Bearings Flashcards
What is an axial or thrust load?
A load that is parallel to the shaft axis
What is a radial load?
A load that is perpendicular to the shaft axis
What is a plain bearing?
A bearing that has no rolling elements
What is the name for the plain bearing that supports radial loads?
Journal bearings
What is the name of the plain bearing that supports axial loads?
Thrust bearing
What are the main functions of the journal bearing?
To hold a journal in it’s required location, to support the intended radial load, and minimize friction
Name the three types of radial loads
Stationary load, oscillating load, and reciprocating load
Define a stationary load
The load generally acts in one direction and on one area of the bearing
Define an oscillating load
The load shifts through an arc less than 180°
Define reciprocating load
A load shifts 180° from one side of the bearing to the other
What happens with the clearance and bearings that support oscillating loads?
They have much smaller clearances
What are some features of a thin shell type split bearing?
They have a thin shell, the shell is flexible, shell consist of a thin overlay on the still backing, the shell must be seated in a strong housing and has a very accurate bore
What are the advantages of split bearings?
Hi load capacity because they are high precision, more compact housing, relatively inexpensive to replace, quick to change out, available in oversizes and under sizes, and consistent quality
What are some applications for thick wall split bearings
Gearboxes, turbines, fans, dynamic compressors
What are the two types of seats for thick wall split bearing?
A plain seat, or spherical seat
What is a bushing?
A type of plain bearing that has not been split and can be designed to handle radial or axial loads
What is a wrapped bushing?
A bushing that consists of a thin steel shell lined with the soft bearing material such as lead bronze
What is an advantage of a wrapped bushing
They have high fatigue strength
What is a solid bushing?
A bushing that is bored out of his solid piece of Bearing material such as lead bronze or Teflon
What is a limitation of the solid bushing
They do not have the fatigue strength of wrapped bushings
What is a floating bushing?
A bushing that consists of an outer bushing with a loosely fit inner bushing
Where are water lubricated bushings used?
They are used in situations where water is continually flushing the bearings and makes it impossible for the mechanism to retain any other lubricant
What type of applications are water lubricated bushings used for?
They are suitable for only very light loads on journals of corrosion resistant material like stainless steel
What is a pre-lubricated bushing
A bushing that is either made of a porous material soaked with lubricant or have a lining made with pockets filled with lubricant
What is the range of porosity in a porous bronze bearing?
3-30% it’s volume in oil
What are some other names of porous bronze bearings?
Oilite, or sintered bronze
What materials are used for a dry lubricated nearing?
A bronze matrix containing graphite, or Teflon. Teflon is self lubricating.
What is a hydrodynamic bearing?
A bearing that at operating speed, develops a full film of lubricant, called an oil wedge.
What determines the minimum speed for hydrodynamic bearing rotation?
The load determines the speed. Oil viscosity and surface area of the bearing also are factors
What type of oil would you use in a high speed, light load application?
Low viscosity oil
What is done differently in hydrodynamic lubrication under a reciprocating or oscillating load?
It may include a circumferential oil distribution groove in the middle of the bearing
What plain bearing is good for heavy radial loads?
The pivoting shoe
When is a hydrostatic bearing used?
In equipment that operates too slow to create a hydrodynamic oil wedge
Where is oil admitted in a hydrostatic bearing?
In the loaded and unloaded zones
How is oil pressure adjusted in a hydrostatic bearing?
The inlet holes or slots are fitted with restrictors to regulate the pressure
What is the minimum speed in a hydrostatic bearing?
There is no minimum speed It can start on a full film of oil with no dry rubbing friction. The result is no wear at start up
What is the load limitations of hydrostatic bearings?
Loads are generally lower than hydrodynamic, but very high loads can still be supported if the speed is zero or a few feet per min (fpm)
What is an oil lift bearing?
The oil lift journal bearing is a hydrostatic bearing with pressurized oil entering under the loaded area only
What is the name of the oil in a oil lift journal bearing?
Jacking oil.
Where are hybrid bearings used?
In situations where there is an imbalance, such as eccentric weight on the rotor that causes the radial load to increase as the speed increases
Which type of plain thrust bearing can support the most load?
The tilting pad thrust bearing. It is also referred to as a Kingsbury, or Mitchell bearing
Where is the area of greatest wear on a tilting pad bearing?
On the trailing end of the pads
What is a gas lubricated bearing?
Pressurized gas (air) can support a loaded journal in lightly loaded high speed applications
What is compressive strength?
The bearing material must be strong enough to support the shaft loads at maximum operating temperature
What is fatigue resistance?
The resistance of the bearing material to cracking and flaking by loads that increase and decrease in rapid cycles
What is high embeddability
How well a material will handle contaminants without failing
What is deformability?
Deformability allows the material to yield to misalignment or imperfections in the shaft
What is wettability?
It is the ability to retain a film of lubricant
What is good thermal conductivity?
Allows for rapid transfer of heat
What is compatibility?
It must not seize or weld to journal under rubbing conditions such as during start up
What are some things that bad it can be made of?
