Case History Feature
Case history feature on Bilco Company for Aercology, Inc.
written by Richard Stewart
Brigade of Air Cleaning Units
Clears Smoke in Welding Shop
Thirty welders produce a lot of smoke and fumes at The Bilco
Company plant in West Haven, Conn. A leading manufacturer
of specialty steel and aluminum doors, with more than a dozen
U.S. and international patents to its credit, Bilco had a problem.
It needed a better way to clear the air in its 35,000-square-foot
metal fabricating shop.
"For years we used huge exhaust fans," recalls Roger Joyce,
Bilco's vp of engineering. "When it got smoky inside, we'd flip
on our fans and suck it all out. We'd run the fans for 10 minutes
to clear the air, which they did very nicely — but they also
removed all the heat from the building!"
Simply exhausting the smoke and fumes outdoors was
inefficient and no longer cost-effective, he felt. During icy New
England winters, the cold make-up air (brought inside to replace
air vented out) had to be heated. As energy costs escalated, shop
heating bills became prohibitive.
Exhausting the air outdoors created another problem in the shop
— negative pressure. Replacement air couldn't enter the building
as fast as the large fans exhausted it, and the pressure
differential affected the efficiency of the plant's paint booth. The
air — and paint — inside the booth wanted to escape into the
shop, making the painting operation somewhat sensitive and
difficult to control.
A Racetrack Overhead
Keeping the air inside the plant — cleaning and recirculating it
— was the solution. To achieve it, rows of self-contained
(unducted) electrostatic precipitators were suspended over the
shop floor. The number of units and placement pattern were
determined by the volume of air to be cleaned and the desired
frequency of air change. The precipitators were arranged so that
the air was moved in a circular pattern, for a "racetrack effect,"
explains David Brennan, president of Brennan Environmental,
Inc. of Guilford, Conn.
"The idea is to position the precipitators so that you're pushing
the airborne smoke and fumes from one unit to the next, forming a
large curtain of air," he says. In this process, called entrainment, air
is continuously drawn into the racetrack and circulated. Brennan
likens the effect to someone smoking a cigarette while driving a car.
"If you crack the window, the pressure difference of the air moving
outside the car draws the cigarette smoke out into the airstream."
He worked closely with Bilco's Joyce to design the plant's air
filtration system. Before committing to a full system, the company
took a "show-me" approach. On a trial basis, several heavy-duty,
industrial precipitators manufactured by Aercology, Inc. of Old
Saybrook, Conn. were installed. "We hung a couple of free-standing
units, and they worked quite well," Joyce remembers. "So we had
them installed throughout the shop." Sixteen precipitators with
blowers, each rated at 2600 cubic feet a minute (Aercology Model
EP-2600D) were installed in the large, central system. Two more
units were hung in a smaller area of the shop.
Aercology, Inc. custom-configured a separate system, using an
existing blower and eight flexible hose-arms. Welders can still
position the hoses near the source of the smoke and fumes, but
instead of being exhausted directly outside, it's all drawn into a large,
blowerless Aercology precipitator, which cleans the air and vents it
back into the shop. Also part of Bilco's air cleaning brigade is a
portable unit (Aercology Model EPP-1200, rated at 1200 cfm) that
can be wheeled into position anywhere it's needed.
Huge Energy Savings
"The money we've saved has probably paid for those units many
times over," Joyce says. "I couldn't quote you any figures, but we've
seen substantial savings in heat. Aercology worked up a cost/benefit
analysis, and it made a lot of sense to us." The move also relieved
the negative pressure condition, he reports. "That allowed us to
better control the painting operation."
Brennan recommends precipitators over other types of filtration for
areas that require a high rate of airflow. Precipitators are especially
effective for removing smoke and fumes. The elements — ionizing
wires and collection plates — present little resistance to airflow.
Dirty air passes through an electrically charged field, where smoke,
fumes and other airborne contaminants are ionized or charged.
These dirt particles are removed from the airstream by a set of
metal collection plates of opposite polarity. Clean air exits the
precipitator and goes back into the shop. No make-up air is needed,
and the air pressure is not affected.
Another advantage of electrostatic precipitators over other types of
filtration is that the precipitator elements are cleanable and reusable.
"You don't incur filter replacement costs, Brennan says, "and you
don't have the costs and problems associated with disposal of filter
Bilco finds that quarterly maintenance is sufficient. "Even with the
volume of fumes that we're pumping into the air, the filter elements
only need to be cleaned four times a year," notes Joyce. "We just
take them out, clean them, and slide them right back in." The
Aercology precipitators in Bilco's central overhead system have
been in place for about eight years, and, according to Joyce, the
units have suffered no loss of efficiency in that time.
He represents the third generation in the family-owned company
that was founded in 1926 by his grandfather, George W. Lyons, Sr.
as a "miscellaneous iron fabricating shop." Nearly 60 years ago, the
founder was awarded a patent for his steel basement door. Today
many thousands of Bilco's basement doors are in use in residential
and commercial structures, according to Joyce. Fabricated from
hot-rolled steel, the doors are sheared, formed, welded, painted,
warehoused and packed for shipping at the Connecticut facility.
Then they're sent to distributors and sold through lumber yards and
building supply centers.
Bilco also pioneered a unique line of specialty "horizontal doors"
or access hatches for floors, roofs, sidewalks and other horizontal
surfaces. These doors, available both in aluminum and steel, account
for most of the company's production volume. With these product
lines, the company has developed a reputation among architects,
engineers and builders, who often design to Bilco specifications. The
company's 100,000-square-foot West Haven facility houses corporate
offices, manufacturing and warehousing operations. Another facility,
totalling 70,000 square feet, is located in Trumann, Ark.; it serves the
southern and western markets.
Says Tim O'Connell, Bilco's plant manager, "You can imagine how
much welding smoke and fumes we produce in a fabricating shop of
our size. If we were to shut down the air filtration system, it would
get very smoky, fast, in here. It has been very effective for us." The
reduction in the amount of welding smoke in the air after the system
was installed was significant, Tim notes. "I don't know how many
other big welding shops there are anymore, but a system like ours is
probably the best way to handle the problem of smoke and fumes.
Venting the smoke outside isn't very practical for us. The precipitators
definitely work well here."