In 2001, SKF acquired the U.S. railroad bearing reconditioning company Roller Bearing Industries to strengthen its position within the North American freight bearing business and to develop its global leadership within the industry.Bearing maintenance within the North American railroad industry is a major activity in which some 1 million combined reconditioned and new-tapered roller bearing units (TBUs) are mounted each year. Roller Bearing Industries Inc. (RBI) is one of the leading bearing service companies supplying reconditioned freight and locomotive bearings to the North American rail industry.
The North American railroad market remains focused on freight transportation, which moves an average of 2.5 trillion tons of freight annually – equivalent to 12,500 trains, with 50 freight cars each, with a payload of some 100 tons per car, going all the way around the world.
Most technical and quality standards for North American railroads are governed by the Association of American Railroads (AAR), specifically in the AAR Manuals of Standards and Recommended Practices.
This rail market comprises eight Class I and 35 Class II railroads. The difference between the two categories is based on total yearly operating revenues: Class I railroads have operating revenues that exceed $262 million annually, and Class II railroads have operating revenues that range between $21 and $262 million annually.
Freight cars are loaded with cargoes ranging on average from 60 tons to 115 tons and operate at speeds ranging from 25 mph to 80 mph. Topography and environmental conditions vary drastically, and thus have a tremendous impact on freight car equipment wear and tear.
This railroad market is quality controlled by the AAR; equipment and rail systems are proactively maintained to control adverse rail incidents. The specifications for acceptable bearing reconditioning requirements and practices are based on the AAR Manual of Standards and Recommended Practices, Section H – Part II. During the early 1980s, the practice of reconditioning and remanufacturing TBUs was applied widely throughout the North American Class I rail industry, although today many of these activities are outsourced to AAR-approved organizations such as RBI.
The reconditioning practice for freight car and locomotive bearings involves the disassembly, cleaning, repair and inspection of bearing components. The reconditioning process begins when the reconditioning facility receives used bearing cores from the customer. The core is usually the entire bearing unit, comprising two tapered roller bearing inner ring assemblies (cones), the outer race (cup), the backing ring, and seal wear rings and cap screws. The unit is dismantled, the grease seals are discarded, and the components are placed in automatic wash systems. Non-hazardous, environmentally friendly wash agents remove the spent lubricant from all rolling components. The components are coated with a rust-prevention agent prior to removal from the wash system and then moved to in-process holding stations. As soon as the ambient temperature is achieved, external component surfaces, such as the outer rings, end caps and backing rings, are buffed and polished to remove accumulated rust and other external build-up, which supports the immediate inspection activities. All components are inspected for visual and dimensional characteristics. Components not meeting specifications are either scrapped, if it is not possible to rework the material defects, or remanufactured. Once all components are certified for utilization in rail service, the units are reassembled, charged with new lubrication, have new grease seals installed and are packaged for shipment.
Remanufacturing bearing components is a process of adding to or removing some of the original bearing component material. Adding to the original material involves a chrome-plating process that provides a layer of chrome plating uniformly across the inner ring bore. This layer of chrome is more durable than the original bearing material and brings the bearing inner diameter back to an acceptable and usable original equipment manufacturer (OEM) limits.
For critical remanufacturing processes, most dimensional tolerances are generally held to within 0.0001″ to 0.0015″ discrepancies, although tolerances that are more stringent do exist.
Maintaining such close dimensional tolerances is achieved by proper employee training, modern machinery and equipment, and sophisticated gauging devices. Specific remanufacturing processes must be requested, examined, audited and approved by the AAR before actual remanufacturing processes can be implemented. Once approved by the AAR, operations such as chrome plating, remanufacturing the backing ring radius, space widths and wear fretting removal on the inner ring assemblies can be performed within the facility. With AAR approval to perform these operations, the work can be carried out more cost-effectively and without compromising quality, performance, safety or reliability.
Components such as seal wear rings, spacers, backing rings and end caps are thoroughly inspected visually and dimensionally. Normally, the acceptable dimensional tolerance levels, per specific AAR rules and standards, allow the bearing material components being reconditioned or remanufactured a dimensional window of 0.001″ to 0.005″ variations in tolerance; however, practical experience is to adhere to recommended OEM bearing specifications.
