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HET Period 3 Hydraulics > Practice Questions > Flashcards

Practice Questions Flashcards

1
Q

The displacement of a pump refers to?

The discharge rate per minute
Discharge rate per hour
Discharge rate per revolution
Discharge rate per cycle

A

Discharge rate per revolution

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2
Q

A Gear type hydraulic motor

Is not reversible
Has more shaft seal protection due to dual rotation
Is similar to a gear pump but contains three pressure plates
Will damage the shaft seal if reversed

A

Has more shaft seal protection due to dual rotation

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3
Q

A piston pump that has the pistons parallel to the drive shaft is called?

Non positive displacement pump
Axial Pump
Radial Pump
Bent Axis Pump

A

Axial Pump

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4
Q

Tandem section gear pumps

Always use two sections of equal size
are two pumps mounted together
always contain two inlets and outlets
Use adjustable gear sections to control output

A

Are two pumps mounted together

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5
Q

Variable Displacement pumps are

The volume can be altered per cycle
The speed of the pump can be altered
The pressure can be altered
The flow rate is fixed

A

The volume can be altered per cycle

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6
Q

Vane pumps may be

Positive displacement
Fixed displacement
Variable Displacement
All of the above

A

All of the above

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7
Q

The pressure that will just open a valve is called

Opening pressure
Main pressure
high pressure
cracking pressure

A

Cracking pressure

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8
Q

A valve section regenerative position

Allows a fast drop of crawler loader boom
Supplies the oil to rear mounted equipment
Connects the becket cylinder rod ends to the head ends for a fast dump
Returns the bucket cutting edge to a digging position

A

Connects the bucket cylinder rod ends to the head ends for a fast dump

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9
Q

A spool valve is used to control

Direction of oil flow
System Pressure
Accumulator pressure
None of the above

A

Accumulator Pressure

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10
Q

When installing hydraulic pumps, the inlet lines should be kept?

As long as possible
Have at least one bend to relieve pressure
As short and as straight as possible
In a slight curve to prevent cavitation

A

As short and as straight as possible

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11
Q

A Pump of unbalanced design is so named because

Its disproportioned weight will cause it to vibrate
There is a side load on the rotor and drive shaft
The design is not balanced to system needs
None of the above

A

There is side load on the rotor and driveshaft

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12
Q

Gear pumps

Use pressurized wear plates
Are variable displacement
Are always non positive displacement
Always use tapered bearings on the shaft

A

Use pressurized wear plates

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13
Q

What is the purpose of a cushion in a cylinder?

Provide a reserve of air
Eliminate fluctuation of pressure
Reduce mechanical shock
Prevent back pressure

A

Reduce mechanical shock

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14
Q

What is used for overload protection in a hydraulic system

The pump
The directional Control
the pressure control
The actuator

A

The pressure control

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15
Q

In any hydraulic circuit if only the actuator area is changed

the speed of operation will be changed
the minimum force exerted will be changed
the maximum pressure obtainable will be changed
the input horsepower will be changed

A

The speed of operation will be changed

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16
Q

Leakage from the housing drain port on axial piston pumps may not be caused by

Damaged drive shaft seal
Scored valve plate or cylinder block face
Cylinder Block Lifting
Return oil from a yoke control unit

A

Damaged drive shaft seal

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17
Q

In a variable radial piston pump, what controls the stroke of the pistons?

System Pressure
Case Pressure
Spring Pressure
Centrifugal Force

A

System Pressure

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18
Q

The maximum safe working pressure of a hydraulic system is reduced by

Installing a smaller pump
Changing relief valve setting
Installing a check valve
Installing a smaller motor

A

Changing a relief valve setting

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19
Q

If two directional control valves are connected in series in a hydraulic system

Both valves must be operated simultaneously
only one can be operated at a time
either one or the other or both can be operated
can not be hooked in series

A

Either one or the other or both can be operated

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20
Q

A detent mechanism is used to

Alert the operator be feel that they are in a certain position
Hold the spool in certain positions
hold the auxiliary valve in the raise position
none of the above

