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77 Cards in this Set
- Front
- Back
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Best split joint design
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Gib joint
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Two basic bearing seals
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* External * Integral rubbing seals or non rubbing shields |
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Rubbing seals
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* Retains oil or grease * Positive seal against moisture and fine contaminants |
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External seal
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Installed on bearing housing |
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Integral seal
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Attached to bearing
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External rubbing seals
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* Lip seals * V-ring seals * Felt seals * Mechanical seals |
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Lip seal contact pressure provided before start up
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* Garter spring keeps seal on shaft * Resilience of seal material combined with light interference fit to shaft |
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Lip seal contact pressure increased after start up
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* Whirling lubricant presses on inside of lip * Gas or liquid pressure acting on lip |
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Disadvantages of lip seals
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* Limited surface speed due to friction but limits doubled with hard finish, polished shaft c45/.8 microns * Limited temp due to non metallic material. -40 to +200 Celsius |
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Lip seal installation notes
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* Must be lubricated on installation * Shaft free of nicks or burrs * Machining or polishing marks must be parallel to axis * No contaminants at seal that would damage lip |
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V-ring seal
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* Contact seal up to 12 meters/sec * Above speed it acts as a flinger * Fitted tightly to shaft * Light axial pressure to machined surface |
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V-ring benifits
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* Tolerates large amount of axial misalignment * Surface smoothness not as critical as lip seals * Installing inside housing enables oil retention |
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Felt seal
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* Mainly for grease retention * Low speed seal * Do not resist chemicals well * Can absorb large amount of lubricant * Must be pre-lubricated |
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Mechanical seal uses/ conditions
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* Relatively low peripheral speeds * Severe service conditions * Wet environments * Dirty environments containing solids * Leak proof retention of lubricants * Most expensive |
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Integral rubbing seals
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* Do not require mounting * Extremely thin * No garter springs * Retain grease and oil * Keep out fine contaminants as well as liquids and vapours * Lower speeds |
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Non rubbing seals
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* No friction * No wear * Not easily damaged * Can operate at high temps * Pressing grease into caps can increase sealing efficience |
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Non rubbing seals limitations
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Effectiveness depends on the narrowest of gaps between rotating and stationary parts
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External non rubbing seals
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Large amount of styles that are mounted on housing and not the bearing
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Smooth gap type seal
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* Simplest and cheapest * Only effective in dust free environments * For grease lubricated bearings |
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Radial labyrinth seals
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* Used in split housing * Tolerates very limited axial or radial movement on shaft * Can better retain oil by adding flinger in one of the grooves * Retains lubricant through pressure drop |
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Axial labyrinth seal
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* Used in one piece housings * Axial movement of shaft does not affect gap width * Gaps can be smaller * Limited radial movement |
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Axial/radial combination seal
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More effective sealing than just axial or radial
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Sealing washer set
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* Pressed steal washers * Cheapest labyrinth seal * Efficiency increased with number of sets * Adding rotating disks to shaft increases efficiency of main seal |
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Flinger ring
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* Added to labyrinth seal for oil retention * Attached to shaft and rotates within groove |
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Integral non rubbing seals
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* Shields * Thin metal attached to outer ring * Cannot keep out fine contaminants * No speed restriction |
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Pillow block types
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* Unit pillow blocks * Flanged bearing housing * Plain bearing pillow blocks |
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Split joint for plain bearing pillow blocks
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* One piece or solid * Angle joint * V-joint * Gibb joint |
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Gibb joint
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* Greatest load * 300 degree load zone |
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Angle joint
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90 degree load zone
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V-joint
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120 degree load zone
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Solid
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* One piece * Generally lighter duity * Impossible to install in middle of shaft without removal of bearings and attatchments |
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Pillow block loading
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* Horizontally split * Radial capacity same as bearing * Can act in all directions |
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Substantial loading of pillow block points
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* 55-120 degrees install stops to maintain alignment * Axial force install stops on both sides of pillow block - capacity = 65% @ 90 degrees * Load not vertically down - capacity depends on cap strength * Load capacity reduced to 1/3 to 2/3 @ 55 degrees as angle increases or loading axially |
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Anti friction bearing pillow blocks
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* One of the most common styles * Slotted holes in base for alignment * Removable cap for lubrication * Dowel pins for allignment * Accurately ground bearing seat with space for axial movement * Two sumps for contaminants * Grease fitting in cap * Locating ring for axial alignment * Grooves in housing for seals |
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Housing material
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* Cast iron * Ductile iron * Cast steel |
