1. VISHWAKARMA GOVT. ENGG. COLLEGE
INDUSTRIAL TRAINING
REPORT
BASIC OF HYDRAULIC SYSTEM
Assembly and testing
SUBMITED BY
REEGAL K. PATEL
VISHAWAKARMA GOVERNMENT ENGINEERING COLLEGE, CHANDKHEDA.
ENROLLMENT NO. : 120170119009
DEPARTMENT OF MECHANICAL ENGINEERING
2. 1 | P a g e
I confirm that this report is my own personal workand that all material otherthan my own is
properly referenced.
Student’sName: PATEL REEGAL KANUBHAI
Student’sSignature:
Date : 26/05/2015
MOBILE NO. 94287 38947
3. 2 | P a g e
Acknowledgement
Apart from the efforts of me, the success of any project depends largely on the encouragement and
guidelinesof manyothers.Itake thisopportunitytoexpressmygratitude tothe people who have been
instrumental in the successful completion of this project.
I wouldlike toshowmygreatestappreciation to Mr. HARISHCHANDRA PATIL. I can’t say thank
youenoughfortheirtremendoussupportandhelp.Ifeel motivatedandencouragedeverytimeIattend
thier meeting. Without thier encouragement and guidance this project would not have materialized.
The guidance andsupportreceivedfromall the memberswho contributed and who are contributing to
this project, was vital for the success of the project. I am grateful for their constant support and help.
STUDENT SIGNATURE
(REEGAL K. PATEL)
4. 3 | P a g e
ABOUT BOSCH REXROTH
Bosch RexrothIndiaLtd.isone of the leadingspecialistsindrive andcontrol technology.The company
suppliestailoredsolutionsfordriving,controllingandmoving.BoschRexrothisapartnerfor industrial
applications(machineryapplicationsandengineeringandfactoryautomation),mobile applicationsand
renewable energies,andisthusa supplierchoice of customersforhighqualityhydraulic,pneumaticand
mechatroniccomponentsandsystems.
Establishedin1975, Bosch RexrothIndiaservescustomersthroughmanufacturingfacilitiesat
Ahmedabadanda customized unitinBangalore withwidespreadsalesandservice offices,aswell as
dealers’networkall overIndia.BoschRexrothIndiaoffersitscustomersall drive andcontrol
technologiessuchasIndustrial Hydraulics,Mobile Hydraulics,Pneumatics,LinearMotion andAssembly
Technology,ElectricDrivesandControl.
Rexrothisa reliable partnerforitscustomers,supportingtheirproductionof safe andefficientmachines
and therebycontributingtothe economical use of natural resources.The companyisaccreditedtoISO
9001:2008, ISO 14001:2004, OHSAS18001:1999 certification.Itoffers:
Manufacture of hydraulicvalves,blocks,cylindersandpowerunitsinAhmedabad.
CustomizingunitinBangalore forpowerunits,pneumaticpanels,cabinetsandcylinders,cutting and
assemblyline forlinearmotionproducts.
Multi-disciplinaryknow-howisthe basisforinnovativesolutionsthatare usedascomponentsor
customizedsystems.Because Rexrothoffersacomplete range of drivesandcontrols.Rexroth
technologyisusedin all branchesof industry.Itscomprehensive service offeringsfortifyRexroth's
leadingpositionworldwide asapartner formachine andsystemmanufacturers.
Economical,precise,safe,andenergyefficient:driveandcontrol technologyfromBoschRexroth moves
machinesandplantsof any size.The companybundlesglobal applicationexperience inthe market
segmentsof mobile applications,plantconstructionandengineering,factoryautomation,and
renewable energiestodevelopinnovativecomponentsaswell astailoredsystemsolutionsandservices.
Bosch Rexrothoffersitscustomershydraulics,electricdrivesandcontrols,pneumatics,drive
technology,andlinearmotionandassemblytechnologyall fromone source.Withlocationsinover80
countries,more than37,500 associatesgeneratedasalesrevenue of approximatelyEUR6.5 bn in 2012.
