Jump to content







Photo

Get started with Hydraulics

Posted by Anand's Technophilia, 02 January 2011 · 112 views

Oil has always been the most beneficial of natural resources, as much as it is useful as a source of power and energy as fuel, like LP gas or Petrol, there are other alternative methods for harnessing its power. This is evident by the abundance of machinery and equipments using this "Fluid Power" as a source for getting useful work done. Isn't it amazing to think that it can also be used to power structures like Cranes and Presses.
        Welcome to the amazing world of fluid power.

        One of the best places to get up close and personal lesson on hydraulics are machines at a construction site. The thing that is most amazing about these machines is their sheer size. From backyard log splitters to the huge machines you see on construction sites, hydraulic equipment is amazing in its strength and agility. On any construction site you see hydraulically-operated machinery in the form of bulldozers, backhoes, shovels, loaders, fork lifts and cranes. In most other hydraulic systems, hydraulic cylinders and pistons are connected through valves to a pump supplying high-pressure oil .

        The word "HYDRAULICS" is derived from the Greek "HYDRO" meaning water. (See Hydraulics at Wikipedia). There are many instances in the past where water was employed for useful work in the distant past to suit our needs. Modern hydraulics, especially in the industrial context is mainly concentrated on Oil as power transmission mediums.

       why fluids...?

       Fluids like water or oil are the best substances to work using pressure.

       "Pressure" is the epicenter of all hydraulic system design calculations. Pressure arises because of the sheer density of water, as we know which is about 1000 kg/cu. meter. The weight of water column increases in proportion to the depth, as in the case of the ocean. The deeper we dive, the higher we feel the pressure.

        The same pressure term can be used, when we are analyzing it in a context of a hydraulic press, which of course is an equipment found in a factory, on land, rather than the sea. And it also does not need lots of water to accomplish the "Pressing". The pressure in a hydraulic press is induced by means of other compression media, pumps for example, which are more compact.

        But... Still what next. How does it still help for oil/ liquid to be used for the working of hydraulic systems?

        The reason, quite simply put it, Fluids (oils talking in industrial context, i.e., everything with specific gravity value less than or equal to 1) are incompressible. (It is known that oils are lighter, specific gravity< 1).

        This brings us to what Pascal discovered, combining pressure and incompressibility, which we know today as the universal law stating...

"Any change of pressure on an incompressible fluid in an enclosed space is transmitted equally and undiminished in all directions on to the surface of the container".
      
        What supports the statement above is that fluids, like water and oil, unlike gases(gases can also be termed fluids because they can flow) are the least compressible. Talking of compressibility, it is known that intermolecular forces are at the least among gases. They are like...free to move about in every direction, spread if allowed to(The open perfume bottle in a room trick) but also compressible into closed containers upto pressures possibly unthinkable. These gases, viz.,atmospheric air, can also be used for power transmission, but their use is limited. Pneumatics, or "air power" as an engineering entity is quite similar to hydraulics using the same fundamentals of pressure causing displacement or useful work, but with a lesser efficiency. Still, gases under pressure do follow the Pascal's Law. It is to be understood that both pneumatics and hydraulics employ fluid power, only difference being the use of medium for power transmission.

        Following Pascal's law...As liquids or oils are incompressible, let us consider any closed container, containing a liquid, such as a piston cylinder assembly. If it is subjected to force along the piston rod, ideally the fluid trapped in would have equal reactive forces acting normally to the inner walls of the cylinder, and also opposing the piston, or in other words....the cylinder walls and piston will the stressed uniformly from within. The fluid pressure acts equally on all the surfaces it comes in contact with.

        We may have another physical interpretation....

        Imagine the Tyre of a vehicle being inflated...It gets all puffed up and stiff from all sides and corners, doesn't it?. All the sides inflate uniformly.Same Logic applies since gases are also fluids. As earlier stated, it is Pneumatic power that is used, but it still works as per law.

        This concludes our first basic insight into how a hydraulic system works.




Search My Blog

Mechanical Engineering Links

May 2012

S M T W T F S
  12345
6789101112
131415161718 19
20212223242526
2728293031  

Recent Entries

0 user(s) viewing

0 members, 0 guests, 0 anonymous users



View ME Stats

All trademarks and copyrights held by respective owners. Member comments are owned by the poster.
Privacy Policy | Disclaimer | Terms Of Service
©2011 Deshna Foundation - All Rights Reserved.