A

Hold the spool in certain positions

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21
Q

Fixed displacement motors have

Variable speed, variable torque
fixed torque fixed speed
fixed torque fixed displacement
fixed torque and speed controlled by system

A

Fixed torque

Fixed displacement

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22
Q

A stop tube

Allows fluid to move in one direction only
overrides pressure relief in case of reservoir loss
minimizes actuator side loads
limits swash plate angle in an axial piston pump

A

Minimizes actuator side loads

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23
Q

A valve that is used to coordinate the times of actuation is

Pressure Relief
Unloading Valve
Sequence Valve
Pressure Reducing

A

Sequence Valve

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24
Q

Hydraulic motors may be of the style

Variable speed
Fixed speed
Reversible speed
All of the above

A

All of the above

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25
Q

The purpose of a lift check is

To allow a fast drop of a cylinder
Prevent cavitation of the pump
Trap flow spikes in the valve
Stop a function from settling just before it starts to move

A

Stop a function from settling just before it starts to move

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26
Q

Piston type pumps

Have the lowest volumetric efficiency
May require supercharging in some applications
if variable displacement should not be operated too near the centre position when the inlet is pressurized
Are not used in high pressure applications

A

May require supercharging in some applications

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27
Q

A style of pump that has a device called a crescent is a?

Gear
Vane
Piston
Centrifugal

A

Gear Pump

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28
Q

The type of pump that cannot be made variable is?

Gear
Vane
Piston
All of the above

A

Gear Pump

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29
Q

Bent Axis Pump is a?

Gear
Vane
Piston
Centrifugal

A

Piston Pump

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30
Q

If you work on or replace a directional control valve you must

Be careful when tightening he mounting bolts
Drain and replace the hydraulic fluid
Also replace the pump
Use a lower viscosity oil during the break in period

A

Be careful when tightening the mounting bolts

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31
Q

The difference between the cracking pressure and the full flow is called

Pressure reducing
Pressure override
Pressure Relief
none of the above

A

Pressure override

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32
Q

Pressure compensated axial piston pumps have the following characteristics

Their displacement is automatically changed to meet system demands
They generate more heat in a system
Always require another relief valve
Displacement is controlled on both sides of the yoke position

A

Their displacement is automatically changed to meet system demands

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33
Q

A directional control valve is rated at 3/4”, this means that the valve is

3/4” High
Mounted with 3/4” Bolts
To be piped with a 3/4” Pipe
All of the above

A

To be piped with a 3/4” Pipe

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34
Q

When a restriction is placed on the return line of an advancing Cylinder, the results would be

System pressure on piston decreases
Tank PRessure increased
Force output of cylinder decreases
Force output of cylinder increases

A

Force output of cylinder decreases

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35
Q

The results of closing off the discharge side of a positive displacement pump would be?

Pump motor would stall
pump casing would split
pump discharge line would burst
all of the above

A

All of the above

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36
Q

In a valve section float position

The pump is connected to the piston end of a cylinder
The pump is connected to the rod end of a cylinder
Work ports, pump supply and return are connected so the cylinder may move freely
Both ends of the cylinder area are connected together to increase its extension speed

A

Work ports, pump supply and return are connected so the cylinder may move freely

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37
Q

An anti cavitation check valve

Stops a function from settling just before it starts to move
Opens to allow oil to fill an actuator when the pump supply is unavailable
Limits pressure peaks in the control valve then the circuit relief valve sticks
B and C

A

Opens to allow oil to fill an actuator when the pump supply is unavailable

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38
Q

A Minimum starting speed of 600 RPM is recommended for vane pumps

To avoid cavitation
to push the vanes into the rotor
To start pumping action
To prevent aeration

A

To start pumping action

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39
Q

Vane motors used on most industrial equipment

Do not contain spring loaded vanes
never use double edged vanes
usually use a replaceable cartridge
all of the above

A

Usually use a replaceable cartridge

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40
Q

A double vane cylinder exhausts oil through

External Drain lines
one way check valves
internal passages
directional control valves

A

Internal Passages

41
Q

When two identical motors are connected in series they will develop

Same torque but different speeds
Same torque same speed
Different torques same speed
Different torques different speeds

A

Different torques

Same Speed

42
Q

if a system is unable to function with full force the problem could be caused by

broken pump drive shaft
low pump flow
relief valve set too low
none of the above

A

Relief valve set too low

43
Q

Shock Loads imposed upon motors may be safeguarded by?