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Contents
1.Introduction to Hydraulics:...............................................................................................................5
Effect of Temperature on Viscosity:......................................................................................................6
2.Basic Symbols:.................................................................................................................................7
3.Hydraulic Pumps:...........................................................................................................................12
BASIC DESIGN OF PUMPS ..............................................................................................................12
External gear pumps:.............................................................................................................14
Internal gear pumps:..............................................................................................................15
Vane pump:...........................................................................................................................15
Variable Displacement Vane Pump:............................................................................................15
Axial piston pumps: ...............................................................................................................16
Bent axis:..................................................................................................................................16
Swashplate:..............................................................................................................................17
Major aspects in the selection of pumps.....................................................................................18
4.Non return valves: .........................................................................................................................20
5.Pressure control valve:...................................................................................................................22
Classification:...............................................................................................................................22
Pressure relief valve:.....................................................................................................................22
Pressure reducing valves...............................................................................................................23
Flow control valve:....................................................................................................................24
6.Directional control valve ................................................................................................................25
Classification:...............................................................................................................................25
Spool directional valve:.................................................................................................................27
Direct operated valves...............................................................................................................28
Pilot operated directional control vales: .....................................................................................29
Poppet directional valves: .............................................................................................................30
Difference between spool directional valve and poppetvalve: ........................................................31
7.Cylinder.........................................................................................................................................32
Properties:................................................................................................................................32
Cylinder types:..........................................................................................................................32
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1.Introduction to Hydraulics:
Mass:
A weightforce iscreatedbymass on the groundinthe gravity.
Force:
Accordingto the newton’slaw,
Force = mass*acceleration
F = m*a
Pressure(P):
If a force acts perpendicularlytoasurface and acts on the whole surface thenthe force Fdividedbythe
area of the surface A is the pressure P.
P = F/A
Work(W):
Work isa productof distance coveredsandthe force F whichacts inthe directionof the displacement
W = F*s.
The SI unitfor the workis the Joule
1 J = 1 Nm = 1 Ws.
Pascal’s law:
The basic ideabehindanyhydraulicsystemisverysimple:force appliedatone pointistransmittedto
anotherpointusingandincompressible fluid,whichisalmostalwaysgoingtobe atype of oil.Insome
systems,suchas brake systemsina car, multiplythe process.A majorpartof hydraulicsisPascal’s
principle:
Changesinpressure atany pointinan enclosedfluidatrestare transmittedundiminishedtoall
pointsthe fluidandact inall directions.
Bernoulli’s Law for incompressiblefluids:
H = z + p/ρg + v2
/2g (fluidisflowingwithasignificantdifference inheightbetweensource &sink)
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Where H=total head pressure,v=fluidvelocity,g=force of gravity,z= the heightof the fluidsource,
p=fluidpressure &ρ=fluiddensity
p0 = p + v2
/2 (fluidheightisinsignificant)
Where p0 = total systempressure,p=staticpressure v= flow velocity
Viscosity:
Viscosityisaquantitative measureof afluid’sresistance toflow.
Dynamic(orAbsolute)Viscosity:
The dynamicviscosity(η) of afluidisameasure of the resistance itofferstorelative shearingmotion.
η= F/ [A×(u/h)]
η= τ /(u/h) N-s/m²
KinematicViscosity :
It isdefinedasthe ratioof absolute viscositytothe densityof fluid.
ν= η/ρ m²/s ; ρ= density of fluid
Effect of Temperatureon Viscosity:
The viscosityof liquidsdecreaseswithincrease the temperature.
The viscosityof gasesincreaseswiththe increase the temperature.
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3.Hydraulic Pumps:
BASIC DESIGN OF PUMPS
The main typesof hydraulicpumpswhichoperate onthe displacementprinciple are outlinedbelow:
1. External gear pump
Volume is createdbetween the gearsandhousingwalls.
