Applications of Hydraulics&Pneumatics : Session 7

8/3/2019 Applications of Hydraulics&Pneumatics : Session 7

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Applications of

HydraulicsPneumatics

&

By: Alireza Safikhani

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2 Accessories Pressure Booster & DePressure Booster & De--boosterbooster

Pressure SwitchPressure Switch Pressure GagePressure Gage

AccumulatorAccumulator

HeatHeat ExchangerExchanger

FiltersFilters

Sealing & PackingSealing & Packing

Fluid ConductorFluid Conductor

3 Pressure Boosters & Debooster The function of a pressure boosterThe function of a pressure booster

is to act like ais to act like a transformertransformer----that is,that is,

itit raises the pressureraises the pressure of a smallof a small

circuit connected to the powercircuit connected to the powersystem.system.

The booster is aThe booster is a cylindercylinder made upmade up

of two pistons of different surfaceof two pistons of different surface

areas that are connected. Theareas that are connected. The

larger surface area (A1) islarger surface area (A1) is

connected to the inlet side of theconnected to the inlet side of the

hydraulic system, and, the smallerhydraulic system, and, the smaller

surface area (A2) is connected tosurface area (A2) is connected to

the outlet side of the hydraulicthe outlet side of the hydraulic

system.system.

4 Pressure Boosters & De-booster Pressure dePressure de--boosters are used toboosters are used to

reduce the pressure in thereduce the pressure in the

system to a level that can besystem to a level that can be

used by certain devices (used by certain devices (damage Prevention ).damage Prevention ).


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Pressure Switch

Pressure switches produce an electrical make/break which isPressure switches produce an electrical make/break which is

triggered when pressure in the hydraulic circuit reaches a giventriggered when pressure in the hydraulic circuit reaches a given

setting.setting.

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Principle of operation

Fluid pressure in the circuitFluid pressure in the circuitoperates a piston (1) fitted withoperates a piston (1) fitted with

adjustable spring bias (2); onceadjustable spring bias (2); once

thethe pressure settingpressure setting is reached,is reached,

the piston is urged forward sothe piston is urged forward so

as toas to actuate a micro switchactuate a micro switch (3)(3)

and make or break its contacts.and make or break its contacts.

TheThe pressure setting is selectedpressure setting is selectedby turning a graduated controlby turning a graduated control

knobknob (4).(4). Clockwise rotationClockwise rotation

increases the setting pressure.increases the setting pressure.

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Industrial Example

Pressure Range

1) 3 to 40 bar

2) 4 to 80 bar

3) 8 to 160 bar

4) 16 to 320 bar

5) 32 to 630 bar

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Circuit Example


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Pressure Gage

used in liquidused in liquid--poweredpowered

systems to measure pressuresystems to measure pressure

to maintain efficient and safeto maintain efficient and safeoperating levels. Pressure isoperating levels. Pressure is

measured inmeasured in psipsi or baror bar

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Principle of Operation

11 Accumulator Like an electrical storageLike an electrical storage batterybattery, a hydraulic, a hydraulic

accumulatoraccumulator stores potential powerstores potential power, in this case liquid, in this case liquidunder pressure, for future conversion into usefulunder pressure, for future conversion into useful

work.work. TypesTypes

bladder accumulatorbladder accumulator:: the liquid and gas are separatedthe liquid and gas are separatedby an elastic bag or bladder.by an elastic bag or bladder.

diaphragm accumulatordiaphragm accumulator:: the liquid and gas arethe liquid and gas areseparated by a flexible diaphragm.separated by a flexible diaphragm.

piston accumulatorpiston accumulator:: the liquid and gas are separatedthe liquid and gas are separatedby a floating pistonby a floating piston

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Types


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Operation14

Animation

Charging Discharging

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Applications: Reduction of installed power Using an accumulator as an energy storage deviceUsing an accumulator as an energy storage device

effectively reduces the required flow rate capacity of theeffectively reduces the required flow rate capacity of the

hydraulic pump. This results in a reduction of the installedhydraulic pump. This results in a reduction of the installed

power.power.

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Animation


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Pump Unloading

an unloading valve is usedan unloading valve is used

to dump a flow back toto dump a flow back totank once an accumulatortank once an accumulator

is charged to the unloadingis charged to the unloading

valve setting.valve setting.

Once the valve closes,Once the valve closes,

pump/electric motor mustpump/electric motor must

therefore generate powertherefore generate power

to recharge theto recharge theaccumulator to theaccumulator to the

unloading valve settingunloading valve setting

18 Control of Usable Volume The usable volume of an accumulatorThe usable volume of an accumulator

should beshould be discharged at a controlleddischarged at a controlled

rate.rate. *Safety Note:*Safety Note: In any accumulatorIn any accumulator

circuit, a means should be availablecircuit, a means should be available

of automatically unloading theof automatically unloading the

accumulator when the machine isaccumulator when the machine is

shut down.shut down. Such a valve could beSuch a valve could be

located at this point in the circuitlocated at this point in the circuit..

