B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2010

B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2010 

Fifth Semester – Mechanical Engineering (Regulation 2004) 

ME 1305 - APPLIED HYDRAULICS AND PNEUMATICS

Time: Three hours

Answer ALL questions. 

Maximum: 100 marks

Part A - (10 × 2 = 20 Marks)

1. Give any two differences between hydraulic power and pneumatic power.

Ans. Refer Chapter 1, Q. No. 18, Two Marks Q&A, Page No. 1.25.

2. Give the expression used to determine friction factor for laminar flow through pipes. 

Ans. Refer Chapter 3, Q. No. 17, Two Marks Q&A, Page No. 3.30.

3. Sketch the graphical symbol of (a) Variable displacement reversible pump (b) Telescoping cylinder.

Ans. Refer Chapters 4 & 5, Q. Nos. 22 & !3, Two Marks Q&A, Page Nos. 4.47 & 5.32.

4. What is pressure compensated flow control? How a variable vane pump can provide this feature?

Ans. Refer Chapter 4, Q. No. 24, Two Marks Q&A, Page No. 4.47.

5. Draw a near sketch of the graphical symbol for 3 position 4 way solenoid energized pilot operated tandem centre direction control valve.

Ans. Refer Chapter 6, Q. No. 14, Two Marks Q&A, Page No.6.48.

6. List any four applications of accumulators.

Ans. Refer Chapter 9, Q. No. 5, Two Marks Q&A, Page No.9.34.

7. Sketch the graphical symbol of pneumatic regulator.

Ans. Refer Chapter 11, Q. No. 14, Two Marks Q&A, Page No.11.22.

8. Draw any one type of cylinder synchronizing circuit.

Ans. Refer Chapter 8, Section 8.12.1, Two Marks Q&A, Page No.8.16.

9. How does a servo valve differ from proportional valve?

Ans. Refer Chapter 6, Q. No.44, Two Marks Q&A, Page No.6.53.

10. List the components associated with PLC systems.

Ans. Refer Chapter 6, Section 15.9, Two Marks Q&A, Page No.15.21.

PART B - (5 × 16 = 80 marks)

11. (a) (i) What are the essential and desirable properties of a hydraulic fluid? Discuss.

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

 (ii) List the precautions to be taken when a mineral oil based fluid is changed into fire resistant fluid. 

Key check points for any conversion of mineral oil based fluid into fire resistant fluid are as follows:

(i) Compatibility of each of the components in the circuit with the fire-resistant fluid to be introduced into the circuit as a replacement (seals, packings, hoses and coatings). 

(ii) Draining and cleaning (pipes, valves, tanks, strainers, filters and cartridges, pumps, etc.).

(iii) Flushing.

(iv) Refilling and checking, including specific system and oil monitoring.

[OR]

(b) (i) Explain how Bernoulli's equation can be used to determine the pressure drop between two stations in a hydraulic system. Assume that there are some number of bends, tees, elbows, globe and gate valves in between these two stations separated by a long distance.

Ans. Refer Chapter 3, Sections 3.15, Page No.3.17.

 (ii) Oil with specific gravity 0.9 enters a tee, as shown in Fig.1, with velocity v1 = 5 m/s. Vi The diameter at section 1 is 10 cm, the diameter at section 2 is 7 cm and the diameter at 3 is 6 cm. If equal flow rates are to occur at sections 2 and 3, find V2 and V3 is m/s.

Ans. Refer Chapter 3, Example 3.10, Page No. 3.21.

12. (a) (i) Explain how positive displacement pumps build pressure compared to rotodynamic pumps. What are the ådvantages of positive displacement pumps?

Ans. Refer Chapter 4, Section 4.4, Page No. 4.4.

 (ii) Using a neat sketch explain the construction and operation of an axial piston pump of swash plate type.

Ans. Refer Chapter 4, Section 4.17, Page No. 4.22.

[OR]

 (b) Explain using a neat sketch “end cushioning” provided in hydraulic cylinders. Also sketch atleast six types of cylinder mounts available. 

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

13. (a) Develop a circuit involving two double acting cylinders A and B operating with the following sequence: Á+B+B-A- where + represents extension of rod and - represents retraction. Use only sequence valves to obtain the sequencing. 

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

[OR]

(b) (i) Consider the charging and discharging of a hydro pneumatic accumulator to be isothermal and explain the procedure to arrive at the size of accumulator. 

Ans. Refer Chapter 9, Section 9.11, Page No. 9.15.

(ii) Draw the circuit employing accumulator for supplying emergency hydraulic, power.

Ans. Refer Chapter 9, Section 9.10.3, Page No. 9.13.

14. (a) (i) Explain how the size of the air receiver and pressure drop in pneumatic pipelines (schedule 40) are determined.

Ans. Refer Chapter 11, Section 11.5.8, Page No. 11.8.

(ii) Using a neat sketch explain the construction and working of a pneumatic regulator. Also give its graphical symbol.

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

[OR]

 (b) A double acting pneumatic cylinder is required to provide the following operation: Fast extension till the mid stroke, slow extension till the end of stroke and on sensing the stroke end provide rapid return. Develop a pneumatic circuit employing a shuttle valve and suitable flow control and other valves.

Ans. Refer Chapter 13, Section. 13.4.3, Page No. 13.7.

15. (a) Draw a neat sketch of an electro hydraulic servo valve and indicate all the components and give their functions. Also develop the transfer function for the open loop gain for this valve.

Ans. Refer Chapter 6, Section. 6.25, Page No. 6.32.

[OR]

 (b) (i) Explain various locations at which filters and strainers are fitted giving reasons.

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

(ii) If a hydraulic circuit has pump inlet and exit ports intercha iged, unloading valve given internal pilot. What happens? Explain.

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