When you are responsible for 25,000 wheels and 5,300 brakes each year, you learn a few things about how to do it better, faster, and with regard for the environment.
In a former Builder’s Square facility covering some 106,000 square feet in Tulsa, OK, is where American Airlines overhauls and repairs 100 percent of the worn wheels and brakes removed from its mixed fleet of Boeing 737, 757, 767, 777, and MD-80 aircraft.
It’s a stand-alone facility, with the engineering, machining, welding, and flame spray capabilities as required to repair any discrepancy indentified during the throughput inspection that starts with two to three stage cleaning process.
All the functions of shipping and receiving the tons of wheels, tires, and brakes take up a lot of time and space; and the assembly and post-assembly balancing and inspections keep the rest of the cross-trained work force busy. (“Wheel” employees stay with wheels; “brake” employees stay with brakes, but each group is flexible in its assignments, so that throughput can be maintained in the face of sicknesses, vacations, etc.)
Movement and cleaning
The large work floor is arranged with the two lines wrapped in two concentric “horseshoes” around the circumference, the wheel line outside the brake line, reflecting the relative sizes and populations of the components. Scott Feldman, manager, Composite Repair Center, Wheel & Brake Center and Outside Services, says that one of the toughest parts of the system is one of the first operations: getting the wheels cleaned for inspection in minimum time, while making minimum impact on the environment. Complicating this job is the fact that 777 wheel halves, for example, weigh 140 pounds each — and these wheel assemblies come in and leave the facility complete with tires.
A powered roller conveyor system does a lot of the transport duty through the process, and specialized machines lift and turn heavy assemblies, but there is plenty of manual labor available, and skill and attention are required at each workstation. Though many employees stay for decades (20- and 25-year anniversaries are relatively common), there is higher turnover among newer hires.
Solvents that would make short work of the wheels’ grease and brake dust can also make short work of tires, and cleaning must be done before disassembly. So, a hot water spray pre-wash line does the majority of the cleaning; then dedicated washers do the rest. The two-stage system saves “tons” of water, and results in less volume of wash-off per unit of waste, making water recovery more efficient, as well. In fact, virtually all cleaning at the Wheel & Brake Center (WBC) is water-based. Even bearings are washed in 180 F high-pressure water rather than solvents.
The components are broken down and sent to their inspections; or sometimes to rework, or to recycling — wheel halves, tires, hardware, bearings, brake components — each gets cleaned and goes through a visual inspection, before being sent to final cleaning and beyond.
American’s efficient high-volume cleaning operations make everything else go faster and make work more accurate. Inspection is tailored to the components: both ultrasonic and eddy current inspections are used on nonferrous parts; magnetic particle inspections are also performed on steel parts, including fasteners.
Tires are not automatically discarded; they are replaced on an as-needed basis. When the wheels come in (typically after three months in service), they are returned to the OEM for recapping and reuse after the inspection at that facility has verified them safe and reliable for the re-treading operation. Many are recycled up to six times before being discarded.
Any specific wheel or brake is usually out the door within a week, though some require repairs and take a couple days longer. Components are not kept together in sets: brake parts or wheel halves will probably not leave the shop mated to the same other parts. Not having to keep sets together means that parts can be used as-available; nothing has to wait for original mates.
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