Sealing and lubrication in mounted bearings webcast: Your questions answered
A recent Plant Engineering webcast featured Jim Madsen and Mac Duke from Baldor-Dodge, on the topic: "The Importance of Sealing and Lubrication in Mounted Bearings." They responded to Webcast attendee questions that were unable to be answered during the Webcast. Those responses appear below.
An archive of the full webcast can be found here:
Q: Will proper seal design minimize seal blowout?
A: Correct. Proper mounted bearing seals should be mechanically retained and purgable so any contaminants are expelled.
Q: What are some alternatives to manage heat to extend bearing service life?
A: It is almost always advantageous to remove heat from your bearing application to improve service life. Depending on your application there are many ways to do this. In fan applications for example, many original equipment manufacturers (OEMs) use a cooling wheel attached to the shaft to keep heat from conducting through the shaft to the bearings.
Q: Please explain the importance of viscosity in the selection of lubricants.
A: Viscosity decreases as temperature increases. Select viscosity at the anticipated operating temperature of the bearing.
- Low speeds, high loads = high viscosity oil for maximum film thickness
- High speeds, light loads = low viscosity oil for minimum shear/churning
Q: What does NLGI stand for?
A: It stands for National Lubricating Grease Institute.
Q: Is 7 to 8 weeks a good rule of thumb for checking the grease?
A: No, relubrication frequency is dependent upon application conditions. Relubrication frequency should be determined by speed, hours/day run and bearing type. Most mounted bearing instruction manuals have lubrication frequency information.