|
Fire in a
tunnel is unquestionably the most feared risk which
could happen to a tunnel operator, not only in terms
of the potential for catastrophic damage, but in
terms of the risk of life. As illogical as it may
seem, traveling in a tunnel conjures up in ones mind
primal fears about entering an abyss of the unknown.
Popular opinion has it that at least 15 % of an
educated public would avoid using a tunnel if an
alternate route would be available. Should a
disaster occur, there are very few options for
escape compared to a surface disaster. This is why
architects of tunnel structures should go to almost
inordinate lengths to put safety and prevention of
disasters at the forefront of tunnel design. There
is a lot of equipment, procedures, attention and
resources to look after a few kilometers of roadway
which on the surface, does not rate much attention.
Click to enlarge.
Fire protection in vehicular tunnels
must be achieved through a composite of facility
design, operating equipment, hardware, software,
subsystems and procedures integrated to provide the
requirements for the protection of life and property
from the results of fire. The level of fire
detection and protection required for the entire
facility should be accomplished by integrating the
requirements developed through proven methodologies
whose operating parameters have been tested,
applied, and have successfully proven their primary
purpose of detection of overheat and fire.
Studies of fire protection for tunnels indicate that
there are three interdependent factors to be
considered.
● The early
detection of overheat or fire and the rapid
transmission of alarms to the proper authorities.
● The response
of appropriate fire fighting personnel with minimal
delay.
● A matter of
rescue operations followed by extinguishment and
control.
Where life is endangered by fire, effective rescue
operations decreases rapidly with any delay. Unless
an effective means of early warning and
communication is established, the reporting of fire
and other emergencies, coincident with ventilation
control, may be of little value in terms of lives
saved.
Click to enlarge.
Of the available fire and heat
detection devices for industrial uses, including
smoke detection, optical detection, incident
detection, the most promising method of providing
the early warning and annunciation of overheat of
fire in a tunnel is with linear heat detection
technology.
|
Protectowire linear heat detectors
are reliable, cost effective, impervious to tunnel
environments including CO, dirt, dust, EMI, and
periodic tunnel washings and are able to monitor
long lengths of a tunnel with an infinite number of
alarm points along its length.
Click to enlarge.
Protectowire is typically used where
other types of detectors would be unsuitable which
has made its use in tunnel environments more
acceptable. Since the introduction of linear heat
detection technology by The Protectowire Company
over 60 years ago, linear heat detection has
replaced other means of fire protection for many
hazards. Major applications for Protectowire
includes conveyor systems, cable trays, dust
collectors, cooling towers, pipelines, fuel
distribution terminals, mines, off shore platforms,
tank farms, refrigerated storage, a wide variety of
industrial and power plant systems, and more
recently, vehicular tunnels. The distinct advantage
of Protectowire is the ability to place the detector
in direct contact with or in close proximity to the
area or equipment being protected, or to monitor
long lengths of areas in a single detection zone.
Installation
Automatic fire detection should be provided within
all tunnel roadways, ramps, and tunnel cross
passages by the installation of listed components of
an early warning linear heat detection system
described below. The zoning of the system should
correspond to the tunnel ventilation zones. When
ventilation zones are not required to coincide with
detection zones, a maximum of 3,500 feet (1,066 m)
should be monitored in a single detection zone.
Protectowire is installed at the apex and both sides
of the tunnel when 2 or more lanes wide, or at both
sides when single lane operation is required.
Click to enlarge.
Install Protectowire linear heat
detection cable using messenger wire supporting the
detector with stainless steel turnbuckles located
between every 250 feet (76 m) of messenger cable. A
standoff with rubber grommet is placed at 55 foot
(17 m) intervals to additionally support the linear
heat detector/messenger cable. Terminate each
detection zone with an end-of-line resistor housed
in a NEMA-4X enclosure with compression strain
relief. Unwrap the Protectowire from messenger far
enough to form a loop in the messenger wire. Clamp
the loop with a U-bolt and slip the loop over the
turnbuckle until the messenger wire has only a small
amount of sag. Provide additional support at 50 foot
(15m) intervals using beam clamp #BC-2.
|
Each detection zone is monitored
at the linear heat detection control panel and
displayed on a digital point location meter to
facilitate pinpointing the exact location of an
overheat or fire along the length of the detection
loop.
Click to enlarge.
Detection zones should be configured
to coincide with tunnel ventilation zones where
possible to provide fan control in the event of
fire. Where long copper feed cable lengths are
required to the start of the detection zone, do not
exceed 100 Ohms of feed cable resistance.
Recent fires and the increasing construction of
vehicle tunnels around the world have shown the need
for greater documentation of fire detection
requirements and technologies for roadway tunnels.
Click to enalarge.
While every country that has a
vehicle tunnel has some sort of standard or criteria
to conform to for these special applications, it
would be difficult to document a single requirement
for a tunnel having different environments with the
various fire detection devices available that could
be utilized.
Currently around the world are many projects in the
design or construction stage with an increasing
number of tunnels being planned for retrofit and
refurbishing of structural improvements. These
projects will enhance safety for both normal
operational environment and emergency situations,
with particular emphasis on safety.
Partial List of Protectowire installed tunnel
systems
AFC Tunnel - Atlanta, Georgia - USA
Parkway Tunnel - Univ. of Wisconsin, Madison,
Wisconsin, USA
McCarron Airport Tunnel - Las Vegas, Nevada -
USA
Denver International Airport Tunnel -
Colorado - USA
Muni-Metro Tunnel - San Francisco, California
- USA
Tuneles del Negron (Asturias) - Northern
Spain
Tuneles de la Autovia de Mataro - Cataluna,
Spain
Berry Street Tunnels - Pittsburgh,
Pennsylvania - USA
Acapulco Tunnel - Acapulco, Mexico
Shanghai Yan An East Road Tunnel - Shanghai,
China
MAI Naftuh Tunnels - Tel Aviv, Israel
Steve Wynn Tunnel - Atlantic City,
New Jersey
Selatin Tunnel - Ismir, Turkey
Alanya Tunnels - Turkey
Hannekleiv Tunnel - Norway
1st Avenue - New York City, NY
Park Avenue - New York City, NY
Battery Park Tunnels - New York City, NY
Kirkeheia Tunnel - Norway
Barranco de La Balliena Tunnel - Barcelona,
Spain
SpainSomport Tunnel - Pyrenees Mountains,
Spain
Guadarrama Tunnel - Madrid, Spain
Pardornello Tunnel - Galicia, Spain
Cadi Tunnel - Catalonia, Spain
Baladino Tunnel - Madrid, Spain
Gagarinski Tunnels - Moscow, Russia |
