Oil Analysis, Vibration Analysis and Thermography
Deliver Savings at Manufacturing Plant
The preventive maintenance team at American Axle and Manufacturing
(AAM) addressed an issue found during a routine preventive maintenance
work order. Relying on their skills and field experience, they corrected
the issue with minimal effect on productive time. Catching the issue in
a timely manner saved the company an estimated $50,000.
A routine preventive maintenance work order was placed to change a hydraulic
filter on one of the Plant 6, front-axle assembly line hydraulic systems;
BT 33608, station 17b. While completing the work order, the hydraulic repairman
believed the system did not sound like it was operating at 100 percent.
He sensed that the pump was generating irregular vibration and submitted
a corrective work order for a vibration analysis test.
Vibration Analysis
After reviewing vibration analysis data, maintenance personnel found accelerated
harmonics of turning speed and high axial and radial readings. Based on the
findings, it was suspected that the unit had a loose condition with misalignment.
This information was reported back to maintenance and production.
Due to production
demands on this line, maintenance personnel were allowed only 30 minutes
to make the correction. In an effort to save valuable time,
they utilized a strobe light during production to read the exact make and
model of the Steelflex coupling. They found a red residue on the outside
of the coupling
(Figure
1), which according to reference materials, is failed grease or separated
grease. Because of the coupling style, maintenance did not have a replacement
coupling on-site. They ordered the current version of the same coupling and
received it during that same shift. The coupling had to be altered in-house
because the manufacturer did not produce the required size. During this time,
maintenance personnel were able to research and acquire a replacement grease
that would not separate under centrifugal forces (Texaco Coupling Grease)
and schedule the 30-minute window for completing the repair.
American Axle
and Manufacturing Production released the unit for 30 minutes to complete
the work order. Based on time constraints, they broke the old
coupling free, leaving the coupling halves/hubs installed on the shaft.
They installed
the new spring and casing, then refilled the coupling with the appropriate
grease. The unit was returned to production within the 30-minute window
and new readings were taken. The high axial and radial readings were returned
to a more tolerable level, but the elevated harmonic readings showed that
the
unit was still misaligned. Knowing that the misalignment could potentially
damage the installed coupling, maintenance personnel ordered a coupling
and
scheduled a laser alignment during a scheduled downtime. Afterward,
the vibration analysis readings were returned to original GM/Delphi readings
(Figure 2).
Thermography to the Rescue
Upon service of the coupling, maintenance noticed and reported the adjacent
hydraulic reservoir was operating substantially hotter than the other units.
Thermography was used to determine the source point of the increased heat
generation. Through thermal imaging, it was determined that the heat was
being generated at the pump. Specifically, the image supports severe internal
leakage and case drain leakage through the case drain (Figure 3).
Oil Analysis
Maintenance personnel scheduled additional vibration analysis and oil analysis
tests to pinpoint the root cause and further component damage while they
located a suitable pump replacement. The pump manufacturer had upgraded the
pump style from the original design, and the two styles were not compatible.
To avoid making adjustments to the new-style pump and incurring several daytime
delays, maintenance personnel placed a special 24-hour order for a pump replacement.
Vibration analysis readings generated no abnormal readings and detected no
metal-on-metal wear. Oil analysis completed sampling and testing to determine
that the oil chemistry had deteriorated well beyond acceptable levels and
the particulate levels were high. Personnel scheduled the unit for repair
during routinely scheduled downtime. They changed the pump and filter and
then drained, flushed and refilled the system. Vibration analysis, thermography
and oil analysis readings were completed after repairs, and all returned
to normal operating levels, well within AAM standards.
The correct hydraulic
operation prevented a catastrophic failure on the front-axle assembly
line station 17b. This hydraulic system feeds the component conveyor
that positions the component for torque testing. If this system fails, the
parts cannot get tested for torque and hence would stop the final assembly
line. Based on the length of time required to properly complete any one of
the above maintenance procedures, a catastrophic failure would have caused
a minimum of four hours of downtime with costs of approximately $96,000.
The cost of this downtime could have easily exceeded $576,000 if the
parts were
not readily available or obtainable.
Written by Rick Kus, Dave Giacobozzi, Julius O’Steen, Jim Panoff, Ron
Radfordand Max Segar, American Axle and Manufacturing Detroit
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