Applied hydraulics and pneumatics

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.

7. Pascal’s Law states that pressure is produced by the pump and motor of a hydraulic system.

A. True

B. False

8. Pressure in a fluid power system comes from:

A. resistance to flow.

B. motor horsepower.

C. pump volume.

9. A pressure gauge reading of 100 BAR would be:

A. 2940 PSI

B. 1070 PSI

C. 1450 PSI

10. When a gas or liquid is heated it will:

A. contract.

B. stay the same.

C. expand.

1. Hydraulic oil is compressible:

A. not at all.

B. by a great amount

C. by a small amount

2. Viscosity is a measure of the hydraulic fluids:

A. color.

B. temperature.

C. thickness.

3. Synthetic fluids:

A. cost more than mineral based fluids.

B. will not burn.

C. are compatible with most seal materials.

4. The main purpose for hydraulic fluids is:

A. to fill the tank.

B. to leak from every opening.

C. transmit energy, lubricate and seal.

5. Over heating hydraulic fluid:

A. makes it last longer.

B. deteriorates the additives .

C. makes it smell better.

6. New hydraulic oil is clean to:

A. 5 microns.

B. 10 microns.

C. 25 microns.

7. Viscosity Index is a measurement of the change of flow characteristics of a fluid from

one temperature another.

A. True

B. False

8. Hydraulic fluid should be stored:

A. in a damp moist atmosphere.

B. in a closed and sealed container.

C. in an open container.

9. A high viscosity number gives:

A. better sealing characteristics.

B. poorer sealing characteristics.

C. has no effect on sealing characteristics.

10. Refined mineral oil has:

A. excellent lubricating qualities.

B. good lubricating qualities.

C. poor lubricating qualities.

 

 

1. A weight loaded accumulator:

A. loses pressure as fluid discharges.

B. gains pressure as fluid discharges.

C. stays the same pressure as fluid discharges.

 

2. A spring loaded accumulator:

A. loses pressure as fluid discharges.

B. gains pressure as fluid discharges.

C. stays the same pressure as fluid discharges.

 

3. Gas charged accumulators use:

A. oxygen.

B. nitrogen.

C. argon.

 

4. The most common accumulator circuit is:

A. supplementing pump flow.

B. making up for system leaks.

C. emergency power supply.

 

5. Precharge pressure should be checked at least every:

A. 1-2 month.

B. 2-3 months.

C. 3-6 months.

 

6. An accumulator may be used to:

A. make a pump run faster.

B. make a valve shift quicker.

C. make up for system leaks.

 

7. Accumulator pre-charge pressure is normally.

A. 95% of minimum system pressure.

B. 85% of minimum system pressure.

C. 75% of minimum system pressure.

 

8. When the pump is on an accumulator dump valve keeps fluid:

A. from going to the accumulator.

B. from going to the circuit.

C. from going to tank.

 

9. An unloading relief valve sends:

A. pump flow to tank at system pressure.

B. accumulator flow to tank at system pressure.

C. pump flow to tank at 25-100 PSI.

10. This symbol is:

A. weight loaded accumulator.

B. gas charged accumulator.

                         C. spring loaded accumulator

 

11. Air to oil intensifier oil output volume is equal to:

A. air input volume.

B. a large portion of air input volume.

C. a small portion of air input volume.

12. Air to oil intensifier output pressure is controlled by.

A. the area ratio of the pistons and/or rams involved.

B. the length of stroke.

C. what size the outlet port is.

 

 

 

 

1. A pneumatic symbol is:

a. different from a hydraulic part used for the same function.

b .the same as a hydraulic part used for the same function.

c. not to be compared to a hydraulic part used for the same function.

 

2. Pneumatic systems usually do not exceed:

      a.½-1 HP.

b.1-2 HP.

c.2-3 HP.

3. A pneumatic symbol is:

a.different from a hydraulic part used for the same function.

b.the same as a hydraulic part used for the same function.

c.not to be compared to a hydraulic part used for the same function.

 

4. Pneumatic systems usually do not exceed:

a.½-1 HP.

b.1-2 HP.

c.2-3 HP.

