The concept behind a hydraulic system is simple. The fluid sued in the system is the hydraulic oil. A hydraulic system has two or more cylinders that are connected to a single pipe containing the oil and the pistons that helps in pushing the fluids in the cylinders.
Hydraulics is used in many machines that we see in our daily lives. Some of its uses are:
Hydraulics is used in heavy equipments like log splitters. You can find the simplest hydraulics system in log splitters as it consists of most of the components of a basic hydraulics system such as the hydraulic pump, an engine, the hydraulic cylinders, the various valves and the hydraulic pistons.
The heavy- duty machines make use of the hydraulics system that is often seen at construction sites and other excavations. A large machine such as the excavator may weigh anything around thirty tons but it has the capacity to move around easily and carry mud weighing about two tones without any difficulty. An excavator has a motor for each of its tracks and a motor for swinging its huge arm that all runs on the system of hydraulics. Other construction vehicles making use of hydraulics system include the loading machines, also known as the skid. This machine makes use of 3 pairs of hydraulics pistons and also hydraulics motors on each of its four wheels. Another vehicle that we often see in our daily routine are the garbage dump trucks. They make use of all the hydraulic components. The only exception in its case is the use of telescopic cylinders that helps them to attain the feat of positioning the dump bucket to an almost vertical stance to allow the garbage fall over.
Hydraulics is also used in mechanical wheel chairs to push the wheel chair forward. It is also used for aircraft landing gears to push the wheels out when landing the plane.
The most exciting part is to see the hydraulic system works. What really amazing is that it is all off the simple Pascal’s Law. When you look closely, there are some basic components needed to make the hydraulic system to work. Here are some basic hydraulic components and roles that they play in the system below.
Hydraulic Cylinders: These components of the hydraulic system are those in which, pressure is applied on the fluids (oil), to get the desired force. The force acquired is used to power the hydraulic machine of car brakes, cranes, turbines and a large number of excavators. These cylinders also include the pistons of different sizes. The hydraulic pistons are used to push down the fluids in the other cylinder, which in turn exerts the pressure and pushes it back again.
Hydraulic Pumps: The hydraulic pump is a component that is responsible for supplying the fluids to the other essential parts of the hydraulic system. The power generated by a hydraulic pump is about ten times more than the capacity of an electrical motor. There are different types of hydraulic pumps such as the vane pumps, gear pumps, piston pumps, etc. Among them, the piston pumps are relatively more costly. But they have a guaranteed long life and are even able to pump thick, difficult fluids.
Hydraulic Wrench: A hydraulic wrench is used to tighten the nuts and bolts.
Hydraulic Lifts: Hydraulic lifts are the similar components used for powering the hydraulic system in cars such as the lowriders. These lift kits are available in any custom- made car shops.
Hydraulic Press: This is a process in which, the pressure is compressed to a full extent. The structure again involves two cylinders of different diameters and two different sizes of pistons. In order to generate a powerful pressure, the basics of Pascal’s Law are followed. The pressure is created by applying force and pushing the smaller piston through the cylinder and the fluids are pushed through the connecting pipe to the larger cylinder till a great pressure is exerted. The use of a hydraulic press is seen in the process of crushing cars. For crushing cars, a motor powers the hydraulic press. A car crushing hydraulic system has the capacity to generate about 2500 pounds per square inch (psi) and apply a force of about 200 tons that is more than enough to crush any car. A hydraulic press has the potential to crush an aluminum metal into a thin scrap of paper. The hydraulic press too is comprised of many components such as the pumps, the various valves, the pipes and the engine.
Hydraulic Motors: This is the one most widely used. The power in hydraulic motors is achieved with the help of exerting pressure on the hydraulic fluids, which is normally oil. The benefit of using hydraulic motors is that when the power source is mechanical, the motor develops a tendency to rotate in the opposite direction, thus acting like a hydraulic pump
Accumulator – A container which stores fluids under pressure as a source of hydraulic power. It may also be used as a shock absorber.
