas fire-extinguishing system was set in important equipment rooms of the station, such as the control center, the power distribution substation the communication equipment room and signals equipment room, etc. At the same time, it was decided that water screen system was set at the entrance of stair between the concourse and platform, hydrant system was in the other places, and sprinkler system was in concourse, which would be as a shop. But when designing stations in Shanghai Metro Line Two, the water screen system was canceled because of promulgation of new related codes and the others were same as Subway One‘s.

1Principles of Fire Fighting Design
· Fire fighting design of subway stations follows the principle — "Precaution must be the first, precaution and fire fighting must be integrated."
· Fire demand of water is decided according to one fire point at the same time along the subway.
· All water sources come from city water supply network and there are no reserved water source.
· Outlay of hydrants assures that, at the same time, two hydrants‘ water columns can reach wherever a fire happens.
· In the station, fire water pipes are detached from domestic water pipes and process water pipes so that fire water pipes are a independent and secure system.

2Fire Water Source

Fire water source directly comes from city water supply network without fire cisterns whether in Shanghai Metro Line One or Two. Fire pumping station is set up respectively in every subway station in order to reach fire pressure. Two-way service pipes should be considered in the design of subway station in principle; that is to say, two sources come from different city water supply pipes. But, in fact, there is only one water pipe can be as the source of fire water pumps near some subway stations. The pipe is usually a part of city ring pipeline. A valve is installed on the pipe and two service pipes come respectively from before and after the valve. Once there is something wrong with the source when a fire happens, close the valve and still guarantee one fire water source.

3Hydrant System

Basically, designs of the hydrant system are same between Shanghai Metro Line One and Two. Hydrant water supply is along all the line. The protected area of every station includes itself and a half line before and after itself. At the same time, a station is assured to supply fire water when there is something wrong with fire pumps of neighbor stations.Hydrant system fire flow is 20l /s. The flow of a squirt gun 5l /s. The shortest water column ≥ 10m . The space between fire hydrant boxes ≤ 50m in the concourse and ≤ 30m in the platform.　The types of fire hydrant boxes in the Shanghai Metro Line Two are listed in table 1. Type Ⅲ fire hydrant boxes are mounted at entrances but not less than two entrances in every station. The hydrant boxes are used only as fire brigade inlets.

The Types of Fire Hydrant Chambers in the Subway Two table 1

Type Size (mm) Subassembly in the hydrant boxes place Ⅰ 1600x750x350 A hydrant of 65mm in diameter; a set of 19mm hose nozzle with a 25m-long hose; a set of hose reel of 25mm in diameter; a button for starting fire pump. Concourse of station; Where the length of a passage is longer than 25m. Ⅱ 1750x750x350 Two hydrants of 65mm in diameter; two sets of 19mm hose nozzle with a 25m-long hose; a set of hose reel of 25mm in diameter; a button for starting fire pump. platform Ⅲ 700x700x300 Two hydrants of 65mm in diameter without hose and hose nozzle Entrances of station

At the same time, the main pipes of hydrant system are arranged into ring pipeline. The ring pipeline in the concourse is along with the horizontal direction; the ring pipeline in the platform is along with the vertical direction. Pipes in the concourse are installed above false walls at both sides of it. Hydrant pipes in the platform of Shanghai Metro Line One are installed length ways below platform‘s boards; hydrant pipes in the platform of Shanghai Metro Line Two and The Second Phase Project of Rail Transit Pearl Line of Shanghai are fixed beside air tubes along with top boards. The diameter of the main pipe is 150mm in diameter and a valve is set at intervals of five hydrants.
Fire pumps are started or stopped by manual control in the pump station, started by button control in hydrant boxes (only started, but not stopped), are remotely controlled by station control room, and tele-monitored by fire center.
A fire main pipe is along every tunnel. Two parallel fire pipes in two tunnels between stations are connected with fire pipes in the stations by linking pipes in the station so that a ring pipeline takes place between stations and tunnels.
Two fire brigade inlets of 100mm in diameter put on above ground level (some on the wall) of the station. The municipal hydrants must exit between 15 - 40 meters away from the fire brigade inlet.
All the fire water supply pipes that go into or out of the station are considered to satisfy the demand of civil air defense.

4Water Screen System

Water screen system is only designed in Shanghai Metro Line One. It‘s at top of the stair and escalator between the concourse and the platform as a protection of separation. Once a fire happens, it separates the concourse and the platform, and prevents fire and smoke to enter into the concourse from the platform if the fire occurs in the platform and the reverse is also true.
Total water demand of water screen system is 60l /s.The water flow from nozzle of the most unfavorable point is ≥ 0.5l /s.m
The screen system adopts dry sprinkler system and type ZSY sprinkler valve, which made in China and by hand control or driving by alarm system. There is the room for sprinkler valve in every stair.
There are two water screen pumps and they are reserved each other. Water screen pumps draw water directly from city water supply pipes. Starting style of the pumps is by hand control through screen valve, is by hand control in the pump station, and remotely control from control room of the station or center room.
Water screen pipes form a ring at top of stair and escalator. A sprinkler head of the open system is made in China and installed at intervals of 1m along the three sides (the last side is closed because of the structure).
Four fire brigade inlets of 100mm in diameter are above ground level(some on the wall) with corresponding municipal hydrants.