5. Comparing operating cost of hydraulic systems to pneumatic systems generally they are.

A.more expensive to operate..

B. less expensive to operate.

                        C. cost about the same to operate

 

6. A pneumatic systems reservoir is:

A. sized 3-4 times compressor CFM flow.

B. sized 6-8 times compressor flow.

                         C. the earth’s atmosphere.

1. Quick exhaust valves allow:
1. air to exit the cylinder rapidly.
2. oil to exit the cylinder rapidly
3. both of the above.

 

1. A quick exhaust valve is always mounted:
1. close to the directional valve port.
2. at the directional valves inlet port.
3. close to the cylinder port.

 

1. Quick disconnects for air circuits:
1. block flow from both lines.
2. block flow from the machine side only.
3. block flow from the supply side only.

 

1. Speed control mufflers only work as:
1. meter out flow controls.
2. meter in flow controls.
3. bleed-off flow controls.

 

1. A pressure gauge reading PSIA shows:
1. only positive pressure.
2. only negative pressure.
3. both positive and negative pressure.

 

 

1. An “AND” element has an output when it has_________input/s.
1. One   
2. two
3. three
2. An “OR” element has an output when it has ________input/s.
1. one
2. two

                        C. three

1. NOT” elements are:
1. normally passing elements.
2. normally non-passing elements.
3. normally exhausting elements.
2. YES” elements can be used as:
1. amplifiers.
2. normally passing elements.
3. 4-way valves.
3. This is a symbol for a/an:
1. “OR” element
2. “NOT” element.
3. “AND” element.
4. “FLIP-FLOP” elements are the same as a:
1. 5-Way valve.
2. 4-Way valve.
3. 3-Way valve.
5. “OR” elements are the same as:
1. directional control valves.
2. shuttle valves.
3. flow control valves.
6. A “TIME ON” time delay:
1. passes air after it times out.

                        b. blocks air after it times out.

                        c. none of the above.

1. A “NAND” element needs:
1. one signal to block through flow.
2. two signals to block through flow.
3. three signals to block flow.
2. A “NOR” element needs:
1. one signal to block through flow.
2. two signals to block through flow.
3. three signals to block flow

 

22.This symbol is for a/an:

A. double rod cylinder.                                               

B. intensifier.

                        C. Hi-Lo pump.

 

 

 

1. +Where and when does the fault occur

1. On all cylinders and motors    b. On only one       c. Under all load conditions

2. Type of fault

1. Complete stoppage   b. Reduced speed or thrust

3. How did the fault occur

a .suddenly   b. gradually    c. periodically

4. Unauthorized adjustment

1. Has someone adjusted the machine?   b. Has any attempt been made to repair the unit?

c.  Has machine been recently modified or repaired?

5. Pump delivering insufficient or no oil
1. Leakage in the pump  b. pump shaft  turning too slowly to prime itself

c.  None of the above  

 

6. Pump developing zero pressure
1. Relief valve setting not high enough    b. cylinder is not moving

c.  None of the above  

7. Pump making noise
1. Miss alignment of pump and prime over       b. Air presence in the oil

c.  both a & b

 

 

QUESTION BANK

UNIT 1

PART-A                                     

1. List out any four desirable properties of hydraulic fluids.

           (i)Stable viscosity (ii)Viscosityindex   (iii)Good Lubricity   (iv)Compatibility

(v)Stable physical and chemical characteristics   (vi) Non-Toxicity

1. Draw the symbol of pressure relief valve.

 

 

1. Define fluid power.

             It is the technology that deals with the transmission, generation and control of power using pressurized fluids

1. What are the basic components of a fluid power system?

           Hydraulics: Tank, Pump, Motor, Filter, Indicator etc.

           Pneumatics: Compressor, FRL Unit, Valves, Actuators etc.

1. Why air is preferred in fluid power systems compared to other gases?

         Since air is easily available, no investment is required, non-toxic, non-explosive air is being widely used.

1. Name the different types of fluid power systems.
2. Based on air. (It is pneumatics system)
3. Based on oil. (It is hydraulics system)
4. Based on combination of both oil and air. (It is pneumo-hydraulics system)
5. List out any four advantages of fluid power.