Actuator – A mechanical device for moving or controlling a load; a cylinder or motor, for example. Area – The total amount of surface on a flat plane. Usually measured in square inches.
Bleed – The process by which air is removed from a hydraulic system.
Bypass – A secondary passage for fluid flow.
Cam Lobe Motor – A hydraulic radial piston motor in which rotational force is created by the outward movement of the pistons against the lobes of a stationary cam.
Cavitation – A phenomenon which occurs when the pressure at a point in a hydraulic system is lowered below the vapor pressure of the oil in the system. This allows bubbles of oil vapor to form in the oil. If this occurs at the pump inlet, the quick pressure rise inside the pump forces these bubbles to collapse violently. This can cause erosion of metal parts, noise and vibration.
Circuit – A series of component parts connected to each other by fluid lines or passages. Usually part of a “system”.
Closed Center System – A hydraulic system in which the control valves are closed during neutral, stopping oil flow. Flow in this system is varied, but pressure remains constant.
Controller – A microprocessor that controls electro-hydraulic valve functions.
Cooler (Oil) – A heat exchanger which removes heat from a fluid. (See “Heat Exchanger.”)
Coupler – A device to connect two hoses or lines, or to connect hoses to valve receptacles.
Cusion – A device sometimes built into the end of a cylinder which restricts outlet flow and thereby slows down the piston.
Cycle – A single complete operation of a compo- nent which begins and ends in a neutral position.
Cylinder – A device for converting fluid power into linear or circular motion. An “actuator”. Basic design types include piston and vane units.
Double-Acting Cylinder – A cylinder in which fluid force can be applied to the movable element in either direction.
Piston- Type Cylinders – A cylinder which uses a sliding piston in a housing to produce straight movement.
Rotary Cylinders – A cylinder in which fluid force is applied to produce circular motion. Single-Acting Cylinder-A cylinder in which fluid force can be applied to the movable element in only one direction.
Vane-Type Cylinder – A cylinder which uses a turn- ing vane in a circular housing to produce rotary movement.
Force – The measured amount of pressure applied to a given area. The weight of the load (pushing or pulling).
Flow – The movement of oil in a circuit from high-pressure to low-pressure along the path of least resistance.
GPM – Gallons Per Minute. A measure of fluid flow.
Power – The measure of the rate at which work is done over time. Usually expressed in Horsepower or Watts.
Pressure – A measure of force on a unit of area. Measured in pounds per square inch (PSI).
Pressure Drop – The difference in pressure between two points in a system. Pressure is lower downstream.
The word “hydraulics” generally refers to power produced by moving liquids. Modern hydraulics is defined as the use of confined liquid to transmit power, multiply force, or produce motion.
Though hydraulic power in the form of water wheels and other simple devices has been in use for centuries, the principles of hydraulics weren’t formulated into scientific law until the 17th century. It was then that French philosopher Blaise Pascal discovered that liquids cannot be compressed. He discovered a law which states: Pressure applied on a confined fluid is transmitted in all directions with equal force on equal areas.
To better understand Pascal’s Law, lets use a bottle full of liquid as an example. Let’s say the bottle has a 1 square inch opening. If we were to apply 10 pounds of force on a cork at the opening, 10 pounds of force would be applied equally to all sides of the bottle. This is expressed as 10 psi or 10 pounds of force per square inch. 10 psi represents the fluid pressure of the system.
Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids.
At a very basic level hydraulics is the liquid version of pneumatics. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties.
In fluid power, hydraulics is used for the generation, control, and transmission of power by the use of pressurized liquids. Hydraulic topics range through some part of science and most of engineering modules, and cover concepts such as pipe flow, dam design, fluidics and fluid control circuitry, pumps, turbines, hydropower, computational fluid dynamics, flow measurement, river channel behavior and erosion.