Deceleration valves
Pressure relief valves
Accumulators
All of the above

A

All of the above

44
Q

A valve used to divery oil to alternate end of a cylinder is

Pressure reducing valve
Check valve
Four Way Valve
Quick Drop Valve

A

Quick drop valve

45
Q

Methods of varying the displacement of variable pumps is?

Moving the pressure ring in respect to the rotor
Varying the angle of bent axis pumps
Varying the stroke of piston pumps
All of the above

A

All of the above

46
Q

Gear pumps are

Fixed displacement
Hydraulically unbalanced
Positive Displacement
All of the above

A

All of the above

47
Q

An anti cavitation valve

Stops a function from settling just before it starts to move
Opens to allow oil to fill a cylinder when the pump supply is unavailable or inadequate
Limits pressure peaks in the control valve when the system relief valve sticks
B and C

A

Opens to allow oil to fill a cylinder when the pump supply is unavailable or inadequate

48
Q

Centrifugal pumps are classed as?

Rotary pumps
Non positive displacement pumps
Axial Flow Pumps
Ram Pumps

A

Non Positive Displacement Pumps

49
Q

According to your module a simple check valve can be considered a

Pressure Relief Valve
Directional Control Valve
None of the above
Both A and B

A

Directional control valve

50
Q

Hydraulic pumps are usually rated in terms of their?

Mechanical and Hydraulic output
Volumetric input and pressure
Volumetric output and pressure
Mechanical input and pressure

A

Volumetric output and pressure

51
Q

A defective shaft seal in an internally drained vane pump will

Leak oil when the pump is running
Have no effect on pump operation
keeps air from entering the system
Make the pump noisy

A

Makes the pump noisy

52
Q

Directional Control Valves may be operated

Manually
Mechanically
Electrically
All of the above

A

All of the above

53
Q

The relief valve in a hydraulic system relieves excess pressure by

Venting to atmosphere
By-passing the fluid to the reservoir
By-passing the fluid to the pump discharge
Venting to the fluid cooler

A

Venting to the fluid cooler

54
Q

When a lower than main pressure is required in a secondary circuit the type of valve that would be used is a

Relief valve
sequence valve
Check valve
Pressure reducing valve

A

Pressure reducing valve

55
Q

To vent a pressure relief valve means that

The valve is uncoupled from the circuit
The valves pilot pressure is increased
The valves pilot pressure is decreased
The valves pilot pressure is returned to tank

A

The valves pilot pressure is returned to tank.

56
Q

An unloader valve

is always set at least 150 psi above relief
is held open by spring pressure
is the only valve that can replace a relief valve
controls slowing down of the load

A

Is the only valve that can replace a relief valve

57
Q

The speed at which a cylinder moves is controlled by?

The pump
the pressure control
the pump or flow control
the flow control

A

The pump or flow control

58
Q

Reversing drive shaft rotation of axial piston pumps

May require a relative change in the valve plate or sub assembly
Will change oil flow direction through the pump unless yoke is moved to opposite side of centre
Should not be tried ever
Can only be done on variable displacement units

A

May require a relative change in the valve plate or sub assembly

59
Q

The swash plate pump is a?

Gear
Vane
Piston
Centrifugal

A

Piston Pump

60
Q

The time taken for a cylinder to make a definite stroke is dependent upon the

Pump output and piston area
pump pressure output and length of stroke
pump volume output stroke length and piston area
pump volume output and length of stroke

A

Pump volume output stroke length and piston area

61
Q

Flow direction through a variable displacement piston type pump is affected by

Direction of drive rotation
Angle of degrees of yoke displacement from centre position
Yoke position one side to the other of centre
Drive shaft speed in RPM

A

Yoke position one side to the other of centre

62
Q

Single section gear pumps do not

contain a driving gear
contain an idler gear
contain pressure plate
have external drains

A

Have external drains

63
Q

Which of the following pumps could not be operated as a variable displacement pump with a fixed speed?

