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Hydralics > hydraulic principles > Flashcards

hydraulic principles Flashcards

1
Q

advantages of hydraulic systems are

A

compact . light weight . powerful . can occupy a small space . more flexible than mechanical . cooling and lubricating easy to accommodate . operator can control several functions at one time . smooth and protected from overload without engine stall

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2
Q

disadvantages of hydraulics

A

fluids under pressure . noise . oil leakege can cause fire or contamination . temp variations can affect performance air pockets can cause spongey operation

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3
Q

what is work

A

work is force acting through a distance

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4
Q

in order for a hydraulic system to do work it must generate what

A

force . is the push or pull that is capable of producing or changing the motion of a body

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5
Q

what id energy defined as

A

energy is the ability to perform work

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6
Q

what are some forms of energy

A

mechanical. hydraulic. heat . electrical . chemical . light sound

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7
Q

some forms of wasted energy in a hydraulic system are

A

noise and heat

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8
Q

energy wasted in the form of heat can be caused by

A

internal leakage and the pressure required to push the oil through the system

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9
Q

what two states dose energy exist in

A

kinetic and potential

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10
Q

what is kinetic energy

A

is responsible for movement and motion

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11
Q

in a hydraulic system kinetic energy is created by what

A

the flow of oil through the system . the greater the rate of flow the greater the speed of the implement

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12
Q

what is potential energy

A

is the energy stored in a body or a substance

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13
Q

if given the opportunity potential energy will change its state to what

A

kinetic energy and work will be accomplished

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14
Q

what is an example of potential energy in a hydraulic system

A

an accumulator

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15
Q

in bernoullis principle as velocity of a fluid decreases

A

pressure exerted by that fluid increases

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16
Q

what dose flow rate determine

A

the speed of a cylinders movement .ie the time required to raise the load

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17
Q

formula for output power (Kw)

A

flowrate (L/min) x pressure (Mpa) x 0.0167

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18
Q

how is hydraulic system efficiency determined

A

by comparing the output power of a system with the amount of power required to drive the system ( input power )

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19
Q

what are the two forms of power loss

A

pressure loss and flow loss

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20
Q

what must there be in order for flow to occur in a hydraulic system

A

difference in potential energy

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21
Q

what is laminar flow

A

oil that moves through a system in straight parallel flow paths

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22
Q

conductors of adequate size with smooth transitions in cross section and direction will provide

A

lower fluid velocity and turbulence resulting in lower pressure losses and heat generation

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23
Q

turbulence can be caused by

A

conductors that are to small . abrubt changes in cross section . abrupt changes in direction

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24
Q

increased friction from turbulence will cause

A

increased power loss to heat generation

25
Q

what is backpressure

A

pressure created by resistance to flow on the return side of a system

26
Q

what will excessive back pressure cause

A

will increase the internal resistance of a system and cause reduced system efficiency

27
Q

why are most hydraulic components designed with small amounts of internal leakage

A

for lubrication of moving parts . seals and supports

28
Q

series hydraulic circuit

A

offer only one path for oil to flow ( lower torque but higher speed )

29
Q

parallel hydraulic circuits

A

divides the oil flow between components ( higher torque but lower speed )

30
Q

series parallel hydraulic circuits

A

can be both series or parallel and uses a pilot operated two position control valve

31
Q

hydraulic systems are expected to

A

transmit increased power . operate at higher pressure . operate with greater efficiency . perform at higher speeds . operate with greater control

32
Q

three general categories of hydraulic oil

A

petroleum based . fire resistant . biodegraeable

33
Q

most commonly used hydraulic oil

A

petroleum based

34
Q

selecting correct viscosity for system requirements and climactic conditions is essential to

A

prevent wear . seal internal parts

35
Q

viscosity index is a term that refers to an oils ability to

A

resist changes in viscosity as temperature rises and falls

36
Q

the lower the VI number of an oil

A

the greater its viscosity will change with temperature variations

37
Q

what is viscosity

A

an oils resistance to flow

38
Q

what do anti wear additives do

A

develop a protective film on moving parts

39
Q

what has a significant effect on oil oxidization

A

oil temperature . the higher the temp the higher the rate of oxidization

40
Q

as oil oxidization becomes more severe

A

smells burnt . leaves varnish and sludge on components . dark in color

41
Q

oil that has been severely oxidized will feel

A

slippery and will not adhere to your fingers

42
Q

all hydraulic oil will contain

A

some water

43
Q

oil with a 0.5% water in emulsion will appear

A

dull or smoky

44
Q

oil with a 1% water in emulsion will appear

A

milky

45
Q

water-oil emulsions consist of a mixture of

A

60% water 40% oil

46
Q

Invert emulsions consist of a mixture of

A

60% oil 40% water

47
Q

water glycol fluids consist of

A

60% glycol 40% water with a chemical thickener added

48
Q

water based hydraulic fluids cannot be operated at a temperature higher than

A

60 C or 140 F because the water will evaporate causing fluid viscosity change

49
Q

synthetic fire resistant fluid

A

chemically remanufactured . most common type is phosphate ester

50
Q

disadvantages to synthetic oil

A

expensive . not compatible with nitrile rubber seals must be replaced with viton seals

51
Q

what two conditions must biodegradable fluids meet

A

70-80% of base fluid must be able to be broken down . non toxic

52
Q

when selecting a proper hydraulic fluid you should

A

consult manufacture . take ambient temps into consideration . fluid is compatible

53
Q

what is one of the main contributors to hydraulic component life

A

contamination

54
Q

four common places for ingressed contamination

A

air breather. pump inlet . cylinder seals. unclean maintenance

55
Q

three types of contamination failures are

A

catastrophic . intermittent . degradation

56
Q

catastrophic failure is

A

rapid or sudden total disabling of a system or component

57
Q

intermittent failure is

A

problem moves from component to component called transient failure > hard to TS

58
Q

degradation failure

A

caused by gradual surface wear . will lead to catastrophic if left un delt with

Hydralics (12 decks)

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