Tin,lead, Copper, antimony
What are some advantages of Babbitt?
It has high imbedability, high conformability, High wetability, good thermal conductivity, good corrosion resistance, an excellent bondability
What is bearing crush?
It is the distance that a new insert protrudes above the split line of the bearing housing
What is bearing spread?
The spread is the amount that the insert diameter is wider than the bearing housing diameter
What is the purpose of locking tabs and dowels?
They are anti-rotation devices
Why is Babbitt scraped after being poured?
They are scraped so that the proper surface area is supporting the journal. You should get a pattern over at least 85% of the surface
What are the three types of friction?
Sliding, rolling and fluid
What are the three purposes of the cage or separator?
To prevent the rolling elements from rubbing against each other, to push the rolling elements through the unloaded zone, and to guide the rolling element with a minimum amount of friction
What is a bearing that starts with the number one
Self aligning ball bearing
What is the Bearing type that starts with the number four?
Deep groove double roll ball bearing
A bearing that starts with number five is what?
Thrust ball bearing
A bearing that starts with the number six is what?
Deep groove single row ball bearing
What is a bearing that starts with the number seven?
Single row angular contact ball bearing
What is a bearing that starts with the number two?
Spherical roller bearing
What is a bearing that starts with the number three?
Tapered roller bearing
What is a bearing that starts with the number eight?
Cylindrical roller thrust bearing
What are the three most common bearings?
Number two, spherical roller bearing number six deep groove single row ball bearing, number seven angular contact ball bearing single row
Which type of bearing gives the best load support?
Needle bearings
What is the area of contact called under a ball bearing?
Point contact
What is the area of contact called under a needle bearing or spherical roller bearing?
Line contact
What is the load called if it has both axial and radial loads?
A combination load
What is another name for a number six bearing?
Conrad bearing
A single row deep groove ball bearing supports what as its main function?
A radio loadbearing since that is the main function it tolerates very little angular misalignment
What is the maximum capacity Deep grove ball bearing?
It has loading slots to put more ball bearings in. It’s axial load capacity is less because of the loading slots, but it has a higher radio load capacity than a regular deep groove ball bearing of the same size
What is a double row deep grove ball bearing?
It’s designed provides a higher radial load capacity without increasing the radial dimensions
What is an externally self aligning ball bearing?
A deep groove ball bearing that has a spherically ground outer ring that mounts in a special housing
What are some features of a single row angular contact bearing?
They support substantial thrust loads in one direction only (against the high shoulder on both races) and must have some axial load as well
What are the arrangements when you mount two angular contact bearings together?
Face to face, back to back, and tandem.
What is the stiffest combination of tandem arrangements?
Back to back
What is a double row angular contact bearing?
It can handle heavy radial and axial loads in both directions, but cannot tolerate any misalignment
What is a four point angular contact bearing?
It can be used for only combination or axial loads, has Gothic arch shaped raceways, is a separable bearing and occupies much less axial space than a pair of single row contact bearings.
What are the four types of roller bearings?
Cylindrical, needle, tapered, spherical
Describe cylindrical roller bearings?
They are separable in both directions, so they can only support pure radial load
What are the three more common needle bearings?
No cage or inner ring, drawn steel cup, machined inner and outer rings
What differentiates between a cylindrical roller bearing, and needle bearings?
Needle bearings are 2.5-10 times as long as their diameter
What are the two parts of a tapered roller bearings?
The inner and outer ring are known as cone and cup
What are some features of a tapered roller bearing?
They are the best bearing for combination loads, you can use them in pairs to accommodate reversing loads
What is the rule of thumb for clearance when installing a spherical roller bearing?
1/2 the bench clearance
What is the rule of thumb for clearance when installing ball bearing applications?
When there is a slight drag when outer race is rotated
What is a CARB bearing?
Compact aligning roller bearings. It’s shape is compact like a needle bearing, but with the misalignment capability of a spherical bearing
What do the last two digits of a bearing represent?
The number X5 is the ID of the bearing
What do the last two digits 00, 01, 02, 03 represent?
10,12,15,17 mm ID
What is the ID of these two bearings
222/07
222/950
07 mm
950 mm
What is a K and a K30 designation?
K is a 1:12 taper
K30 is a 1:30 taper
What things are considered that affect speed of a bearing?
Type of rolling element Size of rolling element Precision of bearing Type of cage Method of lubrication Type of lube Type of seal
What is a z or rs designation?
Z is a shield
RS is a rubbing seal
What are the three types of ring loading?
Rotating load, stationary load, indeterminate load
What should you do if you are cleaning a bearing and using compressed air?
You should hold both races to prevent high-speed spinning
What is the proper oil level in that antifriction bearing with an oil bath
Between the third and halfway up the lowest rolling element
What is the correct grease level in a housing?
Approximately one third full after the bearing is fully packed
What is the number one cause of bearing failure?
Improper lubrication
What is the name of arc damage in a rotating bearing and in the stationary bearing?
In a rotating bearing it is called fluting in the stationary bearing it is called pitting
What are the two most common causes of vibration?
Imbalance and misalignment
