MODULE 2 (1.3) - BEARING TYPE SELECTION Flashcards
dependent on a number of parameters as laid out by engineering advisory organizations, such as ASM (American Society of Materials) and EDSU (Engineering Sciences Data Unit) (UK)
Selection of Bearing Types
also include the following factors: mechanical requirements, environmental conditions and economics
Selection of Bearing Types
Rubbing, porous metal, rolling element, oil film
100
Porous metal, rolling
element, oil film
1,000
Rolling element, oil film
10,000
Oil film
100,000
an advantage of ball and roller bearings
low starting friction under load
usually considered on large, heavy machines such as electric generators at hydroelectirc dams and in utility power plants
Friction and Power Loss
speed limits for fluid film bearings are higher than rolling element bearings
Speed
rolling element bearings are generally more versatile in being able to carry their fatigue rated load at all speeds with normal lubrication
Load
hydrostatic bearings can support enormous structures
Load
rolling element bearings have a distinct fatigue life limit which results from the repeated contact stressing of the balls and rollers
Life
fluid film bearings provide essentially unlimited life
Life
dry and semi lubricated bearings are affected by its wear coeffcient
Life
rolling element bearings require only enough lubricant to provide a film coating over the surface roughness of the surfaces
Lubrication
rolling element bearings require only enough lubricant to provide a film coating over the surface roughness of the surfaces
Lubrication
fluid film bearings (oil) require relatively large quantities of oil to maintain the separating film
Lubrication
dry and semi lubricated bearings require smaller space compared to rolling element and fluid film ones
Space Requirement
temperature range, moisture, dirt and corrosive atmospheres are the important considerations
Environmental Considerations
fluid film bearings generally are limited in temperature range
Environmental Considerations
rolling element bearings can be adapted to meet wide ranging environmental demands
Environmental Considerations
capital costs and maintenance/replacement costs are the usual consideration
Economics
dry and semi lubricated bearings have the lowest costs and are usually mass produced
Economics
rolling element bearings are a step higher in cost, while fluid film bearings are the expensive ones
Economics
fluid film bearings require little or no maintenance, while rolling element bearings require occasional attention for a change of oil, new filter or general cleaning
Economics
