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Modem Fire Protection Systems
Safeguard Venues
By Caterina Tabor
“You just can’t beat very
early warning,” says Hicks. “We knew the center would be a gem of the
Pittsburgh skyline, and we didn’t take any chances when it came to fire
protection. You could say our backup systems have backup systems!”
Overlooking the Allegheny River, the innovative
David L. Lawrence Convention Center stands as a symbol of “the new
Pittsburgh.” The innovation isn’t just skin deep, however. Many of the
center’s operating systems turn science fiction into fact.
The striking structure, designed by acclaimed architect Rafael Vinoly, is
named for David Leo Lawrence, who served as Pittsburgh’s mayor (1946-1958)
and Pennsylvania’s governor (1959-1963). The shape of the building captures
natural airflow from the river. Skylights and glass walls catch sunshine.
Modern HVAC and lighting systems for the center’s 1.5 million square feet
automatically coordinate vents and sense sunlight to minimize energy use.
These features, combined with a water reclamation system and the use of many
recycled and nontoxic materials, such as paints and carpets that do not emit
harmful fumes, earned the center a Gold Leadership in Energy and
Environmental Design (LEED™) rating from the U.S. Green Building Council.
It is no surprise that such foresight extends to the center’s comprehensive
performance-based fire protection program, which was designed by local fire
protection engineering consultant Harold Hicks. A recognized expert in the
field, he and his consulting firm, Atlantic Code Consultants, had previous
experience with other large, high-ceiling facilities and a good rapport with
local permitting authorities having jurisdiction (AHJs). Hicks and project
engineering firm Burt Hill Kosar Rittlemann Associates settled on a
three-prong approach for the convention center’s exhibit hall: smoke
detection, flame detection, and fireboat-style water cannons called water
monitors.
Now a functioning reality after years of meetings, calculations, and
testing, the overall system consists of 29 air sampling smoke detectors, 34
infrared (IR) flame detectors, and 25 water monitors, all integrated through
Fike Cheetah control panels and computerized and interfaced to sense and
suppress a fire automatically.
Hicks chose VESDA® LaserSCANNER™ air sampling smoke detectors for the
earliest possible warning of any smoke throughout the huge area. Before
flames break out, VESDA detectors can detect combustion particles. They work
by continually drawing air from multiple sampling points into inconspicuous
pipe networks and actively transporting it to detection units. Each
detection unit contains a dual-stage filter that removes dust and dirt and
provides a clean air wash that keeps the optical surfaces uncontaminated,
for stable calibration and detector longevity. When the air sample passes
through the detection chamber, it is exposed to a laser light source. If
combustion particles are present, light is scattered within the chamber, a
scanning valve mechanism identifies which pipe is carrying smoke, and
sophisticated circuitry sends a data-rich alarm signal to the automatic fire
suppression control panel.
The multiple-use convention center presented many challenges for effective
fire protection. In addition to 389,900 square feet of exhibit space, there
are 51 meeting rooms, two 250-seat lecture halls, a large ballroom, a
12,000-square-feet kitchen, and a 700-car garage. Because the roof, which
ranges from 40 to 120 feet high, is supported by suspension cables like a
bridge, it flexes by as much as four feet with the wind and sags a bit under
a load of snow. The walls, too, are designed to move. From the outset, the
engineering team knew the design did not lend itself to the rigid piping of
a traditional sprinkler system. In addition to the problem of mounting such
piping to shifting walls, the sprinklers would have to be so high that only
a major fire could set them off.
“A beam system for smoke detection was also out of the question,” Hicks
recalls. “We looked at other facilities, including a sports arena that uses
beam detectors. Even with traditional rigid construction, the walls moved
enough to set off false alarms, especially during a game that inspired fans
to stomp on the bleachers.”
Capable of sensing 0.0015% obs/ft and programmable to the desired level of
sensitivity, VESDA equipment is the convention center’s first line of
defense against fire, capable of warning security guards in time for them to
find and extinguish a smoldering fire with handheld extinguishers.
“You just can’t beat very early warning,” says Hicks. “We knew the center
would be a gem of the Pittsburgh skyline, and we didn’t take any chances
when it came to fire protection. You could say our backup systems have
backup systems! The flame detectors can detect flame from 170-200 feet,
depending on the size of the fire. They triangulate the flame to pinpoint
its location. The computer notifies the Pittsburgh fire department and
decides which water monitors to activate. But let’s face it: To detect
flames, you have to have a fire that is already under way. And water,
whether from our cannons in the wall or from a fireman’s hose, is bound to
do some damage in the process of putting out a fire. Thankfully, the odds
are that we won’t need anything but the VESDA equipment, which can locate
the source of smoke before it transitions to the flaming stage.”
VESDA LaserSCANNERS locate the origin of smoke by identifying the pipe with
the highest concentration of smoke. They continue to sample from all pipes
to monitor fire growth. To compensate for smoke dilution, smoke
stratification, HVAC air flow, and other phenomena common to large, open
spaces with high ceilings, sampling points can be installed at several
different levels in areas to which the smoke can be expected to drift. Two
to four pipes are connected to each of the convention center’s 29
LaserSCANNERs. Each pipe, painted gray to match the cable to which it is
attached, has 12-14 sampling holes.
The LaserSCANNER has the world’s widest sensitivity range, so in addition to
programming the initial alarm to the desired sensitivity level, installers
can program the system to monitor the growth of a fire and generate alarms
at three more stages. In fact, the LaserSCANNER provides four addressable
alarm levels for each individual pipe.
“To get the most out of the VESDA system’s unique capabilities, we
programmed all four alarm threshold levels, to give them starring roles in
the convention center’s futuristic system response matrix,” says Hicks. At
Levels 1 and 2, where small concentrations of smoke are detected, guards
still have the chance to find and put out a small fire or smoldering
“pre-fire” themselves. At Level 3, the system automatically notifies the
fire department and activates a digitized voice evacuation directive over
the center’s main fire alarm system. If a fire progresses to Level 4 and
there are alarms from any two flame detectors within a specified zone, the
powerful water monitors douse pertinent sections of the building.
The system also uses the day/night sensitivity shift features of the VESDA
programming to allow the system to be less sensitive at setup and breakdown
of exhibits and shows. These are times when there can be high ambient smoke
levels due to exhaust from vehicles. Because the building is not fully
occupied at these times, the level of protection can be reduced during the
activity. As soon as setup and breakdown are complete, the systems are
restored to their more sensitive levels.
Caterina Tabor is marketing
manager for Vision Systems Inc. She may be contacted at
cathy.tabor@visionusa.com. |
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