Introduction:
A matter exists in either the solid state or the fluid state. The fluid state is further divided into the liquid and the gaseous states. In fact the same matter may exist in any one of the three states .solid, liquid and gaseous. For example water, which ordinarily occurs in a liquid state, may also occur under natural conditions in a solid state as ice and in a gaseous state as vapor. The two classes of fluids, gases and liquids also exhibit quite different characteristics. Gases can be compressed much readily under the action of external pressure and when the external pressure is removed the gases tend to expand indefinitely. On the other hand under ordinary conditions liquids are quite difficult to compress and therefore they may for most purposes be regarded as incompressible. The following are basic Methods of Transmitting Power:
Electrical : large distance
Mechanical : short distance
Fluid Power : intermediate distance
Fluid Power:
- Fluid power is the method of using pressurized fluid to transmit energy.
- Liquid or Gas is referred to as a fluid.
- Accordingly, there are two branches of fluid power; Pneumatics, and Hydraulics.
- Hydraulic systems use pressurized liquid such as water or other liquids to transfer Power from one point to another.
- Pneumatic systems use pressurized air or other gases to transfer Power from one point to another.
A liquid is a fluid, which possesses a definite volume, which varies only slightly with temperature and pressure. Since under ordinary conditions liquids are difficult to compress, they may be for all practical purposes regarded as incompressible. It forms a free surface or an interface separating it from the atmosphere or any other gas present.
A gas is a fluid, which is compressible and possesses no definite volume but it always expands until its volume is equal to that of the container. Even a slight change in the temperature of a gas has a significant effect on its volume and pressure. . However, if the conditions are such that a gas undergoes a negligible change in its volume, it may be regarded as incompressible. But if the change in volume is not negligible the compressibility of the gas will have to be taken into account in the analysis.
What is hydraulics :
- Two Greek word, hudro (Water) + aulos (Pipe) → hudraulikos
- hudraulikos (Greek) → hydraulic (Latin). early 17th century
The hydraulic is a used for lifting heavy loads by the application of much smaller force. A Hydraulic system is a power transmission system in which the transmission of power takes place through a fluid medium. Hydraulic system is most convenient & highly efficient. It is based on Pascal’s law, which states that intensity of pressure is transmitted equally in all directions through a mass of fluid at rest.
Pascal’s Law:
- Any change in the pressure applied to a completely enclosed fluid is transmitted equally in all directions and walls of enclose without any loss.
- French scientist pascal discovered this law in the 17th century.
- When the syringe is filled with water, pushing the plunger water comes out from all nozzles with equal speed perpendicularly to the surface of the container.
Pressure exerted at any point on a confined liquid is transmitted undiminished in all directions.
Fluid Power Physics:
Force: Force is an agent, that, when applied externally to an object with mass, changes state ( either of rest or of uniform motion ) of the object. Mathematically, F = mass X acceleration
Pressure: The amount of force exerted (thrust) perpendicularly on a surface per unit area is defined as ‘Pressure’. It can also be defined as the ratio of the force to the area (over which the force is acting).
Law of Hydrostatics: The Pressure ‘p’ of a fluid at rest increases on increasing the depth.
The Pressure ‘p’ is dependent on the height of liquid column and its density.
The Pressure ‘p’ is independent of the shape and geometry of container
Brahma’s Press : A hydraulic press is a machine press using a hydraulic cylinder to generate a compressive force. It uses the hydraulic equivalent of a mechanical lever, and was also known as a Bramah press after the inventor, Joseph Bramah, of England.
How Do Hydraulics Work
Hydraulic work composed of pumps, pressure control valve, direction control valve, flow control valve, actuators, Reservoir and accessories, and their composition according to objectives and specifications. Many compositions are possible for single objective.
- The most efficient hydraulic system is,
- 1) Safe and completely optimal to meet objective.
- 2) Capable of smooth movement.
- 3) Energy efficient.
- 4) Effective for initial and running costs.
- 5) Easy to maintain.
hydraulic system operation :
Fluid System Components:
- Pumps
- Actuators
- Valves
- Accumulators and Reservoirs
- Filtration and Conditioning
- Hoses, Pipes, and Tubing
- Seals and Fittings
Hydraulic Pump: A hydraulic pump is a mechanical device that converts mechanical power (received from electric motor; prime mover) into hydraulic energy.
Hydraulic Actuator :The actuators are devices that convert the hydraulic energy into mechanical energy.
Seals: Basic Purpose of seals: i. to arrest both internal and external leakage. ii. prevent dust, dirt and other foreign particles from entering the system
Hydraulic Reservoir : Reservoir is supply source of hydraulic system fluid. A well designed and constructed reservoir assists the separation of contamination and helps to dissipate heat generate with in the system.
Hydraulic Filters: In every closed hydraulic tanks air breather mounted on air chamber side and its function to maintain the pressure on hydraulic oil
Control Valves: Pressure-relief valves limit the maximum pressure in a hydraulic circuit by providing an alternate path for fluid flow when the pressure reaches a preset level.
Actuator: These are linear actuators. The output motion is in straight line. Hydraulic power is converted to
mechanical power. Used for pushing, pulling, tilting, pressing etc.
Application of Hydraulic:
- Hydraulic systems are commonly used where mechanisms require large forces and precise control.
- Hydraulics plays an important role in many industries; there are a lot of hydraulic applications in manufacturing, transportation, and construction sectors.
- Examples include vehicle power steering and brakes, hydraulic jacks, hydraulic elevators, Weapons systems (loading & launching), and heavy earth moving machines
- Heavy duty presses for bulk metal formation such as sheet metal bending, forging, punching etc.
Hydraulic Advantage :
- Higher Efficiency
- Absence of linkage
- Self lubricating & Self cooling
- Leakage is less
- Extremely smooth & jerk free motions
- Good heat transfer characteristics
- Less Noisy
Hydraulic Disadvantage :
- Frictional losses
- Variation of viscosity due to change in temperature
- Structural weight & size of system is more
- Bursting of pipe can cause injury
- The small impurities in the hydraulic fluid can permanently damage the complete system