19 2. Emergency and safety An accumulator which isAn accumulator which is

kept constantlykept constantly underunder

pressurepressure allows forallows for

instant and/or repetitiveinstant and/or repetitiveoperations as requiredoperations as required

(braking, opening of(braking, opening of

door, etc.)door, etc.)

20 Dampening of pulsation and reduction of noise In order to dampenIn order to dampen

pressure changes, whichpressure changes, which

are caused by theare caused by the

pulsation of a pump, anpulsation of a pump, anaccumulator makes itaccumulator makes it

possible, due to the lowpossible, due to the low

inertia of its bladder, toinertia of its bladder, to

improve the precision ofimprove the precision of

operation and to reduceoperation and to reduce

the sound level of thethe sound level of the

installationinstallation


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21 Thermal expansion The pressure differencesThe pressure differences

caused by thermalcaused by thermal

variation in a closedvariation in a closedhydraulic circuit arehydraulic circuit are

absorbed by fitting anabsorbed by fitting an

accumulatoraccumulator

22 Surge control an accumulator correctlyan accumulator correctly

sized and located in thesized and located in thesystem transformssystem transforms

pressure wavepressure wave

oscillations into liquidoscillations into liquid

mass oscillations whichmass oscillations which

are easily absorbed byare easily absorbed by

the accumulator, bringingthe accumulator, bringing

the pressure peak levelthe pressure peak level

back to acceptable levels.back to acceptable levels.

23 Absorbing Shock Shock in a hydraulic systemShock in a hydraulic system

may be developed from themay be developed from the

inertia of a load attached toinertia of a load attached to

a cylinder or motor. Or, ita cylinder or motor. Or, itmay be caused by fluidmay be caused by fluid

inertia when system flow isinertia when system flow is

suddenly blocked or changedsuddenly blocked or changed

direction as a directionaldirection as a directional

valve is shifted quickly. Anvalve is shifted quickly. An

accumulator in the circuitaccumulator in the circuit

will absorb some of thewill absorb some of the

shock and not allow it to beshock and not allow it to betransmitted fully throughouttransmitted fully throughout

the system.the system.

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Contamination of the hydraulic fluid


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25 Filters To keepTo keep hydraulic componentshydraulic components

performing correctly, theperforming correctly, the

hydraulic liquid must be kepthydraulic liquid must be keptas cleanas clean as possible.as possible.

Foreign matterForeign matter andand tiny metaltiny metalparticlesparticles from normalfrom normal wear ofwear ofvalvesvalves,, pumpspumps, and, and otherothercomponentscomponents are going to enterare going to entera system.a system.

Selection and positioningSelection and positioning ofof

the filter is largely based onthe filter is largely based onthethe sensitivity to dirt of thesensitivity to dirt of thehydraulic componentshydraulic components in use.in use.

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Grade of Filtration

Dirt particles are measured inDirt particles are measured in m, the grade ofm, the grade of

filtration is indicated accordingly.filtration is indicated accordingly.

Absolute filtration RatingAbsolute filtration Rating

indicates the largest particle able to pass through aindicates the largest particle able to pass through a

filterfilter

--valuevalue

indicates how many times more particles above aindicates how many times more particles above a

specific size are located in the filter intake than inspecific size are located in the filter intake than in

the filter returnthe filter return

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Absolute filtration Rating

indicates the largest particle able to pass through a filterindicates the largest particle able to pass through a filter

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-Ratio


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ISO 4406

TheThe level of contaminationlevel of contamination in a fluid is covered inin a fluid is covered in

standards ISO 4406standards ISO 4406 ..

Two range numbers must be stated.Two range numbers must be stated.

TheThe first numberfirst number is theis the range of particlesrange of particles inin 1 ml1 ml largerlarger

thanthan 5 microns5 microns and theand the secondsecond the range for particlesthe range for particles

larger thanlarger than 15 microns15 microns..

For example codeFor example code 18/1318/13 means the sample containsmeans the sample contains

1300 to 25001300 to 2500 particles larger thanparticles larger than 5 microns5 microns andand 40 to40 to

8080 particles larger thanparticles larger than 15 microns15 microns..

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ISO 4406

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Strainers

A strainer is the primary filtering system that removesA strainer is the primary filtering system that removes

large particles of foreign matter from a hydrauliclarge particles of foreign matter from a hydraulic

liquidliquid

Strainers are used to pump inlet lines where pressureStrainers are used to pump inlet lines where pressuredrops must be kept to a minimum.drops must be kept to a minimum.

