This is the third installment of a 5 part series on bearing trends.
By David R. Mikalonis
3. APPLICATION-SPECIFIC ENGINEERING
From cryogenic pumps to wind turbines, among other critical equipment applications, focused engineering scrutiny of applications and their challenges for bearings has led to application-specific solutions tailored for the jobs at hand.
Example: In the case of cryogenic pumps, the service life of standard bearings often will be less than six months, directly attributed to constant attacks on the bearing arrangement. Specially engineered bearings developed for cryogenic pumps have been shown to dramatically extend the service life of bearings in these applications by several years.
Compared with standard bearings, cryogenic pump bearings benefit materially from specially heat-treated and super-tough stainless steel delivering improved protection against corrosion, wear, fatigue, and other factors. In addition, such bearings integrate low-friction silicon nitride (ceramic) rolling elements to help prevent electrical erosion by insulating against stray currents and resist any tendency toward surface fatigue, even under poor lubrication conditions inherent with cryogenic pumps.
Cryogenic pump bearings also are designed with single piece, glass fiber-reinforced PEEK (polyetheretherketone) cages. Unlike conventional rigid and riveted steel, brass, or polymer counterparts, a PEEK cage allows liquefied gases in cryogenic applications to flow easily through the bearing. At the same time, the cage will flex away from the dynamic movements of the bearing’s rolling elements to help improve operational efficiency.
Example: The wind industry has similarly been the subject of application-specific engineering to arrive at solutions that can meet specific operating demands. Innovations in bearings for wind turbines have been providing designers with the freedom to develop a wide variety of turbines, whether for those with gearboxes or directly driven, with outer or inner ring rotation, mounted on shafts, or directly bolted onto the surrounding structure.
This engineering has led to the design of bearings that can handle heavy and complex rotor loads carried by a single bearing instead of the traditional two-bearing arrangement. This simplifies mounting, dismounting, and replacement and reduces nacelle weight, among other benefits.
Such bearings specifically for wind turbine applications further integrate a variety of other uniquely engineered features. These include a high-friction coating to minimize relative movement of mating components, single-pocket segmented cage for increased load carrying capacity and higher degree of flexibility, integrated carriers and seals to reduce risk of contamination and increase intervals between maintenance, special greases, and surface treatments.