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Case Studies

From Meeting to Exceeding Expectations

 

LAX airport in Los Angeles, California contains a Central Utilities Plant that helps to supplement the building's water and electricity. The Central Utilities plant has two generators that power many of the accessory needs at the airport. Although these generators only supply auxiliary power, when one of the generators failed in March 2007, the maintenance team at LAX knew they needed to restore it to normal operation as soon as possible. For each day the generator was out of service, LAX was paying for additional energy from public utilities.

 

LAX Airport - Los Angeles, CA

Plant engineer Saif Khorshed brought in Philadelphia Gear’s Onsite Technical Service (OTS) team to inspect the starter drive of the generator and make the necessary repairs. An inspection revealed that the age of the Western Gear turbine starter drive was the culprit. It had experienced a failure in the over-running clutch mechanism, which prevented the drive from rotating and starting the turbine. “We determined that a new clutch housing needed to be manufactured and assembled,

mounted and balanced to the input shaft,” said Chuck Zirkle,

 
Onsite Technical Services Brings Plant Back Online in 10 Days.
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director of project management, Onsite Technical Services, Philadelphia Gear. “Due to the age of the unit and the fact that it would be disassembled for  repair, it made sense to install new bearings throughout and to perform a non-destructive test inspection of the gear set.”

 

After performing lock-out/tag-out procedures, Philadelphia Gear technicians disassembled the unit. Due to tight physical constraints, OTS technicians fabricated a customized lifting device that would enable them to suspend the unit housing and components without having to remove the walls and ceiling of the turbine package enclosure. The input shaft pinion was removed and sent to Philadelphia Gear’s Santa Fe Springs Regional Service Center to be magnetic particle inspected to check for cracks. The pinion was also evaluated for run-out conditions and was found to be within original equipment manufacturer (OEM) specifications.

 

While the pinion repair commenced, the bearing and seal journals were polished to remove surface scratching caused by lubricant breakdown. Finally, the new clutch housing was mounted to the back end of the input shaft and balanced to OEM specifications.

 

Meanwhile, at the LAX Central Utilities Plant, technicians visually inspected the output gear and performed a dye penetrate test on the teeth of the bull gear. The dye indicated that no cracks were present. The gear was then cleaned before the housing lid was lowered back into place, prior to the installation of the input shaft.

 

Before the drive could be reassembled, contaminated oil was removed and an extensive cleaning of the gearbox performed.  Technicians also worked on assembling the starter drive mechanism to as built conditions as completely as possible before reattaching it to the gearbox. During assembly, the Babbitt bearings and thrust plates on the oil pump end of the output shaft were removed and replaced with a new set. The OTS team also reconnected the input coupling to the turbine coupling hub and added sealer to the housing split. Finally, the team reinstalled the shaft-driven lube pump on the output shaft. All remaining hoses and tubing were connected and fresh oil was added. Philadelphia Gear’s OTS team had successfully disassembled, repaired and reinstalled LAX Central Utilities Plant turbine starter drive.

Customized lifting apparatus for
upper housing removal and suspension

 

New Starter drive pinion shaft

 

Replacement over running clutch assembly

   

Close up view of Babbitt bearing contact check

Close up view of gear tooth mesh contact check

 

Philadelphia Gear Solves Unforeseen Problem

 

Before final sign-off, the OTS team returned to the job site to start and test the unit. While trying to spin the starter drive mechanism with the hydraulic motor, it tripped the thermal overloads at 600 amps. After several attempts, the results were the same.

 

 

Defective hydraulic pump was the
source of the turbine restart delay

“We do not normally service hydraulic pumps, but we did not want to leave the LAX maintenance team without a working generator while they waited for another company to service the problem pump,” said Zirkle. “Some of our OTS technicians had experience with the pumps, so we immediately addressed the problem.”

 

The technicians started by bleeding the hydraulic lines with hopes that air was in the lines. Though this helped, the amp draw was still too high to perform a successful restart. The technicians removed the hydraulic motor attached to the starter drive to test it off the unit—making sure it was not the root cause of the problem. After additional tests, the hydraulic pump was identified as the probable cause of the restart failure, and the decision was made to replace it. The OTS team assisted the LAX maintenance crew with changing out the pump. The replacement pump provided adequate RPMs to the starter drive and the turbine fired.

 

“Our work at the LAX Central Utilities Plant is a great testament to the value of Philadelphia Gear’s Onsite Technical Service program,” said Zirkle. “We were able to help the LAX maintenance team meet their goal—ensuring as little downtime as possible during this unplanned outage, even with the defective hydraulic pump.”

 

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