review questions

REVIEW QUESTIONS

On hydraulic cylinders.

1. Write short notes on hydraulic actuators.

[Ans. Refer Sections 5.1.1 & 5.1.2] 

2. Classify the types of hydraulic cylinders.

[Ans. Refer Section 5.2.2]

3. With a neat sketch, explain the construction and operation of a double-acting hydraulic actuator. Also derive an expression for the torque capacity of the cylinder.

 [Ans. Refer Section 5.4]

4. With a neat sketch, explain the 'end cushion' provided in hydraulic cylinders. (or) Explain with a neat sketch, the purpose of cushioning in cylinders,

 [Ans. Refer Section 5.5]

5. Explain any three types of special cylinders used in hydraulics with neat sketch.

 [Ans. Refer Sections 5.6 – 5.8]

6. Explain with a neat sketch, the principle and operation of telescopic cylinder. [Ans. Refer Section 5.6]

7. Describe the working of a double-acting tandem cylinder. Give its graphical symbol. 

[Ans. Refer Section 5.7]

8. Sketch at least five types of cylinder mounts available. (or) Explain 'the various mechanisms of hydraulic cylinder mountings with neat diagram.

 [Ans. Refer Section 5.9]

On Hydraulic Motors

9. What are the different types of fluid motors? Also explain the function of them.

 [Ans. Refer Sections 5.10.1 & 5.10.2]

10. With a neat sketch, explain how torque is developed in a gear motor?

 [Ans. Refer Section 5.11] 

11. With a neat sketch, explain the construction, operation, advantages, limitations, and applications of a vane motor? 

[Ans. Refer Section 5.12]

12. With a neat sketch, explain the working principle of in-line type piston motor.

 [Ans. Refer Section 5.13.2]

13. Explain how an axial type piston motor differ in operation from a radial type piston motor. Also bring out the advantages, disadvantages, and ranges of a piston motor.

14. What is meant by a limited-rotation hydraulic actuator? Explain the operation of any one limited-rotation hydraulic motor.

15. Define the terms used to evaluate the performance of hydraulic-motor.- -

 [Ans. Refer Section 5.15]

16. With reference to hydraulic motors, define the following terms: (i) Volumetric efficiency; (ii) Mechanical efficiency; (iii) Overall efficiency. 

[Ans. Refer Section 5.15]

PROBLEMS FOR PRACTICE

On Hydraulic Cylinders

1. A pump supplies liquid at 84 Lpm to a 45 mm diameter double-acting hydraulic cylinder. If the load is 4750 N (extending and retracting) and the piston rod diameter is 22 mm, find

(i) Hydraulic pressure for the extension and retraction strokes.

(ii) Piston velocity for the extension and retraction strokes.

(iii) Cylinder kW power during the extension and retraction strokes.

[Ans. (i) 29.88 bars and 39.25 bars; (ii) 0.88 m/s and 1.16 m/s ; (iii) 4.18 kW and 5.51 kW]

On Hydraulic Motors -

2. A single-vane hydraulic motor has the following specifications:

Outer radius of rotor 14 mm; Outer radius of vane = 40 mm; Width of vane = 25 mm If the torque load is 120 N-m, what pressure must be developed to overcome the load?

[Ans. 68.37 bars]

3. What torque would a hydraulic motor deliver at a speed of 2000 rpm if it produces a brake power of 5 kW.

[Hint: Use brake power = 2πΝΤ /60]

[Ans. 23.87 N-m]

4. A hydraulic motor has a 0.15 litres volumetric displacement. If it has a pressure rating of 75 bars and it receives oil from a 6 Lps theoretical flow rate pump, find:

(i) Motor speed, (ii) Motor theoretical torque, and (iii) Motor theoretical power.

[Ans. (i) 2400 rpm; (ii) 179 N-m; (iii) 45 kW]

5. A hydraulic motor has a displacement of 80 cm3 and operates with a pressure of 70 bars and a speed of 500 rpm. If the actual flow rate consumed by the motor is 0.0007 m3/s and the actual torque delivered by the motor is 80 N-m, find: (i) volumetric efficiency, (ii) mechanical efficiency, (iii) overall efficiency, and (iv) the actual kW delivered by the motor.

[Ans. (i) 95.24%; (ii) 89.76%; (iii) 85.5%; (iv) 4.19 kW]