Main Propulsion Flashcards
Two main categories of bearing
Plain bearings
Anti-friction bearings
Have a solid surface on which a moving part slides or rolls
Plain bearing
Depends on races containing balls or rollers to make contact with the revolving or sliding surface that it is supporting
Anti-friction bearing
The two categories of bearings are broken down into three main types
Journal bearings
Thrust bearings
Frictionless bearings
Also called split precision bearings
Journal bearings
Support a rotating shaft, support a radial load
Journal bearings
Prevent endwise (axial) motion of a shaft
Thrust bearings
Used for guiding or supporting rotating components
Frictionless bearings
Two concerns that affect choice of bearing type
Load type and motion type
Bearings can be classified by ___
Type of movement allowed
Type of load that it will carry
Type of surface that the bearing will come into contact with
When movement within an engine must be controlled to keep engine components in proper alignment by bearings, the motion is divided into two types ___
Axial
Rotary
Movement along the axis of the shaft that can be in either one direction or back and forth
Axial
Circular movement around the axis of the shaft
Rotary
Load is divided into three types
Radial
Thrust
Radial thrust
Has a load that is at right angles to the axis of the shaft
Radial
Has a load that is along the axis of the shaft
Thrust
Has a load that is a combination of both radial and thrust loads
Radial thrust
Two types of surface contact that classify bearings
Sliding contact (plain bearings) Rolling contact (anti-friction bearings)
These bearings are made of softer material than that of the shaft or slide that the bearing will support
Plain bearings
Also called roller contact bearings
Anti-friction bearings
Have a small contact area between the races and the ball or roller of the bearing supports the load on the bearing
Anti-friction bearings
The balls and rollers of anti-friction bearings are made of ___
Hardened alloy steels
Ball bearings, roller bearings, and needle bearings are all ___
Anti-friction bearings
Ball bearing support a load on a series of hardened steel balls and consist of four parts ____
Inner ring or race
Outer ring or race
Steel balls
Ball retainer or cage
The inner ring or race of a ball bearing is ___ on its outer surface
Grooved
The outer ring or race of a ball bearing is ___ on its inner surface
Grooved
Used for spacing the balls in a ball bearing so that they do not touch each other, thus reducing friction, wear, and noise
Ball retainer or cage
Roller bearings come in three distinct shapes __
Cylindrical
Tapered
Barrel
This roller bearing supports radial load only. Intended to handle the heavy radial loads and to operate at higher speeds
Cylindrical
This roller bearing supports radial load, with an axial load in one direction only
Tapered
This roller bearing supports radial loads. Will handle some axial loads and misalignment
Barrel
Roller bearings using a relatively long and small diameter rollers
Needle bearings
Normally needle bearing rollers are about ___ in diameter
5/64 to 5/32 inch
Most common use of needle roller bearings
Wrist pin bearings in some diesel engines or in high speed applications
___ are 90 degree angular-contact bearings
Thrust bearings
Support thrust loads at moderate speeds, but for practical purposes, their radial load capacity is nil
Thrust bearings
Because thrust bearings cannot support radial loads, ball thrust bearings must be used with ___
Radial bearings
This bearing is of the simplest form, and it consists of several pivoted segments or shoes against which the thrust collar revolves
Kingsbury type thrust bearing
Ahead or astern axial motion of the shaft to which the thrust collar is secured, is thereby restrained by the action of the ___
Thrust shoes against the thrust collar
The shoes and collar of the Kingsbury thrust bearing that are encased within the housing are immersed in ___
Oil
The higher the speed of the shaft, the greater the ___ of the Kingsbury thrust bearing
Load capacity
These bearings are made for vertical and horizontal applications to accommodate either single or double thrust loads
Kingsbury thrust bearing
Thrust bearings work when one flat surface is moved along a second flat surface that is ___
Free to pivot
In a thrust bearing, the second flat surface pivots and assumes an _____ with respect to ___
Inclined position
The first surface
What separates the two surfaces in a thrust bearing?
A thin, wedge-shaped film of oil
In a thrust bearing, the thrust is transmitted from the shoes to the ___, which is attached to the ___
Base ring
Structure of the ship
Never try to repair damaged rolling-element bearings by ___
Replacing balls or rollers
Never use a piece of machinery if the bearings are known to be in ___
Poor condition
Watch the performance of newly installed bearings carefully when first starting a piece of machinery until it is known that they have reached their ___
Safe-running operation temperature
If possible, give newly installed bearings a ___
Run in period applying no load
Do not remove a rolling element type bearing from its original container and wrapping until every ____
Preparation has been made to install it
Excessive lubricant in a roller bearing will ___
Fill the spaces between the elements, impeding free movement and causing early failure
Safe storage for bearings for any length of time requires that the storage area be ____
Dry, heated, and below 120 degrees F
Although bearings are designed to be extremely rugged, they are sensitive to ___
Corrosion, contamination, and abusive handling
Why should bearings not be stored in unheated spaces?
Because condensation may form on cold surfaces
Why should bearings not be stored in temperatures above 120*F?
Because the preservative on them will oxidize more rapidly
When using bearings, always apply the ___ rule of storage
First in, first out
The greatest threats to mounted bearings are ___ which is caused by ___
Brinelling of the races
Poor handling
False brinelling of the races is caused by the ___
Wearing away of material due to vibratory motion during storage or transport and corrosion due to lack of preservative compound on bearing surfaces
If a piece of machinery needs to be stored for prolonged periods, an attempt should be made to select a foundation that is ___
Isolated from other machinery that may cause undue vibrations
If a piece of machinery needs to be stored for prolonged periods, to prevent rust and corrosion the bearings should be ___
Greased. Hand coat the bearings to limit corrosion
Oil bearings. Have the chamber filled with rust preventive oil
If machinery is being stored for prolonged periods, and is directly exposed to weather or adverse atmospheric conditions, rotate the shaft ___, otherwise rotate the shaft ____ to keep ____
Once a month
Every several months
Bearing surfaces lubricated
If machinery to be stored for prolonged periods has partial assemblies, such as rotors that have mounted bearings, the bearings should be ___
Coated with a preservative and wrapped with a plastic for foil
Bearing temperature is a function of ___
Load, speed, lubricant, and outside heat sources
The hand can usually be held in contact with a surface below __
131*F
Do not insert a ____ thermometer into the bearing housing, whether against the bearing or in the grease or oil reservoir to take the temperature of the bearing
Liquid-in-glass
If temperature rises in a bearing immediately after start up in a grease bearing application it is probably because ___
The grease has slumped into the races
If temperature rises in a bearing immediately after start up in an oil lubricated application then ___. If the level is satisfactory, the ___ may be clogged or inoperative
Stop the unit and immediately check that the oil level is in accordance with the instruction
Circulating system
If the temperature rises in a bearing immediately after the bearing has been lubricated with grease then ___
The cause may be an excessive quantity of grease or the wrong type
If the bearing is over greased ___
Remove the drain plug and allow the excess to drain
If the grease in the bearing is the wrong type ___
Disassemble and clean the bearing
If there is excessive loading of the bearing, excessive bearing preload, excessive shaft or housing interference, or external bearing overload then ___
Check the alignment during mounting and check for tight-fitting seals
Maximum temperature limit for general bearing applications
230*F
When bearing temperature is unexpectedly high, or any time the temperature exceeds limitations, an ___ should be completed
Examination of the bearing
In rotating machinery, the amplitude of bearing vibration is a function of ___
Bearing quality, seat geometry, and fit-up
