A Leg Up on Speed and ReliabilityCargill,
Inc. finds innovative gear drive design yields the best results in bucket elevators
 Even
as the light breaks across the plains of southeastern South Dakota,
the trucks are arriving. Seemingly from every direction, creaky
wooden trucks and sleek metal semi-trucks are descending upon the
dirt roads leading to a towering elevator, visible from ten miles
away across the prairie. During harvest season, the trucks will
arrive all day, as farmers drop off the hard-won fruit of their
labor. For the farmers, the trip is a culmination of a season of
hard work, but for the new Dakota Plains Ag Center of Tripp, South
Dakota, the business of the elevator is only beginning.
On its most basic level, an elevator performs a delicate
balancing act between receiving and shipping the enormous amount of crops that
pass through the facility on a single day. Incoming crops are taken in, stored,
and then shipped out on railroad cars to make room for more incoming crops. During
the harvest season when the elevator is filled to capacity and running practically
24-hours a day, it is even more crucial that the facility's equipment is able
to perform flawlessly to balance inflow with outflow.
In 1998, the local
Farmers Elevator of Tripp and Parkston, overwhelmed with the sheer bulk of crops
it was handling for local farmers, approached Cargill, Inc. with a plan to combine
the resources of their two elevators with Cargill's three elevators in Yankton,
Scotland and Avon, South Dakota. Ultimately, that cooperation produced a limited
liability company, Dakota Plains Ag Center, LLC, and led to the construction of
a $10.5 million modern elevator and product facility designed to respond to the
needs of this primarily agricultural community.
Before construction began
on the Dakota Plains Ag Center, partners in the joint venture project wanted to
ensure that the drive systems - the heart of the facility - could deliver the
speed and reliability its high-volume operation demanded. By standardizing on
a simple, single taper bushing drive system, the Ag Center found the performance
and dependability it needed to keep crops moving consistently throughout the facility.
A
Demanding OperationCompleted in October 2000, the facility is the flagship
terminal of the Dakota Plains operation. Storage consists of eight slipform concrete
tanks (34-x-120-foot), with a storage capacity of 800,000 bushels and a circular
360-foot, 2.5 million bushel outside bunker designed to handle overflow. The facility
also includes a dry fertilizer terminal, a liquid fertilizer and chemical facility,
and a bulk seed distribution system.
At the height of harvest season, more
than 400 trucks carrying up to 250,000 bushels of corn or beans can descend upon
the Ag Center on a single day. In less than five minutes, a semi-truck of corn
or soybeans can be emptied into one of two 650-bushel capacity receiving pits.
From the receiving pits, a conveyor belt feeds the product upwards into one of
the facility's three receiving bucket-style elevators or "legs."
Driving
this operation is the gear drive, the "muscle" the facility relies on
to move the crops into one of the eight 86,000-bushel silos or out to the storage
bunker, and eventually, out to waiting railroad cars. The four legs at the facility
can run simultaneously - two 15,000-bph receiving legs, one 30,000-bph shipping
leg, and a 15,000-bph wet leg (feeding the dryer wet grain) - to load hopper railroad
cars at a breath-taking 75,000-bph pace.
Reliability and Speed: Key Design
Factors Because it was building an entirely new facility, Cargill recommended
a drive system that would avoid some of the typical problems associated with gear
drives, including difficulties with installation, mounting and alignment. Speed
was also a key consideration. Prior to the construction of the new terminal, the
fastest either of the two Companies elevators could receive crops was at 5,000-bph.
At this rate, neither of the company's older elevators could keep up during the
busy harvest season.
Cargill found that the simplicity of the beltless,
alignment-free and single taper bushing system of the Falk Drive
One™ gear drive offered the least complex, easiest-to-install, and most maintenance-friendly
package to transmit horsepower from the motor to the shaft on the elevator's largest
shipping leg. Because the patented TA taper® bushing is ductile iron, it
resists the fretting and corrosion common with steel-to-steel connections. The
design allows for quick removal of the drive when needed, without damage to the
driven equipment.
"Reliability and simplicity of design and maintenance
were the key issues for choosing a drive system that could be depended upon to
keep the elevator in production," said Mark Herrick, project engineer, Cargill,
Inc. "If a gear drive fails, the facility could potentially lose $1,000 an
hour, in addition to monthly incentives that aren't realized if railroad cars
are not loaded on schedule. Depending on how long it takes to get the gear drive
functioning and the leg back up, downtime costs could reach as much as $24,000
a day."
While the Drive One is installed on the largest shipping leg
at the Ag Center, smaller Falk Quadrives® - which use the same
TA taper bushing as Drive One - are installed on the three other legs. In addition
to the bucket elevators, Quadrives power all the conveyors for the elevator.
"Our company was interested in standardizing gear drive components with a
supplier that could offer a breadth of drive products and back their products
up with reliable support capabilities," said Herrick. "In addition,
we were also looking for a supplier who could help us improve the maintenance
and reliability end of our cost equation, by eliminating and simplifying the drive
mounting system and reducing the types of drives down to a single package."
Simplicity Yields Big Results The Drive One has simplified the
application, installation and maintenance procedures at the new terminal, while
the outbound capacity of the original elevators has doubled. The bulk of these
benefits can be traced to Drive One's simple design. For example, much of the
intensive gear drive maintenance comes from having to maintain alignment between
the gear drive and the driven equipment. With the Drive One, the drive is mounted
on the driven shaft; there is no need for initial alignment, and realignment is
never required, even with movement in the structure. The elimination of periodic
realignment results in long term cost savings.
"Complete accessibility
and ease of installation makes the Drive One easy to work with," said Kevin
Murtha, operations manager, Dakota Plains Ag Center. "Drive installation
is simplified because it's not necessary to pour a foundation and it doesn't require
costly mountings."
According to Herrick, another key factor in their
decision was the local technical support and emergency repair capabilities.
"Because Drive One can standardize its own product line and thereby reduce
the number of types it offers, it can provide an extremely well-engineered and
well-manufactured product at a very competitive price, "Herrick said.
The Drive One is now a standard on Cargill's new larger horsepower bucket elevators,
and depending on the circumstances of older drives, Cargill is looking into retrofitting
with older elevators with Drive One, as well.
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