          (i) Ease and accuracy of control (ii) Multiplication of forces

         (iii) Constant force and torque (iv) Simplicity, safety and economy.

1. Show the symbol for variable displacement pump and pressure reducing valve.

 

 

1. Define viscosity index.

                                     Rate of change of viscosity

Viscosity Index =         Rate of change of temperature               (No unit)

1. List out any five fields of applications of fluid power.

         (i) Manufacturing Industry (ii) Automobile Industry (iii) Agriculture Industry    

        (iv) Naval Industry (v) Mechatronics Fields     (vi) Construction Field 

1. List out the different types of pumps used in hydraulics.

         Positive Displacement pumps – Rotary type: gear pumps and vane pumps and   

                                                              Reciprocating pumps: piston pump and its types

        Non-Positive Displacement pumps – Centrifugal pumps, axial and radial flow  pumps.

1. What are the important components of a hydraulic power pack?

        Tank, pump, valves, actuators etc.

 

1. What is meant by variable displacement pump?

          Displacement can be varied by changing the physical relationships of various pump elements and this change in pump displacement produces a change in output of fluid flow even the pump speed remains constant.

1. Where are rod less cylinders used?

         When the load needs to be moved some distance from the cylinder itself, material handling,  loading, feeding, lifting and web cutting applications.

1. Distinguish between positive displacement and variable displacement pumps.

Sl.No	Positive Displacement Pumps	Variable Displacement Pumps
(i)	Pressure development is main requirement	Pressure development is main requirement but not with same mechanical structure
(ii)	Changes doesn’t need to be made	Mechanical changes has to be made

1. What is a telescoping rod cylinder? When it would be normally used?

            Telescopic cylinders are a special design of a hydraulic cylinder or pneumatic cylinder which provide an exceptionally long output travel from a very compact retracted length. Typically the collapsed length of a telescopic cylinder is 20 to 40% of the fully extended length depending on the number of stages.

1. How is pumping action in the positive displacement pumps accomplished?

            A partial vacuum is generated in the pump cavity. The vacuum created in the cavity makes the outlet check valve to close the outlet line and also the atmospheric pressure to push the fluid from the reservoir via the inlet and the piston pushing back makes the oil to go to the outlet.

1. What is a hydraulic actuator?

            A linear actuator or a hydraulic cylinder is a device that converts fluid power into linear mechanical force and motion.

1. How are single acting cylinders retracted?

             The piston is retracted by gravity or by a compression spring

1. What is meant by synchronization of hydraulic actuators?

              The movement of two or more cylinders to complete some phase of operation to accomplishthe identical task from the cylinders at the same rate is called synchronization.

UNIT 2

1. List out any four desirable properties of hydraulic fluids.

           (i)Stable viscosity (ii)Viscosityindex   (iii)Good Lubricity   (iv)Compatibility

(v)Stable physical and chemical characteristics   (vi) Non-Toxicity

1. Draw the symbol of pressure relief valve.

 

 

1. Define fluid power.

             It is the technology that deals with the transmission, generation and control of power using pressurized fluids

1. What are the basic components of a fluid power system?

           Hydraulics: Tank, Pump, Motor, Filter, Indicator etc.

           Pneumatics: Compressor, FRL Unit, Valves, Actuators etc.

1. Why air is preferred in fluid power systems compared to other gases?

         Since air is easily available, no investment is required, non-toxic, non-explosive air is being widely used.

1. Name the different types of fluid power systems.
2. Based on air. (It is pneumatics system)
3. Based on oil. (It is hydraulics system)
4. Based on combination of both oil and air. (It is pneumo-hydraulics system)
5. List out any four advantages of fluid power.

          (i) Ease and accuracy of control (ii) Multiplication of forces

         (iii) Constant force and torque (iv) Simplicity, safety and economy.