Vane
Radial Piston
Gear
Axial Piston

A

Gear Pump

64
Q

Circular grooves cut around the valve spool

Serve no purpose
Allow lubrication and sealing of the spool
allow metering of a function
Match the edges of the bore lands to decrease pressure peaks

A

Allow lubrication and sealing of the spool

65
Q

A Fixed Displacement Motor

Provides a variable torque regardless of speed
Provides constant torque regardless of pressure
May be reversed by reversing oil flow to and from motor
Should not be used in a closed loop

A

May be reversed by reversing oil flow to and from motor

66
Q

When it is required to allow flow in one direction and prevent flow in the opposite direction we would use a

Relief Valve
Sequence Valve
Check Valve
Reducing Valve

A

Check Valve

67
Q

The main pressure relief valve in a hydraulic system is located

in the main line to the cylinder
in the oil return line
in the pump suction line
between the pump and the control valve

A

Between the pump and the control valve

68
Q

Air in a hydraulic pump causes?

Smoother operation
Cooler operation
Better operation
Noisy operation

A

Noisy Operation

69
Q

What type of valve is used to control a double acting cylinder?

Two Way Valve
Glove Valve
Four Way Valve
Three Way Valve

A

Four way Valve

70
Q

Oil flow through an open centre control valve when in the neutral position

Returns to the reservoir
is at a pressure as low as possible
is routed through the valve so that all spools can recieve oil
All of the above

A

All of the above

71
Q

A Meter in valve is classified as

Pressure control device
Flow control device
Both flow and pressure control device
None of the above

A

Flow control device

72
Q

Hydraulic pumps are devices used to?

Convert mechanical energy to electrical
Convert Hydraulic energy to electrical
Convert Hydraulic energy to mechanical energy
Convert mechanical energy into hydraulic energy

A

Convert mechanical energy into hydraulic energy

73
Q

Balanced Vane Pumps rated output flow in fallons per minute is determined by

Rise in cam ring
Width of pumping cartridge
Drive shaft rated speed
All of the above

A

All of the above

74
Q

Where fixed output pumps are used, a method of controlling the speed of actuators is by means of?

Meter in valves
Meter out valves
Bleed off valves
All of the above

A

All of the above

75
Q

A Non positive displacement pump refers to a type of pump

Where the inlet must be higher than the outlet
Where the outlet must be lower than the inlet
Which will slip the liquid at a certain pressure
Which will not slip the liquid at a certain pressure

A

Which will slip the liquid at a certain pressure

76
Q

A Pressure relief valve will operate because

Pressure are equal over equal areas
Pressures are unequal over unequal areas
Pressures are unequal over equal areas
A spring setting has been reached or overcome

A

A spring setting has been reached or overcome

77
Q

A pump that could be used without a pressure relief valve is?

vane pump fixed displacement
Manually controlled variable displacement vane pump
Fixed displacement Gear Pump
Pressure Compensated, Variable displacement, Piston Pump

A

Pressure Compensated, Variable Displacement Piston Pump

78
Q

A Hydraulic cylinder is known as

Torque Converter
Rotary Actuator
Linear Actuator
All the above

A

Linear Actuator

79
Q

As the speed at which a pump is driven changes

Its displacement changes
its pressure changes
its swash plate angle changes
its volume changes

A

Its volume changes

80
Q

A Directional control valve is categorized in two types

Low and medium pressure
medium and high pressure
Spool and Rotary
Check and Relief

A

Spool and rotary

81
Q

The purpose of the swash plate in an axial piston pump is

to adjust pump pressure
to open and close the discharge ports
Change pump displacement
Change pump speed

A

Change Pump Displacement

82
Q

Horsepower required at 83% to drive a hydraulic pump is?

