The Show Low facility is 5,000 sq. ft. and
has 20 weld booths, a fabrication area, and
testing facility. Each booth is designed for
flat plate work, and half are equipped for
advanced pipe welding.
With more students came more welding, which in turn generated large amounts
of submicron fume from the weld cells that
needed to be properly collected. The existing ventilation system consisted of exhaust
fans that pushed some of the contaminated
air outdoors, but was unable to recirculate
cleaned air indoors. This resulted in heated
air also exiting the facility and high energy
costs. This became expensive in the winter,
as northern Arizona can be very cold.
“We had a homemade rig when we first
started about 10 years ago and it didn’t
work very well. We were on a shoestring
budget,” Casey said.
NAVIT staff became familiar with
United Air Specialists’ air pollution control
equipment while discussing their challenge
with NPC. The college had purchased a
UAS downward-flow cartridge collector for
its Holbrook welding facility in 2004, and
was very satisfied with its performance.
NPC/NAVIT needed a more effective solution to efficiently clean each weld cell, as
well as save costs associated with external
venting in both its Show Low and St. Johns
locations. With a safe student work environment as the top priority, and energy costs
also part of their challenge, NPC/NAVIT
staff knew they needed to take immediate
action to find a better solution to fit their
specific welding facilities.
The bulk of weld fumes are submicron in size, with average diameters of 0.3 to 0.7 micron
(µ). Particles ranging from 0.5 to 8 microns are retained in the lungs. Normally, lung retention
in the 0.3- to 0.7-micron range is minimal. However, thermal effects can cause agglomeration,
in which particles grow larger and can be retained in the lungs.
Average Particle Size Distribution by Percentag
Aerodynamic FCAW Globular
Diameter (µm) GMAW
< 0.4 75.1
0.4 – 0.7 15.2
0.7 – 1.1 8. 30
1.1 - 5. 8 0.61
> 5. 8 0.77
ss Fume Collected
For the Kids
The process to install new fume extraction
equipment for the two NPC/NAVIT welding locations started with a visit from UAS
manufacturer’s representative Shawn
Valandra of Total Filtration Services (TFS),
Phoenix, who evaluated NPC/NAVIT’s
Show Low welding facility by collecting
measurements, taking pictures, and
discussing the school’s expectations for air
pollution control. He also consulted with a
UAS application engineer to generate drawings for an SFC downward-flow cartridge
dust collector with customized ducting to
20 weld cells. Valandra recommended this
Source: Jenkins, N. T., Pierce, M.G., and Edgar, T. W., 2005 Particle Size Distribution
of Gas Metal and Flux Cored Arc Welding Fumes
particular system based on airflow (CFM)
requirements and its ability to capture submicron weld fume before it enters the
welder’s breathing zone.
The collector draws smoke and fumes
from each weld cell, pushes the contaminated
air through its 24 nanofiber cartridge filters,
and recirculates clean air back into the facility
without losing heat. At the same time, the
system’s self-cleaning mechanism periodically
shoots a blast of compressed air through the
center of each filter, causing weld particulate
to pulse off the cartridges and into a hopper
“Even though it was a little louder [than
exhaust fans], I immediately noticed the
difference in air quality,” Casey said.
The NPC/NAVIT staff was happy with
the cost savings in heating bills, but also
very pleased that the fume collector was
able to remove hazardous submicron contaminants that more than 75 percent of
welding processes generate (see Figure 1).
This is possible because of the combination
of the system’s optimized pulse-jet self-cleaning mechanism and ProTura™
nanofiber cartridge filters.
“Basically this was for the students’ health,
but also for my health. I knew I’d be there
long term and my other instructors would be
there long term. I just don’t want to have any
[health] surprises later in life,” Casey said.
Nanofiber filters are coated with a surface
treatment of fibers about 0.1 to 0.5 micron
layers deep, which capture submicron particles and prevent them from passing back
into the airstream. This means that the most
hazardous fume particulate is contained
within the collector and not reintroduced
into the welders’ area. This provided efficient fume capture right at the source of
generation for each student.
“There is a noticeable lack of dust particulates in our welding facility since the
system installation, and the ability to return
filtered air back inside the welding lab
instead of exhausting it outdoors has led to
an increase in energy savings,” NAVIT
Superintendent Chester Crandell said.
“The difference is obvious,” Casey
added. “The allergy symptoms I might have
displayed before are gone now. Healthwise,
I knew this was the right thing to do, and
it’s been well worth the investment.
“You can’t put a price on your lungs.” ■
Northern Arizona Vocational Institute of
Technology, 1320 E. Thornton Road, Show Low,
AZ 85901, 928-532-0269, www.navit.k12.az.us
Northland Pioneer College, P.O. Box 610,
Holbrook, AZ 86026, 800-266-7845,
United Air Specialists, 4440 Creek Road,
Cincinnati, OH 45242, 800-252-4647,
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