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Model #455 Coolant Purifier is
an essential component in the Stevens Manufacturing program
for maximizing shop efficiency. Two Keller coolant purifiers,
cleaning tramp oil from each of 20 sumps every other week,
have increased coolant life from 3 months to one year.
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In addition to benefiting machine efficiency, the removal
of tramp oil by the Keller purifiers eliminates the source
of smoke and odor in the shop air and helps overall housekeeping,
as shown by the above illustration of the exceptionally
clean Stevens shop.
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OTHER APPLICATIONS FOR
KELLER COOLANT PURIFIERS
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Model #315 portable unit, with
a small bag filter and large oil separation section, is a
good choice as a tramp oil separator for sumps with moderate
floating solids and a large quantity of tramp oil.
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Model #152, operating continuously
on one sump, makes a clean split of tramp oil from coolant,
even with a slow separating coolant.
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Portable Model #365, containing
a large bag filter and large oil separation section, is used
for sumps with a high tramp oil content and a high loading
of floating chips (for example, when cutting aluminum).
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| Model #455, with the large separator
tank, can cleanly separate tramp oil even when a large quantity
of oil is present. |
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Well before “Lean Manufacturing” had
become the standard term for efficient manufacturing, Stevens
Manufacturing Co. (Milford CT), a supplier of precision parts
to the aerospace aftermarket, was implementing the principles
of lean manufacturing with its on-going process improvement programs.
In fact, Steve Fogler Jr., shop manager, credits Stevens’
success in maintaining its competitive position during difficult
times to its emphasis on continually upgrading the processes.
One aspect of the operation to which Steve has
devoted continuing attention is maintenance of the coolant. Stevens
runs 20 CNC machines, none older than 10 years, cutting everything
from plastics to steel to titanium in relatively short production
runs. Their customers, such as Boeing, Sikorsky, and the U. S.
government, set extremely tight dimensional and surface finish
specifications. Tramp oil and other contaminants in coolant greatly
increase the difficulty in meeting the tight specifications. High
levels of tramp oil in coolant cause accelerated tool wear, degradation
of parts finish, and the requirement to adjust machine settings
frequently to achieve the dimensional specifications. In addition,
tramp oil in the coolant generates smoke in the shop, plus odor
and the potential for operator dermatitis as a consequence of
bacteria attack on the oil. Also, when cutting relatively low
density materials such as plastics and titanium, the chips which
remain suspended in the coolant are picked up by the coolant pump
and sprayed onto the working part, compromising the surface finish.
In order to maintain product quality and achieve production targets,
Stevens was dumping coolant and recharging with new coolant every
three months. The cost was substantial––not only the
cost of new coolant and disposing of about 100 gallons of spent
coolant for each of 20 machines every three months, but also the
roughly four hours of labor per machine to drain and clean the
sump, and replenish the coolant. In addition, each machine is
down during coolant changeover.
Steve Fogler recognized that the coolant problem
had to be solved in order to improve shop efficiency and reduce
costs. It was clear that belt or disc skimmers, a conventional
method for removing tramp oil from sumps, would not address the
Stevens requirements, because a skimmer does not create circulation
in a sump and therefore is ineffective on larger sumps, and a
skimmer does not reduce the quantity of solids suspended in the
coolant. To improve the situation significantly, Stevens required
a coolant purifier which would separate tramp oil efficiently,
recirculate the coolant at high rate even when the machine tool
is idle, and filter to remove suspended chips.
In 1998, Stevens purchased a coolant purifier
supplied by Keller Products, Inc. (Lexington MA), which met all
these requirements. With the new purifier, coolant life was immediately
extended from 3 months to one year. After recently adding several
new machining centers, Stevens purchased a second Keller coolant
purifier, the Model #455 Separator. Steve Fogler says, “The
money saved on hauling waste coolant and buying new coolant by
greatly extending the coolant life is only a small part of the
savings. The biggest saving is in the labor and downtime to dump,
clean, and recharge the sumps of 20 machines every three months.”
A Keller coolant purifier operates by pulling
oily coolant from the surface of the sump via a compact inlet
device and then through a high capacity bag filter to remove suspended
solids. The coolant/tramp oil mixture, free of solids, is pumped
through the patented Keller oil separator elements, which are
immersed in a plastic tank. The permanent oil separator elements,
constructed from stacks of plastic discs with fine flow passages,
efficiently split oil from coolant at high flow velocity, creating
the opportunity to design high flow rate separators in compact
packages. The cleaned coolant is continuously returned to the
sump, and the tramp oil collected in the separator tank is drained
to a waste oil container periodically, usually once per day. A
sump typically can be cleaned in a few hours, and then the pump/separator
can be easily moved to another sump and set up to run in about
five minutes. The Keller separator, which requires only a 1/4-inch
compressed air line for operation, can be run while the machine
tool is operating or when shut down.
Despite the fact that the Model #455 is the largest
separator in the Keller line, capable of treating individual sumps
up to 1000 gallons, it requires only 20” x 30” of floor
space and is easily portable. With a coolant recirculation rate
of 180 gallons per hour, a Model #455 can clean a 100 gallon sump
in less than two hours. Steve Fogler says, “I can easily
cover the whole shop with the two Keller units. I run for about
one or two hours every other week on each sump, and the coolant
looks like swimming pool water.” The resulting operating
benefits are: improved machine efficiency, extended tool life,
better parts finish, and greatly reduced machine downtime. Another
advantage to operating with clean coolant, obvious to any visitor,
is the overall cleanliness of the Stevens shop and the absence
of smoke in the air which can be caused by tramp oil in the coolant.
Steve Fogler says, “To stay competitive,
I have to stay lean, and to me lean means minimizing time spent
on non-value-added projects. Lean isn’t about not spending
money, and it is not always about exotic new machines or programs.
Sometimes lean is just making sure your existing assets are operating
at maximum efficiency. Our coolant maintenance system is an important
element in our on-going program to maximize operating efficiency.”
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| #555-09 Large Floating Inlet Device works perfectly even
in the presence of floating aluminum chips. |
#555-05 Compact Floating Inlet Device, in a typical installation,
sweeps tramp oil from the sump surface. |
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