V=m*z*b*h*
m= module,z=numberof gears,b= widthof gears,h= height
of gears
2. Internalgear pump
Volume iscreatedbetweenthe gears,housingandspacing
Hydraulic
Pumps
Gear
External
gear
pump
Internal
gear
pump
Gear
ring
pump
Vane
Single
chamber
Double
chamber
Piston
Radial
piston
Ecentric
cylinder
block
Ecentric
shaft
Axial
piston
Swashp
late
Bent
axis
14. 13 | P a g e
element.
V= m*z*b*h*
m= module,z=numberof gears, b= widthof gears,h= heightof
gears
3. Ring gear pump
The rotor has one gear lessthanon the internallygearedstator.
Planetarymovementof the rotor.
V= z*(Amax-Amin)*b
z= numberof gears,b= widthof gears
4. Screw pump
The displacement chamber is formed between threads
and housing.
𝑉 =
4
( 𝐷2 − 𝑑2) ∗ 𝑠 ∗ 𝑐
C<1
The correctionfactor c especiallytakesthe interlockingof
threadsof both spindlesinto consideration.
5. Single chambervanepump
Volume iscreatedbetweenthe circularstator,rotorand
vanes.
V= 2**b*e*D
b= vane width
6. Double chambervanepump
Due to the twincam formsof the stator,twodisplacement
processesoccurper revolution.
𝑉 =
4
( 𝐷2 − 𝑑2)∗ 𝑘 ∗ 𝑏
b= vane width,k= vane stroke perrevolution
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7. Radialpistonpump with eccentriccylinderblock
The pistonsrotate withinthe rigidexternalring.
Eccentricity‘e’determinesthe stroke of the pistons.
𝑉 =
4
( 𝑑 𝑘
2) ∗ 2𝑒 ∗ 𝑧
z= numberof piston
8. Radialpistonpump with eccentricshaft
The rotatingeccentricshaftcausesradiallyoscillating
pistonmovementtobe produced.
𝑉 =
4
( 𝑑 𝑘
2) ∗ 2𝑒 ∗ 𝑧
z= numberof piston
External gear pumps:
External pumpsare usedinlarge numbersinmobile hydraulics.
Features:
- Relatively high pressure for low weight
- Low cost
- Wide range of speeds
- Wide temp./viscosity range
Function:
Gear isconnectedviacouplingwiththe drive.
Gears are positionedinsuchwaybythe bearingblocksthatthe
gearsmeshon rotationwiththe minimumclearance.
Fluidisfedintothe gearchambersand viapressure portof the
pumpintothe hydraulicsystem.Hence aprerequisite forthe pump
to functionisthatthe gearchambersare sealedtosuchan extent
that fluid canbe transportedwithas little lossaspossible.
Importantparameters
Displacementvolume 0.2 to 200 cm3
Max. pressure up to 300 bar (size dependent)
Range of speeds 500 to 6000 rpm
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Internal gear pumps:
The most importantfeature of internal gearpumpsisthe verylow noise level.Hence theyare primarily
usedinindustrial hydraulicsandinvehicleswhich operate inanenclosedspace.
Function
The gear rotor is connectedtothe drive.Whenthe gearrotor and internal gearrotate,the space
betweenthe gearsincreases.The pump“sucks”.
Thisincrease inspace occurs overan angle about120˚. Hence the displacementchamberisfilledslowly.
Whenthe chambersare full,the fluidistransportedwithoutchange involumetothe pressure port.
Importantparameters
Displacementvolume 3 to 250 cm3
Operatingpressure up to 300 bar (dependentonsize)
Range of speed 500 to 3000 rpm (dependentonsize)
Vane pump:
Function:
1- As the rotor rotates and fluid enters the pump, centrifugal force, hydraulic pressure, and/or
pushrods push the vanes to the walls of the housing. The tight seal among the vanes, rotor, cam, and
side plate is the key to the good suction characteristics common to the vane pumping principle.
2. The housingand cam force fluidintothe pumpingchamber through holesin the cam. Fluidenters
the pocketscreated by the vanes,rotor, cam, and side plate.
3. As the rotor continuesaround, the vanes sweepthe fluidto the opposite side of the crescent
where it is squeezedthroughdischarge holesof the cam as the vane approaches the pointof the
crescent. Fluidthenexitsthe discharge port.
