Remanufactured air
compressors have always
been accepted within the bus
and coach industry. With soaring fuel costs and corporate pressure to recycle wherever possible, it is an obvious route both for reducing costs and the company's impact on the environment. . One reason that several national bus fleets are now specifying remanufactured compressors for their vehicles is that todays products are produced to high standardards that will deliver reliable in-service performance. Remanufacturing is shedding its
image as second-best. The best
remanufacturing practices these days more closely resemble original equipment manufacturing, working to set documented procedures and tolerances. Components used in the remanufacturing process are obviously critically important, and must be at least as good as the OEM specification. The component traceability control system should go hand in hand with an ISO approved certification. Use a reputable
supplier and it should actually be
possible to not only trace the finished unit itself back to the assembly technician, but each component should also be traceable back to the supplier
and particular batch that the goods were supplied against.
A remanufacturer is in a unique
position in that they are able to study the condition of the old compressors as they arrive. It is not inconceivable that the life of a compressor can be enhanced, by modifying the remanufactured compressor, as a result of those studies.
 

Demanding service
Bus operations place great demand on air systems and, therefore on the compressors themselves. Because of this it is critical that the engineering and technical procedures at the remanufacturers are in good order. At Fleetparts, for example, we have taken the boring and honing process a step further. We have developed a process to run-in the compressor, taking the peaks off the cross-hatching
in the cylinder bore. Thisliminates the need for the piston rings to
do this job and means that thecompressor is immediately ready for service.

Quality counts
The crankshafts can be ground or
metal-sprayed, although not the
journals. The valve seats are always recut, bringing them back to their original dimensions, and the cylinder head valve seats are always surface ground. Paying attention to the piston and rings is critically important. Some remanufacturers cut costs here by
using cheaper components, but this
will result in the reduced performance and life of the  compressor. Of equal importance are the cylinder head reed valves and valve discs. Reed valves are subject to extreme heat and stresses, so it is necessary to closely control the quality with tight batch control and certificates of conformity.

..Testing testing

Once the compressor has been rebuilt, it undergoes tests to check its performance. The crankshaft must rotate freely and there should be no tighter spots. There should, however, be a noticeable backlash at the top and bottom of each stroke. A pressure test of the cooling system will ensure the unit is leak free, which includes leakage into the cylinders. The air Intake / delivery function is tested to establish the correct suction of the Inlet, and compression of the delivery
ports. Final batch tests are carried out on an electronic dynamic compressor test bench, which fully simulates the compressor function.
 

8 CVW SEPTEMBER2007