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millwright level 2 > plain bearings > Flashcards

plain bearings Flashcards

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1
Q

name 3 types of radial loads?

A

stationary
osculating load
reciprocating load

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2
Q

stationary load?

A

present on bearings supporting a horizontal rotor

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3
Q

oscillating load?

A

act on bearings in the crank end of connecting rods in engines.
much smaller clearances

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4
Q

advantages of split bearings?

A

very high load capacity ,high precision ,inexpensive to replace, quick to change out, available in over sizes and undersizes, wide range of material can be used in their construction

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5
Q

spherical seated bearings are usually used where?

A

turbines with a vary long span between bearings

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6
Q

what are bushings?

A

type of plain bearing that has not been split and can handle radial and axial loads

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7
Q

advantages of a wrapped bushing?

A

high fatigue strength
available in pre-finished sizes that are oversized until installed
(should only be used in lightly loaded non critical applications.

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8
Q

what is a solid bushing?

A

bored out of a solid piece of bearing material ( lead,bronze, teflon)

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9
Q

advantages of solid bushings?

A

can be bored out to non standard sizes,easily made from suitable round stock
they can accommodate deep lubricant grooves

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10
Q

limitations of solid bushings?

A

do not have the fatigue strength of wrapped bushings

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11
Q

what is a floating bushing?

A

consists of an outer bushing with a loosely fitted inner bushing

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12
Q

applications of water lubricated bushings?

A

used when water is continuously flushing the bearing and makes it impossible to retain any other lubricant

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13
Q

limitations of water lubricated bushings?

A

only suitable for light loads such as vertical shafts with out side load.

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14
Q

pre lubricated bushings are made of?

A

porous material soaked with lubricant ,lubricant squeezed out under load

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15
Q

dry lubricated bushing?

A

can run dry or with lubricants
available with large range of liner materials
not good for high speeds or heavy loads

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16
Q

hydro dynamic bearing is ?

A

most widely used type of plain bearing
depends on rotation of shaft to drag oil into the loaded area
at normal speed the bearing is supported on a full film of oil

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17
Q

What kind of Bearing at start up has virtually no oil in the loaded area which results in dry rubbing friction and boundary lubrication

A

Hydro dynamic bearings

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18
Q

Hydro dynamic bearings are designed to carry any load at?

A

Very high speeds

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19
Q

And unsteady load at high speeds, and develop a condition called what?

A

oil whirl

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20
Q

hydrostatic bearings are found on equipment that operate to?

A

To slowly to form a Hydro dynamic film or to operate with heavy shock loads. I can breakthrough Hydro dynamic film.

21
Q

What is the minimum speed on a hydrostatic Bearing?

A

There is no minimum speed load supporting film can be provided at zero speed
Full film of the oil with no dry rub in friction or boundary lubrication on start up

22
Q

Where is an oil left journal Bearing commonly used

A

Large turbines and compressors this bearing uses hydrostatic pressure to lift the shaft off the Bearing surface before it starts to turn and continues to support it until reaches a speed with the Hydro. Dammit lubrication can take over.

23
Q

Jacking oil must be up to what on a oil lift journal bearing

A

Must be up to pressure before the shaft just turned, if not, could result in immediate destruction of the Bearing

24
Q

Where is a hybrid bearing used?

A

Used in situations where there is an imbalance such as an Ecentric weight on the load or that causes radial load to increase as speed increases

25
Q

What does a thrust bearing do?

A

Function of a thrust bearing us to hold a shaft Axially in the required positions

26
Q

Where are magnetic bearings used?

A

They are used on large, high-speed, central, fugal compressors

27
Q

What is compressive strength?

A

Bearing material must be strong enough to support the shops load at maximum operating temperature

28
Q

What is fatigue resistance?

A

Is the resistance of the bearing material to cracking and flaking by loads that increase and decrease in rapid cycles, fatigue resistance can be increased by keeping the liner material as thin as possible to allow the backing to handle the stress

29
Q

What is high embeddability

A

Determines how well a material handles contaminants without failing

30
Q

what is deformability?

A

Allows the material to yield to misalignment or inperfections in the shaft, insurers all parts of the bearing carry a share of the load

31
Q

what is wet ability?

A

Ability to retain a film of lubricant

32
Q

What is compatibility?

A

Must not seize or weld to journal under rubbing conditions, such as during start up

33
Q

What is Babbitt?

A

Babbitt is a white metal alloy is composed of soft alloys, such as tin lead copper and add atimony

Lead provides the bearing properties while bronze or copper, provides the strength

34
Q

Where is Teflon used?

A

It is used for light duty bushings and it is used in bronze matrix for extra strength

35
Q

What are some advantages of Teflon?

A

It is self lubricating. It is chemically inert
It can be used with soft journals

36
Q

What are the disadvantages of Teflon?

A

It is limited by temperature it emits poisonous gas when burned it absorbs water

37
Q

What is a limitation of aluminum alloys?

A

They have less embeddability and conformability than babit

38
Q

What is false loading?

A

A small chip or burr can cause a bearing to support the load on only part of its surface. It results in premature wear

39
Q

What is crush and spread?

A

crush-crush and spread ensure the insert is mated tightly to the bearing housing bore.
Spread is the amount that the insert diameter is wider than the bearing housing diameter

40
Q

Using a vernier, check the journal for taper, and out of round to check for out of round three measurements are taken at what intervals

A

60 deg intervalls

41
Q

true or false-Plane bearings can be either journal bearings to support radialloads or thrust bearings to sport axial loads

A

true

42
Q

true or false ?Water lubricated bearings are made of rubber but can be nylon or Teflon.

A

true

43
Q

true or false–Dry bushings are made of graphite, or Teflon or a bronze matrix containing graphite or Teflon.

A

true

44
Q

What kind of bearings are found on equipment that operate two slowly to form a Hydro dynamic film

A

hydrostatic bearings

45
Q

What is another name for the tilting pad thrust bearing?

A

Kingsbury

46
Q

Where are magnetic bearings used?

A

large high speed centrifugal compressors

47
Q

Where are gas lubricated bearings used?

A

They are used for lightly loaded, high-speed applications

48
Q

Use a driver and a ____ when removing a bushing?

A

adapter

49
Q
A

millwright level 2 (17 decks)

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