In this application, 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 Problem

The offshore platform had only one of these units installed, so when the gearbox blew, it effectively shut down. This happened at a particularly bad time because they were rushing to meet a production deadline, with severe penalties if the contract wasn't fulfilled on time. 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.

Fortunately, no one was hurt when this unit went down. If the teeth had not been broken, personnel on the rig would have attempted to repair it by simply changing the sleeve bearings or replacing the external lubricator. Once it became clear that the gear teeth were irreparably damaged, the customer called the Philadelphia Gear Regional Service Center in Houston, Texas.

The Solution

The call came into Wylie Wilson, operations manager for the Houston Regional Facility. Wylie authorized direct shipment of the damaged gear set and the bearings for inspection and evaluation. The customer sent the parts via helicopter from the offshore rig to the airport, where a courier delivered them to Houston.

The parts underwent the following examination:

• Magnetic particle inspection of all gear elements (a sophisticated black light test revealing pits, cracks, etc.)

• Because the damage was so severe, the normal process of measuring and charting the tooth geometry at this point was irrelevant

• Visual inspection of bearings to evaluate cause of failure

A comprehensive report was then sent to the customer advising them of the inspection results and that an expedited lead time for replacement of the gear set would be four weeks - half the industry standard.

Facing the aforementioned penalty, the customer asked Philadelphia Gear to try and come up with an interim plan. The Houston engineers, in consultation with the Engineering and Technical Center in Norristown, Pennsylvania, settled on the idea of making a "tough-hardened" set of gears that could operate at a reduced service factor. Though this set would not be carburized, it was determined that they'd last a minimum of six weeks, allowing the platform to continue operations while it waited for the replacement set to be manufactured.

After the customer gave an enthusiastic approval, Philadelphia Gear manufactured and balanced the alternative gear set to AGMA quality 14 accuracy, inspecting them, testing them, and getting them back to the offshore platform in only four days.

This enabled the platform to begin pumping again, while Philadelphia Gear began manufacturing another set of carburized gears. Sharing the customer's sense of urgency, the Houston facility was able to manufacture and ship the replacements 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.

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