Each bearing component is 100% inspected and measured for compliance to AAR-acceptable quality tolerances or to elevated customer quality specifications and requirements. Within the reconditioning process, it is imperative that each component is inspected in detail. Failure to uncover one abnormality could result in bearing failure while in service. Inner ring assemblies and outer rings are visually inspected for wear and bearing damage – for example, water and acidity damage, known as “etching,” or stain discoloration caused by acidity in the lubricant. Additionally, corrosion, pitting, rust, brinell marks, metal smearing, electrical marks, heat discoloration, metal flaking, metal indentations, fatigue spalling and fatigue cracks are included within the search. Each characteristic is detailed within the AAR specifications for conformance and non-conformance properties.
Inner ring and outer ring components have the narrowest acceptable tolerance variations and are inspected at two or more workstations before achieving full component certification within the production facility.
Reconditioned TBUs have lateral movement measured to within the prescribed limits. At this stage the bearing unit will be staged in groups and processed to the lubrication area. New lubricant is injected into the bearing by a pressurized lubrication device that evenly distributes the grease into the internal rolling components and spacer area. Each bearing unit processed has the grease weight measured for accuracy and recorded, assuring that each bearing unit has a fully loaded lubricant charge and is ready for field service. Once lubricated, the bearings are fitted with new grease seals. A sensorized seal press unit is used, which confirms that the seal retaining lip is properly seated in the outer ring grease seal groove. Sensors fitted within the grease presses consequently assure that proper sealing pressures and contacts have been achieved.
The bearing unit is then placed in a staging area, where production associates clean the external surfaces and fit the appropriate backing rings, seal wear rings and end caps to the finished product. New cap screws and new locking plates are added at the final packaging station. As an option, especially for harsh chemical car applications, a unique AAR unconditionally approved stainless steel locking plate can be offered. Once on the conveyor belt, the finished bearing units are audited one additional time for quality conformance, wrapped and shipped to the customer’s destination for use.
RBI has one of the most rigorous quality programs in the rail industry. The RBI quality department is autonomous and reports directly to the president of the company. Its ratio of auditors to production personnel is 1:8. Stationed at key points to sample and test for product conformance, the auditors perform random audits throughout the plant and are empowered to stop production should they observe or encounter any product non-conformance.
All employees are trained and certified – a practice RBI implemented long before the AAR M-1003 training requirements went into effect. All reconditioned components are 100% approved by certified production inspectors during the reconditioning and remanufacturing processes.
After each certified procedure, parts are held in a mandatory inspection hold area until 15% of the components are inspected, audited and documented by quality auditors. Other quality system controls and checks include: barrier gates, electronic/computer-aided transducers and keyed lockout systems. All workmanship can be traced to the individual performing the work. Statistical Process Control (SPC) and Process Failure Modes and Effects Analysis (PFMEA) are in place to ascertain trends and proactively respond to non-conformance issues. RBI also contracts with a retired AAR inspector to perform quarterly independent third-party audits to further strengthen the quality system, effectively administering changes imposed by the AAR quality system and those of customers.
Two of the United States’ largest power utility companies specify RBI Power-Plus premium bearings for their bearing maintenance requirements. During 2000 they experienced a combined total of 435 bearings removed from service, none of which were RBI reconditioned product. In that year, the power utility companies enjoyed a 33% reduction in AAR billing costs related to the removal of bearings from service. During the third quarter of 2000, they initiated a program to purge all pre-1997 bearings in service and replace them with 100% RBI Power-Plus bearings. To date, both companies have experienced product cost savings and reduced maintenance costs.
In April 2002, RBI will receive the prestigious TTX Company SECO (Supplier Evaluation Consensus) Rating Award for 2001. RBI has been a recipient of this award continuously since 1991. SECO was instituted as a performance program in 1991. The aim of the program was to recognize and commend the TTX supplier community’s commitment to continuous quality improvement. Annually, the TTX Company evaluates some 140 suppliers based on the following criteria: product quality, product performance, cost, delivery, service, financial and administrative functions. After the results are accumulated and tabulated, the TTX Company SECO committee presents the SECO Award to the supplier companies earning “Excellent Supplier” status and acknowledges the entire supplier base for its commitment to continuous improvement.
Looking to the future, RBI is committed to introducing SKF technologies and associated bearing mechanical advancements to its customer base and railroad markets. This includes new SKF reconditioning techniques and bearing-related products to provide better reliability, safety and performance while continuing to collaborate with the AAR organization, gaining full approval for SKF bearing products introduced to the North American market.
SKF Roller Bearing Industries, Inc.,
and Gottfried Kuře,
SKF Global Railway Marketing, Steyr, Austria