1. Show the symbol for variable displacement pump and pressure reducing valve.

  

1. Define viscosity index.

                                     Rate of change of viscosity

Viscosity Index =         Rate of change of temperature               (No unit)

1. List out any five fields of applications of fluid power.

         (i) Manufacturing Industry (ii) Automobile Industry (iii) Agriculture Industry    

        (iv) Naval Industry (v) Mechatronics Fields     (vi) Construction Field 

1. List out the different types of pumps used in hydraulics.

         Positive Displacement pumps – Rotary type: gear pumps and vane pumps and   

                                                              Reciprocating pumps: piston pump and its types

        Non-Positive Displacement pumps – Centrifugal pumps, axial and radial flow  pumps.

1. What are the important components of a hydraulic power pack?

        Tank, pump, valves, actuators etc.

 

1. What is meant by variable displacement pump?

          Displacement can be varied by changing the physical relationships of various pump elements and this change in pump displacement produces a change in output of fluid flow even the pump speed remains constant.

1. Where are rod less cylinders used?

         When the load needs to be moved some distance from the cylinder itself, material handling,  loading, feeding, lifting and web cutting applications.

1. Distinguish between positive displacement and variable displacement pumps.

Sl.No	Positive Displacement Pumps	Variable Displacement Pumps
(i)	Pressure development is main requirement	Pressure development is main requirement but not with same mechanical structure
(ii)	Changes doesn’t need to be made	Mechanical changes has to be made

1. What is a telescoping rod cylinder? When it would be normally used?

            Telescopic cylinders are a special design of a hydraulic cylinder or pneumatic cylinder which provide an exceptionally long output travel from a very compact retracted length. Typically the collapsed length of a telescopic cylinder is 20 to 40% of the fully extended length depending on the number of stages.

1. How is pumping action in the positive displacement pumps accomplished?

            A partial vacuum is generated in the pump cavity. The vacuum created in the cavity makes the outlet check valve to close the outlet line and also the atmospheric pressure to push the fluid from the reservoir via the inlet and the piston pushing back makes the oil to go to the outlet.

1. What is a hydraulic actuator?

            A linear actuator or a hydraulic cylinder is a device that converts fluid power into linear mechanical force and motion.

1. How are single acting cylinders retracted?

             The piston is retracted by gravity or by a compression spring

1. What is meant by synchronization of hydraulic actuators?

              The movement of two or more cylinders to complete some phase of operation to accomplishthe identical task from the cylinders at the same rate is called synchronization.

1. What are control valves? Name the various types of pressure control valves.

          Control valves are the devices used to control the fluid pressure in a system.

The types of pressure control valves are (i) Pressure relief valve, (ii) Pressure regulating valve, (iii)Pressure sequence valve, (iv) Pressure switch etc.

1. Draw the graphical symbol for a solenoid actuated, spring return 4/3 way DCV.

 

 

1. What is an air-oil intensifier?

           Air to oil intensifiers also known as pressure boosters, are used to compress the liquid into a hydraulic system by supplying high amount of air at the input side of a larger cylinder area.

1. What is a check valve? Draw its symbol.

            It is a two way valve because it contains two ports. Also a check valve is analogous to diode in electrical circuits.

1. Name the three basic types of accumulators.

       (i) Weight loaded type accumulator(ii) Spring loaded type accumulator and

       (iii) Gas loaded type accumulator

1. What is the difference between pilot operated and direct operated pressure relief valve?

          The direct operated type is operated by a spring, whereas pilot operated is actuated by a pilot.The direct operated type has only one stage, whereas pilot operated has two stages namely (i)Direct type stage and (ii) Pilot operated stage

1. How sizing of accumulators is done?

           (i) Capacity of accumulator (ii) The pressure and velocity of the accumulator (iii) The total volume of the accumulator and (iv) The power  accumulator needs to develop

1. Define Cracking pressure in control valves.

The pressure at which the valve just opens and allows the oil to the tank is called as the cracking pressure. This is mainly applicable for all types of pressure relief valves and other devices too.

1. What is an electrical relay?

            The electrical relays offer simple ON/OFF switching action in response to a signal issued by a control system. In other words a relay is nothing but an electrically operated switch.

