Unit -I
1. Define Hydraulics
The engineering
science pertaining to liquid pressure and flow.
2. What is a Fluid Power System?
A system that
transmits and controls power through use of a pressurized fluid within an
enclosed circuit.
3. Define Pascal's -Law
A pressure
applied to a confined fluid at rest is transmitted with equal intensity
throughout the fluid.
4. What is the function of hydraulic
actuator?
Hydraulic
actuators convert the pressure energy of fluid into mechanical output to
perform useful work.
5. Define back Pressure.
The pressure
encountered on the return side of a fluid system.
6. Define Pump.
A device which
causes a liquid to flow against a pressure. It converts mechanical energy into
fluid energy. .
7. How pumps are classified?
1. Positive displacement
pumps
2.Hydrodynamic
(or) Non-positive displacement pumps.
8. Write about positive displacement
pumps?
Positive
displacement pumps have the internal working elements which make a very, close
fit together so that there is very little leakage (or) slippage between them.
This type of pumps ejects a fixed quantity of liquid into the hydraulic system
per revolution of the' pump
shaft.
9. How gear pumps are classified?
1. External gear
pump
2. Internal gear
pump
3. Lobe pump
4. Screw pump
5. Gerotor pump
10. Define Axial Piston pump &
Radial Piston pump
A pump having
multiple pistons disposed with their axes parallel to shaft axis. A pump having
multiple pistons disposed radially to the shaft axis, actuated by an eccentric
element.
11. Define Gear pump & Vane pump.
A pump having two
or more intermeshing gears or lobed members enclosed in housing. A pump having
multiple radial vanes within a supporting rotor.
12. Define Motor
A device which
converts .fluid power into mechanical power. It usually delivers Torque and
rotary motion to a shaft.
13. Define Viscosity .
A measure of the
internal friction or the resistance to fluid flow.
14. Differentiate between liquid
pressure and liquid flow rate?
The liquid
pressure is responsible for the force developed at hydraulic actuator while the
liquid flow rate is responsible for the speed of the hydraulic actuator.
15. How velocity of the hydraulic
actuator is calculated?
Velocity of the
hydraulic actuator = Input flow rate Area
of piston
16.State the Bernoulli’s principle?
If the flow rate
in the system is constant, then the total energy in the system will also be
constant irrespective of the variation
in the cross section of the fluid passages.
17. What are the factors to be
considered for pump selection?
1. Discharge 2.
Performance 3. Operating speed 4. Reliability
5. Pressure
rating 6. Maintenance 7. Cost 8. Noise
18. How Vane pumps are classified?
1. Unbalance vane
pump
2. Balanced vane
pump
3. Variable
displacement vane pump
19. How piston pumps are classified?
1. Radial piston
pump
2. Piston pump
with stationary cam and rotating block
3. Axial pump
with swash plate
4. Bent axis pump
20. How the displacement of the gear
pump is determined? '
The displacement of
the .gear pump is determined by
1. Volume of
fluid between each pair of teeth
2. Number of
teeth
3. Speed of
rotation
Unit-II
1. Define Accumulator
A container in
which liquid is stored under pressure as a source of fluid power.
2. What are the three basic types of
accumulators used in hydraulic systems?
1. Gravity type
(or) weight loaded type
2. Spring loaded
type
3. Gas loaded
type.
3. Name the two types of gas loaded
accumulator?
1. Non-separator
type
2. Separator type
4. Explain non-separator type gas
loaded accumulator?
In this type, the
gas is filled at the top and the heavy oil at the bottom of the shell. There is
no separator between the gas and oil and thus the pressurized gas pushes the
oil directly.
5 . What are the three basic types of
separator type gas loaded accumulator?
1. Piston type
2. Diaphragm type
3.Bladder type
6. What are the most common
applications of accumulators in hydraulic system?
1. Accumulator is
used as an auxiliary power source
2. Accumulator is
used as a compensator for an internal (or) external leakage.
3. Accumulator is
used as an emergency power source
4. Accumulator is
used as a hydraulic shock absorber.