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Assembling pillow blocks
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* Matched sets - don't mix * Locating dowels - ensure proper fit * Cap bolts - sufficient preload required * Grease 1/2 to 2/3 free space around bearing * Oil 1/2 way up lowest rolling element * Grease fitting - located opposite retaining nut |
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Locating rings
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* None = free floating. Allows thermal expansion * One = located bearing usually drive end to prevent misalignment of attachments. install opposite retaining nut for unrestricted re-lubrication |
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Pillow block seals
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* External seals * Felt * Lip * V-ring * Various labyrinth combinations |
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Unit pillow block
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* One piece * No reduction in capacity by angular loads * Spherical aligning seat * Loading slots for bearings * Extended inner ring for eccentric collar or set screws * Speed reduced by set screws |
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Flanged bearing housing
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* Base @ 90 degrees to axis of insert * Various bolt hole configurations with type of material |
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Axial labyrinth seal
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Grooves parallel to shaft
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Babbitt
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* Soft anti friction alloy * Combinations of tin. copper, antimony(previously lead) |
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Cartridge style pillow block
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One piece housing with loading slots and a spherical bearing seat allowing axial insertion and alignment
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External seal
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Located on housing
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Felt seal
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Lubricated strip of felt retained by groove in the housing and contacting the shaft
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Flanged bearing housing
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Mounts on surface at right angles to axis of shaft
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Garter spring
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Small diameter coil spring with hooked ends to form a loop fitted in a lip seal to keep contact to shaft
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Pillow block bearing insert
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The bearing that fits in a cartridge style one piece pillow block
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Integral seal
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Attached to bearing
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Labyrinth seal
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Non contact seal consisting of a series of gaps between two rotating parts. each gap progressively restricting leakage through pressure drop
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Lip seal
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Contact seal with thin lip(s) that contact shaft
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Locating rings
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Spacer rings with large gaps for slipping over shafts and fill the axial space next to a bearing in a pillow block
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Non rubbing seal
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Does not contact shaft. Also called non contact or shield as used with and internal seal
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Pillow block
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Self contained bearing housing to hold either friction or non friction bearings
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Plain bearing
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Plain surface instead of rolling elements
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Radial labyrinth seal
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Grooves at right angles to shaft
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Rubbing seal
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Contacts shaft
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Surface speed
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Surface speed = circumference X rotating speed
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Best lip seal against vapours
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Lip seal
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Main function of bearing seals
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* Protect from contaminants * Retain lubricant |
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Rubbing seal advantages
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* Protect from fine contaminants * Better lubrication retention |
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Advantages of rubbing seals
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* Higher max speed * Protect from larger contaminants * No rubbing friction * Can seal at higher temps |
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Disadvantages of rubbing seals
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* Reduces maximum speed * Friction |
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Observations when installing lip seal
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* Garter spring present * Shaft has no burrs or nicks * Lip seal is lubricated to shaft * Machining/polish marks circumferential and not spiral or axial |
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Limitations of felt seal
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* Limits top speed * Must be lubricated * Vulnerable to some corrosives |
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How can a labyrinth seal retain oil
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Adding a flinger to one of the grooves
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Common name for an integral non rubbing seal
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Shield
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Types of bearings in anti friction pillow blocks
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* Double row spherical * Double row deep groove ball |
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Purpose of locating rings in pillow blocks
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To ensure proper alignment of cap with base
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Where should single retainer ring be placed in pillow blocks
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Same side as locking nut
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Purpose of grease fitting on a labyrinth seal
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More efficient sealing
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Four split joints for pillow blocks
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* Horizontal * Angle * V-joint * Gibb joint |
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How bearing is mounted in a unit pillow block |
* Eccentric collar and set screw * Two set screws |
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Difference of a unit pillow block and flanged bearing housing
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Base 90 degrees to shaft on flanged
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Direction lock collar tightened
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Direction of rotation
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When cutting new ring gaskets out of sheet rubber it should be
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Larger diameter than the flange face ID
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