 

 

Unit 3

Part-B

2Marks Questions and Answers

 

1. What is a Servo valve?

             A servo valve is a direction control valve which has infinite variable positioning capacity. Thus it can control not only the direction of the fluid but also the amount.

1. What is the purpose of regenerative circuit?

            Regenerative circuit is used to speed up the extension stroke of the double acting hydraulic cylinder. It is possible to get more speed than the retraction stroke if the diameter of rod is so small.

1. What are synchronizing circuits?

            Many times in hydraulic machines some object or platform is to be lifted with the help of two or more hydraulic cylinders simultaneously. In such cases it becomes absolutely necessary that both cylinders must be synchronized. The circuits designed for these purpose are called as synchronizing circuits.

 

1. Define the function of pressure intensifier.

                        An intensifier is a device which converts low pressure fluid power into high pressure fluid power

1. What is meant by an air-over-oil system?

            Some times circuits using both air and oil are utilized to obtain the advantages of both. The surge tank is pressurized by air and pushes oil out in to the system. This system eliminates the need of the costly hydraulic pump and tank unit. This system is called as air-over-oil system.

 

1. What is the function of accumulator in hydraulic circuits?(Ap-May-04)

                        The function of the accumulator is to store the potential energy of an incompressible fluid held under pressure

1. What is automatic cylinder reciprocating system?

            The pilot signal shifts the DCV automatically by employing two sequence valves and hence the cylinder reciprocates continuously (Automatically).

1. What are the three basic types of accumulators?

i) Weight loaded (or) gravity type.    ii) Spring loaded type   iii) Gas loaded type.

1. What are the types of gas loaded accumulators?

i) Non- separator.                               ii) Separator.

1. Name the major classifications of separator accumulator.

i) Piston type.                                    ii) Diaphragm type.      iii) Bladder type.

 

 

1. What are the advantages and disadvantages of piston type accumulator?

            Advantage: This type of accumulator is its ability to accommodate very high or low temperature of the system.

Disadvantage: The main disadvantages of the free piston type accumulator are its cost and size. Piston and seal friction may also be a problem in a low pressure system.

 

1. What are the advantages of diaphragm type accumulator?

            The greatest advantages of this type of accumulator are its small weight to volume ratio, characteristics that makes it suitable for aircraft application.

 

1. Bladder type accumulators provide quick pressure response than piston type                      accumulators. Reason out.

Two reasons,

1. Rubber bladders do not have to overcome the static friction which a piston seal must.
2. The piston mass does not need to be accelerated and decelerated.

 

1.  What is the application of counterbalance valve?

            A counter balance valve is used to maintain back pressure on a vertical cylinder to prevent it from falling due to gravity. The applications are presses, loaders, lifts, trucks etc.

1. What is called Meter-out circuit?

                        The meter-out circuit is commonly used in machine tools that require precise control of the fluid on discharge from the exhaust side of the cylinder. Machine tools like mills and drills employs meter-out circuits

1. Write short notes on pump unloading circuit.

            In this circuit there are two pumps used viz, High Pressure low flow pump and High Flow low pressure pump. The High Flow pump is responsible for Speedy stroke and High Pressure pump is responsible for taking higher load. In certain circuits like punching press operation, initially the extension stroke speed may be higher ( both the pumps are in operation), finally ie., during pressing operation it should take more load (High pressure pump should only be in operation). During pressing the High flow pump is unloaded to tank through unloading valve.

1. What is”metre- in” circuit? What is its limitation? (AP-May-04)

                        The flow control valve is located in the pressure line leading to the work cylinder and hence is called as”metre- in” circuit. The limitation of this type is that the circuit can only be used when the load characteristics are constant and positive

1. What is the component used in fail safe circuit for overload protection?

            Emergency cut-off valve is installed in the fail safe circuit for overload protection

 

19. What is called hydropneumatics?

             Hydro pneumatics combines two fluids – air and the oil for the power transmission. By the use of the two media, the quick action of air and the smooth high pressure action of oil blend can be utilized in hydropneumatics.

