Quiz on Applied Hydraulics and Pneumatics

Quiz on Applied Hydraulics and Pneumatics

UNIT 1

1. Most hydraulic circuits are designed by:

A. mechanical engineers.

B. fluid power engineers.

C. fluid power distributor salesmen.

2. Atmospheric pressure at sea level is equal to approximately:

A. 14.7 Hg

B. 14.7 PSI

C. 30 PSI

3. Gauges that read Pounds Per Square Inch Absolute (PSIA):

A. show atmospheric pressure on their scale.

B. do not show atmospheric pressure on their scale.

C. have nothing to do with atmospheric pressure.

4. Static head pressure of hydraulic oil is equal to approximately:

A. .1 PSI per foot of elevation.

B. .2 PSI per foot of elevation.

C. .4 PSI per foot of elevation.

5. The power of vacuum comes from:

A. the power of a pump.

B. earth’s atmosphere.

C. the size of a pump.

6. Vacuum generators use:

A. compressed air to create a vacuum.

B. an electric motor to create vacuum.

C. an air motor to create vacuum.

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APPLIED HYDRAULICS AND PNEUMATICS SYSTEMS - UNIT-1

TWO MARK QUESTIONS AND ANSWERS

1. What is fluid power?

The technology of generating, controlling and transmitting power using pressurized fluids is termed as fluid power.

2. State the basic methods of transmitting power.

1. Electrical - Power transmission over large distance.

2. Mechanical - Power transmission to short distance and

3. Fluid power - Power transmission for intermediate distance.

3. State the type of fluid systems.

Fluid power systems - used to perform work.

Fluid transport systems -used for transporting fluids from one place to another.

4. State the law of conservation of energy.

Energy can neither be created nor be destroyed but can be changed from one form to another.

5. State the Pascal’s law.

Pressure applied on a confined fluid at rest is transmitted undiminished in all directions and acts with equal force on equal areas, and at right angles to them.

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APPLIED HYDRAULICS AND PNEUMATICS - 2 Mark Q & A for Unit-2 & 3

UNIT - II

1.     What is the function of a pump in a hydraulic system?

                        A pump which is the heart of the hydraulic system converts mechanical energy in to hydraulic energy. The mechanical energy is delivered to the pump via a prime mover such as an electric motor.

2.     What is the function of hydraulic actuator?

                        The fluid discharged by the pump is directed to the hydraulic actuator. The actuator converts the pressure energy of the fluid in to mechanical energy.

3.     A pump has a displacement volume of 98.4 cm^{3 /} rev. It delivers 1.52 litres/sec. at 1000 rpm and 70 bar. If the prime mover input torque is 120 Nm. What is the over all efficiency of the pump? (Ap-May-04)

            The volumetric displacement is,

                  V_D = 98.4 cm^{3 /} rev * (1m / 100 cm) 3 = 0.000100 m^{3 /} rev

            Now we have,

                  Q_T =   V_D . N = (   0.000100 m^{3 /} rev) (1000 / 60 rev/sec) = 0.00167 m³/ sec

            Now the volumetric efficiency is,

                  η_V  = ( Q_A/ Q_T ) * 100 = ((0.00152 m³/ sec) / ( 0.00167)) * 100 = 89.8%

            Now the mechanical efficiency is,

                                                                          (70*10⁵ N/ m²) (0.00167 m³/ sec)

                  η_m = ( P.Q_T / T_A . N) * 100  =       _____________________________ 

                                                                          (120 Nm) (1000 * 2╥ / 60 rad / sec)

                  η_m = (11,690 / 12570) * 100 = 93.0 %

            Therefore the overall efficiency is ,

                  η_o  = (η_{v *} η_m) / 100 =(89.8 * 93) / 100 = 85.5%

4.     What do you mean by cushioning of Fluid power actuators?

                        Due to the inertia force, the piston will hit cylinder head at full speed. To overcome this, cylinder cushioning is provided by which the hydraulic cylinder can be slowly retarded or cushioned.

5.     Define mechanical efficiency.

                        It indicates the amount of energy losses that occur due to the reasons other than leakages. This includes friction in bearings and between other mating parts.

                                    Theoretical Power required for operating the pump

             η_mech  =         ---------------------------------------------------------         * 100

                                    Actual power delivered to the pump

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ME 2305-APPLIED HYDRAULICS AND PNEUMATICS- Unit-1 Question & Answers

1.      What is fluid power?

      The technology of generating, controlling and transmitting power using pressurized fluids is termed as fluid power.

2.      State the basic methods of transmitting power.

      1. Electrical     - Power transmission over large distance.

      2. Mechanical - Power transmission to short distance and

      3. Fluid power - Power transmission for intermediate distance.

3.      State the type of fluid systems.

      Fluid power systems               - used to perform work.

      Fluid transport systems           -used for transporting fluids from one place to another.

4.      State the law of conservation of energy.

      Energy can neither be created nor be destroyed but can be changed from one form            to another.

5.      State the Pascal’s law.

      Pressure applied on a confined fluid at rest is transmitted undiminished in all         directions and acts with equal force on equal areas, and at right angles to them.

     

7.      Name some of hydraulic fluids.

      Water, petroleum oils, water glycols, water oil emulsion, phosphate esters and   silicones are some of the hydraulic fluids used in fluid power.

8.      Name few properties which a hydraulic fluid should posses?

      Viscosity, Demulsibility, Viscosity Index, Lubricity, Rust Prevention, Pour point, Flash Point and fire point and Oxidation stability. 

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