Two marks questions and answers

TWO MARKS QUESTIONS AND ANSWERS

On Pneumatic Valves

1. What are the functions of air control valves? 

The main functions of pneumatic valves are: 

(i) To start and stop pneumatic energy;

(ii) To control the directional flow of compressed air;

(iii) To control the flow rate of the compressed air; and

(iv) To control the pressure rating of the compressed air.

2. Mention the applications of a 2 way, 3 way, and 4 way DC valves.

Generally two way DC valves are used as on-off type valves; three way DC valves are used to control single-acting linear actuators; and four way DC valves are used to control double-acting actuators.

3. What is the purpose of a shuttle valve in a pneumatic circuit? 

Shuttle valves are used when control is required from more than one power source. They are generally used to shift the fluid flow from the second and back up source, when the main source becomes inoperative.

4. What is the purpose of a quick exhaust valve? Where is this valve installed?

The quick (or fast) exhaust valve is used to exhaust the cylinder air the atmosphere quickly, so as to increase the piston speed of cylinders. This valve is installed between the interface valve and the actuator.

5. 'Quick exhaust valve is used to increase the piston speed of spring return single-acting pneumatic cylinder' - Justify. 

The higher speed of piston in a cylinder is possible by reducing the resistance to flow of the exhausting air during motion of the cylinder. The resistance can be reduced by expelling the exhausting air to the atmosphere quickly by using the quick exhaust valve.

6. What is the function of an air pressure regulator ?

The function of the air pressure regulator is to regulate the pressure of the incoming compressed air so as to achieve the desired air pressure at a steady condition.

7. What is the function of a flow control valve in a pneumatic circuit?

Flow control valves are used to regulate the volumetric flow of the compressed air to different parts of a pneumatic system.

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

The quick exhaust valve is used to exhaust the cylinder air to the atmosphere quickly, so as to increase the piston speed of cylinders. On the other hand, flow control valves are used to regulate the volumetric flow of the compressed air to different parts of a pneumatic system.

On Pneumatic Actuators

9. What is the function of a pneumatic actuator?

Pneumatic actuators are the devices used for converting the pressure energy of air into mechanical energy to perform useful work.

10. How do pneumatic actuators differ from hydraulic actuators? 

Pneumatic actuators are of lighter construction and of lesser weight when compared to that of hydraulic actuators. This is because the pneumatic actuators are used mostly for low or medium pressure applications only.

11. What is the function of a pneumatic cylinder?

Pneumatic cylinders are the devices used for converting the air pressure into linear mechanical force and motion.

12. What is the function of an air motor ?

The function of an air motor is to convert the pressure energy of the compressed air into rotary mechanical energy.

13. Name the different types of air motors.

1. Continuous rotary actuator, and

(a) Gear motor, (b) Vane motors, and (c) Piston motors.

2. Limited rotation hydraulic motors.

(a) Vane type, and (b) Piston type.

14. Mention advantages of air motors over electric motors.

Air motors are well-suited to those applications that require a compact, lightweight source of smooth, vibration-less power. Air motors stop and start almost instantly and provide extremely variable torque and speed without complicated controls. They can operate in hot, corrosive, and wet environments without damage, and are unaffected by continuous stalling or overload.