Semi Final Hydraulics Lecture
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Transcript of Semi Final Hydraulics Lecture
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Hydraulic system
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Advantages
It is almost 100 percent efficient. The slight loss of
efficiency (a fraction of 1 percent) is due to internal
friction in the system machinery.
Moving parts of a hydraulic system are lightweight and
can uic!ly "e put into motion or "rought to rest. The
valves in a hydraulic system uic!ly start or stop the
flow of fluid under pressure# very little effort is neededto operate them. $or these reasons% the system Is easy
for the operator to control.
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Hydraulic lines can "e routed almost anywhere. &nli!e
mechanical systems which must follow straight
pathways% the lines of a hydraulic system can easily "e"ent around o"structions. Also% ma'or parts of hydraulic
systems can "e located in a wide variety of places.
ince components of a hydraulic system are smaller
than those of other systems% the space reuirement issmall.
Most of the parts of a hydraulic system operate in a
"ath of oil% ma!ing the system practically self
lu"ricating.
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* physical ualities
Incompressi"ility
+,pansion and contraction
-ressure transmission
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elationship "etween pressure%
force and area
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elationship "etween area%
distance and volume
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-ascal/s law
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Important properties of hydraulic
fluids
iscosityis internal resistance to flow.
hemical sta"ilityit is the a"ility of the liuid2fluid to
resist o,idation and deterioration for long periods.
$lash pointthe temperature at which a liuid gives off
vapor in sufficient uantity to ignite momentarily when
a flame is applied.
$ire pointis the temperature at which a su"stance givesoff vapor in sufficient uantity to ignite and continue to
"urn when e,posed to a spar! or flame.
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Types of hydraulic fluid
egeta"le"ase fluid
MI3H4566 fluid was used in the past. This fluid is
essentially castor oil and alcohol. And is used primarily in
older aircraft. 7yed "lue for identification.
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Mineral"ase fluids
MI3H8505 is the most widely used hydraulic fluid in
general aviation aircraft today. It is "asically a !erosene
type petroleum product% having good lu"ricating
properties and additives to inhi"it foaming and prevent
the formation of corrosion.
ROYCO 756
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ynthetic fluid2phosphate ester
9onpetroleum "ase hydraulic fluids. $ire resistant
Most common type is Skydrol.
Dyed light purple
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Hydraulic eals
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Hydraulic Fluid Contamination
Two general contaminants are:
A"rasives% including such particles as core sand% weld
spatter% machining chips% and rust.
9ona"rasives% including those resulting from oil
o,idation and soft particles worn or shredded from seals
and other organic components.
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Contamination Check
To determine which component is defective% liuid
samples should "e ta!en from the reservoir and various
other locations in the system.
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Hydraulic Sampling Schedule
; outine sampling
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Contamination Control
As an aid in controlling contamination% the following maintenance and servicing procedures
should "e followed at all times:
Maintain all tools and the wor! area (wor!"enches and test euipment) in a clean% dirtfree
condition.
A suita"le container should always "e provided to receive the hydraulic liuid that is spilled
during component removal or disassem"ly procedures.
=efore disconnecting hydraulic lines or fittings% clean the affected area with dry cleaning
solvent.
All hydraulic lines and fittings should "e capped or plugged immediately after
disconnecting.
=efore assem"ly of any hydraulic components% wash all parts in an approved dry cleaningsolvent.
After cleaning the parts in the dry cleaning solution% dry the parts thoroughly and lu"ricate
them with the recommended preservative or hydraulic liuid "efore assem"ly. &se only
clean% lintfree cloths to wipe or dry the component parts.
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All seals and gas!ets should "e replaced during the
reassem"ly procedure. &se only those seals and gas!ets
recommended "y the manufacturer.
All parts should "e connected with care to avoidstripping metal slivers from threaded areas. All fittings
and lines should "e installed and torued in accordance
with applica"le technical instructions.
All hydraulic servicing euipment should "e !ept cleanand in good operating condition.
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Health and Handling
!ydrol> fluids are phosphate ester"ased fluids
"lended with performance additives. -hosphate esters
are good solvents and dissolve away some of the fatty
materials of the s!in. epeated or prolonged e,posure
may cause drying of the s!in% which if unattended%
could result in complications% such as dermatitis or even
secondary infection from "acteria.