7. What is the function of
accumulator?
Accumulator is
used as an auxiliary power source. It is a device which stores the potential
energy of the fluid. The stored potential energy in the accumulator acts as a
quick secondary source of power and does useful work as required by the system.
8. What are the conditions for the two
cylinders to be synchronized?
For the two
cylinders to be synchronized, the piston area of cylinder 2 must be equal to
the difference between areas of the piston and piston rod for cylinder 1. i.e. Ap2
=Ap1 –AR1 Also, the pump should be capable of delivering a pressure force
P1 ApI in cylinder 1 to overcome the loads F I and F 2
acting on both cylinders. i.e. P1Apl =FI +F2
9. Name three speed control circuits?
1. Meter - out
circuit
2. Meter - in
circuit
3. Bleed - off
circuit
10. What is the use of bleed-off
circuit?
Bleed off circuit
is used to .control the flow of fluid in both directions of flow (or) on a
Specific line and limits speed in only
one direction of the cylinder travel.
Unit-III
1. Name the important auxiliary
components used in the hydraulic circuits?.
1. Hydraulic
reservoir
2. Filters and
strainers
3. Sealing
4. Hydraulic
accumulators
5. Pressure
intensifiers (or) Boosters.
2. What are the factors to be
considered while designing a hydraulic circuit?
1. Safety of
operation
2. Performance of
desired function
3. Efficiency of
operation
3. What is the use of regenerative
circuit?
Regenerative
circuit is used to increase the speed of extension stroke of the double acting
hydraulic cylinder.
4. What is the circuit for shaping
machine?
Quick Return
Motion Circuits.
5. What is automatic sequencing
circuit?
By sequencing a
number of pneumatic cylinders, various machining and tooling operations may
easily be obtained in a machine. By using this technique, the cylinders can be actuated
one after another in sequences like clamping, feeding and ejecting (or) lifting,
pushing and clamping (or) in various other combinations. The pneumatic circuit
utilizing this 5 technique is known as automatic sequencing circuit. Correct
sequence of motion of each cylinder and the respective cycle time, should be
carefully studied before designing such a circuit.
6. What is a sequencing circuit?
Process control
pneumatics is also called as sequencing. It means performing number of
actions one after another which
follows each other in a simple order or with an order determined by sensors.
7. Draw a hydraulic circuit for a
machine tool with the following features:
(a) Clamp the job
(b) Slow movement
(extension) of the cutting tool.
(c) Rapid return
of tool
Unit-IV
1. What is pneumatic direction control
valve?
Pneumatic direction
control valve is used to control the direction of air path. These Valves have
generally two, three, four (or) five ports: These ports are designated as P:
Compressor line port R: Exhaust port (T is case of hydraulics) A, B: Working
ports connected to actuator.
2. What is the use of Time Delay
Valves?
Pneumatic time
delay valves are used to delay operations where time based sequences are
required.
3. What is a fast exhaust valve?
A fast exhaust
valve is used to vent cylinder quickly. It is primary used with spring return
(single acting) pneumatic cylinders.
4. Differentiate between hydraulic and
pneumatic systems?
The working fluid
of hydraulic system is water (or) oil (or) any liquid. The working fluid of
pneumatic circuit is air Hydraulic systems are designed for heavy loads where
as pneumatic systems are designed for low (or) medium loads.
5. What is the function of pneumatic
circuit using quick exhaust valve?
By quickly
exhausting the air from the cylinder, the cylinder speed can be exhausted.
6. What is Time delay circuit?
In certain
applications, the impulse to the main direction control valve may have to be delayed
to pre-determined time for different operational reasons. A pneumatic time
delay valve may be used in such cases. A pneumatic circuit using this time
delay valve is known as time delay circuit.
7. What is the use of compressor?
A compressor is a
machine which compresses air (or) any other gas from atmospheric pressure to a
desired higher pressure level.
8. Name two basic types of compressors?
1. Positive
displacement compressors
2. Dynamic
(Turbo) compressors.
