Fluid Power Application - 005 Hydraulic Valves Control Components

8/13/2019 Fluid Power Application - 005 Hydraulic Valves Control Components

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Fluid PowerFluid Power

ApplicationApplication(Hydraulic Valves & Other Control Components)(Hydraulic Valves & Other Control Components)

Hydraulics & Pneumatics KMDHydraulics & Pneumatics KMD31333133

By,By,

MohdMohd DarnalisDarnalisA.RahmanA.Rahman

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Learning ObjectivesLearning Objectives

Upon completing this chapter, students should be able to:Upon completing this chapter, students should be able to:

1.1. DescribeDescribe the purpose, construction & operation of various directionalthe purpose, construction & operation of various directionalcontrol valves.control valves.

2.2. DifferentiateDifferentiate between 2between 2--way, 3way, 3--way, & 4way, & 4--way directional control valves.way directional control valves.

3.3. IdentifyIdentifythe graphical symbols used for directional, pressure, and flowthe graphical symbols used for directional, pressure, and flowcontrol valves.control valves.

4.4. ExplainExplain how valves are actuated using manual, mechanical, fluid pilot,how valves are actuated using manual, mechanical, fluid pilot, &&electric solenoid methods.electric solenoid methods.

5.5. DescribeDescribe the purpose, construction, & operation of various pressurethe purpose, construction, & operation of various pressurecontrol valves.control valves.

6.6. DifferentiateDifferentiate between a pressure relief valve, a pressurebetween a pressure relief valve, a pressure--reducing valve, areducing valve, asequence valve & an unloading valve.sequence valve & an unloading valve.

7.7. DescribeDescribe the purpose , construction, and operation of various controlthe purpose , construction, and operation of various controlvalves.valves.

8.8. DifferentiateDifferentiate between abetween a noncompensatednoncompensated & a compensated flow control& a compensated flow controlvalve.valve.

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IntroductionIntroduction

Is one of the most important considerations inIs one of the most important considerations in

any fluid power system.any fluid power system.

Entire system will not function as required ifEntire system will not function as required if

the control components are not properlythe control components are not properly

selected.selected.

Control valvesControl valves the primary control devices inthe primary control devices in

fluid power.fluid power.

SelectionSelection type, size, actuating technique,type, size, actuating technique,

remote control capability.remote control capability.


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IntroductionIntroduction

3 basic types of control3 basic types of control

valves,valves,

1.1. Directional control valvesDirectional control valves

2.2. Pressure control valvesPressure control valves

3.3. Flow control valvesFlow control valves

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Types of valvesTypes of valves

Directional control valvesDirectional control valves Determine the path through which a liquid traverses a givenDetermine the path through which a liquid traverses a given

circuit.circuit.

E.g. check valves, shuttle valves, 2E.g. check valves, shuttle valves, 2--way, 3way, 3--way & 4way & 4--waywaydirectional valve.directional valve.

Pressure control valvesPressure control valves Protect the system against overpressure.Protect the system against overpressure.

E.g. pressure relief, pressure reducing, sequence, unloadingE.g. pressure relief, pressure reducing, sequence, unloading

& counterbalance valves.& counterbalance valves.

Flow control valvesFlow control valves Controlling flow rates which control the actuator speeds.Controlling flow rates which control the actuator speeds.

E.g.E.g. NoncompensatedNoncompensated flow control valves, Pressureflow control valves, Pressurecompensated flow.compensated flow.

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ApplicationApplication

Figure 8-1 Welding machine

application using hydraulic

control valves

Figure 8-2 Hydraulic circuit showing control

valves used for welding application


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Directional Control ValveDirectional Control Valve

Check ValveCheck Valve

Figure 8-4 Operation of check valve

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PilotPilot--Operated Check ValveOperated Check Valve

Another type of check valve.Another type of check valve.

Figure 8-5 Pilot-operated check valve

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ThreeThree--WayWay

ValvesValves

TypicallyTypically

made of spoolmade of spool

design ratherdesign rather

than poppetthan poppet

Figure 8-6 Two spool positions inside a

three-way valve


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ThreeThree--WayWay

ValvesValves


Used on aUsed on a

singlesingle--actingacting

cylinder.cylinder.

Figure 8-7 Three-way DCV controlling flow

directions to and from a single-acting cylinder.

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FourFour--WayWay

ValvesValves

FigureFigure

shows ashows a

fourfour--way,way,

twotwo--

positionposition

directionaldirectionalcontrolcontrol

valve.valve.

Figure 8-8 Two spool positions inside a

four-way valve

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FourFour--Way ValvesWay Valves


Used on a doubleUsed on a double--acting cylinders.acting cylinders.


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Shuttle ValvesShuttle Valves

Permits a system to operate from either of twoPermits a system to operate from either of two

fluid power sources.fluid power sources.

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Control Valve ActuationControl Valve Actuation

Manual Actuated ValvesManual Actuated Valves

Using hand levers & spring loaded at both endsUsing hand levers & spring loaded at both ends

Figure 8-10 Manually actuated,

spring centered, three-position,

four-way valve.

