Oil & Gas Products News May, 2003 — A catastrophic lubrication malfunction caused a failure
in a Philadelphia Gear gearbox on an offshore gas production platform
in the Gulf of Mexico. The platform, owned by one of the world's
largest petrochemical companies, utilized gearboxes designed for
high-speed pumping applications. On average, the platform generated
approximately $1.5 million of revenue a day for its parent company
- one of the top five petrochemical companies in the world.
In the case of the offshore platform, the lubrication
malfunction would prove particularly damaging - the platform was
located miles from shore and faced severe logistical challenges
for the repair and re-installation of the damaged gearbox.
Effective lubrication is extremely critical to high-speed
gearboxes, especially when there is metal-to-metal contact. The
gearbox was a compressor drive located between a gas turbine and
a gas compressor, and was used for pumping material through undersea
lines directly to the customer's processing plants located on shore.
The damaged gearbox required an externally "forced" lubrication
system (as opposed to an internally designed "splash"
It is typical for such offshore platforms to
have stored an additional lubrication unit designated as a
"critical spare." However, on this particular platform,
the lubrication failure was so abrupt that it went unnoticed
- until a lack of lubrication led to the gearbox failure.
This lack of lubrication caused the babbitt (an alloy material
used to line the sleeve bearings) to actually melt within
minutes of the malfunction. In addition, the gear set - now
turning at approximately 14,000 RPM - soon became overheated
due to a lack of lubrication, causing the gear teeth to crack
and break apart inside the gearbox.
The offshore platform had only one compressor
drive installed, so when the gearbox blew, it effectively
shut the platform down. The timing of the failure was not
ideal, as the staff was rushing to meet a production deadline
(with severe penalties if the contract wasn't fulfilled on
If the teeth of the compressor drive had not
been broken, personnel on the rig would have attempted to
repair it by changing the sleeve bearings or replacing the
external lubricator. But once it became clear that the gear
teeth were irreparably damaged, the customer outsourced the
repair job to Philadelphia Gear's Regional Service Center
in Houston, Texas.
Long term wear on the damaged gear set.
The staff at the offshore platform contacted
Wylie Wilson, Southeast Regional Manager and Operations Manager
at the Houston Regional Facility. Wilson authorized direct
shipment of the damaged gear set and bearings to Houston for
inspection and evaluation, and the parts were shipped via
helicopter from the offshore rig to the airport, where a courier
delivered them. At the Houston facility, the parts underwent
the following examination:
A magnetic particle inspection of all gear
elements. Magnetic particle inspection is a sophisticated
black light test revealing pits, cracks, and other damage.
A visual inspection of bearings to evaluate
cause of failure.
The normal process of measuring and charting
the tooth geometry was unnecessary due to the severity of
the gear damage.
After completion of the examination, a comprehensive
report was sent to the customer advising them of the inspection
results. Also suggested within the report was an expedited
lead-time of four weeks for replacement of the gear set -
half the industry standard.
The repaired gear set after regrind.
Faced with a looming production deadline, Philadelphia
Gear offered the staff at offshore platform an interim platform
-producing a set of "tough-hardened" gears that
could operate at a reduced service factor. Though a temporary
set would not be carburized, it would last a minimum of six
weeks, allowing the platform to continue operations while
Philadelphia Gear manufactured a more permanent replacement
Upon receiving enthusiastic approval of the
interim plan, Philadelphia Gear manufactured and balanced
the tough- hardened gear set to AGMA quality 14 accuracy,
inspecting them, testing them, and getting the set back to
the offshore platform in only four days.
The quick turnaround in producing the temporary
gear set enabled the platform to begin operation again, while
Philadelphia Gear was able to manufacture and ship the permanent
set of carburized gears in three weeks, less than half the
normal 6-8 week turnaround time. All parts and workmanship
carried Philadelphia Gear's "best in industry" one
year warranty. Though the warranty allows up to six additional
months in which to re-install a gearbox, it certainly wasn't
applicable in this case