slewing or swing bearings are used for heavy industrial projects in construction, mining, marine and defense. They have been utilized in space observatories and giant shovels. Spherical roller thrust bearings are fairly common in turning bridges (SKF has installed one on the 3rd Avenue Bridge in New York City). Both spherical roller bearings and swing bearings are key components in wind mills. If the project involves heavy machinery, you can bet the components usually match both the size and scope of the operation.
“In newer windmill designs, the shaft support function is integrated into the gearbox; these bearings are large ‘unitized’ taper roller bearings,” says Victoria Wikstrom, marketing manager general industry at SKF. “Large bearings are also used in the power transmissionand wheel reduction gears of huge mining trucks.”
Customers purchasing bearings look at application data including loads, speeds, orientations, and the component’s intended environment before selecting the right type. In the case of big bearings, other factors might include delivery, installation, lubrication, inspection and re-manufacture. With large manufacturing projects come bigger costs; executives tend to feel better about purchase decisions if service life, safety, maintenance and engineering aspects are top of the line. A rumored big bearing boom could be in the works if global infrastructure projects and alternative energy advancements continue to make noise in the industrial market. SKF Worldwide,
NTN Bearing Corporation of America and Kaydon Bearing are three companies that handle the demands of these heavy industrial applications.
Many power transmission components require a certain level of customization for each individual project. The big bearing market is no exception.
Construction, mining, steel, marine and wind applications aren’t exactly areas where customers buy bearings in bulk. “These bearings are an integral part of the structure, and therefore they are selected—a better word is ‘designed’— simultaneously with the entire project,”
Wikstrom says. “Looking up a giant bearing in a catalogue and finding the right designation is not possible—the work is done in close cooperation between the bearing company and the design firm/contractor/machine builder.” This may be the most significant difference between the small bearings
typically found in general industrial applications and the big bearings used in heavy equipment. These are custommade pieces that have to follow strict design, safety and maintenance regulations in order to provide the proper service life for multi-million dollar operations.
“The smaller applications don’t have as much visibility from the higher-ups,”says Todd Franiuk, market specialist at NTN Bearing. “These heavy-duty applications rely on higher standards, more personnel and a lot more investment. They tend to get the most interest from management for obvious reasons.” Chris McGovern, a market analyst in the construction segment at NTN, adds that big bearings use more complex materials and require much more design and engineering. “These bearings typically need special materials and service treatments that you don’t find in the smaller sizes.”The extra attention given to design is due to the unique set of parameters for each individual market segment.
“For marine applications, you’re dealing with a salt spray environment. With steel applications, you have to have special design capabilities to handle the heat,” says Rick Shaw, business manager for heavy equipment at Kaydon. “Mining is all about cleanliness. How can we keep these components clean and working properly? It’s an interesting dilemma for each market.Experience helps.”
Small or large, quality is an important consideration in custom bearings. “Material specifications and initial quality control are crucial,” Wikstrom says. “So are a highly skilled workforce, production equipment, process control and the inspection of the final product to specification.”
But safety tops the list when an engineering team sets out to design a new bearing. “When you’re dealing with critical applications—whether it’s a wind tower hundreds of feet up in the air or a mining facility underground—the focal point is always safety,” Franiuk says.“Our engineering review team is very conservative whenever we look at applications with a human operator,” Shaw says. “This is the most significant concern for the heavy industrial market. It’s a premium at Kaydon.” The safety of shovel operators or engineers replacing components in a wind turbine is always discussed with large slewing bearing manufacturers during the design phase. They also come up with some form of a maintenance strategy.“Because these bearings are unique, there’s usually not a spare. One exception would be bridges. If, worst case, a ship would hit the bridge pivot pillar, road authorities cannot afford to reroute traffic until a new bearing has been produced. Therefore, there is normally a spare bearing nearby the turning bridge,” says Johan Ander, product manager for spherical roller bearings at SKF. “For wind energy, the number of mills is growing rapidly, implying that the production of large bearings will grow, too. Some users might find it attractive to keep bearings on