Pneumatic System Components | Interview Question and Answers

Pneumatic System Components – Hydraulic and Pneumatic| Interview, viva ,oral Question and Answers

1. What is the difference between a strainer and filter?

Strainer is a device for the removal of solids from a fluid wherein the resistance of motion of such solids is in a straight line. Filter is a device for the removal of sol ids from a fluid wherein the resistance of motion of such solids is in a tortuous path.

2. Name the various filter media.

(i) Woven wire cloth (ii) Paper filter (iii) Woven cloth media (iv) Sintered metal powders (v) Ceramic and plastic media.

3. List out the basic types of filtering methods used in hydraulic system.

The basic filtering methods are,
(i) Surface type (ii) Depth type (iii) Edge type.

4. List the various locations where filters are installed in hydraulic systems?

(i) Suction line filter (ii) Pressure line filter (iii) Return line filter (iv) By pass and bleed-off filter.

5. What is meant by synchronisation of cylinder motion? Name the various methods to achieve it.

If a load is to be lifted with the help of two or more hydraulic cylinders, the cylinders are connected by some means to synchronise their motion.

The various methods are,

(i) Tie cylinders (ii) Series piping (iii) Synchronizing with flow control valves (iv) Synchronizing with matching pumps (v) Synchronizing with
flow dividers.

6. What is the purpose of regenerative circuit and how is it attained?

A regenerative circuit is used to speedup the extending speed of a double acting cylinder. This is attained by connecting the return flow from cylinder to pump flow.

8. For the above problem, if the system pressure is 86 bar, what is the load carrying capacity of the system.

Load carrying capacity = Au x P = 1.5 x 10-3 x 86 x 105=10.2 kN

9. What is banked unit and mention one of its applications?

The directional control valves, usually six port valves are grouped together and is called banked unit. Banked units are mainly used in mobile applications like elevators. cranes, fork Lifts etc.

10. When is pneumatics preferred over hydraulics?

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

11. Name the three types of positive displacement compressors that are commonly used in industry?

(i) Reciprocating piston type (ii) Rotary vane type (iii) Rotary screw type

12. What is a multistage compressor?

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

13. What is the purpose of a dryer?

The purpose of the dryer is to reduce the relative humidity and dew point of the compressed air from the compressor.

14. What is the function of an air filter?

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

15. What is the purpose of a pressure regulator?

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

16. Why should a lubricator be used in a pneumatic system?

Air is not a good lubricant. So to lubricate the moving parts in the pneumatic system, a fine mist of oil is discharged into the air by a lubricator.

17. What is an F-R-L unit and give the graphic symbol of it?

F-R-L unit is a combined unit of Filter-Regulator-Lubricator.

18. What is the need for mufflers?

The use of exhausted air in industries has created noise problems. This air generates high intensity sound energy, which causes fatigue to an operator. The muffler is used to reduce the energy of exhausted air, thereby reducing the noise.

20. What is the purpose of a shuttle valve?

The shuttle valve delivers an output when one input is present or when both are present.

21. What is the purpose of a two-pressure valve?

The two-pressure valve delivers an output when both input signals are present.

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

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

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

Due to the compressibility characteristic of 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.

28. Classify the pneumatic cylinders based on principle.

(i) Single acting cylinder (ii) Double acting cylinder (iii) Tandem cylinder (iv) Three position cylinder (v) Through rod cylinder (vi) Adjustable stroke cylinder (vii) Telescoping cylinder.

29. Name the different types of air motors.

(i) Piston type motors–Axial, Radial
(ii) Vane type motors-Nan-reversible, Reversible
(iii) Turbine motors.

30. Mention few advantages of air motor over electric motor.

(i) Air motors do not require electrical power. So they can be used in volatile atmospheres.
(ii) Air motors can stall under full load for indefinite periods of time, while electric motors will be damaged by heat generation when stalled.
(iii) Air motor speed can be regulated through simple flow control valve instead of expensive and complicated electronic speed controls.

31. Where are 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 ill industries like glass, TV, printing, sheet handling, packaging etc.

32. Define the terms running torque, starting torque and stall torque of an air motor.

The torque generated when the motor is rotating at a particular speed is ‘running torque’. The maximum torque the motor can produce when starting under load is ‘starting torque’. The torque required to stop the motor at a particular supply pressure is ‘stall torque’.