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We
view maintenance not as a necessary cost but as a strategic
asset," says John Guydan, director of maintenance and services at
National Steel’s Great Lakes Division. "Maintenance influences
the entire operation, from product quality to on-time delivery. Poor
maintenance procedures can cost you millions of dollars in repairs and
poor quality and lost production"—whereas good maintenance
practices can cut production costs immensely.
In
1990, U.S. Steel inaugurated a comprehensive program of predictive
maintenance called All-Maintenance Excellence (Amex) to improve
maintenance practices and lower maintenance costs. Focusing on
employee involvement, training, and team activity, Amex is designed to
detect potential maintenance problems and stop them from happening.
Amex
recorded a notable success in 1993 when U.S. Steel’s Gary (Ind.)
Works won the National Maintenance Excellence Award for maintenance
and equipment reliability. Gary Works was the first steel plant to
receive the honor. In 1995, U.S. Steel’s Mon Valley (Pa.) Works won
the same award.
"Years
ago, people expected equipment to fail from time to time," says
Jack Helfrich, Mon Valley’s director of plant services. "But in
today’s market, reliability is essential. It’s the key to customer
service, which is the name of the game."
In
the past, traditional preventive-maintenance programs were time-based.
A bearing, for example, would be rated for so many hours or months of
operation and was always replaced as the end of its life cycle
approached. "This was based on crude information," explains
Tom McNeil, Amex manager at Gary Works.
Now
U.S. Steel relies primarily on predictive, not preventive,
maintenance. "Preventive maintenance is when you change the oil
in your car every 3,000 miles whether it needs it or not," McNeil
says. "Predictive maintenance is when you sample the oil from
time to time and check for any changes in its characteristics. You may
find out you need to change the oil more often. It’s a much more
accurate maintenance technique and reduces costs by keeping you from
discarding perfectly good equipment."
Seven
diagnostic tools
Like
other U.S. Steel mills, Gary Works uses seven major diagnostic tools
in its predictive-maintenance program on a regularly scheduled basis:
·
Vibration
analysis. "There are 1,800 machine trains throughout the
plant," McNeil says. "They’re checked monthly to detect
any variations from the last reading."
·
Thermography.
More than 700 heat-generating points are checked each month, mostly
with infrared equipment, to detect thermal anomalies.
·
Fluid
analysis. Each month employees take and analyze more than 800
samples of fluids from gearboxes, transformers, and other equipment.
·
Visual
inspection. Inspectors travel scheduled routes checking such things as
the presence of coupling guards and the integrity of belts. Sometimes
steel mills overlook this important maintenance tool, McNeil says.
·
Operational-dynamics
analysis. Using various devices, employees check equipment to make
sure it’s meeting design specifications. A damper might be checked
to make sure it’s receiving a 50-percent airflow, as designed.
·
Electrical
monitoring. Technicians regularly check all electrical components
with voltmeters, infrared equipment, and other devices to guarantee
their operational integrity.
·
Failure
analysis. This determines why a piece of equipment failed and how that
can be prevented in the future.
In
the past several years, U.S. Steel has been using lasers to check the alignment
of rotating equipment in everything from gears and couplings to shears
and pumps. "Our vibration program found a lot of misalignment, so
we added laser equipment to solve the problem," McNeil says.
"In 1990, about 15 percent of our rotating equipment would go out
of alignment. By 1996, it was down to 1 percent."
For
Complete article: http://www.newsteel.com/features/NS9709f5.htm
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