B.E./B.Tech. Degree Examination, November/December 2005

B.E./B.Tech. Degree Examination, November/December 2005 

Sixth Semester - Mechanical Engineering (Regulation 2001) 

ME 341 - HYDRAULIC AND PNEUMATIC CONTROLS

Time: Three hours

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

Maximum: 100 marks

1. Define fluid power.

Ans. Refer Chapter 1, Q. No. 1, Two Marks Q&A, Page No. 1.22. 

2. How do you classify direction control valves?

Ans. Refer Chapter 6, Q. No. 5, Two Marks Q&A, Page No. 5.47.

3. Draw the symbol for pressure relief valve.

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

4. What is the purpose of regenerative circuit ?

Ans. Refer Chapter 8, Q. No. 2, Two Marks Q&A, Page No. 8.36. 

5. What is the function of an accumulator ?

Ans. Refer Chapter 9, Q. No. 9.1, Two Marks Q&A, Page No. 9.33.

6. How do you select hydraulic pipes for a hydraulic system ? 

The hydraulic pipes are selected based on the following factors: 

1. System pressure, 

2. Pressure pulses,

3. Velocity of fluid flow,

4. Fluid compatibility, and

5. Environmental conditions.

7. What is a ladder diagram?

Ans. Refer Chapter 14, Q. No. 13, Two Marks Q&A, Page No. 14.17. 

8. What is air-oil intensifier ?

Ans. Refer Chapter 9, Q. No. 16, Two Marks Q&A, Page No. 9.35.

9. What is a power pack?

Ans. Refer Chapter 16, Q. No. 5, Two Marks Q&A, Page No. 16.39.

10. How do microprocessors differ from PLCs ?

Ans. Refer Chapter 15, Q. No. 16, Two Marks Q&A, Page No. 15.29.

Part B - (5 × 1680 marks)

11. (i) When designing a hydraulic circuit, enunciate the important factors that must be taken into account?

Ans. Refer Chapter 8, Section 8.2.3, Page No. 8.2.

(ii) What are main parameters affecting the performance of a pump? Briefly discuss. 

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

12. (a) (i) How do you classify pumps? Explain with suitable sketch the working of vane pump?

Ans. Refer Chapter 4, Section 4.3, Page No. 4.3.

(ii) Explain the working of four way two position direction control valve. 

Ans. Refer Chapter 6, Section 6.93, Page No. 6.14.

 [OR]

(b) (i) With a sketch describe the construction and operation of a pressure compensated flow control valve.

Ans. Refer Chapter 6, Section 6.22, Page No. 6.27.

(b) (ii) A pump has a displacement volume of 0.0819 × 10−3 m3. Ít delivers 0.0758 m3/min at 1000 rpm at 67 bar. If the prime mover input torque is 100 N-m.

(1) What is overall efficiency?

(2) What is the theoretical torque required to operate the pump? 

Ans. Refer Chapter 8, Exercise 8, Page No. 4.52.

13. (a) (i) Describe an hydraulic circuit for synchronising two cylinders with flow control valves.

Ans. Refer Chapter 8, Section 8.12.3, Page No. 8.18.

(ii) Design a hydraulic sequence circuit for a milling machine with one cylinder for operating the power vice jaw and the other for controlling the cutler travel.

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

 [OR]

 (b) (i) A press cylinder has to exert a force to lift the crosshead and tooling. The cylinder is rigidly fixed by front flange and the load is pivoted and fully guided. Maximum thrust from the press is 260 kN with a stroke of 1.4 m. Determine the size of suitable cylinder. The system working pressure should not exceed 200 bar.

Ans. Refer Chapter 5, Example 5.2, Page No. 5.23.

(ii) Briefly describe the construction of any two types of accumulators.

Ans. Refer Chapter 9, Sections 9.2-9.5, Page No. 9.2.

14. (a) (i) Describe various pneumatic actuators with neat sketches.

Ans. Refer Chapter 12, Sections 12.8 & 12.9, Page No. 12.10.

 (ii) Develop an electropneumatic circuit for the following sequence A+ B+ A− B where A and B stand for cylinders, (+) indicates extension and (−) retraction of cylinders.

Ans. Refer Chapter 13, Example 13.5, Page No. 13.23.

[OR]

(b) Design an electrohydraulic circuit for the following sequence: A+ B+ B- A- where A and B stand for cylinders, + indicates extension and retraction. Incorporate provision for auto-manual selector and emergency stop. 

Ans. Refer Chapter 13, Example 13.3, Page No. 13.22.

15. (a) (i) What are PLCs? Explain their application in low cost automation. 

Ans. Refer Chapter 15, Section 15.8, Page No. 15.20.

 (ii) Give the procedure of the cascade method of designing sequencing circuits. 

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

 [OR]

 (b) (i) List out various operating problems associated with pumps and valves and the corresponding possible causes and suitable remedy for each problem.

Ans. Refer Chapter 17, Section 17.44, Page No. 17.6.

(ii) Enunciate various criteria for the selection of pneumatic components. 

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