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ENGINEERING CHALLENGES
One of the major challenges project engineers faced was the assurance
of laboratory integrity - the ability to maintain a tightly controlled
laboratory environment. Every penny spent by researchers on a new
pharmaceutical development could be wasted if laboratory integrity
was compromised.
The enormous scope of the project dictated total
air-handling capacity of 1.8 million cfm. The largest structure
on the campus, the 450,000-sq-ft Discovery building (primarily used
for laboratory space), required a once-through air-handling capacity
of almost 820,000 cfm, nearly half the total project volume.
The building features 39 custom designed air-handling
units (AHUs), all mounted indoors.
In addition to the Discovery building, HVAC engineers
were required to achieve laboratory integrity throughout each of
the other four buildings, which feature diverse space utilization
plans and air-handling needs.
Air-handling unit pressure and air volume turndown
in laboratory space is dictated primarily by occupancy and user
demand. According to P&G projections, the units needed to meet
air volume turndown requirements from 1.5:1 to 4:1, or from 100%
of capacity to approximately 30%. These projections were based on
the number of chemical fume hoods in use at any given time, as well
as general laboratory occupancy (standard business day vs. holiday,
weekend, or nighttime use).
While turndown is important primarily for energy
efficiency and decreased power consumption, minimum air pressures
must be maintained or laboratory spaces will be susceptible to cross-contamination.
Inconsistent or incorrect air volume turndown could
cause an imbalance in air pressure that would allow contaminants
to leak into or out of laboratories. Accordingly, each of the 75
AHUs was required to produce a strict and application-specific range
of air volumes.
"Coupled with all of the technical specifications
we demanded from the AHU manufacturer, we also had a very tight
schedule for delivery and installation," said Dan Streyle,
Corporate Facilities Engineering project manager at Procter &
Gamble, who managed construction of the project.
"Additionally, we were asking for a total
project air capacity of 1.8 million cfm, and we required once-through
air distribution for the labs. We knew these challenges could not
be met easily."
Procter & Gamble turned to Air Enterprises,
Inc., Akron, OH, to supply AHUs and engineering expertise. The sole
supplier of air-handling equipment for the project, Air Enterprises
was the largest component manufacturer involved in the design and
construction of the Health Care Research Center.
The AHUs vary in size from approximately 7,000
to 50,000 cfm. Most units were between 22,000 and 32,000 cfm.
Pre-design bidding procedures permitted earlier-than-expected
groundbreaking for the project, and allowed final design work to
parallel AHU construction. This compressed the time of the construction
phase to its practical minimum, but also led to several last minute
changes. Nevertheless, all project suppliers were expected to complete
their portion of the project on time.
In addition to manufacturing all AHUs and factory
testing at least one of each type of AHU supplied, the manufacturer
oversaw shipping, delivery, installation, and field pressure testing.
All units were designed and manufactured to be split for shipping.
Installation involved landing the units through designated openings,
for access to sub-grade mechanical spaces.
To meet the strict construction schedule and budget,
Air Enterprises used its own trucks and drivers, as well as contract
haulers when necessary.
"Procter & Gamble was extremely sensitive
to the hiring of qualified contractors and subcontractors,"
said Tim Blackburn, national sales manager at Air Enterprises. "We
frequently used our trucks and drivers to meet P&G's delivery
timetable, but we worked with P&G's contractors on-site to coordinate
field installation and wiring.
"Everyone involved was committed to keeping
this project on schedule."
AIR HANDLING UNIT CONSTRUCTION
One problem common to all AHUs is panel surface condensation. Heavy
condensation, particularly with a unit that is installed indoors
in an unconditioned mechanical space, can create safety, housekeeping,
and IAQ concerns.
All units at the Procter & Gamble site were
specified to include thermal break panel construction where required,
to minimize surface condensation.
Air Enterprises' thermal break technology, known
as "no-through-metal" construction, employs a substantial
resin bridge as an integral element of all panel system extrusions.
