B.E./B.Tech. Degree Examination, May/June 2006

B.E./B.Tech. Degree Examination, May/June 2006

Sixth Semester - Mechanical Engineering (Regulation 2001) 

ME 341 - HYDRAULIC AND PNEUMATIC CONTROLS

Time: Three hours

Maximum: 100 marks

Answer ALL questions. Part A - (10 × 2 = 20 marks)

1. Define viscosity and bulk modulus of a hydraulic fluid.

Ans. Refer Chapter 2, Q. No. 4, Two Marks Q&A, Page No. 2.21.

2. Give the expression used to determine the wall thickness and inside diameter of a hydraulic conductor.

where Do = Conductor outside diameter, and A = Required pipe flow area.

3. Give the hydraulic symbol for a 3-position, 4-way, closed centre solenoid operated direction control valve.

Ans. Refer Chapter 6, Q. No. 11, Two Marks Q&A, Page No. 6.48.

4. What is the difference between pilot operated and direct operated pressure relief valve?

Ans. Refer Chapter 6, Q. No. 22, Two Marks Q&A, Page No. 6.50.

5. Distinguish between the pressure reducing valve and pressure relief valve by giving the graphical symbols.

Ans. Refer Chapter 6, Q. No. 23, Two Marks Q&A, Page No. 6.50.

6. What is "meter-in" circuit? What is its limitation?

Ans. Refer Chapter 8, Q. No. 12, Two Marks Q&A, Page No. 8.38. 

7. What is a relay?

Ans. Refer Chapter 14, Q. No. 9, Two Marks Q&A, Page No.14.16.

8. Give the standard graphical symbol for FRL unit.

Ans. Refer Chapter 11, Q. No. 19, Two Marks Q&A, Page No. 11.22.

9. Give the Harris formula used to determine the pressure drop in pipes for pneumatic circuits.

Ans. Refer Chapter 13, Q. No. 13.2.4, Two Marks Q&A, Page No. 13.2.

10. What is a microprocessor?

Ans. Refer Chapter 15, Q. No. 17, Two Marks Q&A, Page No. 15.29.

Part B - (5 × 16 = 80 marks)

11. (i) Discuss the factors to be considered in the selection of hydraulic fluids.

Ans. Refer Chapter 2, Section 2.8, Page No. 2.18.

(ii) Explain the factors which affect the selection of pumps and discuss in detail the classification and performance features of different types of hydraulic pumps. 

Ans. Refer Chapter 4, Sections 4.3, 4.20 & 4.23 Page Nos. 4.3, 4.27 & 4.34.

12. (a) (i) Explain a hydraulic press circuit which employs double pump unloading principle.

Ans. Refer Chapter 8, Section 8.7, Page No. 8.10.

(ii) Draw a single cylinder continuous reciprocation circuit using suitable components and give the specifications of them.

Ans. Refer Chapter 8, Section 8.11, Page No. 8.15.

[OR]

(b) (i) Give any two application circuits employing accumulator for different purposes. 

Ans. Refer Chapter 9, Sections 9.10.1-9.10.4, Page No.9.10.

(ii) Develop a two-handed safety circuit for the operation of a press and explain. 

Ans. Refer Chapter 8, Section 8.13.3, Page No.8.21.

13. (a) (i) A hydraulic pump delivers oil at 60 bar, 120 lpm into a circuit laid on a horizontal plane. There are 4 elbows (k = 0.75), one globe valve fully open (k = 10) and a direction control valve (pressure drop = 3 bar) with the inside diameter of the pipe as 30 mm. The total length of the straight run pipe is 20 m and the specific gravity of the oil is 0.9. The kinematic viscosity of the oil is 0.0001 m2/s. Determine the pressure in bar at the exit point of the pipe.

Ans. Refer Chapter 3, Example 3:15, Page No.3.25.

 (ii) Explain how the pressure relief valve and its variants could be used for unloading applications.

Ans. Refer Chapter 6, Sections 6.13-6.15, Page No.6.20.

[OR]

(b) (i) List the need and application of synchronising circuits.

Ans. Refer Chapter 8, Section 8.12, Page No.8.16.

(ii) With simple sketches, explain the various types of synchronising circuits. 

Ans. Refer Chapter 8, Sections 8.12.1-18.12.3, Page No.8.16.

14. (a) (i) Draw a neat sketch of pneumatic filter and explain its construction and working. Also give the graphical symbol.

Ans. Refer Chapter 11, Section 11.7, Page No.11.11.

(ii) Develop a continuous single cylinder reciprocation circuit for pneumatic system using limit switches and relays.

Ans. Refer Chapter 13, Section 13.6, Page No.13.10.

[OR]

 (b) (i) Draw a neat .sketch of an electro-hydraulic for sequencing drilling and clamping cylinders.

Ans. Refer Chapter 14, Section 14.7, Page No.14.10.

(ii) Explain the working principle of any two types of pneumatic position sensing devices.

Ans. Refer Chapter 15, Section 15.5, Page No.15.11.

15. (a) (i) Explain with block diagram the components present in a PLC and give their functions.

Ans. Refer Chapter 15, Section 15.9, Page No.15.21.

 (ii) What is cascade control? Explain giving suitable example circuit. 

Ans. Refer Chapter 13, Section 13.12.1, Page No.13.18.

 [OR]

(b) (i) Briefly explain the maintenance requirements for hydraulic power packs. 

Ans. Refer Chapter 17, Section 17.3, Page No.17.3.

(ii) Explain the lay out of pneumatic systems with emphasis on sizing of conductors, cleanliness, traps and pressure regulation.

Ans. Refer Chapter 1, Section 1.8, Page No.1.15.

(iii) Explain the principle of low cost automation.

Ans. Refer Chapter 16, Section 16.15.3, Page No. 16.31.