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!ydrol> fluids could cause itching of the s!in "ut have
not "een !nown to cause allergictype s!in rashes.
Always use the proper gloves and eye protection when
handling any type of hydraulic fluid.
?hen!ydrol>2Hy'et mist or vapor e,posure is possi"le%
a respirator capa"le of removing organic vapors and
mists must "e worn. Ingestion of any hydraulic fluid
should "e avoided. Although small amounts do not
appear to "e highly ha@ardous% any significant amountshould "e tested in accordance with manufacturer/s
direction% followed with hospital supervised stomach
treatment.
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a!ic Hydraulic Sy!tem!
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Hydraulic system components
eservoir The reservoir is a
tan! in which an adeuate
supply of fluid for the system is
stored. $luid flows from the
reservoir to the pump% where it
is forced through the system
and eventually returned to the
reservoir. The reservoir not only
supplies the operating needs ofthe system% "ut it also
replenishes fluid
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Re!er%oir pre!!ure relie& %al%e prevents over pressuri@ation of the
reservoir. alve opens at preset value.
Sight gla!!e! 'lo( and o%er&ull)provides visual indications for flight
crews and maintenance personnel that
the reservoir needs to "e serviced.
Re!er%oir !ample %al%e used to
draw sample of hydraulic fluid fortesting.
Re!er%oir drain %al%e used to drainthe fluids out of reservoir for
maintenance operation.
Re!er%oir temperature tran!ducerprovides hydraulic fluid temperature
information for the flight dec!
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$I3T+
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$I3T+ I A ++9I9B C TAI9I9B
7+I+ &+7 TC 3+A9 TH+ HD7A&3I
$3&I7% -++9TI9B $C+IB9 -ATI3+A97 C9TAMI9ATI9B &=TA9+ $CM
+MAI9I9B I9 TH+ DT+M.
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The filtering elements in fluid filters are normally made of
paper or stainless steel. Paper elements are used mostly in
low-pressure systems and are thrown away when removed.Stainless steel elements are used in both high-pressure and
low-pressure systems and may be reused.
$I3T+ 7I$$++9TIA3 -+&+ I97IATC
+lectrical switches% continuous reading visual indicators
(gauges)% and visual indicators with memory. isual indicators
with memory usually ta!e the form magnetic or mechanically
latched "uttons or pins that e,tend when the differential
pressure e,ceeds that allowed for a servicea"le element.
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Hand pump
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-ower driven pumps
+nginedriven pump
+lectricaldriven pump
Airdriven pump
-ower transfer unit (-T&)
-ower driven "y AT (am Air Tur"ine)
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Berator pump
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lassification of pumps
-ositive displacement
9onpositive displacement
C t t Di l t P
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Constant-Displacement Pumps
A constantdisplacement pump% regardless of pump
rotations per minute% forces a fi,ed or unvarying
uantity of fluid through the outlet port during each
revolution of the pump
They deliver a fi,ed uantity of fluid per revolution%
regardless of the pressure demands.
G T P P
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Gear-Type Power Pump
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+lectric motor pump
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Piston Pump
-iston pumps can "e constantdisplacement or varia"ledisplacement pumps.
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ane pump
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*al%e!
Flow Control Valves
Selector Valves
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elector valve
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poppet type selector valve
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ervo valve
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hec! valve
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euence valve
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huttle valve
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huttle valve
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-ressure relief valve
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Pressure Regulators
The term pressure regulator is applied to a device used
in hydraulic systems that are pressuri@ed "y constant
delivery type pumps. Cne purpose of the pressureregulator is to manage the output of the pump to
maintain system operating pressure within a
predetermined range. The other purpose is to permit
the pump to turn without resistance (termed unloading
the pump) at times when pressure in the system iswithin normal operating range.
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Pressure Reducers
-ressure reducing valves are used in hydraulic systemswhere it is necessary to lower the normal system
operating pressure "y a specified amount
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The function of an accumulatoris to:
Dampen pressure surges in the hydraulicsystemcaused by actuation of a unit and the eortof thepump to maintain pressure at a preset level.
Aid or supplement the power pump whenseveral units are operatingat once bysupplying extra power from its accumulated,or stored, power.
tore power for the limited operation of a
hydraulic unit when the pump is notoperating.
upply !uid under pressure to compensatefor small internal or external "not desired#lea$s that would cause the system to cycle
continuously by action of the pressure
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am air tur"ine