When a knowledge engineering company invites you to its annual technical day, you go. Who wouldn't?
The day turned out to be right on target, with many of the presentations aligning perfectly with the topics we're covering on www.plantservices.com.
Paul Jeppesen, president and CEO of SKF North America, introduced the Philadelphia gathering to his company’s BeyondZero program, designed to reduce the negative environmental impact from SKF’s operations and those of its suppliers. Certainly, a noble and world-class initiative, worthy of noting.
Both Jeppesen and Jon Stevens, vice president of solution factories, SKF North America, spoke extensively on SKF’s groundbreaking initiatives, and Plant Services was there: http://www.plantservices.com/articles/2012/02-Where-in-the-World.html. Stevens is busy overseeing the creation of SKF’s 24th Solution Factory worldwide, this one in Cleveland. The only other U.S. installation is in Houston.
Although SKF’s offerings run the gamut for maintenance and reliability programs, most people know SKF for bearings. Matt McCormack, application engineer at SKF USA, addressed the advancements that have impacted the bearing industry.
"Motor manufacturers are pushing boundaries," he explained. “Increased machine speed means increased production. And manufacturers want machines that are more precise.”
Energy-efficient bearings can reduce frictional losses in a bearing by 30%, due to redesigned internal geometry, low friction cage, and low friction grease, said McCormack. This means reduced friction, reduced bearing torque, and reduced total cost of ownership.
As he ran down the list of new bearing innovations, it reminded me of Sheila Kennedy’s recent Technology Toolbox column on better bearings: http://www.plantservices.com/articles/2012/02-Technology-Toolbox-better-bearings.html.
McCormack said the functions of rolling bearings in electric motors are to support and locate the rotor (shaft), to keep the air gap between the stator and rotor as small and consistent as possible (to increase motor efficiency), to transfer loads from the shaft to the housing (the motor frame), to allow low to very high speeds, to reduce friction (it’s easier to roll across than to slide), and to save power (because of the lower friction).
Design parameters for bearing selection include machine design requirements, operating conditions, required bearing life, machine warranty. bearing availability (readily available anywhere in the world), economics (economics of the bearing matches the economics of the motor), maintenance, handling and transportation, and mounting tools (are any special tools needed?).
Bearing failure modes include electrical erosion, transportation and vibration, and improper lubrication, among others, said McCormack.
“Electrical erosion is caused by stray shaft current, such as sparking across the bearing that melts the steel,” he said. “It’s often caused by frequency inverters from a VFD or pulse width modulation. You can insulate with a ceramic coating to prevent or divert current.”
Transportation or vibration causes false brinelling. “As a bearing is sitting idle, the vibration from nearby equipment causes micromovements, which causes metal-to-metal erosion,” said McCormack. “Don’t store motors near vibrating equipment. Avoid storing near noisy compressors, even though the replacement equipment often is stored next to the existing equipment.”
Improper lubrication seems self-evident. “Without adequate film, you get metal-to-metal friction,” said McCormack.
Regarding bearings and lubrication, you can’t really discuss one without the other. “Sixteen percent of bearings fail because of how they’re installed,” explained Paul Michalicka of SKF North America’s maintenance products division. “Thirty-six percent fail when they’re coupled together, causing alignment problems. And 33% fail due to lubrication errors, either too little or too much. And for every dollar spent on lubrication, the disposal cost is three times as much. Lubrication software allows for the management of the lubrication process.”
I was only mildly surprised by Michalicka’s endorsement of lubrication software, especially after the column from NewPage’s Tammy Needham that we’d run on the subject recently: http://www.plantservices.com/articles/2012/07-thousand-points-lubrication.html.
All in all, it was a great event, with lots to take back and spread around. SKF is much more than bearings.