UNIVERSITY FOR DEVELOPMENT STUDIES
SCHOOL OF ENGINEERING
DEPARTMENT OF MECHANICAL & INDUSTRIAL ENGINEERING
END OF FIRST TRIMESTER EXAMINATIONS
FOURTH YEAR
MEE 431: PNEUMATICS & HYDRAULICS (3 CREDIT HOURS)
BSC. MECHANICAL ENGINEERING
MARCH 30, 2022
TIME: 3 HOURS
Index Number: ……………………………………………………………………………………..
INSTRUCTIONS:
i.
ii.
Answer ALL Questions in both Section A and Section B
Circle the correct answer from (A) to (B) in Section A or fill in the spaces provided
where necessary.
iii.
Choose only ONE answer for each question. Each question carries 1 mark. Multiple
choices will not attract a mark.
iv.
Do all rough work on the question paper where necessary.
v.
vi.
Write your ID number clearly on each page of the paper
Make sure you have signed the attendance sheet before leaving the exam room
SECTION A [25 MARKS]
Instruction: Answer all questions in section
1. The shaft power of a pump is 1.24 W with a revolution of 2 rpm. Calculate the torque
produced by the shaft.
A. 12.12 Nm
B. 15.01 Nm
C. 5.91 Nm.
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D. 59.10 Nm
Use the figure A to answer questions 2 and 3
Figure A
2. Identify the figure (A).
A. A single acting cylinder
B. A double acting cylinder
C. A compound cylinder
D. A single cylinder
3. What is the function of the figure (A) in the fluid power system?
A. Converts fluid power into mechanical power
B. Converts electrical power into mechanical power
C. Converts mechanical power into fluid power
D. Controls the direction fluid flow
4. Which fluid is used in hydraulic power systems?
A. water
B. oil
C. non-compressible fluid
D. all of the above
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5. Why is fluid power preferred in mobile vehicles?
1. Power can be transmitted without any delay
2. When overloaded, fluid power systems stop without damaging the components
3. Speed variation cannot be achieved
4. Fluid is non-compressible
A. 1 and 4
B. 2, 3 and 4
C. 1, 2 and 4
D. 1 and 2
6. How is power transmitted in fluid power systems?
A. transmitted instantaneously
B. transmitted gradually
C. both A. and B
D. none of the above
7. In hydraulic systems,
A. the mechanical energy is transferred to the oil and then converted into mechanical energy
B. the electrical energy is transferred to the oil and then converted into mechanical energy
C. the mechanical energy is transferred to the oil and converted into electrical energy
D. none of the above
8. Which of the following is used as a component in hydraulic power unit?
A. pressure gauge
B. filler gauge
C. Valve
D. reservoir
9. In a fixed displacement vane pump,
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A. flow rate decreases with increase in working pressure
B. flow rate increases with increase in working pressure
C. flow rate is constant and does not change with working pressure
D. none of the above,
10. What is the function of electric actuator?
A. converts electrical energy into mechanical torque
B. converts mechanical torque into electrical energy
C. converts mechanical energy into mechanical torque
D. none of the above
11. What is the function of a flow control valve?
A. it changes the direction of oil flow
B. it can adjust the flow rate of hydraulic oil
C. both A and B
D. None of the above
12. Which area does the part shown below indicate?
A. rod area
B. full bore area
C. annulus area
D. none of the above
13. Which of the following systems generate more energy when used in industrial applications?
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A. hydraulic systems
B. pneumatic systems
C. both systems generate same energy
D. cannot say
14. Which of the following is a component used in air generation system?
A. pressure switch
B. pressure gauge
C. drier
D. intercooler
15. A lifting is to lift a load of 15kN and is to have a system pressure of 75 bar. How large does
the piston surface need to be?
A. 0.004 m3
B. 2 m3
C. 0.02 m2
D. 0.002 m3
16. Electrical transmission is to wiring systems as fluid power is to?
A. Transmission systems
B. Piping systems
C. Power systems
D. Actuator systems
17. Which of the following is a stationary hydraulic system?
A. Automobiles
B. Tractors
C. Boats
D. Lifting and conveying devices
18. The word Pneumatics originated from the Greek word pneuma, meaning:
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A. Liquid
B. Plasma
C. Air
D. Substance
19. The main feature of stationary hydraulics is that valves are mainly:
A. Solenoid operated
B. Electrically operated
C. Physically operated
D. Manually operated
20.A pressure of 95Pa is required to drive a hydraulic oil through the piping system of pipe dimeter
30 cm. Calculate the force needed by the motor to drive the fluid.
A. 72.62 N
B. 6.72 N
C. 2.69 N
D. 6.50 N
21. All the flowing are types of Flow control hydraulic valves, except?
A. Needle Valves
B. Pressure-Compensated Flow Control Valves
C.
Sequence Valves
D. Temperature-Compensated Flow Control Valves
22. All the following are types of symbols used in fluid power system except
A. Pictorial Diagrams
B. Cast diagrams
C. Cutaway Diagrams
D. Graphic Diagrams
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23. The shaft of a pump transmits a torque of 6 Nm with a revolution of 3 rev/min. What would
be the shaft power?
A. 1.89 Watt
B. 18.88 Watt
C. 0.018 Watt
D. 2.23 Watt
24. A color code AAHM in the laboratory means what?
A. Green and oxidizing materials
B. Yellow and flammable materials
C. Brown and toxic and poisonous material
D. Blue and anesthetics and harmful materials
25. Fluid power circuits use schematic drawings to:
A. Simplify component function details
B. Make it so only trained persons can understand the functions
C. Make the drawing look impressive
D. Make untrained person to understand
SECTION B [75 MARKS]
ANWERS QUESTION ONE (1) AND ANY OTHER TWO (2)
Question 1
1. a.
i) Define a pump.
2 Marks
ii) State the purpose of the pump in a hydraulic system.
5 marks
1. b.
i) Differentiate between a Positive Displacement Pump and a non-Positive Displacement Pump.
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8 Marks
ii) State any two advantages and disadvantages of the poppet valves.
The pipe which is used in the fluid power system is made of steel, coppers of cors &
4 Marks
1. c..Define fluidics and mention the needs for fluidics in fluid power systems.
6 Marks
Total 25 Marks
Question 2
2 a. In a Tabular form, differentiate between hydraulics and pneumatics systems.
16 Marks
2 b. State and explain into details the three main types of maintenance systems in pneumatics and
hydraulics machines.
6 Marks
2 c. What is a stationary hydraulics system?
3 Marks
Total 25 Marks
Question 3
3. a) A pump delivers 10 dm3/min with a pressure rise of 80 bar. The shaft speed is 1420 rev/min
and the nominal displacement is 8 cm3 /rev. The torque input is 11.4 Nm.
Calculate,
i) The volumetric efficiency
5 Marks
ii) The shaft power
5 Marks
iii) The overall efficiency
5 Mark
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3 b) What is color coding?
5 Marks
3c) State any five (5) importance of color coding in hydraulic and pneumatic systems.
5 Marks
Total 25 Marks
Question 4
4. a. What are the three main types of valves used in pneumatics and hydraulics systems?
6 Marks
4 .b. List any three (3) vales under any of the above qualifications?
3 Marks
4. c.
i) The indicated work found for a single cylinder reciprocating air compressor is found to be 120
joules per cycle when rotating at 360 rev/min. The shaft power is determined as 910 watts. What
is the mechanical efficiency?
10 Marks
ii) Define the term fluid power
u
6 Marks
Total 25 Marks
E, A, Akurugu
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