VariableDisplacementVanePump:
In variable displacementthe discharge of pump can be changedby varying the eccentricitybetween
rotor and pump cam-ring. As eccentricityincreasespumpdischarge increases.Withdecrease in
17. 16 | P a g e
eccentricitydischarge decreasesand oil flowcompletelystopwhen rotor becomesconcentric to pump
cam ring.
Axial piston pumps:
These consistsof a numberof pistonswhichare causedto reciprocate bythe relative rotationof an
inclinedplate orbyanglingthe pistonblock.
There are twotypesof axial pistonpumps:
1. Bent axis
2. Swashplate
Bent axis:
1- BentaxispistonPumpshave a rotatingcylindercontainingparallelpistonsarrangedradiallyaround
the cylindercentre line.
2- The pressure inthe fluidcausesthe pistonstoreciprocate over astroke basedonthe relative angle of
the shaftand cylinder.
3- The motionof the pistonsresultsinthe rotationof the shaft.
4- The cylinderisdrivenbyanshaftwhichisarrangedat an angle tothecylinderaxis.
5- The shaftincludesaflange withamechanical connectiontoeachpiston.
6- The greaterthe angle of the cylinderstothe shaftaxesthe longerthe pistonsstroke andthe lessthe
rotationspeedperunitfluidflow rate.
Features:
Typical displacementsto500 cm3
/hr
Typical pressuresto350 bar
No throughshaftoption(multiple assembliesnotpossible)
18. 17 | P a g e
Highoverall efficiency
Compactpackage.
Swashplate:
1- Swashplate pumpshave a rotatingcylindercontainingpistons.
2- A springpushesthe pistonsagainstastationaryswashplate,whichsitsatan angle to the cylinder.
3- The pistonssuckinfluidduringhalf arevolutionandpushfluidoutduringthe otherhalf.
4- It containstwosemi-circularports.
5- These portsallowthe pistonstodraw influidastheymove towardthe swashplate and discharge itas
theymove away.
6- For a givenspeedswash platepumpscanbe of fixeddisplacementlikethisone,orvariable byhaving
a variable swashplate angle.
19. 18 | P a g e
Majoraspectsinthe selectionofpumps
1-Flow rate requirement 2-Operatingspeed
3-Pressurerating 4-Performance
5-Reliability 6-Maintenance
7-Cost and Noise 8-Fluid Type
ASSEMBLY :-
a group of machine parts,
especially one forming a self-contained,
independently mounted unit.
What to assemble ?
Company assmbel the diff. parts in a housing
of metal where diff. type
Rings
Spring
Spring sheet
Spool
Controlling parts of valves etc.
20. 19 | P a g e
Nut & bolt for fixing.
Washer
Different valves have a diff. parts to
assemble as per requirement of function
of valve.
Now
the classification of hydraulics valves.
note:
in bosch reorth sanad, each screw driver
work on pneumatic system and other
small riveting machine etc. also work on
its.
21. 20 | P a g e
Sign.
4.Non return valves:
Theyhave the task to allowthe flowinone directiononly.Inthe otherdirectionthe flow isprevented
fromflowingusuallybyaconical or spherical element (poppetvalves).There are alsospool valvesbut
theydo notseal so well.The elementispressedtothe seatbya spring force.Usuallyneedsmetallic
surfaceswithveryaccurate machining.Valve seatswithelasticsurface didnotprove tobe verygood.
Importantparameters
Sizes: 6 to 150 flow:upto 15000 L/min operatingpressure:upto315 bar
cracking pressure :withoutspring;
22. 21 | P a g e
0.5;1.5;3 or 5 bar
Pilot-operated checkvalves:
Withan outside pressure the valve canbe openedagain.There isapistonwithalargersurface whichis
operatedwithalowerpressure thanthe closingpressure the valvecanbe opened.Main application:
holdingof loadsandwhendesired,sinking.
