CHAPTER 3CHAPTER 3HYDRAULIC VALVESHYDRAULIC VALVES

VALVEVALVE

Learning Objectives:Learning Objectives:

Explain types and function of valveExplain types and function of valve Different between Directional control valve, Different between Directional control valve,

Flow control valve and Pressure control valve.Flow control valve and Pressure control valve. Comprehend the basic construction and Comprehend the basic construction and

application of valves usedapplication of valves used Comprehend the basic operation and Comprehend the basic operation and

application of different valvesapplication of different valves

IntroductionIntroduction

1)1) Valve used to control the hydraulic Valve used to control the hydraulic and pneumatic system.and pneumatic system.

2)2) 3 basic types of valves;3 basic types of valves;

a) Directional control valvea) Directional control valve

b) Pressure control valveb) Pressure control valve

c) Flow control valvec) Flow control valve

Directional control valveDirectional control valve Primary functions of DCV is; Primary functions of DCV is;

to stop, start, check, divert,to stop, start, check, divert,

shuttle, divide proportionally the shuttle, divide proportionally the flow of hydraulic fluids in one or flow of hydraulic fluids in one or more waysmore ways

commonly types of DCVcommonly types of DCV1) One-way valve/Check valve1) One-way valve/Check valve

2) Two-way valve (Globe, Turn cock, Gate, 2) Two-way valve (Globe, Turn cock, Gate, Needle)Needle)

3) Three-way valve ( Shuttle)3) Three-way valve ( Shuttle)

4) Four-way valve4) Four-way valve

Check ValvesCheck Valves

Controls direction of flowControls direction of flow Operated by flow of fluid in pipeOperated by flow of fluid in pipe Types:Types:

Swing check - disc moves through an arcSwing check - disc moves through an arc Lift check - disc moves up and downLift check - disc moves up and down Ball check - ball is located at end of stem and Ball check - ball is located at end of stem and

lifts to allow flowlifts to allow flow

DCV TypesDCV Types

Check valveCheck valve

Swing-check ValveSwing-check Valve

Terms in DCV ( >1 way)Terms in DCV ( >1 way)

4/2 Directional control valve

P T

A B

4 – mean four port (A,B,P,T)

2 – mean two position ( Square)

A- pipe line AB- pipe line BT- TankP- Pump

Example 1

p110

continuecontinueExample 2 Example 2

                                                  

3/3 directional control valve, controlled by solenoid with spring return.

P

A

T

3 port ( A,P,T)

3 Position ( 3 Square)

Spring Solenoid

How DCV work?How DCV work?

Flow Direction

Pump to line A

Line B to Tank

Flow Direction

Line B to pump

Tank to line A

Flow Direction

Operation stop

?X ?X

Directional Control ValvesDirectional Control Valves Directional Control ValvesDirectional Control Valves

Direct flow path of fluidDirect flow path of fluid System Applications System Applications

Open center systemsOpen center systems - - at idle; maximum flow, near 0 pressureat idle; maximum flow, near 0 pressure

Closed center systems - Closed center systems -

at idle; near 0 flow, relief pressure.at idle; near 0 flow, relief pressure.

Directional Control ValvesDirectional Control Valves Directional Control ValvesDirectional Control Valves

Open center typeOpen center type closed port - locking position controlclosed port - locking position control open port - floating position controlopen port - floating position control

St find out…..

P110-114 – spool type DCV

Directional Control ValvesDirectional Control Valves Directional Control ValvesDirectional Control Valves

Closed center typeClosed center type open port - floating position controlopen port - floating position control closed port - locking position controlclosed port - locking position control

St find out…..

Flow capacity in DCV depend on;Flow capacity in DCV depend on;

Viscosity and temperature of fluidViscosity and temperature of fluid Area of fluid flow.Area of fluid flow. Flow force.Flow force. Contaminant in fluid.Contaminant in fluid. Type of DCV valve.Type of DCV valve.

DCV size DCV size

Depend on;Depend on;

a) Diameter matching with flow path.a) Diameter matching with flow path.

b) Maximum flow rate recommend from b) Maximum flow rate recommend from

manufacture.manufacture.

c) Standard num. (ISO,CETOP,ANSI..)c) Standard num. (ISO,CETOP,ANSI..)

Types of PCVTypes of PCV

Simple and Compound Pressure Relief Simple and Compound Pressure Relief Pressure Reducing (p76)Pressure Reducing (p76) Sequencing (p74)Sequencing (p74) Unloading (p69)Unloading (p69) Counterbalance (p71)Counterbalance (p71)

a) Pressure Relief Valvea) Pressure Relief Valve

Function – to control maximum pressure inFunction – to control maximum pressure in

hydraulic system.hydraulic system. Three pressure related to relief valvesThree pressure related to relief valves

CrackingCracking Full-flowFull-flow ClosingClosing

Types, simple and compound pressure Types, simple and compound pressure relief valve.relief valve.

Relief Valves (cont)Relief Valves (cont)

Used to protect piping system from Used to protect piping system from excessive pressureexcessive pressure

Opens automatically when fluid pressure Opens automatically when fluid pressure becomes too high (pressure acts against becomes too high (pressure acts against spring pressure)spring pressure)

Relieving pressure set by an adjusting Relieving pressure set by an adjusting screwscrew