 

 

Part-C

1. Name and explain three major classifications of a separator accumulator
2. Explain in brief about the sequence valve with its application circuit.
3. Describe the purpose, construction, and operation of various accumulators.
4. Explain the operation of accumulator circuits.
5. Describe the operation of pressure intensifiers and identify typical applications.
6.  Explain electrical control solenoid valves, relays & ladder diagram.
7. Construct a hydraulic circuit to explain the application of regenerative system in a drilling machine.
8. Construct a double pump hydraulic circuit employed in a punching press and explain how it functions.
9. While designing the hydraulic circuit what are the important considerations must be taken into account?
10.  What is the difference between closed circuit and open circuit hydrostatic transmission.
11. Describe the application of synchronizing circuit for series pumping.
12. Explain with neat sketch hydro pneumatic circuit.

 

Unit 4

 

Part-B

2Marks Questions and Answers

 

1. Define pneumatic system.

            Pneumatic systems are one which uses pressurized air as a medium to transmit and control power.

 

1. Name three reasons for considering the use of pneumatics instead of hydraulics.

            As the name implies pneumatic systems typically use air as the fluid medium, because air is a safe, low-cost and readily available fluid. Liquids exhibit greater inertia than do gases and hence the problem of accelerating and decelerating actuators and opening and closing valves gets eliminated in pneumatics. Also pneumatic systems are less expensive than hydraulic systems.

 

1. Name three types of air compressors.

            1. Piston compressor              2. Vane compressor                3. Screw compressor

 

1. Describe the function of air filter.

            The function of the air filter is to remove contaminants from air before it reaches the pneumatic components such as valves and actuators.

 

1. Why a lubricator is used in pneumatic system?

            The function of the lubricator is to insert drops of oil into the air stream and hence facilitates the lubrication of moving parts.

 

1. What is the function of muffler in pneumatic system?

            A pneumatic exhaust silencer called muffler is used to control the noise caused by the exhausting air stream.

 

 

 

 

1. What is the function of compressors?

            A compressor is a machine that compresses air or gas from a low inlet pressure to a higher desired pressure level. This is accomplished by reducing the volume of the gas. Air compressors are generally positive displacement units and are either of reciprocating piston type or the rotary screw or rotary vane types.

 

1. List the hydro pneumatic appliances.

            The hydro pneumatic appliances are,

            1. Air-oil reservoir                  2. Air- oil cylinder                 3. Air- oil intensifier

 

1. Write the applications of air motors.

             They may be used in conjunction with hydraulic power units, bench grinders, conveyer belts, agitators and mixers, feeding devices, hoists, machine feeders, pipe theraders, tool devices, vibrators and many others. 

 

 

1. Compare the hydraulic and pneumatic circuits with respect to their characteristics        (Ap-May-04).

            The liquids exhibit greater inertia than gases and hence the force required to accelerate oil is greater than air. The liquids exhibit greater viscosity than gases and hence results in larger frictional pressure and power losses. Due to compressibility of air, it is impossible to obtain a precise control of actuator velocities in pneumatic systems. The hydraulics can be used in high power systems whereas pneumatics are confined to low power applications

 

1. Name the methods used for designing pneumatic circuits.

1. Classic method             2. Cascade method                 3. Step-counter method                        4. Logic design method (with Karnaugh – Veitch maps)     5. Combinational  circuit design. 

 

1. What is F-R-L and what is the function of a lubricator?

             FRL means Filter, Regulator and Lubricator. The lubricator lubricates the moving parts of the pneumatic system and eliminates the friction.

 

1. What is a Pneumatic Vacuum System?

            When a vacuum air pressure is used to perform useful function, the system is called as Pneumatic Vacuum System. Industrial applications like material handling, clamping, sealing and vacuum forming are uses this kind.

 

1. What is the function of pneumatic shuttle valve?

            The pneumatic shuttle valve automatically selects the higher of the two input pressures and connects that pressure to the output port while blocking the lower pressure.

 

1. What is the function of AND type valve?

      In this valve an output is produced if both the input signals are fed.

 

 

 

1. What is the use of quick exhaust valve?   

             The return air from the cylinder will exhaust directly to the atmosphere without passing through the DCV.

