Test Review

Question 1

Main functions of a bearing are to…

Answer 1

• Reduce wear
• Absorb and dissipate heat
• Guide and aid moving parts

Question 2

Three types of loads are…

Answer 2

• Thrust or axial
• Radial
• Combination

Question 3

The main bearings in a turbine generator are what type?

Answer 3

Plain bearings

Question 4

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

Answer 4

Keeps elements precisely aligned and in position

Question 5

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

Answer 5

speed limitations of the bearings

Question 6

What is the function of the bearing housing?

Answer 6

Protection and alignment

Question 7

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

Answer 7

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

Question 8

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

Answer 8

Press fit

Question 9

A bearing should not be heated above 250* because…

Answer 9

the bearing will lose the temper (hardness)

Question 10

What are two methods to heat a bearing?

Answer 10

Induction heater and electric oven

Question 11

Why is lubrication necessary?

Answer 11

Heat transfer and reduces friction

Question 12

What determines condition of a bearing?

Answer 12

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

Question 13

True or false:

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

Answer 13

True

Question 14

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

Answer 14

Direct-coupled

Question 15

True or false:

Radial bearings support axial loads.

Answer 15

False

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

Question 16

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

Answer 16

Spalling

Question 17

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

Answer 17

A servomotor

Question 18

A common mechanical reason for excess vibration is ______.

Answer 18

A clogged or broken impeller

Question 19

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

Answer 19

The speed of the drive shaft rotation

Question 20

The propeller turbine develops its power almost entirely from ______.

Answer 20

The weight of the water

Question 21

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

Answer 21

Hydraulic turbines

Question 22

True or false:

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

Answer 22

True

Question 23

Cavitation occurs in any point in a hydraulic system where…

Answer 23

A reduction of pressure causes water vapor to form

Question 24

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

Answer 24

Needle valves

Question 25

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

Answer 25

Under the rotor

Question 26

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

Answer 26

Operating head

Question 27

True or false: | Fluid is drawn into a positive displacement pump as a slight vacuum forms at the pump outlet.

Answer 27

False | A slight vacuum forms at the pump inlet

Question 28

True or false: | A centrifugal pump can not operate against a deadhead or closed valve.

Answer 28

False

Question 29

A ______ turbine has the greatest capacity among turbines.

Answer 29

Francis

Question 30

How do you determine the proper lubrication schedule for equipment?

Answer 30

Equipment application and speed

Question 31

What is a common cause of premature bearing failure?

Answer 31

Improper installation

Question 32

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

Answer 32

It can melt

Question 33

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

Answer 33

Middle

Question 34

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

Answer 34

Kingsbury shoes are completely submerged in oil

Question 35

What are the six ways to classify a centrifugal pump?

Answer 35

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

Question 36

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

Answer 36

Francis vane

Question 37

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

Answer 37

L rings

Question 38

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

Answer 38

Center the impeller

Question 39

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

Answer 39

The suction valve and casing vent

Question 40

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

Answer 40

Lose prime

Question 41

What are the steps in securing turning off a pump?

Answer 41

- Close discharge valve - Stop the motor - Close suction valve

Question 42

What is a symptom of misalignment?

Answer 42

Vibration

Question 43

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

Answer 43

Centrifugal pump

Question 44

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?

Answer 44

Positive displacement pump

Question 45

In external gear pumps, pumping chambers are formed between...

Answer 45

The gear teeth and pump housing

Question 46

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

Answer 46

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

Question 47

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

Answer 47

Impulse

Question 48

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

Answer 48

To increase velocity of water entering the turbine.

Question 49

Which is not a classification of impeller type runners? - auto adjustable - fixed blade - impulse - manually adjustable

Answer 49

Impulse

Question 50

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

Answer 50

100

Question 51

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

Answer 51

To prevent excess negative pressure beneath the turbine cover

Question 52

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

Answer 52

In the direction of rotation

Question 53

Define: | Hydrostatic

Answer 53

Load supported by high pressure fluid

Question 54

Define: | Journal

Answer 54

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

Question 55

Define: | Spalling

Answer 55

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

Question 56

Define: | Fretting

Answer 56

Damage caused by rubbing, chaffing or wearing away

Question 57

Define: | Radial

Answer 57

In the direction extending from the center point of the shaft

Question 58

Define: | Volute

Answer 58

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

Question 59

Define: | Hydrodynamic

Answer 59

Load supported by a lubricant film

Question 60

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

Answer 60

Pitting

Question 61

What allows cooling fluid into the stuffing box?

Answer 61

Lantern ring

Question 62

Define: | Axial

Answer 62

In the direction of or along the axis

Question 63

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

Answer 63

Specific speed

Question 64

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

Answer 64

Stay vanes

Question 65

What is a load supported by balls or rollers?

Answer 65

Rolling contact

Question 66

Define: | Thrust runner

Answer 66

Provides circular flow and drags a film of oil with it

Question 67

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

Answer 67

Clearance

Question 68

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

Answer 68

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.

Question 69

Explain the purpose of the wear/seal rings.

Answer 69

- 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

Question 70

What are the five principle effects of cavitation?

Answer 70

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

Question 71

What can be done to minimize the formation of cavitation?

Answer 71

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

Question 72

How is damage caused by cavitation repaired?

Answer 72

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

Question 73

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

Answer 73

Draft tube