85-Year-Old Drive System Replaced With Compact Mixer Drive
 HUTCHINSON, KS -- Morton Salt, Hutchinson Division, a
producer of salt for nearly a century, experienced growing pains recently
when an 85-year-old drive system on the company's calandria
pans needed to
be replaced.
"Business was at the point where we needed the pan
up and running all the time," says Sr. Assistant Engineer Jerry McGonigle.
"Basically, when they are turned on, they stay on for four to
six weeks."
The 18 to 20 foot diameter calandria pans are a
crucial part of the production process. Brine, at a 100 percent
concentration, is pumped from one of Morton Salt's solution mines and
circulated through the pans where an evaporating process takes place. If
one of the pans experiences a
breakdown,
production could dip by as much as 50 percent.
The original solution called for upgrading the
drive system by removing the line shaft and flat belts. Despite the
upgrade, the drive system continually tripped up the production process
due to
frequent failures of the pinion and open bevel gearing during high production demands.
A
more permanent solution was needed. And so, to solve the ever-growing
production problems, two of the three pans received new drive systems
including Falk Right Angle Mixers drives, Steelflex tapered grid
couplings, 75 hp Siemens-Allis 1,750 rpm motors, and mechanical
pan
seals. The drive systems were installed not a moment too soon.
Open Gearing Problems
Shortcomings in the pinion/open bevel drive system
were becoming more evident as the
demand of Morton Salt-Hutchinson's four salt
grades continued to grow.
Individual 50 hp motors and shaft-mounted speed
reducers drove pinions and bull gears. Motors were mounted directly to the
gearboxes and located on one side of the pan. A 10-foot shaft/pinion
transferred power from the speed reducer to the 4-foot diameter bevel
gear. As planned, the system reduced problems associated with an original
line-shaft type system that created high noise levels and danger from
exposed drive belts. Additionally, pan drive systems now
operated
independently from one another.
It was evident that a torque arm could support
variations in load better than the original drive belt system. However,
mesh problems between pinion and bull gear created vibrations which were
amplified by the pinion shaft and transferred into
the gear box.
In fact, pinions were being
replaced every six to 12 months as vibration from the 2-1/2 in.
variation in gear mesh pitch battered the gear boxes.
"Vibration didn't get along too well with the gear
box," says McGonigle. "It was more than the gear box could handle. The
gearing would be severely damaged and we would actually fret the
pinion shaft to the gear box."
After 85 years, the open gearing system had come
to the end of its useful life. Despite the system adjustments and
upgrades, it continued to be a source of operational and maintenance
frustration. Drive system repairs still took an average of up to four
hours. To even maintain consistent operation, open gearing needed constant
attention and lubrication, which proved to be a
difficult task.
Says McGonigle: "There is really no easy way to
lubricate open gears without the lubricant
`throwing
off'."
Future Concerns
McGonigle and Power and Production Foreman Mark
Estes also worried about future gearing changes. "The faster we can run,
the more salt we can make," Estes says. The bull gear and
pinion system didn't allow for easy upgrades.
The most damaging shortfall of the open gear
system, however, was the use of rope packing to seal the agitator shaft
from air leaking into the vacuum pans. The side thrust created by the
pinion
to the bull gear induced excessive side loads to the original 6 in. diameter babbitted bearing. As the
bearing wore, so did the packing.
"The negative pressurized vessels would draw air
into the pan, which created additional
process problems,"
adds Estes. The packing had to be constantly monitored and maintained.
Frequently, the thick packing would create enough friction on the
shaft
to increase the torque load beyond the capacity of the pinion
gear.
Enclosed Speed Reducers
Growing weary of the problems associated with the
five-year old upgrade, which was supposed to solve these ongoing problems,
Morton Salt called in local power transmission equipment distributor
Horsepower Control Systems (Kansas City, MO). The distributor
recommended a solution that included enclosed mixer speed reducers, grid-type couplings and
mechanical seals to
replace the 85-year-old open gear system. It would meet demands of safety,
service and
reliability while offering the flexibility to accept simple gearing changes.
To replace the pinion/open gearing system on two
of the calandria pans, two Falk 900 MDXQ2 drives, with 24.82:1 ratio and
2.25 service factor, were installed. Falk Steelflex grid
couplings were also outfitted on the system.
"We looked at other options for a mixer drive, but most required the
use of a kit to adapt parallel shaft reducers to right angle," says Estes.
"We chose the Falk Ram drive based on the fact that it is designed to operate
as a mixer drive and because we can easily change gearing in the future if
needed."
The new drive package also accepts installation of a mechanical seal
between the drive system and calandria pan since agitator shaft is mounted
directly to the gear box. The hollow output shaft in the gear boxes run in
lubricated Timken bearings which hold the run-out of the agitator shaft
well within specified limits. The mechanical seals eliminate concerns over
acuum leaks in the calandria pans and problems with ineffective rope
packing.
"Any bit of air that gets into the system has to
be evacuated or performance and production
are affected," says McGonigle. "The
mechanical seals will eliminate that concern."
Additionally, the new enclosed gear drive
eliminated safety concerns as well as old
problems with vibration, lubrication, and gear
mesh.
Installation Challenges
Installation of the system presented numerous
challenges to Morton Salt crews. For instance, mounting frames were
prefabricated off site and then brought to the site. Gear boxes were
attached to the frame and the entire structure was hoisted about 60 ft. into position with the shaft.
The
assemblies were then aligned to the vacuum pans.
"Just like the old systems, we couldn't just put a level on the gear box and
say, `OK, everything is fine,'" says Estes. "But, since everything is located on
the same mounting plate, all we had to do was shim the mounting to the pan."
The new system provides more reliability and
dependability to McGonigle and Estes, which is important since Morton Salt
recently implemented a new maintenance management program as part of its
Total Quality Management effort. A predictive maintenance program can be
more easily followed on the RAM drives including periodic checks of
temperature, oil, and
vibration.
Such a program was unheard of with the open
gearing system since performance was so sporadic. Additionally, routine
predictive maintenance was complicated by the dangerous condition
caused by the open belts and gearing.
"We constantly had problems with our open
gearing," McGonigle notes. "One day it could be working great and the next
it could be down. By monitoring temperature, noise and vibration in
the gear box, we can make maintenance adjustments before
problems occur."
At Morton Salt, the saying goes, "When it rains it
pours." As equipment and processes are targeted for improvement, including
the remaining pinion drive system, it's up to McGonigle and
Estes to make sure the axiom is correctly applied to product and not equipment downtime.
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