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Solvent Waste Cut with Spray Nozzle
Selection when Cleaning Paint Straining Equipment
| Company |
Crenlo, Inc.
Rochester, Minnesota |
| Industry |
Manufactures
cabs for agricultural and construction equipment;
electronic cabinets and enclosures; and NEMA
electrical enclosures |
| Waste
stream |
Flammable solvent
containing Toluene, MEK and similar solvents |
| Process |
Cleaning paint
straining and filtering equipment used to
prepare paints for spray application |
| Change |
Changed to
low flow nozzles for spray cleaning equipment |
| Cost |
$120 for equipment
and $150 for tests and troubleshooting |
| Results |
Reduced solvent
waste by 80 percent or 11,000 gallons per
year. Saved approximately $13,000 per year
on solvent purchase and disposal costs. |
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Crenlo, Inc.
manufactures products from steel and aluminum. Finished
products are coated with baked enamel paint. Most paint
colors are prepared on-site. Unused paint from any prepared
batch may be stored for future use. This paint was remixed
and strained to remove solids larger than roughly 90
mesh screen size before delivery to the spray booths.
Before the changeover, the straining
equipment was cleaned using fresh solvent sprayed from
a hose fitted with a nozzle spraying a flat fan of solvent
from a 0.172 inch diameter orifice. This nozzle was
rated for 4.3 gallons-per-minute (gpm) flow at a 30
pounds-per-square-inch (psi) supply pressure. Annual
cleaning of the straining equipment produced about 14,000
gallons of waste costing at least $16,000 per year.
The cleanup solvent was a recycled blend that was distilled
off-site and returned to Crenlo. A single charge covers
both purchase and processing costs. The 4.3 gpm nozzle
was originally selected because it was already in use
on an aqueous spray wash line at the plant, so a supply
was available on-site. The idea to evaluate other nozzles
came from a U.S. EPA-funded1
waste assessment that identified this equipment cleaning
operation as a major source of solvent waste at Crenlo,
and concluded that nozzle size was a key factor affecting
the volume of solvent used.
Waste Reduction
Technique
Three nozzles were purchased and tested in the cleaning
system. Flow rates for these nozzles ranged from 1/4
to 1/50 of the original nozzle flow rate. The smallest
of these nozzles (orifice 0.026 inch) cleaned the equipment
acceptably in 60 to 90 seconds at 30 psi, and also used
80 percent less solvent than the original nozzle. Waste
accumulation from this source was monitored for the
next two months and confirmed the effect of the lower
flow nozzle.
Implementation Problems
Foreign particles. Foreign
particles (rust, etc.) in the solvent feed line plugged
the nozzle orifice frequently over the first two weeks
of operation. Plugging was eliminated by installing
a small in-line basket filter to remove solids before
they reached the nozzle.
Cleaning time. Cleaning time
with the low-flow nozzle was doubled or tripled compared
with the original nozzle. The new 60 to 90 second cleaning
time was judged acceptable although it was moderately
annoying to operators. This cleaning time was reduced
to 30 seconds by instituting a presoak step. The presoak
used a dirty solvent bath to remove or loosen most of
the paint. The equipment was then sprayed with fresh
solvent for a final rinse. The presoak resulted in additional
waste reduction which is not quantified in this case
study.
Economic Benefit
No capital investment was needed. Supplies included
the purchase of three nozzles for testing ($70) and
a small, in-line basket filter (approximately $50).
Six hours of labor was needed to test the nozzles, and
an estimated four hours was spent unclogging the nozzle
orifice over the first two weeks of operation and installing
the filter. Total implementation cost was approximately
$270.
Waste reduction resulting from using
the lower flow nozzles was about 11,000 gallons per
year. Savings were about $13,500 per year.
Implication/Application
to Other
Companies
Nozzle selection is an important factor in raw material
use and waste generation whenever the sprayed material
is used once and discarded. Other common applications
are pressure washing or a spray wand use. When nozzles
are used in a spray-to-waste application ask, “Is
there a better nozzle for this application?” This
is especially true if a nozzle was chosen because of
availability rather than performance. In the Crenlo,
Inc. case study the nozzles were borrowed from a different
cleaning system in the plant. Whenever equipment has
been borrowed from another application, stretched, or
jerry-rigged, further examination may uncover waste
reduction opportunities.
Because nozzles come in a wide variety
of sizes and spray patterns, the low cost of nozzles
usually makes testing nozzles for optimal performance
practical. Assistance in selecting nozzles is available
from a number of nozzle manufacturers including: Spraying
Systems Company, 952/944-7202; and Lechler, Inc., 800/777-2926.
For More Information
MnTAP has a variety of technical assistance services available to help Minnesota businesses implement industry-tailored solutions that maximize resource efficiency, prevent pollution, increase energy efficiency, and reduce costs.Our information resources
are available online. Or, call MnTAP at 612.624.1300
or 800.247.0015 from greater Minnesota
for personal assistance.
1 The waste assessment and
labor for nozzle testing was funded entirely by a RCRA
Integrated Training and Technical Assistance (RITTA)
grant awarded to the Minnesota Pollution Control Agency
(MPCA) by the U.S. EPA in 1988. MnTAP was a subcontractor
to the MPCA on this project. Equipment, space, and part
of the total staff time were provided by Crenlo, Inc.
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