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Tuesday, June 7, 2011

Fundamental of Hydraulic Pump

In hydraulic systems forces and motion are transferred by liquids. By means of the transferring liquid it is possible to convert the forces and to control the movements precisely.
Example of application
Machine tools: Table movement in grinding machine; copy turning; transporting 2nd clamping of workpieces on transfer line; feed motion of machining units.
Vehicles: Brakes, automatic gears, tilting of loading surface, steering gear magnifier.
Crane, excavator: lifting and lowering motion of cantilever, gripper and boom.
Presses: Movement of plunger of press, generation of large pressures.
Mining plant: Hydraulic tunnel supports.
Aeroplanes: Movement of landing gear and empennage (tail group)

Advantages: convertion of large forces (pressures).
Continuous regulation of speed (feeds), precise control and actuating accuracy, bridging of long distances between drive and work units, mobility through flexible hose connection, starting from rest position under load, smooth running.

Basic definitions Hydrostastics
Hydro = water = liquid (fluid)
Static = rest.
Hydrostatics = static of fluid
When the liquid in a closed system of container and pipelines is set under pressure by the application of a force at any point, the resultant pressure energy may be received as force at any other point of the system, since work equals force multiplied by distance. Thus in hydraulic systems few law of hydrodynamics also occur.

Hydrodynamics = dynamic of fluid.
In an open system of a tank and pipelines/penstock the liquid attains a very high flow-speed due to large gradient (height difference). At the end of the pipeline the energy of the following fluid can be converted into mechanical work, rotary motion, for example of a hydraulic turbine.

Whether a system is hydrostatic or hydrodynamic depends on the type of energy transfer, hydrostatic = pressure energy, hydrodynamic =motion energy. Although few laws of hydrostatic also apply, hydrolic systems are basically hydrostatic in nature because the energy transfer is carried out fundamentally by means f pressure energy.

Propagation of Pressure
In a close system, if the liquid at a point is set under pressure the whole of the liquid comes under the same pressure at all other points. The force developed acts normal (in perpendicular direction) to the inner walls of the container. Pressure vessels have, for safety reasons. Outward or inward curved bottoms; spray cans, steam boiler, champagne bottle, oxygen cylinder, etc.