The manufacturer said this bridge interrupts any through-metal path
from the unit interior to the exterior. As a result, the technology
was extensively employed in units throughout the project, particularly
adjacent to and downstream of the chilled-water coils.
Furthermore, all of the AHUs were constructed of
aluminum to decrease maintenance requirements. Painted or galvanized
steel casing material on AHUs needs to be regularly inspected, cleaned,
and repaired to prevent corrosion, particularly with constant exposure
to moisture.
"One traditional problem with condensation
has been pooled water," said Phil Ritola, sales engineer at
Air Enterprises.
"Over the past several years, AHU manufacturers
have become particularly cautious to design AHUs that will not allow
water to pool on any surface. This not only reduces concerns about
unit corrosion, but also about the health hazards that standing
water can pose."
Future expansion of the Health Care Research Center
was another consideration. One additional building is already under
construction and is scheduled to open this year, and another is
scheduled to open in 1997.
The AHUs installed in the six original buildings can accommodate
higher levels of filtration, as well as chemical or gas phase filtration
required by expansion or a change in space utilization, according
to P&G.
TESTING PROCEDURES
Due to the project's strict performance parameters, extensive factory
testing of each type of AHU was conducted before shipping.
Testing procedures were designed to assess the
performance of each unit regarding delivery of the required air
volumes at the design operating pressures, and within design power
requirements.
Tests to determine whether the units met flow and
pressure requirements were conducted using duct traverses, which
measure airflow in the discharge ducts while the fans are operating
at specific pressures. Power consumption data was obtained by measuring
line amps at operating voltages.
All data was corrected to standard air characteristics
by calculating the air density using measured values for temperature
and barometric pressure, in accordance with AMCA Standard 20390.
The procedures detailed in Standard 203-90 also were used to compare
measured and calculated data to the fan performance curve provided
by the fan manufacturer.
Discharge air temperature stratification tests
also were conducted by the manufacturer before shipment.
Two airflows differing 60°F in temperature were introduced into
the inlet section of the AHU. The temperature of the air leaving
the blender was then measured at multiple points 42 in. downstream.
All units met the ±6°F standard deviation
specified by P&G. Air temperature was consistent across the
measurement grid, proving that the blender section of the AHUs functioned
as designed.
The heat of the supply air fan also was tested
to determine its impact on discharge air temperature. This test
was conducted by measuring the change in airstream temperature before
and after the fan. The impact of the fan on the temperature of the
discharge air was within P&G's specifications, and was factored
into all air temperature calculations.
Most units supplied for the P&G project were
of a draw-through design. Accordingly, the unit casings were tested
for leakage by introducing negative pressure with a high-pressure
blower.
Flow was calculated by measuring the pressure drop
across an orifice plate within a straight section of tube. The flow
in the tube was considered casing leakage.
Project specifications permitted up to 1.5 % leakage.
All units tested exceeded the specifications, according to P&G,
permitting less than 0.5% leakage.
PROJECT COMPLETION
With the initial 1.3 million sq ft of space under roof, the last
of the 75 original AHUs was being readied for shipment when P&G
engineers arrived at Air Enterprises' Akron facility for a surprise
final-unit celebration party.
"This was a win-win situation for both P&G
and Air Enterprises," Streyle said. "Our demands were
extremely strict, but Air Enterprises met them consistently. I have
tremendous respect for their abilities." Blackburn could smile
over the results.
"When a potential customer comes to you and
says, `We need to move 1.8 million cubic feet of air per minute,'
you can't really fathom the enormity of the project," he said.
"I knew we could get the job done competitively, but our whole
team is proud to have been involved in such an enormous project."
While the success of the P&G expansion in the
prescription pharmaceuticals market will ultimately dictate future
building needs, there currently are plans for several additional
buildings on the campus.
For now, however, after having successfully met
the challenges posed during the first phase, everyone involved is
taking a breather.
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