Gallons Per Min X PSI X 0.000583
Gallons Per Min X PSI X 0.00583
Gallons Per Min X PSI X 0.007
Gallong Per Min X PSI X 0.0007

A

All of the above

83
Q

A Power beyond feature

Allows a second control valve to receive oil when the system control is in neutral
Allows a second control valve to receive oil through the main system control valve at all times
Supplies pressure oil to the crawler dozer selected valve
None of the above

A

Allows a second control valve to receive oil when the system control is in neutral

84
Q

Two gear pumps placed in series will

Affect the pressure
Affect the flow
Not work unless mounted within 2” of tank
None of the above

A

Affects the pressure

85
Q

A Piston pump that has the pistons arranged at right angles to the drive shaft is called?

Non Positive Displacement Pump
Axial Pump
Radial Pump
Bent Axis Pump

A

Radial Pump

86
Q

A Positive displacement pump refers to a type of pump where?

The liquid is discharged by a flexible delivery hose
The inlet of the pump is sealed from pump discharge
The inlet of the pump is a flexible hose
The inlet is not sealed from the outlet

A

The inlet of the pump is sealed from pump discharge

87
Q

Single direction hydraulic motor is usually controlled by

Two way two position
Two way four position
Four way two position
Four way four position

A

Four way

Two Position

88
Q

When two identical hydraulic motors on the same output shaft are connected in parallel with each other they will develop

Twice the speed and twice the torque
Half the speed and half the torque
Twice speed half torque
Half speed Twice torque

A

Half the speed

Twice the Torque

89
Q

When a telescoping cylinder actuates it usually has

The smallest diameter piston first
The largest diameter piston first
All the pistons at the same time
None of the above

A

The largest piston first

90
Q

When it is required to allow a pump to run when the system is not being used, it is useful to fit a ___________ valve in the system

Relief
Sequence
Unloading
Reducing

A

Unloading

91
Q

Jerky or erratic motion in a hydraulic cylinder is usually due to

Presence of water in system
Presence of air in system
presence of oil in system
synthetic fluids are being used

A

Presence of water in system

92
Q

An accepted point of control valve leakage is

Between the valve spool and its bore
relief valve seats
anti cavitation check valve seats
circuit relief valve o rings

A

Between the valve spool and its bore

93
Q

On a axial piston pump, which statement does not apply?

Excessive valve plate or cylinder block wear may cause cylinder block lift
Replenishing pumps are required on all piston unit circuits
The housing drain port should be piped in such a way that the case is always full of oil
The housing or case of a piston unit should be filled with oil before it is operated

A

Replenishing pumps are required on all piston unit circuits

94
Q

A reversible hydraulic motor that is required to coast or free wheel in the neutral position is usually controlled by

Three position, four way open centre valve
Four position, four way closed centre valve
Four position, three way tandem centre valve
Three position, four way tandem centre valve

A

Three position
Four way
Open centre valve

95
Q

The force output of a conventional cylinder is the greatest when

The piston is advancing
the piston is retracting
the cylinder is mounted horizantally
the cylinder is mounted vertically

A

The piston is advancing

96
Q

The volumetric efficiency of a vane pump

Increases with an increase in drive shaft RPM within recommended operation range.
remains constant under all operating conditions
decreases as oil temperature decreases

A

Increases with an increase in drive shaft RPM within

97
Q

Delivery in a Gallons per minute of a variable displacement piston type pump is affected by?

Direction of driveshaft rotation
Angle of degrees of yoke displacement from centre position on the same side
Yoke position, one side or other of centre on same angle
The size of the drain line hose

A

Angle of degrees of yoke displacement from centre position on the same side

98
Q

A restricted hydraulic pump suction line

Cut down pump oil intake without damage
Damages the pump
Causes excessive oil back pressure
Blow out the filter gasket

A

Damages the pump

99
Q

Notches or holes in a valve spool land

Allow the operator to precisely meter or feather oil to a cylinder
Restrict the flow of oil to a circuit relief valve
Allows the gradual stoppage of oil through the valve center which limits pressure peaks
All of the above

A

Allow the operator to previsely meter or feather oil to a cylinder

HET Period 3 Hydraulics (9 decks)

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