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Pumps, Bearings, And Turbines > Test Review > Flashcards

Test Review Flashcards

1
Q

Main functions of a bearing are to…

A
  • Reduce wear
  • Absorb and dissipate heat
  • Guide and aid moving parts
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2
Q

Three types of loads are…

A
  • Thrust or axial
  • Radial
  • Combination
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3
Q

The main bearings in a turbine generator are what type?

A

Plain bearings

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4
Q

In a rolling element bearing, what is the cage used for?

A

Keeps elements precisely aligned and in position

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5
Q

When multiplying the shaft diameter times the rpm, the result represents the…

A

speed limitations of the bearings

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6
Q

What is the function of the bearing housing?

A

Protection and alignment

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7
Q

When handling new small bearings, the first step after removing from the package should be…

A

Clean with solvent, wipe dry, and lubricate with proper oil or grease

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8
Q

What is one method that guarantees no movement between the bearing and shaft?

A

Press fit

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9
Q

A bearing should not be heated above 250* because…

A

the bearing will lose the temper (hardness)

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10
Q

What are two methods to heat a bearing?

A

Induction heater and electric oven

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11
Q

Why is lubrication necessary?

A

Heat transfer and reduces friction

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12
Q

What determines condition of a bearing?

A

Temperature, proper lubrication, changes in noise and vibration, and condition of bearing seals

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13
Q

True or false:

In a stuffing box, the cooling liquid is injected into the lantern ring to cool and lubricate packing and seals.

A

True

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14
Q

Pumps connected to their driver with a coupling is said to be ______.

A

Direct-coupled

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15
Q

True or false:

Radial bearings support axial loads.

A

False

Thrust bearings support axial loads. Journal bearings support radial loads.

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16
Q

When small pieces of metal flake off a bearing, it is a clear sign of ______.

A

Spalling

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17
Q

Blade angle adjustment on a Kaplan turbine is controlled by ______.

A

A servomotor

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18
Q

A common mechanical reason for excess vibration is ______.

A

A clogged or broken impeller

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19
Q

A pumps delivery rate can be changed by varying a pumps displacement or ______.

A

The speed of the drive shaft rotation

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20
Q

The propeller turbine develops its power almost entirely from ______.

A

The weight of the water

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21
Q

What are the mechanical devices that convert water power potential into usable power?

A

Hydraulic turbines

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22
Q

True or false:

To control runaway speeds in case of load rejection on an impulse wheel, deflector plates and tilting nozzles are used.

A

True

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23
Q

Cavitation occurs in any point in a hydraulic system where…

A

A reduction of pressure causes water vapor to form

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24
Q

The size of the jet of water on the discharge line of an impulse wheel is usually controlled by ______.

A

Needle valves

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25
Q

On an umbrella turbine unit, where are the thrust collar and runners located?

A

Under the rotor

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26
Q

The principle factor in the selection of a turbine is the ______.

A

Operating head

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27
Q

True or false:

Fluid is drawn into a positive displacement pump as a slight vacuum forms at the pump outlet.

A

False

A slight vacuum forms at the pump inlet

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28
Q

True or false:

A centrifugal pump can not operate against a deadhead or closed valve.

A

False

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29
Q

A ______ turbine has the greatest capacity among turbines.

A

Francis

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30
Q

How do you determine the proper lubrication schedule for equipment?

A

Equipment application and speed

31
Q

What is a common cause of premature bearing failure?

A

Improper installation

32
Q

What can happen to a plain bearing when there is frictional heat?

A

It can melt

33
Q

On a GE thrust bearing the greatest pressure area is on the…

A

Middle

34
Q

What is the advantage of a Kingsbury pivoted shoe over a plain or pillowback thrust bearing?

A

Kingsbury shoes are completely submerged in oil

35
Q

What are the six ways to classify a centrifugal pump?

A

Volute design, suction position, impeller design, shaft position, single-stage, or multi-stage

36
Q

One classification of the centrifugal pump characterized by shape is the …

A

Francis vane

37
Q

Which wear rings have clearance in an axial and radial direction?

A

L rings

38
Q

In addition to supporting the shaft, what else do pump bearings do?