5Fire Sprinkler System

The sprinkler system is placed in the underground market of concourse, which is built up at the same time with the subway. Sprinkler flow is 30l /s after calculation based on the formula of codes; the lowest pressure ≥ 50kPa; system operating time is 1 hour. There are two fire sprinkler pumps, one is in use, the other is reserved. The pumps draw water directly from city water supplies pipes. Sprinkler system consist of the control valve, ZSS wet alarm valve, the delay unit, the pressure switch, the water pressure alarm bell, the system test equipment, pressure meters, system drainage valves and pipes. Indication device of start/stop are in the control valve. Indicator of water flow are in the system. Automatic air valves are fixed on the top of main pipes. All of the sprinkler heads are closed, whose action temperature is 68 ℃ (red) . Sprinkler heads are fixed below air tubes and concrete installation places are corresponded with the figment in the station. Sprinkler systems are set in only some stations of Line One, but in all the stations of Line Two. In the design of The Second Phase Project of Rail Transit Pearl Line of Shanghai are fixed beside air tubes along with top, the place of the sprinkler pumps and related pipes are vacated in the majority of the stations. Sprinkler pumps can be controlled by alarm system or manual control inside the pump station, or can be remotely controlled by the control center.
Two fire brigade inlets of 100mm in diameter are placed on the ground of the station. The hydrants must exit between 15 and 40 meters away from the fire brigade inlets.

6Gas Fire Fighting System

1301 halogenated alkyl fire-extinguishing system is placed in Line One. After field survey and study, Inerge has been used in the design of Line Two. Inerge is in use in the design of The Second Phase Project of Rail Transit Pearl Line of Shanghai, too.
Full automation and submerge chemicals systems, consisting of automatic fire-extinguishing sprinkler equipment(the sprinkler system) and control-monitor equipment(control system), are set in the underground substation, center control room, the communication equipment room, the signal equipment room, the capacitor room, the high-low voltage distribution room, computer rooms and so on.
Because of absence of the code for full automation and submerge 1301 halogenated alkyl fire-extinguishing system in the course of design of Line One, the American related code (NFPA 12A -1980) was referred to. The complete set of American full automation and submerge 1301 fire-extinguishing system was expensively introduced into the subway.
Full automation and submerge chemicals system includes gas storage steel-containers, the container entrance valve, air jetting pipes and sprinkler heads. Control ways consist of automatic control, manual control and mechanical emergency control (semi-automation)
The place of fire extinguishers follows "Code for design and allocation of fire extinguishers in the building". Fire extinguishers are allocated based on "A" type of fire disaster in the middle-class danger.

7 Drainage of Wastewater from Fire Fighting

A wastewater cistern and a wastewater pump station are placed in every platform. The cistern volume and pump units are designed mostly according to drainage of fire water, besides seepage water from structure of the station. So the cistern volume and drainage capacity of pump units are above the total of fire water demand.

8 Prevention Electro-corrosion from Leakage of Current

One of duties in the subway station design is to prevent electro-corrosion from leakage of electricity in the subway station. What‘s leakage current? The subway train is driven by DC electric motor, which is supplied with 1500 v DC by a single trolley wire. The rails become back flow wires of drawing by electricity supply. As a result of electrical impedance in the rails, a voltage drop appears when drawing current enters the rails. A difference of electric pressure exists between the rails and the ground at the same time. So a leakage current appears between rails and underground structures and covered pipes. The current reaches near negative feedback point and enters rails again along underground structures and pipes. The leakage current is named as the leakage current. It can erode rails, their accessories, reinforcing steels of the underground structures and metal pipes. For prevention of erosion of fire water supply pipes and pump units, the fire water supply pipes link a 1-2meter-long insulator pipe (PVC-U pipe) which is 1.5m far away from the main structure body of station before fire water supply pipes enter into the concourse. The insulator pipes are in the place that is in dryness and easy for examination and repair. The pipes that cross the rail bed use plastic insulator pipes.
Rubber units of Insulate against vibration use as insulators for protection of pumps. A short insulator pipes are fixed in effluent pipe as an insulating way between pipe system and pump units.

9Pipe Materials

1) Fire water supply pipes(diameter ≤ DN100) adopt galvanizing steel pipes with screwed connection.
2) Fire water supply pipes(diameter > DN100) install seamless steel pipes with flange connection.

10Discussion and Suggestions

1) In design of Shanghai Metro Line One, water screen system is as a method of separation and protection at the top of stairs and escalators between the concourse and the platform. As experiments test, water screen can prevent the fire to spread and separate the concourse and the platform completely. At the same time, passengers search water for a feeling of security to be on fire psychologically so that they often hurried toward the entrance of stair with water. Obviously, the water screen system will help passengers to disperse and make passengers have the hopes of escaping with their life. So it‘s suggested that the water screen system should be set at the top of stairs and escalators between the concourse and the platform in the design of subway station.
2) There were no hose reels in the fire hydrant boxes in the design of Shanghai Metro Line One. It won‘t be disadvantage for the initial phase of fire fighting.
3) Sprinkler systems should be set not only in the concourse but also in the platform so that there is enough security for business development in the future in subway station. Though it‘s feasible that the room for prospective sprinkler pumps is left, it will be more difficult and more expensive to install these pipes in the future.