Rebuild Option on Failed Drive Doesn't Mix with Superwood Corp.
A right angle mixer drive (inset) was installed on a ground-wood slurry vat.
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When the going gets tough in hardboard manufacturing applications, many
"not-so-tough" mixer drives break down. Then maintenance managers
face the tough question: Rebuild or replace?
Gary Farell, Superwood Corp. maintenance manager, had to make this important
decision when a mixer drive failed in one of the company's ground-wood slurries.
After more than a decade of use, one of the Superwood's six mixer drives began
buckling under the rigorous demands of maintaining a 6-percent consistency in
the ground-wood slurry vat. "The mixer drive that failed was in our toughest
application," Farell explains.
Superwood, a subsidiary of Georgia-Pacific, manufactures up to 1 million square
feet of hardboard a day out of its Duluth plant. Five production lines, some
constructed in the mid 1950's, produce hardboard for use in automobiles, television
sets and garage doors in sizes to 5' x 16'; and thicknesses from 1/10 in. to 1/4 in.
Superwood also produces hardboard in Superior, WI, and Bemidje, MN.
Regular maintenance procedures tipped off Farell to possible problems with the
gear box. For starters, temperatures often ran 30°F above normal in the gear box,
which should have operated at about 175°F. "On the hot side, the old gear
box got up to 200°F," Farell notes. "High operating temperatures
accelerated the aging process."
Constant service to gears and bearings, however, proved more destructive to
operations than high operating temperatures.
Destructive downtime
At almost $1,300 per hour in lost production, unplanned service proved costly
since the entire line had to be shut down to repair the faulty gear box. Problems
multiplied when during such delays, material in slurry vats often settled and
solidified. Crews would then have to be called to clean out the vats.
"We had to open our old gear box at least every 30 days because it was
falling apart," says Farell. Tests revealed that a major gear within the drive
was failing.
Superwood's first plan called for rebuilding the old gear box. Farell sought
answers from Rice Industrial Supply, a local industrial distributor serving the paper,
hardboard and wood industries.
Final numbers on a rebuilt gear drive, however, proved discouraging. "We
quickly realized that we could buy a new unit for less than we could rebuild the old
gear box," notes Superwood Maintenance Supervisor Mike Lofald.
Indeed, a replacement for the damaged gear came only as part of a complete gear
set. And bearings added further expense to the rebuilding procedure. On top of these
expenses, shipping time ran 10 weeks.
Instead, Farell had Rice size a Falk Ram Model 600 MDX Right Angle Mixer. "Among
other things, the Falk Ram drive looked like a more solid unit than others,"
Farell notes. "And, one of the most important characteristics I needed in a
replacement drive was longevity."
The gear box has a 39.39:1 ratio, which reduces an input of 1,750 rpm to 56 rpm
output. Completing the package are a high-speed Falk Steelflex coupling and
coupling guard, transmission adapter plates and mating 1/2 coupling, which mate
with existing hubs on the mixing shaft.
"Rice Industrial Supply asked us what kind of mixer drive we currently had
and sized the Ram unit to fit perfectly on our existing base," notes Lofald.
As a result, the replacement drive was installed in about six hours during a
standard eight-hour shutdown. Scheduled shutdowns every six weeks give maintenance
technicians a chance to adjust wear plates and check lubrication on all equipment.
"We never missed a beat," Farell is quick to add.
Accessories simplify installation
An easily accessible gear drive helped save time. But the accessories,
including adjustable mount and coupling guard, also contributed to time savings
and precision installation. Adapter plates were built and the motor aligned
prior to installation.
"Having the coupling guard in place when we received the Ram unit probably
saved four or five hours," says Lofald.
"Basically, all we had to do was disconnect the motor wires, remove the
coupling, unbolt the old unit and bolt in the new Falk Ram," Lofald remembers.
"The replacement was so simple that a new shop employee, with no mixer drive
installation experience, installed the unit with no problems. In fact, he was able to
get the drive within 1/8th an inch of shims on the high speed side."
The distributor contributed to simplification as well with an informative seminar
on the installation of the drive, operating temperature ranges, and mechanical
support. "Rice Industrial Supply was with us throughout the entire procedure,"
Lofald says.
Farell adds, "After the normal 15-year cycle for gear drives, we usually go
right back to the company that sold the original gear drive. The Falk
product name, ease of
installation and price changed our mind."
A perfect fit
The Falk Ram drive solved several problems for Superwood. First, and most
importantly, the drive fit the immediate replacement need.
"Our basic concerns were that we needed a reliable mixer that could handle high
loads and we needed it to be installed in an eight-hour window," Lofald says.
"We were pleasantly surprised with the Falk unit."
Solid Ram drive construction and performance allows Superwood to follow a less
intensive maintenance program. The new Ram unit operates at about 160°F, well
within healthy operating temperatures. Because high operating temperatures are not
causing breakdowns, Superwood does not have to repair their mixer drive every 30 days.
"We plan to include the Ram as part of our regular gear drive maintenance
program. As part of this program we conduct an oil analysis each month and, every six
months, we take the cover off the drives and check the gear mesh," Farell notes.
"We also have a weekly maintenance routine to check a variety of things from
vibration to bolt tightness."
Ease of operation comes as a welcome addition to Superwood mixer drives.
The Ram gear box already tops the company's expectations for reliability. "We know
Falk gear drives are reliable. There are Ram mixer drives that have been in operation since
before I started here," says Lofald, an 18-year Superwood veteran.
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