Maintenance Technology August 2016 - (Page 6)
UPTIME
Don't Overlook
Spare-Parts Reliability
Bob Williamson
Contributing Editor
M
aintenance management covers a
variety of functions, including the
managing of spare parts. We know that
the quality of those parts has a direct
impact on the reliability and maintainability of
equipment, machinery, and facilities. There's more
to it, though, than simply managing a storeroom.
How spare parts are specified, purchased,
shipped, stored, dispersed, and installed reflects
critical elements in physical-asset performance and
operating cost. Unfortunately, the parts are often
overlooked in ways that compromise equipment
reliability.
Real-world impact
Even the most reliable equipment can fail if the
right spare parts-fit for service and mission
ready-aren't installed properly. While a maintenance staff 's skill and knowledge is an important
reliability factor, the inherent reliability of spare
parts at the time of installation is even more so.
Consider these examples of how spare parts can
contribute to machine failures, excessive downtime,
higher costs, and financial losses.
Transportation damage. Several catastrophic
failures of the fan in a plant's heat-treatment carburizing furnace led to enormous production and
financial losses, not to mention a disruptive domino
effect on production schedules. Removing and
replacing the fan is difficult and time consuming,
given its location in the bottom of the furnace.
A failure analysis determined that cracks in the
fan cooling jacket led to bearing failures. These
events continued even after months of discussing
fan construction with the OEM, changing welding
methods, and carefully installing new fans.
Eventually a root-cause analysis session was
held with operators, maintainers, supervisors, area
managers, plant engineers, and the fan company's
owner. All potential failure causes were quickly
ruled out based on prior actions. The facilitator
then asked the group to take a hard look at the fan
currently installed in the furnace and a new spare
in the storeroom.
6|
MAINTENANCE TECHNOLOGY
As participants checked out the new spare firmly
strapped to a wooden pallet with its shaft in a
horizontal orientation, the fan manufacturer asked
a question that ultimately unraveled the mystery of
repeated failures: "Is that how we ship these fans to
you?"
At this point, a mechanic interjected that when
a fan is installed, its shaft is vertical. "That could
cause bearing problems," he said. Others weren't so
sure.
The OEM began speculating: "These fans are
shipped more than 800 miles to your plant by
truck," he said. "Imagine the bumping and jarring
with the weight of the fan and shaft supported by
the bearings on the cooling jacket. The cracks in
the failed units seem to start around the upper side
of the shaft-bearing mounts. Shipping them flat,
in the same orientation as they are installed in the
furnace, may prevent the cracking." Was he on to
something?
Once the manner of shipping was changed,
i.e., with the fans strapped to pallets in the same
orientation as they were to be installed, the failures
ceased. The maintenance group also found that the
fan bearings lasted longer.
In-plant moving methods. "It's a big electric
motor. How did you expect me to move it?" The
speaker was a forklift operator who found it easier
to pick up large motors by the shafts located at each
end of the units. After all, they fit nicely between
the forks, with minimal adjustment, and would roll
to the back of the forks when they were tilted back
slightly. Great move for the forklift driver.
As for the motors, their shafts were becoming
hammered, especially at the keyway. Maintenance
techs thought the units sometimes seemed to be
out of balance. Taking note of the forklift operator's
preferred methods, they finally realized the cause of
the problems: improper handling of electric motors
from the receiving dock to the storeroom and from
the storeroom to the job site.
Behind-the-scenes. One of the most frequent
and penalizing mechanical failures on a brewery's
packaging lines was attributed to conveyor-belt
AUGUST 2016
Table of Contents for the Digital Edition of Maintenance Technology August 2016
Editorial
Uptime
On The Floor
Accepting The Challenge
Advanced Software In The Jungle
Put Efficiency in MRO Storerooms
Rethink Overall Vibration Monitoring
Reliable Pumping Supplement
Practical Oil Analysis: Why and What For?
SAP Tips and Tricks
Maximize Ethernet
Compressed Air Care
Nurture STEM Learning
Heed Drive-Belt Temps
Internet of Things
ISO 55000
Products
Showcase
Ad Index
Final Thought
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