Chemical Processing - August 2007 - (Page 29) nating direction, these bearings must be combined with a second bearing capable of supporting axial loading. A combined load results when radial and axial loads act simultaneously. The most common bearing solutions in these cases are single- and doublerow angular-contact and single-row tapered ball bearings (although deepgroove ball bearings may also be appropriate, depending upon the ratio of axial to radial loading). Further factors Other primary factors for bearing selection include: Connection type. The nature of the device placed between the drive and the driven unit (coupling, belt or gear drive) influences the loads on motor bearings and resulting performance. Good alignment is important in both flexible and rigid coupling drives because misalignment can induce additional forces into the bearing system and reduce service life. Proper alignment is particularly crucial with a rigid coupling where typically three bearings are on a shaft (two in the motor and a third in the coupled device). When rigid couplings are aligned very accurately, the drive-end bearing might become relatively unloaded. In these cases, a deep-groove ball bearing would be recommended at the drive end. A belt or gear drive frequently will load the motor bearings more heavily than a coupling drive; cylindrical roller bearings most often are used at the drive end where significant loads are encountered. In applications with heavy loads as well as the possibility of misalignment or shaft deflection, spherical and toroidal roller bearings offer solutions. Speed. The rpm influences operating temperature and, in turn, bearing and lubricant life. So, cage, lubricant, running accuracy and clearance of the bearings, the resonance frequency of the system, and the balancing of the rotating components are significant factors in bearing selection. www.chemicalprocessing.com For high-speed applications, ball friction and corresponding low heat bearings generally prove more appro- generation inside the bearing will priate than roller bearings. In very- work well in high speed operation. high-speed applications, precision or The highest speeds can be achieved hybrid bearings may offer benefits. with deep-groove ball bearings when Temperature. The permissible loads are purely radial and with anbearing operating temperature in gular-contact ball bearings for coma motor application will limit the bined loads. This holds especially speed at which rolling bearings can true for such bearings with ceramic perform. Bearing types with low rolling elements. Page 1 CONVEYOR putnam 6_07.qxd 6/12/2007 10:38 AM Sanitary Hygienic Dust-Free The best solution for moving bulk materials is with PIAB Vacuum Conveying. Whether you're feeding material to a form, fill, seal machine or a volumetric feeder or feeding material to a mixer or a blender, PIAB's C-Series vacuum conveying systems make it all happen. Sanitary - 3-A & USDA accepted. Hygienic - quick-change filters prevent cross-contamination of ingredients. Dust-Free - vacuum technology by compressed air prevents product blow-by or leakage. For more information, call (800) 321-7422/(781) 337-7309 or e-mail us at info@piab.com www.piab.com August 2007 • 29 http://www.piab.com http://www.piab.com http://www.chemicalprocessing.com
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