Fluid Power System Basic – Hydraulic and Pneumatic| Interview Question and Answers
Fluid Power System Basic – Hydraulic and Pneumatic| Interview, viva ,oral Question and Answers
1. Define fluid power.
Fluid power technology is a means to convert, transmit, control and apply fluid energy to perform useful work. Fluid power includes hydraulics and pneumatics.
Read more : What is Fluid Power | Advantages , Application
2. Differentiate oil hydraulics and pneumatics.
- Oil hydraulics employs pressurized liquid and pneumatics employs compressed air.
- Oil hydraulic systems operate at pressures up to 200 bar or even much higher. Pneumatic systems operate in a pressure range of 5 to 10 bar.
- Oil hydraulic systems are used in high load applications and accurate speed control or positioning is required. Pneumatic systems are used in low or medium load application and high velocities are required.
3. What is the basic law that is important in applying fluid power?
Pascal law is the basic law used in fluid power. According to Pascal law, the pressure generated at one point in a confined liquid acts equally in all directions.
4. List five fields of applications of fluid power.
Agriculture, Aviation, Fabrication industry, Machine tools, Oil industry and Pharmaceuticals.
5. Why is hydraulic power especially useful with heavy work?
Hydraulic systems generally operate at high pressures and provide high forces. So they are useful with heavy work.
6. Where are pneumatic systems preferred?
Pneumatic systems are preferred where low or medium size forces are required and velocities are high. Because of their low cost, they are preferred in industrial automation.
7. What are the primary functions of hydraulic fluid?
(i) Transfer fluid power efficiently.
(ii) Lubricate the moving parts.
(iii) Absorb, carry and transfer the heat generated within the system.
8. Name few properties of a hydraulic fluid.
(i) Viscosity (ii) Viscosity Index (iii) Oxidation stability (iv) Demulsibility (v) Lubricity (vi) Rust prevention (vii) Flash point and fire point (viii) Neutralization Number.
9. What are the undesirable results when an oil viscosity is too high?
When the viscosity is too high,
(i) The viscous oil may not be able to pass through the pipes.
(ii) The working temperature will increase because there will be internal friction.
(iii) The consumption of power will increase.
10. What are the undesirable results when an oil viscosity is too low?
When the viscosity is too low,
(i) The internal and external leakage will increase.
(ii) It cannot lubricate properly and will lead to rapid wear of the moving parts.
11. What is Viscosity Index and Give is its significance?
The rate of change of viscosity with temperature is indicated on an arbitrary scale called Viscosity Index (vi). The lower the viscosity index, the greater the variation in viscosity with changes in temperature and vice versa.
12. What is demulsibility?
The ability of a hydraulic fluid to seperate rapidly from moisture and successfully resist emulsification is known as demulsibility.
13. Why should a hydraulic fluid have good lubricating ability?
If the hydraulic fluid does not have good lubricating ability it will not lubricate moving parts properly, causing wear. Wear results in increased clearance, which leads to all sorts of operational difficulties including fall of efficiency.
14. What is neutralization number of hydraulic fluid and Give its significance?
The neutralization number is a measure of acidity or alkalinity of a hydraulic fluid. High acidity causes the oxidation rate in an oil to increase
15. Define the term pour point and its importance.
The temperature at which oil will congeal is referred to as the pour point, i.e. the lowest temperature at which the oil is able to flow easily. It is of importance in cold countries where the system is exposed to very low temperatures. The pour point must be well below the minimum temperature expected in normal condition.
16. Name three fire resistant fluids.
(i) Water glycols (ii) Water oil emulsions (iii) Phosphate esters.
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