Pneumatic valves and circuit development

Pneumatic valves and circuit development

1. Lecture - 17

2. 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

3. Valve Symbol Close Open Infinite Position Valves

4. Direction Control Valve Finite Position Valves

5. 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

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

7. 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

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

9. 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

10. 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

11. Spool Valves : 5/3

12. 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

13. 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

14. Hydraulic circuit development 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. -------------------------------------------------------------------------------- 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.

15. 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.

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

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

18. 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

19. 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 ....................... .

20. Questions ?

21. Thank You