Maintenance Technology September 2016 - 42
POWER SYSTEMS
Handle
Bearings
With Care
Handling and installation damage
Use care when handling and assembling bearings so their rolling
elements, race surfaces, and edges aren't damaged. Gouges in the
raceway or battered and distorted rolling elements will raise metal
around the damaged area. This condition causes localized spalling
as rolling elements pass over these areas.
Damaged bearing cages or retainers
Careless handling and use of incorrect tools during installation
may damage cages or retainers (typically constructed of mild
steel, brass, or bronze) and shorten the bearing's life.
High spots and fitting practices
Carelessness or damage when driving outer races out of housings
can cause burrs or high spots in the outer-race seats. If a tool
damages the housing-seat surface, it can leave raised areas that
transfer through the outer-race rolling surface, causing stress and
shorter operating life.
Excessive preload or overload
Excessive preload can generate heat and cause damage similar to
inadequate lubrication.
Excessive end-play
This situation results in a very small load zone and excessive
looseness between the rollers and races outside the load zone.
In turn, the rollers become unseated and skid and skew as they
move in and out of the load zone. The problem is common with
non-drive-end bearings, especially on vertical machines, and
even more so with cylindrical roller bearings.
Handling practices are an important factor in a bearing's ability to live up
to its full potential.
MODERN ROLLING CONTACT bearings, when installed
and lubricated properly, can outlast the machines in which
they function. In practice, though, less than 10% of all
rolling-element bearings reach their full design life. As for
the others, 30% of premature failures can be attributed to
incorrect installation or damage done during (or prior to)
installation.
Jason Tranter, founder and managing director of Mobius
Institute, has been involved with machine-vibration analysis,
condition monitoring, and reliability improvement since
1984. He offers these important reminders for anyone who
handles bearings.
Mobius Institute (Melbourne, Australia, and Bainbridge
Island, WA) is a worldwide provider of a variety
of reliability-improvement, vibration-analysis, and
precision-maintenance training and certification services. For
more information on the company and its upcoming International Machine Vibration Analysis Conference (IMVAC), in
Orlando, visit mobiusinstitute.com.
42 |
MAINTENANCE TECHNOLOGY
Misalignment and inaccurate seat, shoulder
machining
The seats and shoulders supporting the bearing must be
within specified limits set by the bearing manufacturer. When
misaligned, the load on the bearing won't be distributed along the
rolling elements and races as intended, but concentrated on only
a portion of the rollers or balls and races.
Improper fit in housings or shafts
The bearing race where the rotating load exists should be applied
with a press fit. The stationary race would normally be applied
with a light or loose fit. Where the shaft rotates, the inner race
should normally be applied with a press fit and the outer race may
be applied with a split fit or even a loose fit.
Impact and high static-load damage
Improper mounting practices and/or extremely high operational
impact or static loads may lead to brinelling. When mounting a
bearing on a shaft with a tight inner race fit, pushing the outer
race will exert an excessive thrust load and bring the rolling
elements into sharp contact with the race, causing brinell.
Electric current arcing
Arcing inside a bearing happens when an electric current passes
through the component between the races and rolling elements.
Each time the current is broken while passing between the ball
or roller and race, a pit is produced on both surfaces. Eventually
fluting develops.
According to Tranter, since premature bearing failure can
result from issues other than improper handling, it's important to
always consult your bearing OEM and/or supplier for productspecific best practices. MT
-Jane Alexander, Managing Editor
SEPTEMBER 2016
http://www.mobiusinstitute.com
Table of Contents for the Digital Edition of Maintenance Technology September 2016
Editorial
Uptime
On The Floor
Old-School Approach To New-World Technology
Art Meets Reliability Science
Commit To Safety
Robot-Human Interaction Getting Safer
Sanitary, Stainless Conveyors Not The Same
Reduce Hidden Process-Safety Costs
Pace Your Reliability Program
Win The War With 'Lubrication By Design'
SAP Tips And Tricks
Understand Pump Vibration
Select The Right Relay
Bearing Care
Clear Up HOA Confusion
Potato Waste Becomes Clean Water, Energy
Products
Showcase
Ad Index
Final Thought
Maintenance Technology September 2016 - 1
Maintenance Technology September 2016 - Cover1
Maintenance Technology September 2016 - Cover2
Maintenance Technology September 2016 - 1
Maintenance Technology September 2016 - 2
Maintenance Technology September 2016 - 3
Maintenance Technology September 2016 - Editorial
Maintenance Technology September 2016 - 5
Maintenance Technology September 2016 - Uptime
Maintenance Technology September 2016 - 7
Maintenance Technology September 2016 - On The Floor
Maintenance Technology September 2016 - 9
Maintenance Technology September 2016 - Old-School Approach To New-World Technology
Maintenance Technology September 2016 - 11
Maintenance Technology September 2016 - 12
Maintenance Technology September 2016 - 13
Maintenance Technology September 2016 - 14
Maintenance Technology September 2016 - 15
Maintenance Technology September 2016 - Art Meets Reliability Science
Maintenance Technology September 2016 - 17
Maintenance Technology September 2016 - 18
Maintenance Technology September 2016 - 19
Maintenance Technology September 2016 - Commit To Safety
Maintenance Technology September 2016 - 21
Maintenance Technology September 2016 - 22
Maintenance Technology September 2016 - 23
Maintenance Technology September 2016 - Robot-Human Interaction Getting Safer
Maintenance Technology September 2016 - 25
Maintenance Technology September 2016 - Sanitary, Stainless Conveyors Not The Same
Maintenance Technology September 2016 - 27
Maintenance Technology September 2016 - 28
Maintenance Technology September 2016 - Reduce Hidden Process-Safety Costs
Maintenance Technology September 2016 - 30
Maintenance Technology September 2016 - Pace Your Reliability Program
Maintenance Technology September 2016 - 32
Maintenance Technology September 2016 - 33
Maintenance Technology September 2016 - 34
Maintenance Technology September 2016 - 35
Maintenance Technology September 2016 - Win The War With 'Lubrication By Design'
Maintenance Technology September 2016 - 37
Maintenance Technology September 2016 - 38
Maintenance Technology September 2016 - SAP Tips And Tricks
Maintenance Technology September 2016 - Understand Pump Vibration
Maintenance Technology September 2016 - Select The Right Relay
Maintenance Technology September 2016 - Bearing Care
Maintenance Technology September 2016 - 43
Maintenance Technology September 2016 - Clear Up HOA Confusion
Maintenance Technology September 2016 - Potato Waste Becomes Clean Water, Energy
Maintenance Technology September 2016 - 46
Maintenance Technology September 2016 - 47
Maintenance Technology September 2016 - 48
Maintenance Technology September 2016 - 49
Maintenance Technology September 2016 - 50
Maintenance Technology September 2016 - 51
Maintenance Technology September 2016 - 52
Maintenance Technology September 2016 - Showcase
Maintenance Technology September 2016 - Ad Index
Maintenance Technology September 2016 - 55
Maintenance Technology September 2016 - Final Thought
Maintenance Technology September 2016 - Cover3
Maintenance Technology September 2016 - Cover4
Maintenance Technology September 2016 - 62
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Maintenance Technology September 2016 - 65
Maintenance Technology September 2016 - 66
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