A

Center the impeller

39
Q

To remove trapped air in a pump, what must be opened?

A

The suction valve and casing vent

40
Q

Air entering the suction side or packing may cause a pump to…

A

Lose prime

41
Q

What are the steps in securing turning off a pump?

A
  • Close discharge valve
  • Stop the motor
  • Close suction valve
42
Q

What is a symptom of misalignment?

A

Vibration

43
Q

In which type of hydraulic pump does delivery dramatically decrease as fluid pressure increases?

A

Centrifugal pump

44
Q

In what type of pump do sealed chambers increase in size to draw fluid in the pump and decrease in size to force fluid out of the pump?

A

Positive displacement pump

45
Q

In external gear pumps, pumping chambers are formed between…

A

The gear teeth and pump housing

46
Q

In vane pumps, reverse flow thru the pump can be achieved by…

A

Moving the cam ring to an under-the-center position

47
Q

At a head of 1400 ft, what type of wheel would normally be used?

A

Impulse

48
Q

What is the purpose of speed rings on a Francis turbine?

A

To increase velocity of water entering the turbine.

49
Q

Which is not a classification of impeller type runners?

  • auto adjustable
  • fixed blade
  • impulse
  • manually adjustable
A

Impulse

50
Q

With reaction turbines, water enters ______% of the wheel.

A

100

51
Q

One of the accessories installed on a turbine is a vacuum breaker. What is the purpose of the vacuum breaker?

A

To prevent excess negative pressure beneath the turbine cover

52
Q

The spiral or scroll of a turbine case is always arranged so the direction of flow of water is…

A

In the direction of rotation

53
Q

Define:

Hydrostatic

A

Load supported by high pressure fluid

54
Q

Define:

Journal

A

The part of a rotating shaft, axle, roll, or spindle that turns in a bearing.

55
Q

Define:

Spalling

A

The chipping or flaking of metal from the surface of a bearing

56
Q

Define:

Fretting

A

Damage caused by rubbing, chaffing or wearing away

57
Q

Define:

Radial

A

In the direction extending from the center point of the shaft

58
Q

Define:

Volute

A

Designed so that the speed of a liquid is converted into pressure without shock

59
Q

Define:

Hydrodynamic

A

Load supported by a lubricant film

60
Q

What are indentations formed in the surface of a bearing called?

A

Pitting

61
Q

What allows cooling fluid into the stuffing box?

A

Lantern ring

62
Q

Define:

Axial

A

In the direction of or along the axis

63
Q

What compares the speed of all types of turbines for a given head and capacity?

A

Specific speed

64
Q

What are the vertical ribs that separate and support the speed ring called?

A

Stay vanes

65
Q

What is a load supported by balls or rollers?

A

Rolling contact

66
Q

Define:

Thrust runner

A

Provides circular flow and drags a film of oil with it

67
Q

What is the amount of space between the component parts of a bearing assembly?

A

Clearance

68
Q

Where are wear/seal rings located on pumps and turbines?

A

Each runner has rotating/impeller wear rings located on the top and bottom. The two stationary/casing wear rings are located on the head cover and in the pump case.

69
Q

Explain the purpose of the wear/seal rings.

A
  • Provide a replaceable wear surface and renewable clearance between the impeller and casing.
  • The tight clearance between the suction side and discharge side of the impeller maintains a seal
  • Flat rings are for axial or radial seals
  • L rings are for both axial and radial seals
  • Labyrinth seals dissipate pressure
70
Q

What are the five principle effects of cavitation?

A
  1. Discharge of water is lowered
  2. Reduces output power
  3. Reduces efficiency of unit
  4. Unusually noisy operation
  5. Increased vibration
71
Q

What can be done to minimize the formation of cavitation?

A

Admission of air to turbines at light loads sometimes aids in controlling turbulence and cavitation.

72
Q

How is damage caused by cavitation repaired?

A

Cavitation results in pitting and honeycombing exposed surfaces. Damage is repaired by arc welding and rebuilding the damaged area.

73
Q

The portion of the water passage of a reaction turbine which conducts the water discharged from the turbine runner to the tailrace is the

A

Draft tube

Pumps, Bearings, And Turbines (1 decks)

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