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Filters

PartialPartial--Flow FiltersFlow Filters FullFull--Flow FiltersFlow Filters


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Placement34

Placement

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Pressure Drop

Pressure filter:Pressure filter:

p ~ 1 to 1.5 bar at operating temperaturep ~ 1 to 1.5 bar at operating temperature

Return line filter:Return line filter:

p ~ 0.5 bar at operating temperaturep ~ 0.5 bar at operating temperature

Intake filter:Intake filter:

p ~ 0.05 to 0.1 bar at operating temperaturep ~ 0.05 to 0.1 bar at operating temperature

36 Contamination indicator It is important that the effectiveness of the filter can beIt is important that the effectiveness of the filter can be

checked by a contamination indicator.checked by a contamination indicator.

The contamination of a filter is measured by the drop inThe contamination of a filter is measured by the drop in

pressure. As the contamination increases, the pressure aheadpressure. As the contamination increases, the pressure aheadof the filter rises. This pressure acts on a springof the filter rises. This pressure acts on a spring--loadedloaded

piston. As the pressure increases, the piston is pushed againstpiston. As the pressure increases, the piston is pushed against

the spring.the spring.


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37 Heat Exchanger friction causesfriction causes energy lossesenergy losses when the hydraulic fluid flowswhen the hydraulic fluid flows

through the lines and components.through the lines and components.

This causes the hydraulic fluid to heat up. To a certain extent,This causes the hydraulic fluid to heat up. To a certain extent,

this heat is given off to the environment via the oil reservoir,this heat is given off to the environment via the oil reservoir,

the lines and other componentsthe lines and other components

Operating temperatureOperating temperature should not exceedshould not exceed 5050 6060 CC. Where. Where

there is a high temperature,there is a high temperature, the viscosity of the oil falls by anthe viscosity of the oil falls by an

unacceptable amount, leading tounacceptable amount, leading to premature ageingpremature ageing. It also. It alsoshortens the service life of sealsshortens the service life of seals

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Types

39 Fluid Conductor 40 Pipes PipesPipes are specified by theirare specified by their nominal borenominal bore diameterdiameter

Pipes are still commonly made to imperial sizesPipes are still commonly made to imperial sizes

(British Standard Pipe) and(British Standard Pipe) and 1 inch1 inch BSP means it has aBSP means it has a

11--inch nominal boreinch nominal bore.. Metric pipes are often just inch sizes converted to mmMetric pipes are often just inch sizes converted to mm

so that a 1so that a 1--inch pipe becomes a 25 mm pipe and a 2inch pipe becomes a 25 mm pipe and a 2--

inch becomes a 50 mm pipe.inch becomes a 50 mm pipe.

Tubes are specified by their outside diameter and theyTubes are specified by their outside diameter and they

are made to standard sizes. Sizes in fractions of anare made to standard sizes. Sizes in fractions of an

inch are still available but metric is becoming moreinch are still available but metric is becoming more

popular such as 15 mm, 16 mm and so on.popular such as 15 mm, 16 mm and so on.


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Velocity in Conductor

Pressure lines:Pressure lines:

up to 50 bar operating pressure: 4.0up to 50 bar operating pressure: 4.0 m/sm/s





Suction lines: 1.5Suction lines: 1.5 m/sm/s

Return lines: 2.0Return lines: 2.0 m/sm/s

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Hose

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Hose44

Pipes


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Pipes46

Tube

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Tube48

Sizing


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Manifold50

Manifold Assembly

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Power Pack52 Power Pack


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Power Pack54

Standard Components

((11)) Electric motor coupledElectric motor coupled

(2) Hydraulic pump(2) Hydraulic pump

(3) Intake submersed filter(3) Intake submersed filter (4) Suction filter(4) Suction filter

(5) Pressure relief valve(5) Pressure relief valve

(6) Pressure gage(6) Pressure gage

(7) Shut off valve(7) Shut off valve

(8) Reservoir(8) Reservoir

(9) Visual oil level(9) Visual oil level

(10) Filling plug(10) Filling plug

(11) Drain plug(11) Drain plug

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Power Pack56

Power Pack


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61 Hydraulic oils 62 Example Hydraulic oil HLP 68Hydraulic oil HLP 68

H hydraulic oilH hydraulic oil

L with additives to increase corrosion protection and/ orL with additives to increase corrosion protection and/ orageing stabilityageing stability

P with additives to reduce and/or increase load carrying,P with additives to reduce and/or increase load carrying,

abilityability

68 Viscosity code as defined in DIN 5151768 Viscosity code as defined in DIN 51517

Documents

Applications of Hydraulics&Pneumatics : Session 7