B.E./B.Tech. Degree Examination, April/May 2005

SOLVED ANNA UNIVERSITY QUESTIONS PAPERS

B.E./B.Tech. Degree Examination, April/May 2005 

Sixth Semester - Mechanical Engineering (Regulation 2001)

ME 341 - HYDRAULIC AND PNEUMATIC CONTROLS

Time: Three hours

Answer ALL questions.

Part A (10 x 220 marks)

Maximum: 100 marks

1. Name any four desirable characteristics of hydraulic pumps. 

Ans. Refer Chapter 4, Q. No. 38, Two Marks Q&A, Page No. 4.49 

2. Name any four drawbacks of fluid power systems.

Ans. Refer Chapter 1, Q. No. 8, Two Marks Q&A, Page No. 1.23. 

3. State the need for synchronization of hydraulic cylinders.

Ans. Refer Chapter 8, Q. No. 7; Two Marks Q&A, Page No. 8.37. 

4. What is a hydraulic fuse ?

Ans. Refer Chapter 6, Q. No. 28, Two Marks Q&A, Page No. 6.51. 

5. What are the functions of reservoir ?

Ans. Refer Chapter 6, Q. No. 47, Two Marks Q&A, Page No. 6.53. 

6. What is two-way valve?

Ans. Refer Chapter 6, Q. No. 8, Two Marks Q&A, Page No. 6.47. 

7. What is the function of bleed off circuits ?

Ans. Refer Chapter 8, Q. No. 14, Two Marks Q&A, Page No. 8.38. 

8. What is meant by interlock contacts ?

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

9. Mention any two roles of pneumatic systems in low cost automation. 

Ans. Refer Chapter 16, Q. No. 4, Two Marks Q&A, Page No. 16.39.

10. What do you understand by single shot sequencing ?

Ans. Refer Chapter 8, Q. No. 5, Two Marks Q&A, Page No. 8.37.

Note: For the benefit of Students, all the previous years' Anna University Question Papers (starting from the inception of Anna University, Chennai) are presented. Since the syllabus of the subject is being updated from time to time through various regulations, the students are suggested to pay more attention to the question papers pertaining to the current regulation.

Part B - (5 × 16 = 80 marks)

11. (i) A double acting cylinder is hooked up in regenerative circuit as shown in Fig.1. The relief valve setting is 105 bars. The piston area is 130 cm2 and the rod area is 65 cm2. If the pump flow is 0.0016 m3/s, find the cylinder speed and load carrying capacity for (1) Extending stroke, (2) Retracting stroke.    

Ans. Refer Chapter 8, Example 8.5, Page No. 8.8.

(ii) Which kind of accumulator operates at constant pressure? How can the pressure be changed?

Ans. Refer Chapter 9, Section 9.2, Page No. 9.2.

12. (a) (i) The power and load carrying capacity of a hydraulic cylinder (Extension) are 10 kW and 20,000 N respectively. Find the piston velocity during extension. 

For the above system if the area of piston side and rod side is 2: 1, find the retraction speed. The pump delivers oil at 0.2 m3/min.

Ans. Refer Chapter 5, Example 5.4, Page No. 5.25.

(ii) What are the factors to be selected in selection of a pump for automobile lift? 

Ans. Refer Chapter 4, Section 4.23, Page No. 4.34.

 [OR]

(b) (i) How will you measure the pump performance? Explain each with suitable examples.

Ans. Refer Chapter 4, Section 4.20, Page No. 4.27.

(ii) A pump has a displacement volume of 98.4 cm3. It delivers 0.00152 m3/s of oil at 1000 rpm and 70 bars. If the prime mover input torque is 124.3 N-m (1) What is the overall efficiency of the pump? (2) What is the theoretical torque required to operate the pump?

Ans. Refer Chapter 4, Example 4.8, Page No. 4.41.

13.  ́(a) (i) Draw and explain hydraulic cylinder sequence circuit.

Ans. Refer Chapter 8, Section 8.10, Page No. 8.13.

(ii) Explain the working principle of a fail safe circuit with overload protection. 

Ans. Refer Chapter 8, Section 8.13.2, Page No. 8.20.

 [OR]

(b) (i) Draw and explain the hydraulic circuit used in milling machine. 

Ans. Refer Chapter 16, Section 16.5, Page No. 16.6.

(ii) Discuss the applications of hydraulic circuits in press and planner.

Ans. Refer Chapter 16, Sections 16.7 & 16.6, Page Nos. 16.8 & 16.7. 

14. (a) (i) A rotary vane air motor has a displacement volume of 80 cm3/rev and operates at 1750 rpm using 700 kPa gauge pressure air. Calculate the standard m3/min rate of consumption and kW power output of the motor. Assume the temperature remains constant.

Given Data: 

VD = 80 cm3/rev; N = 1750 rpm; P = 700 kPa.

Solution: It may be noted that the equations for determining the output torque and power for air motors are identical to those used for hydraulic motors.

(1) To find m3/min rate of air consumption:

(2) To find kW power output of motor :

(ii) Describe the function of an air pressure regulator with neat sketch.

Ans. Refer Chapter 11, Section 11.8, Page No. 11.12.

 [OR]

 (b) (i) Explain with neat block diagram, an air pilot control circuit for a double-acting cylinder.

Ans. Refer Chapter 13, Section 13.4.2, Page No. 13.6.

(ii) Describe any one of the electro-hydraulic circuits used in robotic systems.

Ans. Refer Chapter 16, Section 16.9, Page No. 16.11.

15. (a) (i) What are the advantages of programmable logic controller? 

Ans. Refer Chapter 15, Section 15.84, Page No. 15.20.

 (ii) Explain the working principle of a PLC with a neat block diagram. 

Ans. Refer Chapter 15, Section 15.12, Page No. 15.25.

(iii) How does a PLC differ from microprocessor?

Ans. Refer Chapter 15, Section 15.8.3, Page No. 15.20.

 [OR]

(b) (i) Describe various selection criteria for pneumatic components. 

Ans. Refer Chapter 16, Section 16.11, Page No. 16.13.

(ii) Explain the application of hydraulic and pneumatic system for low cost automation with suitable examples.

Ans. Refer Chapter 16, Sections 16.16 & 16.17, Page No. 16.32.

(iii) Write a note on power packs.

Ans.  Refer Chapter 16, Sections 16.18 & 16.19, Page No. 16.33 & 16.36.