PilotoperatedcheckPilotoperatedcheck
valve withoutdrainportvalvewithdrainport
Sandwich type check valve:
23. 22 | P a g e
5.Pressure control valve:
Classification:
• pressure reliefvalves
• pressure reducingvalves
• pressure sequencevalve
Pressure relief valve:
Has the task to limitthe pressure inahydraulicsystemorina part of the system.
The pressure can rise ina hydraulicsystemif:
- the flowrate from the pumpis largerthanthe flow rate throughthe actuator
- the volume of a closedsystemisreduced
- the loadof the actuator rises
- heatis introducedintoaclosedsystem
24. 23 | P a g e
- the hydraulicresistance of the systemrises
Direct operated pressurereliefvalve:
The valve whichisscrewedintoa housingora control blockcomprisessleeve,spring,adjustment
mechanism,poppetwithdampingspool andhardenedseat.
The springpushesthe poppetonto itsseat.The springforce can be steplesslyadjustedbymeansof the
rotary knob.The pressure isthusalsoset accordingly.portpisconnectedtothe system.Pressure inthe
systemacts onthe poppetsurface.If pressure liftsthe poppetfromitsseat,the connectiontothe port
isopened.The poppetstroke islimmitedbyapininthe dampingbore.
Pilot operated:
Directoperatedvalvesare limitedasthe flow increasesdue tothe space requiredforthe control spring.
A Large flowrequiresalarge poppetorspool diameter.The areaandhence the springforce increases
proportionallytothe diametersquared.
In orderto keepthe space requiredforthese valvesdowntoa sensiblelevel,pilotoperatedvalvesare
usedforlarge flows.Theyare usedto limitthe operatingpressureorlimitandunloadthe operating
pressure bymeansof solenoidoperation.
1 - Main valve 2 - Pilotvalve
3 – Main spool 4 - 5 - 11 - Throttle
6 - 7 - 13 - Operationline
8 - Valve body 9 - Spring
15 - Discharging
Pressure reducing valves
In contrast to pressure relief valves which affect the input pressure,
pressure reducing valves are used to infulence the output pressure.
Pressure
relifevalve
Direct
operated
Pilot
operated
25. 24 | P a g e
The reducingof inputpressure orthe maitenance of outputpressure isachieved at a set value, which is
below the charging pressure available in the main circuit. It is thus possible to reduce the pressure in
one part of the system to a level lower than system pressure.
Flow control valve:
Flowcontrol valvesare usedtokeepa setflow constantregardlessof pressure variations.Thisis
achievedinthatinadditiontoadjustmentthrottle an adjustmentmovingthrottleisbuiltintothe
system,whichoperatesasacontrol throttle andat the same time as a comparisonelementinthe closed
loopcontrol circuit.
26. 25 | P a g e
6.Directional control valve
Classification:
1. Spool valvesorpoppet valves
2. Switchingorcontinuouslyadjustable valves
3. Numberof portsand positions
27. 26 | P a g e
4. The kindof governingandpositioningunit
Directional
valves
Spool valves
Direct
operated
Manually
Operated
Mechanically
Operated
Hydraulically
Operated
Pneumatically
Operated
Electrically
Operated
Pilot operated
Electro-
hydraulically
Poppet valves
Direct
operated
Manually
operated
Mechanically
operated
Hydraulically
operated
Pneumatically
operated
Electrically
operated
Pilot operated
Electro-
hydraulically
28. 27 | P a g e
Spool directional valve:
Directional spool valves in which a moving spool is situated in the valve housing.
When the control spool is moved, it connects or separates the annular channels in the
housing.
29. 28 | P a g e
Directional spool valves are sealed along the clearance between the moving spool and the
housing.
The degree of sealing depends on the clearance, the viscosity of fluid and especially on
the level of pressure.
Amount of leakage is dependent on the clearance between spool and the housing. Hence
in theory, the clearance must be reduced or the length of overlap increased as the
operating pressure increases.
There are twosubdivisionsindirectionalspool valves
1. Direct operated valves
2. Pilot operated valves
Directoperatedvalves
Directoperateddirectional spool valves“implythattheyare directional spool valvesthe control spools
of whichmaybe operateddirectlyby solenoid,pneumatic/hydraulicforcesorbya mechanicallyacting
device withoutanyintermediate amplification.
