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Hydraulics > Third Year Millwright Hydraulics > Flashcards

Third Year Millwright Hydraulics Flashcards

1
Q

Flow control valves control:

A

speed

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2
Q

Pressure Control valves control:

A

force

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3
Q

Flow control valves can be either:

A

compensated or non-compensated

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4
Q

Flow control valves can be used for:

A

metering

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5
Q

Needle Valves include a:

A

fixed orifice

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6
Q

Compensated control valves:

A

adjust for pressure and temperature changes

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7
Q

When fluid gets hot it becomes less viscous, therfore it may be best to use a:

A

Compensated needle valve

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8
Q

A hydraulic vane motor without springs would never

A

get started, the springs are necessary to hold out the vanes against the stator.

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9
Q

If the veins are non metallic, the vane compressor does not need

A

oil in the stator (dry compressor)

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10
Q

of vanes x max volume between vanes x number of vanes =

A

Maximum Displacement

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11
Q

Increasing RPM on a Vane Compressor

A

Increases Output

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12
Q

In a vacuum pump situation, the discharge is:

A

exhaust

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13
Q

Liquid Ring compressors offer:

A

cool, clean, pulse free air with little vibration

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14
Q

Are reservoirs obligatory on Rotary Compressors:

A

No, they run for extended periods of time and can provide output when needed downstream

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15
Q

The minimum pressure valve sends a signal to the compressor to:

A

start up

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16
Q

The more open the inlet valve, the more:

A

volume is delivered

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17
Q

The butterfly valve is involved in:

A

modulation control

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18
Q

The oil bypass valve senses oil is:

A

cold, so it keeps it in the sump until it warms up from discharge pressure

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19
Q

The safety relief valve is used when:

A

there is a stuck minimum pressure valve or blocked labyrinth passages

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20
Q

Bearing Carriers:

A

Locate the rotor(s) in the correct position

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21
Q

Holes drilled in Vanes decrease:

A

the weight

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22
Q

When the compressor is not running, the oil level in the separator is:

A

high

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23
Q

Vane compressors can overheat from:

A

running too much

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24
Q

metering in can cause

A

cavitation

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25
Q

If a meter valve is placed before the directional valve then:

A

both directions are metered

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26
Q

meter in and meter out do not control

A

pressure, they only control flow

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27
Q

pumps can produce flow, but not

A

pressure

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28
Q

in a stack valve the pressure relief valve should be placed closest to the

A

subplate

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29
Q

System for stack valves:

A

ISO

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30
Q

If a stack valve needs to be able to handle higher pressure, a higher:

A

flow capability is needed

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31
Q

cartridge valve advantage:

A

are less expensive

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32
Q

Screw in Cartridge valves are good for:

A

30-35 GPM

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33
Q

Slip in type cartridge valves:

A

slip into standardized cavities in manifold block

34
Q

Proportional Valves get their name because:

A

spool can be infinitely positioned, proportional.

35
Q

Coil current proportional valves:

A

moderately precise

36
Q

Dead Band

A

distance armature moves before spool functions

37
Q

Gain formulae is

A

output volts divided by input volts

38
Q

A subplate is located where stacking valves meet:

A

hydraulic lines, or conductors

39
Q

An amp card controls:

A

electrical input to the solenoid

40
Q

Dither is a:

A

high frequency AC signal superimposed onto the valves DC signal

41
Q

DC current gives more torque and it is

A

easier to use

42
Q

DC signal tells us where the valve:

A

is (it’s position in a proportional valve)

43
Q

Histerisis definition

A

dependency of a condition on the previous condition

44
Q

Ramp Functions

A

increase or decrease voltage to the solenoid, this way we can eliminate shocks from fast stops and starts.

45
Q

Non feed back control:

A

used for smooth control of actuator speed.

46
Q

Non feed back control offers:

A

moderate accuracy

47
Q

Internal feed back senses where the:

A

Directional Control Valve is

48
Q

Closed outer loop reads where the:

A

actuator is

49
Q

Closed inner loop tells us:

A

where the spool is

50
Q

Open loop

A

non feedback

51
Q

A type of proportional relief valve that uses a simple spindle to close the opening of a small nozzle:

A

Nozzle Type

52
Q

A nozzle type relief valve is set by:

A

electronic pressure, not hydraulic

53
Q

When the armature is pulled in on a nozzle type relief valve, the spindle moves in and allows:

A

oil to return to tank when over pressure limit

54
Q

plate type

A

when hydraulic force overcomes electrical force the oil will flow

55
Q

poppet type LVDT

A

proportional spool type valves have bleed screws

56
Q

servo valve

A

has a feedback wire for torque motor

57
Q

Mechanical servo valves

A

essentially a force multiplier

58
Q

Flapper nozzle type

A

two stage, infinite positioning, servo spool for dead band

59
Q

Jet pipe Type

A

Pressure at each end of the valve spool, signal to torque motor changes jet pipre and more fluid flows to one side than the other.

60
Q

single stage servo valve

A

direct, moves spool one way or the other

61
Q

Filtration and servo valves

A

located in valve and before the valve

62
Q

pumps convert

A

mechanical energy into hydraulic energy

63
Q

To have a positive flow to pumps at all times:

A

they must not suck air

64
Q

reservoirs are pressurized on mobile equipment for two reasons:

A

to keep dirt out, and so pump does not need to suck air

65
Q

hydrodynamic pumps

A

non positive seal, primarily for fluid transfer

66
Q

on a positive displacement pump, if it is shut off:

A

no fluid flows from discharge to suction

67
Q

Positive Displacement Pumps are unloaded by:

A

pressure relief valves

68
Q

Closing the inlet port will cause:

A

cavitation and ruin the pump

69
Q

Positive displacement pumps work on a

A

pressure differential

70
Q

Pump efficiency

A

(GPM delivered divided by theoretical GPM capacity) X 100

71
Q

Pressure Gauges require

A

calibration

72
Q

pump efficiency decreases as

A

pressure increases, due to slippage

73
Q

volumetric efficiency of the pump is affected by:

A

pressure

74
Q

Vane Pumps are rated at what RPM?

A

1200rpm

75
Q

If we keep the pump RPM at the engineered spec then we know pump:

A

displacement is correct

76
Q

four types of piston pumps:

A

in-line, bent axis, rotary, radial

77
Q

oil holes in a piston pump allow oil to flow to the:

A

low pressure side and prevent metal to metal contact, this is why a case drain is necessary

78
Q

All piston pumps have a:

A

squash plate

79
Q

If there is a hump on the pump casting then the:

A

squash plate can be moved

80
Q

If the flow remains constant but we change the swash plate angle it changes the:

A

displacement

81
Q

High Pressure on secondary piston (yoke) moves the:

A

swash plate

82
Q

30 degrees from perpindicular is the swash plates

A

maximum displacement

Hydraulics (1 decks)

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