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hydraulic principles Flashcards

(58 cards)

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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

Study These Flashcards
A

increased power loss to heat generation

25
what is backpressure
pressure created by resistance to flow on the return side of a system
26
what will excessive back pressure cause
will increase the internal resistance of a system and cause reduced system efficiency
27
why are most hydraulic components designed with small amounts of internal leakage
for lubrication of moving parts . seals and supports
28
series hydraulic circuit
offer only one path for oil to flow ( lower torque but higher speed )
29
parallel hydraulic circuits
divides the oil flow between components ( higher torque but lower speed )
30
series parallel hydraulic circuits
can be both series or parallel and uses a pilot operated two position control valve
31
hydraulic systems are expected to
transmit increased power . operate at higher pressure . operate with greater efficiency . perform at higher speeds . operate with greater control
32
three general categories of hydraulic oil
petroleum based . fire resistant . biodegraeable
33
most commonly used hydraulic oil
petroleum based
34
selecting correct viscosity for system requirements and climactic conditions is essential to
prevent wear . seal internal parts
35
viscosity index is a term that refers to an oils ability to
resist changes in viscosity as temperature rises and falls
36
the lower the VI number of an oil
the greater its viscosity will change with temperature variations
37
what is viscosity
an oils resistance to flow
38
what do anti wear additives do
develop a protective film on moving parts
39
what has a significant effect on oil oxidization
oil temperature . the higher the temp the higher the rate of oxidization
40
as oil oxidization becomes more severe
smells burnt . leaves varnish and sludge on components . dark in color
41
oil that has been severely oxidized will feel
slippery and will not adhere to your fingers
42
all hydraulic oil will contain
some water
43
oil with a 0.5% water in emulsion will appear
dull or smoky
44
oil with a 1% water in emulsion will appear
milky
45
water-oil emulsions consist of a mixture of
60% water 40% oil
46
Invert emulsions consist of a mixture of
60% oil 40% water
47
water glycol fluids consist of
60% glycol 40% water with a chemical thickener added
48
water based hydraulic fluids cannot be operated at a temperature higher than
60 C or 140 F because the water will evaporate causing fluid viscosity change
49
synthetic fire resistant fluid
chemically remanufactured . most common type is phosphate ester
50
disadvantages to synthetic oil
expensive . not compatible with nitrile rubber seals must be replaced with viton seals
51
what two conditions must biodegradable fluids meet
70-80% of base fluid must be able to be broken down . non toxic
52
when selecting a proper hydraulic fluid you should
consult manufacture . take ambient temps into consideration . fluid is compatible
53
what is one of the main contributors to hydraulic component life
contamination
54
four common places for ingressed contamination
air breather. pump inlet . cylinder seals. unclean maintenance
55
three types of contamination failures are
catastrophic . intermittent . degradation
56
catastrophic failure is
rapid or sudden total disabling of a system or component
57
intermittent failure is
problem moves from component to component called transient failure > hard to TS
58
degradation failure
caused by gradual surface wear . will lead to catastrophic if left un delt with

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