Two marks questions and answers

TWO MARKS QUESTIONS AND ANSWERS

1. What is the function of an accumulator ?

An accumulator is a pressure storage reservoir in which a non-compressible hydraulic fluid is retained under pressure from an external source.

2. Highlight the need of using an accumulator in hydraulic circuits.

• The function of hydraulic accumulator is analogous to that of the flywheel of a reciprocating engine and a capacitor in an electronic circuit

• In hydraulic systems like crane or lift, the liquid under pressure needs to be supplied only during the upward motion of the load. This energy is supplied from hydraulic accumulator. But when the lift is moving downward, no large external energy is required and during that period the energy from the pump is stored in the accumulator. 

3. What electrical device is accumulator analogous to ?

The function of hydraulic accumulator is analogous to that of a capacitor in an electrical circuit.

4. Name the basic types of accumulators used in hydraulic systems.

1. Weight-loaded (or dead-weight) accumulators,

2. Spring-loaded accumulators, and

3. Gas-loaded accumulators.

5. What are the uses/functions of accumulators? (or) List any four applications of accumulators.

Accumulators are used as :

(i) Leakage compensator,

(ii) Auxiliary power source,

(iii) Emergency power source,

(iv) Hydraulic shock absorber,

(v) Fluid make-up device,

(vi) `Holding device, etc.

6. Which type of accumulator operates at constant pressure? How can the pressure be changed?

• Weight-loaded (or dead-weight) accumulator operates at constant pressure. 

• The pressure can be changed by changing the dead-weight of the accumulator. 

7. Why weight loaded type accumulator is undesirable for mobile equipment?

Because of the weight loaded type accumulator is very heavy; not portable; and do not respond quickly to changes in the system demand.

8. What type of gas is used in gas-loaded accumulators? Why is oxygen not used for this purpose?

• The inert gas such as nitrogen gas is used in gas-loaded accumulator. 

• The air or oxygen are not used due to the danger of explosion.

9. Explain briefly the non-separator type gas loaded accumulator. 

In the non-separator type gas loaded accumulator, pressurisation is achieved by introducing a pressurizing gas into a container above the oil level. When the system pressure increases, the oil enters through oil port and pushes the gas. The reduction of volume of gas increases its pressure. This gas pressure is used as the potential energy to force the oil out when it is required in the circuit.

10. What is meant by sizing of accumulators? (or) What is meant by the term 'capacity' of an accumulator? 

The maximum amount of energy that the accumulator can store is known as the capacity of the accumulator.

11. What are three significant accumulator operating conditions ?

1. Recharging condition.

2. Charging (the fluid to maximum pressure) condition, and

3. Discharging (the fluid to minimum pressure) condition.

12. What is the function of a pressure intensifier ? (or) What is an intensifier?

Pressure intensifier, also known as pressure booster, is used to compress the liquid in a hydraulic system to a value above the pump discharge pressure.

13. What is gained and what is lost in an intensifier?

In intensifier, pressure is gained and the volume is lost.

14. What electrical device is pressure intensifier analogous to ?

Pressure intensifier is analogous to a step-up electrical transformer.

15. List the applications of an intensifier.

Intensifiers find most useful applications where the output pressure requirements are much higher than that are obtainable from a pump. Typical applications include punching presses, riveting machines, spot-welders, and in many high-pressure testing machines such as tubing fixtures for testing bursting pressures and high pressure holding fixtures.

16. What is meant by air-oil intensifier?

Air-over-oil intensifier is used for driving a cylinder over a large distance at a low pressure and then over a small distance at high pressure (such as in punch press application). 

17. Define the term intensifier ratio.

18. Draw the fluid power symbols for (i) a pressure intensifier and (ii) gas-loaded type accumulator.