The document discusses various types of hydraulic valves used to control fluid flow in hydraulic circuits, detailing types, functions, and symbols. It covers circuit development for both single and double acting cylinders and motors, emphasizing standard symbols and specific applications. Additionally, it describes components such as poppet valves, spool valves, and check valves with their operational characteristics.

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Lecture - 17

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Hydraulic Valves
 Functions: To DIRECT and REGULATE fluid-flow in hyd. circuit.
 Types : Finite position Infinite position
DIRECTION CONTROL
 Check Valve
 Poppet
 Rotary
 Spool
 Shuttle
 Twin
Pressure
FLOW DIVIDER
 Flow Divider
 Temperature
Compensated
 Pressure
Compensated
FLOW CONTROL
 Globe
 Gate
 Needle
 Restriction
PRESSURE CONTROL
 Relief
 Reducing
 Sequence
 Unloading
 Counter-
Balance

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Valve Symbol
Close
Open
Infinite Position Valves

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Direction Control Valve
Finite Position Valves

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Valve Symbols
 Finite position valve is described as, No. of Ports / No. of Positions
e.g. 4/2, 4/3, 3/2, 2/2, etc
 Ports : Valve connections : P, T , A, B
 Positions : Extend, Retract, OFF
 Valve Actuations & their symbols:
Pushbutton Spring Lever Solenoid
Limit switch Pilot Paddle Detent

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Hydraulic circuit development
1. Development of simple hydraulic circuits such as direction control of
Single acting and Double Acting Cylinder using different valve
actuators.
2. Development of simple hydraulic circuits such as direction control of
unidirectional and Bi-directional motor using different valve
actuators.
3. Draw a hydraulic circuit using standard symbols for a cylinder to
move with same forward and return speed.
4. Draw a hydraulic circuit for verification of Pascal’s law using
standard symbols.
5. Draw a hydraulic circuit to know Force-Pressure relationship in
linear actuator using standard symbols.
6. Draw a hydraulic/pneumatic circuit set up to know Speed-Flow
relationships in motor using standard symbols.

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Poppet Valve
 ON-OFF Valve
 Normally Closed by spring
 Pushbutton operated 2/2 D.C.
Valve
 Symbol:
 Parts :
- Body with seat
- Ball
- Push Button
- Spring

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a) 2/2 DCV
b) 3/2 DCV
c) 4/2 DCV
d) 4/3 DCV
a) 2/2 DCV
Poppet valve is ............... .

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Spool Valves
3/2 DIRECTION CONTROL
 3 Ports & 2 Positions
 OFF: P Blocked (Spring)
 ON: P-A Connected
 SAC & Unidirectional Motor
2/2 DIRECTION CONTROL
 2 Ports & 2 Positions
 OFF: PA Blocked (Spring)
 ON: P-A Connected
 For Domestic Water Taps

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Spool Valves
4/3 DIRECTION CONTROL
 4 Ports & 3 Positions
 EXTEND, RETRACT, OFF
 Open Centre
 DAC & Bi-directional Motor
4/2 DIRECTION CONTROL
 4 Ports & 2 Positions
 RETRACT: PB & AT-Spring
 EXTEND: PA & BT-P.Button
 DAC & Bi-directional Motor

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Spool Valves : 5/3

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Check Valve
 Allows Flow in only one Direction; Reverse Flow is Blocked.
 Normally Closed by Spring (NRV : Non-Return Valve)
 Valve opens when Fluid Pressure-Force > Spring Force
 Process Connection : Flanged / Screwed
 Supposed to have Zero Leakage

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Types of Check Valves
Pilot Operated
 Free Flow ( P → A)
 Pilot Flow ( A – P)
 Hold Up Vehicle
Right Angled
 Screwed
 High Pressure
 MOC – Hard Steel
Restriction
 Free Flow ( P → A)
 Reduced Flow ( A → P)
 Deceleration Circuit

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Hydraulic circuit development
1. Hydraulic Deceleration circuit.
A machine tool-post slide is moved by means of hydraulic cylinder.
Initially it moves through some distance rapidly towards the job for
cutting. As cutting starts, it should move slowly for getting good
finish. When cutting is completed it should be return and the return
stroke is as fast as possible.
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1. Deceleration circuit. (Same problem but for circuit Design)
A machine tool-post slide is moved by means of hydraulic cylinder.
Initially it moves through a distance of 200 mm rapidly (against a
min. load of 12 kN) in about 3 sec. It is followed by a working
stroke of 100 mm slowly (against effective load of 35 kN) within 30
sec. The return stroke is as fast as possible.

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a) simple
b) right-angled
c) restriction
d) pilot-operated
d) pilot-operated
To hold-up car without creeping in service station
.................... check valve is used.

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a) Much leakage.
b) Zero leakage.
c) Little leakage.
d) Moderate leakage.
b) Zero leakage.
Check valves are considered to have .....................

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a) Simple
b) Right-angled
c) Restriction
d) Pilot operated
c) Restriction
.................. check valve is used in deceleration
circuit.

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Rotary Valve
Features
 Hand Operated
 Compact & Simple
 Small force
 Leakage Problem
Working
 Extend : P-A & B-T
 OFF: PATB Blocked
 Retract : P-B & A-T
Applications & Symbol
 For Motor & Cylinder
 For Pilot Flow

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a) 2 ports, 2 positions
b) 3 ports, 2 positions
c) 4 ports, 2 positions
d) 4 ports, 3 positions
d) 4 ports, 3 positions
Rotary valve used in hydraulics having
....................... .

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Questions ?

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Thank You