Electrical operation:
Thistype of operationisthe mostcommon,due to the automatic processesrequiredinindustry.
Solenoidisusedascontrollerinthisoperation.solenoidcontrolsthe movementof spool.
30. 29 | P a g e
Manually operated directionalcontrolvalve:
The spool is fixedrigidlytothe operatingmechanismandfollowsitsmovement.
The spoolsisreturnedbysprings, whichpushthe spool
back to itsoriginal positiononce the operatingforce
has beenremoved.If adetentisfittedandthe spool
cannot be returnedbycentringsprings,the spool
positionisfixedbythe detentandcan thenonlybe
changedagainby means of an operation.
Pilotoperateddirectional control vales:
There are twomodelsinthe pilotoperatedvalves.
1. Spring centred
2. Pressure centred
Springcentred model
On the springcentredmodel,the maincontrol spool isheldincentre positionbythe springs.
Both springchambersare thus connectedinneutral positionviathe pilotvalvewiththe tankatzero
pressure.Thusthe centre positionforthe pilotvalve isfixed.
31. 30 | P a g e
Pressurecentred model
In the centre positionof pressure centredvalvesboth control chambersare connectedwiththe control
pressure.The maincontrol spool isheldinthe centre positionbythe effectof the pressurisedsurfaces
of spool centringbushandcentringpin.
Poppet directional valves:
Directional poppetvalves are directionvalvesinhousingbore of
whichone or more suitablyformedseatingelementsinthe form
of balls,poppetsorplatesare situated.Withthisdesignas
operatingpressure increases,the valvebecomesmore tightly
sealed.
Main featuresof directional poppetvalvesare:
No leakage
Long idle times possible, as there are no leakage oil
flows and throttle clearances which could float
Isolating function without additional isolating
elements
Large pressure drop due to short strokes
Loss of performance due to incomplete balancing of pressures on the valve axis.
1 – ball2 – spring3 – poppet, 4 –
housing 5 – lever 6 – operatingpin, 7–
ball8- poppet
32. 31 | P a g e
Difference between spool directional valve and poppet valve:
Spool directional valve Poppet valve
1.spool isusedas a closingelementinspool
directional valve
1. ball or poppetisusedas a closingelementin
poppetvalve
2. Annularclearance isalwaysthere. 2. No clearance isthere.
3. Leakage flowiscontinuouslypresentbetween
P and L
3. No Leakage flow isthere.
4. low pressure dropas compare to poppetvalve 4. highpressure drop
5. Needrelativelylarge displacementsbecausea
positive overlapisneededforsealing.
5. Needsmallerdisplacementstoletfluidthrough.
6. Designforlowpressure as comparedto
poppetvalve andhighflow.
6. Designforhighpressure andlesserflow
comparedto spool valve.
33. 32 | P a g e
7.Cylinder
Properties:
The cylindershave tobe good qualitysteel withclose tolerances.There have tobe goodsealingbothat
the pistonrod andat the cylinder.Withtime dirtmaycome inand damage the surfaces.Thishasto be
possiblyreduced.Inthiscase, the leakagewillincreaseall the time.
Cylindertypes:
Singleacting: Doubleacting piston:
workcan bedoneonlyin onedirection Work isdone inboth directions
Plunger Plunger
Piston Pistonrodon bothsides
Telescopic Telescopic
Fast moving Fast moving
34. 33 | P a g e
Testing :-
the trial of the quality of
valves for proper condition which is
required for functioning at certion
condition and cheked out error in it if it is
present.
In a testing process each test batch have
a separate power pack applied and
testing is done by them
Now valve which have to be test is set in
a fix condition after that the flows pipe
are connected with it then start the
testing of valve
Valve is testing for diff. condition
Diff. switching postion
Leakage in valve etc. are checked there.
35. 34 | P a g e
Testing require very small time and its
give accurate result by test batch testing.