 

1. What is the use of time delay valve?

            This valve is used in the pneumatic system to initiate a delayed signal.

 

1. Name the materials used for making the pneumatic cylinders.

            Pneumatic cylinder construction makes extensive use of aluminum and other non-ferrous alloy materials to reduce the weight and the corrosive effects of air and to improve heat transfer capabilities.

 

1. What are air motors?

            To generate rotary motion in a pneumatic system an air motor is used.

 

 

1. How does a hydro pneumatic system differ from hydraulic system?

      In the hydro pneumatic system both air and oil are used to do the useful work.

 

1. What are the basic components of logic controls?

             The basic components of logic controls are sensors and switching elements called binary elements.

 

1. What are the advantages of pneumatic logic controls?

     They are,

1. Used in specialized applications like explosive environments.
2. Simple in design.
3. Having higher response than electrical systems.
4. Durable than electrical systems.

 

1. Name pneumatic position sensors.

             Pneumatic limit valves, back pressure sensor, proximity sensor, gap sensor and limit      switch.

 

1. What is the use of pressure sensors?

             When the preset pressure level is reached, the pressure sequence valve provides a signal. This in turn can be used for further switching combinations.

 

1. What is a solenoid?

             A solenoid is an electromechanical device which can convert electrical signal into       mechanical force and motion.

 

1. What are relays?

             Relays are used for energizing and de-energizing solenoids which operate at high current level.

 

1. What is the use of timers?

             Timers are used to control the time duration of a working cycle. In this way a dwell can be provided when needed.

 

29. When is the pneumatics preferred over hydraulics?

             Pneumatics is preferred over hydraulics when the high speed and lower forces are required and do not require high precision.

 

30. What is a multistage compressor?

             A compressor that draws in air and compresses it to its final pressure in two or more stages is called a multistage compressor.

 

31. What is the purpose of a pressure regulator?

             The purpose of pressure regulator is to regulate the incoming pressure to the desired pressure.

 

 

32. State the difference between quick exhaust valve and flow control valve.

             The flow control valve is used to reduce the actuators speed from its normal speed. But quick exhaust valve accelerates the speed of the actuators.

 

33. Why air cylinders cannot be used for precise speed control?

             Due to the compressibility characteristic of an air, the air cylinder tends to slow down on meeting increase in load and to accelerate when the load suddenly decreases. So air cylinders cannot be employed for precise control.

 

34. Classify the pneumatic cylinders based on principle.

            1) Single acting cylinder                               2) Double acting cylinder

            3) Tandem cylinder                                       4) Three position cylinder

            5) Through Rod cylinder                               6) Adjustable stroke cylinder

            7) Telescoping cylinder

 

35. Where is the suction cups used?

             Suction cups can be used to pickup and hold work pieces with smooth and impervious surfaces. They are commonly used in pick and place application in industries like glass, TV, sheet handling, packaging etc.

 

 

 

Part-C

1. Discuss the application of fluidics pneumatic logic circuits
2. How does a hydro-pneumatic system differ from hydraulic system?
3. Explain the purpose, construction, and operation of filter, regulator & lubricator unit in pneumatic system.
4. Draw a pneumatic circuit for table movement and explain its principle.
5. What is an air-oil intensifier? Explain its application with example.
6. Briefly describe various pneumatic valves.
7. Explain vane type air motors with sketches.
8. What is cascade system? Design a pneumatic circuit using cascade method for the

             Sequence of A⁺ B ⁺A ^–B^-

1. State some important parameters which may require constant attention in a pneumatic system.
2. If the pressure in the pneumatic system is too low, what are the possible causes and give remedies for them?
3. Describe the purpose, construction, and operation of compressors.
4. Discuss the construction and operation of pneumatic cylinders and motors.
5. Explain the working of (i) quick exhaust valve and (ii) time delay valve with neat sketch.
6. Design a system in which cylinder A is used to clamp the workpiece; cylinder B is used for punching and cylinder C moves the workpiece from the station.by using cascade method.

