Emergency Ventilation and Smoke Management July 2010

 

By
Gerard Hillenbrand, P.E.

That subject is of critical importance to all mechanical engineers, of course, but even more vital for engineers with the NYC Transit Authority, where they must ensure the safety of millions of daily passengers in the subway systems tunnels and stations. So Met Section was fortunate that the Transit Authority sent one of its principal engineers to address our July 17th, 2010 technical dinner meeting on this timely subject. That principal engineer was Robert Montfort, P.E., who gave us an overview of his organization’s emergency tunnel ventilation and smoke management systems, all of which are designed and constructed to meet the fire and life safety regulations established by the National Fire Protection Association’s standard code #130. Registered Professional engineers attending this meeting qualified to earn one professional development hour of credit toward satisfying their professional continuing education requirements.

Mr. Montfort supplemented his lecture with an impressive computerized display of the Transit Authority’s ventilation and control facilities including site plans and sectional drawings illustrating the complex designs required to satisfy the city’s very complex real estate and utility realities. Mr. Montfort holds a Master’s Degree in Mechanical Engineering and Naval Architecture and Marine Engineering from the University of Michigan. He served 27 years in the U.S. Coast Guard and retired with the rank of Captain, after which he has worked for the Transit Authority’s Capital Management Program. He is the principal Mechanical engineer assigned to his agency’s line equipment program and is the lead mechanical engineer for the 2nd Avenue and #7 Line extension projects.

Mr. Montfort began his presentation by noting that NYC’s subway system has 145 miles of route tunnels all requiring ventilation and emergency controls. This tunnel mileage is broken down into 230 sections each consisting of a ventilation facility with accompanying controls. Of these 320 systems, 14 are located in tunnels under the city’s rivers and 306 are located on land. Of the 306 land-based facilities, 204 are located close to the surface and employ some form of natural ventilation. Hence, 102 of these land-based sections require forced ventilation systems and these systems are provided by 165 individual plant installations. Correspondingly, 30 plants serve the 14 sections under the rivers. Some of the natural ventilation systems date from the IRT original construction in 1907 and utilize undersized equipment requiring upgrading and/or replacement.

The Transit Authority is concluding its seventh consecutive 5-year modernization programs with expenditures varying from $200 to $600 million in each 5-year period. The Authority upgraded and/or rebuilt 60 land-based plants during this period all in conformance with the NFPA’s code #130, which is the international standard for tunnel ventilation, smoke and temperature control. The modernized designs include construction of a single plant in each section, rather than the multi-plant systems built previously. The redesigned river tunnels still use 2 plants, one at each end. Each updated design must include a clearly defined path for evacuating passengers and ventilation equipment with the strength to contain any tendency of fires and smoke to pass backward into unaffected portions of the subway tunnels. The newly designed plants cost between $40 and $75 million.

In 1992 a fire in one of the East River tunnels caused the deaths of 2 passengers. This fire, primarily in overloaded electrical equipment, energized the Authority to develop even more stringent guidelines for tunnel design and these have been in effect since 1994. The enhanced features include computerized modeling of such variables as critical train velocities, tunnel wall types, (open, porous, and solid), smoke flow studies through complex ducting, and ventilation capacities of at least 300,000 cfm for a maximum fire generating heat energy of 50 million Btu/hr (or 14 megawatts). Each new design much consists of 2 fan installations to compensate for one being temporarily out of service. Ventilation capacity must be large enough to exhaust fires in 2 trains simultaneously, sustain a smoke removal speed of 200 feet per minute, and compensate for 50,000 CFM of tunnel leakage. Furthermore, passenger egress time must be completed in 4 to 6 minutes in the event of an 8 megawatt rated fire. Passenger visibility must be over 8 feet above the train or station floor level, and all fires must be contained within 3 car lengths of all trains. These guidelines must be compliance tested at three points within a station area.

Mr. Montfort then proceeded to describe and illustrate several completed or soon to be completed new plant installations, including:

    • The 6th Avenue subway lines from West 4th to 34th Streets. As originally constructed in two separate phases (local tracks before World War II and express tracks in the late 1960’s), this line had 4 plants at 3 different locations (2 plants for local tracks and 2 for express tracks). The upgraded system utilizes 1 plant for express traffic located at 23rd Street and 2 plants for local traffic, one at each end of the line. The new system design included tunnel wall removal and/or modification as well as trackage revisions to increase train capacity and reduce obstructions. The new 30th Street plant is particularly complex since it had to be extended below the path line and to the east to accommodate the huge volume of real estate required to house the equipment.
    • The complex interchange under 53rd Street, and northward to 57th Street on the “F” Line, required 3 plants occupying more than 5,000 square feet with extensive ducting and plenum chambers to avoid existing property rights and complex utility installations between 52nd and 53rd Streets.
    • The largest plant in the system is located at Lafayette Street in downtown Brooklyn where several subway lines converge in complex track configurations. This installation covers the largest land area and is deep enough to fit four stacked fan installations.
    • The new Jackson Avenue fan plant in Long island City now under construction to ventilate the “R” and “E” Lines as well as the expanded terminus for the “g” train at 23rd Street and Ely Avenue.
    • The new terminal for the #1 train in lower Manhattan near the Staten Island Ferry complex. This new plant provides 200,000 CFM of ventilation exhaust for the tunnel and each of the station tracks and mezzanine.
    • Two new plants are under construction along 63rd Street for the eventual connection of the “F” and “W” lines with the 2nd. Avenue subway. Design work is now being completed for stations at 72nd, 86th, and 96th Street also.
    • The new Cortlandt Street Station just south of the World Trade Center on the IRT 7th Avenue line will have enhanced smoke containment features for both trains and the station.

In the question and answer period, Mr. Montfort described how the same ventilation equipment, usually compound axial-flow fans, is used both for normal and emergency operation. The changeover facilities and techniques are confidential because of the danger of terrorist attacks but there are fast response teams strategically located throughout the system to actuate the changeover controls when necessary to change operational modes of this equipment. Mr. Montfort also referred to the computer modeling techniques involving computerized fluid mechanics and environmental simulation systems employed in the design and study processes. These computerized systems can absorb and evaluate more than 600,000 discrete local factors in arriving at optimum plant designs. He also paid special tribute to Greg Sanchez. P.E., who is the Transit Authority’s computer modeling expert for these highly technical emergency tunnel ventilation and fire and smoke management systems. We are proud to note that Mr. Sanchez is a member of the Met Section who served as Section Treasurer about a decade ago.

This type of technical dinner meeting is typical of the meetings that Metropolitan Section periodically presents throughout the year. We urge all Section members to attend as often as possible. The Section’s executive committee looks forward to greeting each of you at our future events.

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