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ManualManual

ActuatedActuated

ValvesValves

Using handUsing hand

levers &levers &

springspring

loaded atloaded at

one end.one end.

Figure 8-11 Manually actuated, two-

position, spring offset, four-way valve.


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MechanicallMechanically Actuatedy Actuated

ValvesValves ActuatedActuated

mechanicallmechanically rathery ratherthanthanmanual.manual.

Using a camUsing a camtypetypemechanismmechanism(roller).(roller).

Figure 8-12 Mechanically actuated, spring offset,

two-position, spring offset, four-way valve.

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PilotPilot--Actuated ValvesActuated Valves

Shifted by using airShifted by using air--pressure.pressure.

Figure 8-13 Air pilot-

actuated, three-position,

spring-centered, four-

way valve.

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SolenoidSolenoid--Actuated ValvesActuated Valves

Shifted by using electric solenoid (magnetic force).Shifted by using electric solenoid (magnetic force).

Figure 8-14

Operation of

solenoid to shift

spool of valve.


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3/43/4 way solenoid valve.way solenoid valve.

Figure 8-15 Solenoid-

actuated, three-position,

spring-centered, four-way

directional control valve.

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Figure 8-16 Single solenoid-

actuated, four way, two

position, spring-offset


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Control Valve ActuationControl Valve Actuation SolenoidSolenoid--Actuated, PilotActuated, Pilot--Operated ValvesOperated Valves


Pilot operationPilot operation-- pneumaticpneumatic

Figure 8-17 Solenoid-

controlled, pilot-operated



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Center Flow Path ConfigurationsCenter Flow Path Configurations

For ThreeFor Three--Position, FourPosition, Four--Way ValvesWay Valves

Most threeMost three--position valves having aposition valves having a

variety of possible flow pathvariety of possible flow path

configurations.configurations.

Most fourMost four--way having identical flowway having identical flow

pathpath configconfig.. actuated position.actuated position.

But, having different springBut, having different spring--centeredcentered

flow pathflow path

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Center FlowCenter Flow

PathPath

ConfigurationsConfigurations

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Pressure Control ValvePressure Control Valve Simple Pressure Relief ValvesSimple Pressure Relief Valves

Widely used pressure control valveWidely used pressure control valve practical.practical.

Normally closed valveNormally closed valve function to limit the pressure to afunction to limit the pressure to aspecified max value by diverting pump flow back to thespecified max value by diverting pump flow back to thetank.tank.


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Pressure Control ValvePressure Control Valve

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Compound Pressure Relief ValvesCompound Pressure Relief Valves Operates in two stages.Operates in two stages.

Balance of pressure from two hydraulic sources.Balance of pressure from two hydraulic sources.

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Pressure Control ValvePressure Control Valve CompoundCompound

PressurePressureRelief ValvesRelief Valves Operates inOperates in

two stages.two stages.

Balance ofBalance ofpressurepressurefrom twofrom twohydraulichydraulicsources.sources.


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Compound Pressure Relief ValvesCompound Pressure Relief Valves Remote operation capabilitiesRemote operation capabilities

Solenoid actuatedSolenoid actuated

Figure 8-25 Compound

pressure relief valve with

integral solenoid-actuated,

two-way vent valve.

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Pressure Control ValvePressure Control Valve PressurePressure--

ReducingReducingValvesValves SecondSecond

type oftype ofpressurepressurecontrolcontrolvalve.valve.

NormallyNormallyopenopen used toused to

maintainmaintainreducedreducedpressure.pressure.

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Flow Control ValvesFlow Control Valves Needle ValvesNeedle Valves

To regulate the speed of hydraulic cylinders & motors.To regulate the speed of hydraulic cylinders & motors.

By controlling the flow rate.By controlling the flow rate.

Might be a fixed orifice or an adjustable needle valve.Might be a fixed orifice or an adjustable needle valve.

Needle valvesNeedle valves designed to give fine control of flow in smalldesigned to give fine control of flow in small--diameter piping.diameter piping.


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Flow Control ValvesFlow Control Valves

Needle ValvesNeedle Valves

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Flow Control ValvesFlow Control Valves NonNon--PressurePressure Compensated ValvesCompensated Valves

Used where system pressures are relatively constant &Used where system pressures are relatively constant &motoring speeds are not too critical.motoring speeds are not too critical.

PrinciplePrinciple flow through orifice will be const. if the press dropflow through orifice will be const. if the press dropremains const.remains const.

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Flow Control ValvesFlow Control Valves PressurePressure Compensated ValvesCompensated Valves

If the load on an actuator changes significantly, systemIf the load on an actuator changes significantly, systempressure will change.pressure will change.

Thus the flowThus the flow--rate through a nonrate through a non--compensated valve willcompensated valve willchange for the same flowchange for the same flow--rate setting.rate setting.


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Flow Control ValvesFlow Control Valves

PressurePressure Compensated ValvesCompensated Valves

Figure 8-37 Pressure-

compensated flow

control valve

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Fluid Power Application - 005 Hydraulic Valves Control Components