9. Differentiate between single acting
and double acting compressors.
In a single
acting compressor, the compression takes place 011 one side of the piston for
each revolution of crank shaft.
In a double acting cylinder, compression takes
place on both faces of the piston giving two compression strokes for each
revolution of the crankshaft.
10. Define FRL unit?
Air is not clean
and hence contamination may result in pneumatic circuit. Also, due to time
fluctuations, the receiver air pressure does not remain constant. Also, some
parts of the
Pneumatic system have to be lubricated
for proper maintenance. For cleaning the air, regulating the pressure of air
and lubricating pneumatic parts, three units 'Filter - Pressure Regulator -
Lubricator' (Trio unit) are put together and this combined unit - Trio unit -
is called FRL unit.
Unit-V
1. What is Low Cost Automation?
There are five
stages of manufacturing process for automation namely 1. Loading 2. Clamping 3. Machining 4. Unclamping
5. Unloading. The cost involved in loading and unloading stages is very high.
So, in semi automation, these two states are done manually and other stages are
automated. Semi automation can be profitably being incorporated in manufacturing industries. This type of
automation is called "Low Cost Automation" Also, in many industries,
automation is done in selected areas to enhance the productivity. Material
handling and machine sequence are examples of such type of automation.
2. What is meant by automation?
Automation of a
process plant (or) a flow line is done by means of specially designed machinery
and equipments, which represent the highest level of automation. Chemical processing
and automated assembly lines are examples of such automation.
3. What are the salient features of
"Low cost Automation".
In most of the
industrial plants, centralized compressed air supply will exist. Hence, simple
automation of machining sequences (or) material handling can be done without
much expense. Low cost automation is attempted without going for a major
alteration of the existing set up. Low cost automation enhances productivity. The
sequencing pneumatic circuit is an example of "Low cost Automation"
4. Name two types of control systems?
1. Open loop
control system
2. Closed loop
control system.
5. Explain the closed loop control
system for a flow through a pipe?
A flow through
pipe is continuously measured and compared with the desired value to get the error
signal (error signal is a difference between actual and desired values). Based
on this error signal, the controller gives a signal to actuate the valve to
adjust the flow (increase (or) decrease depending on the value of error being
positive (or) negative). This is called a closed loop control system.
6. Explain Fluidic Logic Control?
In many plants,
closed loop control is achieved by electronic devices based on I different
logic functions such as AND, OR, NOT and MEMORY. Logic controls can be defined
as design of control system based on reasoning arising out of deductive
principle. However, the electronic control system is not only control system
used in industries. If the pneumatic control system using low pressure air is
used to achieve the above logic control functions, then it is known as fluidic Logic Control.
7. What is fluidics?
Fluidics is the
technology that utilizes fluid flow phenomena in components and circuits to
perform a wide variety of control functions including sensing, logic and m more
functions.
8. How pump cavitation is identified?
Cavitation is the
inability of a pump to draw a full charge of oil either because of air leaks or
restrictions in the inlet line. When a pump starts to cavitate, its noise level
increases and it may become very hot around the shaft and front bearing. Other
symptoms of cavitation are erratic movement of cylinders, difficulty in
building up full pressure, and a milky appearance of the oil.
9. Write about leakage testing of air
cylinders?
Piston seals and
rod seals become worn to the point that cylinder performance (or) I efficiency
is affected. Leakage around the rod seal can easily be detected and the seal
can be replaced. At that time, the rod bearing which is usually brass, bronze
(or) Teflon, It should also be replaced.
10. What is air receiver?
Air receiver is a
large cylindrical vessel used to store high pressure air from the compressor.
Large surface area of the receiver dissipates the heat of compression (heat in
the compressed air) to the surrounding atmosphere. It will have safety relief
valve, pressure indicator and temperature switches.
11. What is meant by fluidics?
Fluidics is the
branch of science which deals with Liquids, Gaseous systems, components,
design, and applications of above in the industries to perform useful work.
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