Hydraulics and Pneumatics - Jun 2015

Mechanical Engg (Semester 5)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.

Answer any one question from Q1 and Q2

1 Distinguish between Hydraulics and Pneumatics systems.(6 marks) 10 (a) Draw and explain position dependent sequencing circuit for two cylinders in pneumatics.(8 marks) 10 (b) Compare Air Motors with Electric Motors.(4 marks) 10 (c) Classify different actuators used in pneumatics with symbols.(4 marks)

Answer any one question from Q11 and Q12

11 Movement of a machine is obtained by using hydraulic system. Load on the cylinder during the forward stroke is 12kN while that the return stroke is 10kN.
Requirement of the machine is such that the forward speed and the return speed are to be equal. Range of speeds for the cylinder is between 2m/min and 4m/min. The total stroke of the cylinder is 350mm.
Draw a circuit which will fulfill these requirements. Select different components used in the circuit from the data given. Mention ratings of components in case it is not available in the given data (Suitable system requirements can be assumed, if required).(16 marks) 12 A machine tool cross slide is moved by means of a hydraulic system. The motion of the cylinder is as follows:
a) Initially it moves through a distance of 150mm against a load of 15kN in about 4 seconds.
b) It is followed by a working stroke of another 150mm against an effective load of 25kN. The feed rate during this part of the stroke is required to be 1m/min.
c) The load during return stroke is 15kN.
A meter -in type of circuit is used. Draw a circuit which will fulfill these requirements. Select different components used in the circuit from the data given. Mention ratings of components in case it is not available in the given data.(16 marks) 2 Draw ISO symbols for the following components:
a) Unidirectional, fixed displacement pump
b) Quick disconnect coupling with check
c) 3/2, solenoid operated, spring return DCV
d) 4/3, tandem centre, spring centered, oil pilot operated DCV
e) Muffler
f) Double acting cylinder with both side variable cushioning.(6 marks)

Answer any one question from Q3 and Q4

3 (a) Classify and Explain hydraulic accumulators.(4 marks) 3 (b) A gas charged accumulator supplies energy to a system with 15 litres of oil within the range of 125 bar (abs) to 175bar (abs). If the accumulator has pre-charged pressure of 90 bar (abs). Size the accumulator for Adiabatic process.(4 marks) 4 (a) Classify hydraulic Pumps & define various efficiencies of a pump?(6 marks) 4 (b) Draw symbolic representation of Hydraulic Power Pack unit.(2 marks)

Answer any one question from Q5 and Q6

5 What is Cushioning of Cylinders? Explain with neat sketch with symbolic representation.(6 marks) 6 Explain with neat sketch Piston type Hydraulic Motors.(6 marks)

Answer any one question from Q7 and Q8

7 (a) Draw neat sketch and explain the following with their application in circuit:
i) Three Way, Two Position Direction Control Valve
ii) Four Way, Three Position Direction Control Valve (Closed Centre)(12 marks) 7 (b) Draw & Explain Meter-In speed control circuit. Specify its application.(6 marks) 8 (a) For the circuit diagram given in Fig.1, identify the type of Circuit & the numbered Components, also describe the circuit's operation.(8 marks) 8 (b) Draw a circuit for automatic cylinder reciprocation using sequence valves & explain its operation.(10 marks)

Answer any one question from Q9 and Q10

9 (a) Explain the working of a FRL unit with neat sketch and symbols.(8 marks) 9 (b) Write a short note on the following with application in the circuit:
i) Shuttle valve (OR Gate)
ii) Quick Exhaust Valve(8 marks)