Rock Products

APR 2018

Rock Products is the aggregates industry's leading source for market analysis and technology solutions, delivering critical content focusing on aggregates-processing equipment; operational efficiencies; management best practices; comprehensive market

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24 • ROCK products • April 2018 critical to isolate vibrations in associated equipment as they can cause uneven running and unusual noises. Environmental Influence Even with the best design, lubrication and installation fail- ures will occur if the operating environment is not taken into consideration. While there are many potential issues, the primary ones are:  1. Dust and dirt, which can aggressively contaminate a bearing. Great care should be given to use proper seal- ing techniques.  2. Aggressive media or water. Once again, sealing is pri- mary. The use of specialty type seals is recommended such as pump mechanical or labyrinth style seals that do not score the shaft.  3. External heat. The ambient operating temperature mandates many choices in radial internal clearance, high temperature lubricants, intermittent or continu- ous running and others, which affect bearing life.  4. Current passage or electrolytic corrosion. If current is allowed to flow through the rolling elements, sparks can create pitting or fluting on the bearing surfaces. This should be corrected by creating a bypass circuit for the current or through the use of insulation on or within the bearing. This should be an inherent design consideration in applications such as wind turbines and all power generating equipment. In conclusion, the first step in the overall prevention of bearing failure lies in the consideration of bearing technolo- gies that are most suitable to the application with regard to specifications, recommendations, maintenance strategies, fatigue life and wear resistance of the bearing in relation to the application. That being said, premature bearing failure within a proper application is typically attributed to one or more of the causes discussed (lubrication, mounting, operational stress and bearing selection or environmental influence) which can and should be corrected in order to avoid future bearing fail- ures and additional cost. Steven Katz is the president of Emerson Bearing, a provider of bearings to OEM and markets in the United States and inter- nationally. Emerson Bearing operates from a 23,000-sq.-ft. facility to provide bearings ranging in size from 3-mm to tun- nel-boring 15-ft.-diameter giants. The Boston-based company provides worldwide sourcing, a fixed price program and 24/7 service. For more information, contact 800-225-4587 or visit Table 1: What is That Sound? Sound Other Indicators Causes Hiss Small bearings. Raceway, ball or roller surfaces are rough. Buzz to Roar Loudness and pitch change with speed. Resonation. Poor fit. Bearing rings deformed. Vibration of raceways, balls or rollers. Brinelling. Crunch Felt when bearing is rotated by hand. Scoring of raceway surfaces. Scoring of balls or rollers. Dust/contamination. Hum Disappears when power supply is shut off. Electromagnetic sound of motor. Clatter Noticeable at low speeds, continuous at high speeds. Bumping in cage pockets due to insufficient lubricant. Screech/Howl Occurs mainly on cylindrical roller bearings. Sound changes with speed. Goes away temporarily with lubrication. Large radial clearance. Poor lubrication. Squeak Metal to metal spalling sound. High pitch. Small clearance. Squeal Generated irregularly due to grating. Slipping of fitting surfaces. Rustle Sound quality remains same even if speed changes. Dirt or raceways, ball or roller surfaces are rough. Growl Continuous at high speeds. Scoring on raceway, balls or rollers. Quiet Fizzing or Popping Generated irregularly on small bearings. Bursting sound of bubbles in grease. Large Sound Pressure Large sound pressure. Rough raceway, roller or ball surfaces. Raceways, rollers or balls deformed by wear. Large internal clearance due to wear. Sources: Barden Corp. Machine Tool technical bulletin for Engineer- ing and Lubrication. 2010. FAG Bearings Corp. Rolling Bearing Damage. Publ. No. WL 82 102/2 December 1997. Fersa Bearings. Roller Bearings: Failure Diagnosis. 2009. Koyo Bearing Corp. Rolling Bearings: Failures, Causes and Countermeasures. Catalog No. 322E. December 1995. NTN Bearing Corp. Products and Technology. Care and Maintenance of Bearings. 2009. Bearing Failure

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