B.E./B.Tech. Degree Examination, November/December 2008

B.E./B.Tech. Degree Examination, November/December 2008 

Fifth Semester – Mechanical Engineering (Regulation 2004) 

ME 1305 - APPLIED HYDRAULICS AND PNEUMATICS 

Time: Three hours

Answer ALL questions. 

Part A - (10 × 2 = 20 marks)

Maximum: 100 marks

1. State the effect of temperature and pressure on viscosity of gases.

Ans. Refer Chapter 2, Q. No. 10, Two Marks Q&A, Page No. 2.22.

2. For the following graphical symbõls shown, identify their modes of operation.

Ans. Refer Chapter 7, Q. No. 7, Two Marks Q&A, Page No. 7.11.

3. How do you specify a pump?

Ans. Refer Chapter 4, Q. No. 13, Two Marks Q&A, Page No. 4.45.

4. Draw the graphical symbol for: push button operated, four way, two position, spring offset DCV.

Ans. Refer Chapter 6, Q. No. 13, Two Marks Q&A, Page No. 6.48.

5. What are the functions of accumulators?

Ans. Refer Chapter 9, Q. No. 1, Two Marks Q&A, Page No. 9.33.

6. What is the purpose of an air pressure regulator?

Ans. Refer Chapter 11, Q. No. 13, Two Marks Q&A, Page No. 11.21.

7. What is the purpose of fail-safe circuit?

Ans. Refer Chapter 8, Q. No. 9, Two Marks Q&A, Page No. 8.37. 

8. What is bistable flip-slop?

Ans. Refer Chapter 15, Q. No. 7, Two Marks Q&A, Page No. 15.28. 

9. What are servo valves? Write their purpose in fluid power systems? 

Ans. Refer Chapter 6, Q. No. 36, Two Marks Q&A, Page No. 6.52. 

10. State 'Coanda effect'.

Ans. Refer Chapter 15, Q. No. 5, Two Marks Q&A, Page No. 15.28.

Part B - (5 × 16 = 80 marks)

11. (a) (i) Compare and contrast hydraulic, pneumatic and electromechanical power systems.

Ans. Refer Chapter 1, Section 1.9, Page No.1.19.

(ii) Write briefly about the following hydraulic fluids.

(1) Petroleum oils

(2) Emulsions

(3) Glycols

Ans. Refer Chapter 2, Sections 2.6.1, 2.6.2.2 & 2.6.2.3, Page Nos.2.14, 2.15 & 2.16.

[OR]

(b) (i) List all properties that a good hydraulic fluid should possess. 

Ans. Refer Chapter 2, Section 2.5, Page No.2.12.

(ii) Fluid is flowing through a tapering pipe having diameters 50 mm and 25 mm at sections 1 and 2 respectively. The discharge through the pipe is 7.5 Lps (litres per second). The section 1 is 3 m above datum and section 2 is 1.25 m above datum. If the pressure at section 1 is 200 kPa, find the pressure at section 2. The specific gravity of the fluid is 0.9.

Ans. Refer Chapter 3, Example 3.11, Page No.3.22.

12. (a) Explain the following:

(i) Pump characteristic curves

Ans. Refer Chapter 4, Section 4.21.1, Page No.4.29. 

(ii) Pump cavitation

Ans. Refer Chapter 4, Section 4.22.3, Page No.4.33. 

(iii) Pump noise

Ans. Refer Chapter 4, Section 4.22.1, Page No.4.33. 

(iv) Pump selection

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

[OR]

(b) (i) With a neat sketch, explain the ‘end cushion' provided in hydraulic cylinder. 

Ans. Refer Chapter 5, Section 5.5, Page No.5.6.

(ii) Explain with neat sketch, the principle of operation of telescopic cylinder. 

Ans. Refer Chapter 5, Section 5.6, Page No.5.8.

13. (a) (i) Explain the construction and working of pilot operated sequence valve. 

Ans. Refer Chapter 6, Section 6.19.2, Page No.6.24.

(ii) Make a circuit sketch, showing the use of an accumulator, as a hydraulic shock absorber.

Ans. Refer Chapter 9, Section 9.10.4, Page No.9.14.

[OR]

(b) (i) Draw and explain the ladder diagram connections for a regenerative circuit.

Ans. Refer Chapter 14, Section 14.8, Page No.14.12.

(ii) Write and explain the working principle of pressure intensifier, with neat diagram.

Ans. Refer Chapter 9, Section 9.12, Page No.9.24.

14. (a) (i) Determine the actual power required to drive a compressor that delivers air at 3.5 standard m3/min at 8 bar gauge. The overall efficiency of the compressor is 74%.

Ans. Refer Chapter 11, Example 11.3, Page No. 11.9.

(ii) Make a circuit sketch for control of a double-acting hydraulic cylinder. 

Ans. Refer Chapter 8, Section 8.4, Page No.8.5.

 [OR]

(b) Design an electropneumatic circuit using cascade method for the following sequence A+B+B-A- where A and B stands for cylinders, (+) indicates extension and (-) indicates retraction of cylinders.

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

15. (a) (i) Explain the construction and working principle of hydromechanical servo valves with neat diagram.

Ans. Refer Chapter 6, Section 6.24, Page No.6.30.

(ii) What are proportional control valves? Write the types of proportional control valves?

Ans. Refer Chapter 6, Section 6.26, Page No.6.37.

 [OR]

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

Ans. Refer Chapter 16, Section 16.12, Page No.16.14.

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

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