Cylinder extension position-(clamping, punching and remove the workpiece)

Cylinder retraction position-(unclamping, after punching and after removal of workpiece)

 

 

 

 

 

UNIT 5

Part-B

2Marks Questions and Answers

1. What are all the basic requirements for a trouble free hydraulic system?

      The basic requirements are,

            1. Properly installed equipments                               2. Properly trained personnel

            3. Planned preventive maintenance                           4. Efficient trouble shooting.

 

1. What is called trouble shooting in a hydraulic system?

             The term trouble shooting means an organized and systematic study of the problem and a logical approach to the difficulty faced in the system.

1. List the basic elements of PLC construction.

      The three basis elements of PLC are,

            Central processing unit          Input modules             Output modules.

 

1. List the various approaches for entering program into the PLC.

            There are various approaches for entering the program into PLC,

1. Ladder diagram
2. Low level language based on Boolean expressions.
3. Functional blocks.
4. High level languages.
5. What is called trouble shooting chart?

            A trouble shooting chart is one which shows the complete details of trouble, possible causes and remedies. An operator can easily identify and rectify the problem with the help of this chart.

 

1. What is the reason for frequent packing failure of cylinders?

            The improper mountings will cause damage of the packing very soon.

 

1. What is the reason for relief valve failure?

            The relief valve may fail due to dirt present in oil, due to worn-out poppet and due to piston sticking in the main body.

 

1. What is preventive maintenance?

             With the help of periodical maintenance schedule, the components are maintained in good condition before the problem arises and hence it is called as preventive maintenance.

 

1. Identify any three reasons for the excessive noise of pumps.

            The reasons may be due to,

1. Misalignment of pump and prime mover.
2. Air remains in pump casing
3. Very high viscosity

 

1. What may be the reason for faulty shifting of DCV?

            The reasons may be due to, worn out control linkage, insufficient pilot pressure, burnt out solenoid etc.

 

1. What are the causes for the failure of unloading valve?

            The unloading valve may fail due to, too high valve setting, too low remote pressure and valve spool binding in body.

1. What is called trouble shooting chart?

            A trouble shooting chart is one which shows the complete details of trouble, possible causes and remedies. An operator can easily identify and rectify the problem with the help of this chart.

 

1. What is the reason for frequent packing failure of cylinders?

            The improper mountings will cause damage of the packing very soon.

 

1. What is the reason for relief valve failure?

            The relief valve may fail due to dirt present in oil, due to worn-out poppet and due to piston sticking in the main body.

 

1. What is preventive maintenance?

             With the help of periodical maintenance schedule, the components are maintained in good condition before the problem arises and hence it is called as preventive maintenance.

 

1. Identify any three reasons for the excessive noise of pumps.

            The reasons may be due to,

1. Misalignment of pump and prime mover.
2. Air remains in pump casing
3. Very high viscosity

 

1. What may be the reason for faulty shifting of DCV?

            The reasons may be due to, worn out control linkage, insufficient pilot pressure, burnt out solenoid etc.

 

1. What are the causes for the failure of unloading valve?

            The unloading valve may fail due to, too high valve setting, too low remote pressure and valve spool binding in body.

 

Part-C

1. Explain in detail about the hydraulic operation of a planning machine.
2. Brief the hydraulic operation of press with neat circuit.
3. Explain the hydraulic circuit for a robotic arm.   
4. Draw a hydraulic circuit for forklift.
5. What are the various approaches for entering the program in the PLC?
6. With a neat circuit explain the drilling circuits
7. Draw a circuit for a hydraulic shaping machine and explain how it works?
8. Explain a circuit for surface grinding machine.
9. What is low cost automation and explain the same with a simple LCA circuit.
10. Draw a hydraulic power pack with all elements and explain how it works.
11. Design a fluidic sequencing control of two pneumatic cylinders using flip-flop, OR Gate, Push buttons, Directional control valves etc for the following sequence;

               Cylinder 1 extends

               Cylinder 2 extends

               Both cylinders retract together.                                     

1. Briefly explain the various electrical devices used in the control of Fluid Power systems.
2. What is PLC? Explain the elements of PLC with block diagram.   
3. Write down the advantage of PLC over electro mechanical relays system