Mounting Bearing Myths and Mounting Bearing Myths and MisconceptionsMisconceptions

Brought to you by Power Transmission Solutions

Mounting Bearing Myths and Mounting Bearing Myths and MisconceptionsMisconceptions

Brought to you by Power Transmission Solutions

2

Reasons Bearings FailReasons Bearings FailReasons Bearings FailReasons Bearings Fail

Other

Installation

Misalignment

Shaft Lock Failure

Lubrication Problems &

Contamination

Source: Combined published industry data and Emerson – Power Transmission Solutions compiled records. For more details visit www.emerson-ept.com.

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Misapplication Myth #1:Misapplication Myth #1:Misapplication Myth #1:Misapplication Myth #1:

Sealed / Lubed For Life Means It Should Last Forever. FALSE

• Grease Life Depends On– Operating Conditions (Speed, Load)

– Environment (Temperature, Contamination Level)

• Increasing Grease Life– Enhanced Sealing

– Proper Installation

• L10 Does Not Apply to Sealed for Life Bearings– L10 is Based on Laboratory Conditions

– Once the Grease Goes, So Does the Bearing

Sealed for Life Bearings Only Last as Long as the Grease Does

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Misapplication Myth #1 (cont’d): Misapplication Myth #1 (cont’d): Misapplication Myth #1 (cont’d): Misapplication Myth #1 (cont’d):

• Variables– L10: Theoretical Bearing Life (Hours)

– BDR: Basic Dynamic Load Rating (LBS)

– Load: Equivalent Applied Radial Load (LBS)

– Speed: Shaft Speed (RPM)

• Operating Conditions (Impact Life But Not In L10 Equation)– Environment: Clean, Dirty, Wet

– Temperature: Stable, High, Low

– Proper Relubrication: Frequency, Amount, Type

Ball Bearing Life (Theoretical)

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Misapplication Myth #2:Misapplication Myth #2:Misapplication Myth #2:Misapplication Myth #2:Bearing Failures are Always the Manufacturer’s Fault. FALSE• Bearing Failures

– Manufacturing Anomalies Are Rare

– Typically Misuse / Application Related

– End of Useful Life

• Application Related Modes of Failure– Contamination

– Inadequate Lubrication

– Misalignment

– Loss of Shaft Lock

– Over-Loading

– Vibration

– Corrosion

Corrosion

Electric Arcing

Thrust Load

Over-Loading

Particle Denting

Vibration Over-Heating

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Misapplication Myth #3:Misapplication Myth #3:Misapplication Myth #3:Misapplication Myth #3:Bigger Bearings Are Always Better. FALSE

• Bigger Bearings– Carry More Load– May Show an Increased L10– As Bearing Size Increases, Limiting

Speed Decreases

• Skidding– Sliding Instead of Rolling – May

Generate Increased Friction, Heat – Greater Potential in Applications with

Lighter Loads & Higher Speeds

Skidding

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Misapplication Myth #4:Misapplication Myth #4:Misapplication Myth #4:Misapplication Myth #4:Bearings Can Only Rotate in One Direction. FALSE• Bearing Rotation

– Clutches Rotate in Only One Direction– Bearings Rotate in Both Directions

• Eccentric Locking Mechanism Restrictions– Lock in Direction of Shaft Rotation– Opposite Rotation Can Cause Loss of Shaft Lock

Eccentric – Lock in Direction of Shaft

Rotation

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Misapplication Myth #5:Misapplication Myth #5:Misapplication Myth #5:Misapplication Myth #5:

Locking Mechanisms Are All the Same. FALSE

• Locking Mechanisms– Set Screw (Mars Shaft)

– Eccentric Collar (Mars Shaft / Friction Grip)

– Concentric Collar (Friction Grip)

– Tapered Adaptor Sleeve (Friction Grip)

• Locking Factors– Ease of Installation

– Repeatability

– Concentricity

– Roundness

– Effectiveness

– Thrust Load

Set Screw

Eccentric Collar

Concentric Collar

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Misapplication Myth #6:Misapplication Myth #6:Misapplication Myth #6:Misapplication Myth #6:Bearings Will Not be Hot to the Touch. FALSE

• Normal Bearing Operation– Rated For -20°F to 200°F

– Can Generally Accept Intermittent to 250°F

– General Operating Range 80°F to 150°F

• Temporary Temperature Spike– Start-Up +50°F approx.

– Relubrication +30°F approx.T

emp

erat

ure

(°F

)Time (Hours)

125°F @ 45 min

100°F @ 3 Hrs

Example Mounted Ball Bearing Operating Temperature Graph

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ConclusionsConclusionsConclusionsConclusions

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More is Not Always Better. . . Bigger is Not Always Better. . .

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