Control System

Hydraulic System Basics

What is a Hydraulic system basically?

The basic principle of a hydraulic system is derived from Pascal’s law, basically stating in a closed vessel that there are several holes in the same end so it will be emitted in all directions with the same pressure and flow amount. Where the pressure in a static fluid must have the following properties:

–  The pressure works perpendicular to the surface of the plane.
–  The pressure at each point is the same for all directions.
–  The pressure given to some fluid in a closed place propagates.


The figure shows two cylinders containing the liquid that are connected and have different diameters. If the load F is the small cylinder, the resulting P pressure will be passed on a large cylinder (P = F / A, load divided by the cylindrical cylinder) according to this law, the pressure increase with the area of the small cylinder and large cylinders ratio, or F = P.A

The picture above in accordance with the pascal law, can be obtained the following equation:

Where :
F1 = Force applied at A1
F2 = Forceout at A2
r1 = small piston radius
r2 = big piston radius


The above equation can be seen that the magnitude of F2 is affected by the size of the cross-sectional area of the A2 and A1 pistons.

In a hydraulic system, this is used to change the fluid compression force produced by the hydraulic pump to shift the working cylinder forward and backwards and up / down according to the location of the cylinder. The power produced by the hydraulic cylinder is greater than the power released by the pump. The size of the power produced by the hydraulic cylinder is influenced by the size of the cross-sectional area of the hydraulic working cylinder.

Components of the Hydraulic System:


The motor functions as a modifier of electric power into mechanical power. In the hydraulic system the motor functions as the main driver of all hydraulic components in this circuit. The work of the motor by rotating the pump shaft which is connected to the motor input shaft. The motor used is a single phase AC motor ¼ PK.

Clutch (Coupling)

The main function of the clutch is as a round connector produced by the drive motor to be forwarded to the pump. As a result of this rotation, the pump works (rotates).

Hydraulic Pump

This hydraulic pump is driven mechanically by an electric motor. The beginning of the control and regulation of the hydraulic system always consists of an element of pressure generator, so the function of the element is met by a hydraulic pump. The hydraulic pump serves to convert mechanical energy into hydraulic energy by pressing the hydraulic fluid into the system. In a hydraulic system, the pump is a device for generating or generating fluid flow (to move a number of fluid volumes) and for providing power as needed.


In the hydraulic system, the valve functions as a pressure regulator and fluid flow that reaches the working brightness. According to usage, hydraulic valves are divided into three types, including:
1. Relief Valve
2. Direction Control Valve
3. Flow Control Valve

Hydraulic Work Cylinders

Hydraulic work cylinders are the main component that serves to change and forward power from fluid pressure, where the fluid will push the piston which is the only component that moves to perform translational motion which is then passed to the engine through the piston rod. According to construction, hydraulic working cylinders are divided into two types in hydraulic systems:

Single Acting cylinder:

This type of working cylinder only has one working fluid chamber in it, namely the cylinder chamber above or below the piston. This condition causes the working cylinder to only be able to do one movement, namely the press movement. Whereas to return to its original position, the piston rod tip is pushed by gravity or external force.

Double Acting working cylinder

This working cylinder is a working cylinder that has two fluid chambers in the cylinder, namely the cylinder chamber above the piston and below the piston, only the space above this piston is smaller than the one below the piston because part of the space is taken up by the piston rod. With this construction the working cylinder allows it to be able to perform alternating or backward movements.


Usually, the pressure regulator is installed and equipped with a device that can indicate a fluid pressure coming out. The working principle of this tool was discovered by Bourdon and insrument is Bourdon tube. The oil enters the pressure regulator through the P channel hole. The pressure in the curved pipe Bourdon causes the pipe to extend. Greater pressure will result in a larger radius turns. The pipe extension motion is then changed to a pointing needle via the connecting lever, tending gears, and pinion gear.

The pressure on the inlet can be read on the curved point of the indicator scale. So, the principle of reading this manometer pressure measurement is that it works based on an analogous principle.

Oil Filter

The filter functions to filter impurities from hydraulic oil and is classified into channel filters used by pressurized channels. The filter is placed in the tank at the inlet that will go to the pump. With the filter, it is expected that the efficiency of hydraulic equipment can be raised and the service life is longer.

Hydraulic Fluid

Hydraulic fluid is one of the important elements in hydraulic equipment. Hydraulic fluid is a material that delivers energy in hydraulic equipment and lubricates each equipment as well as heat-relieving media arising from increased pressure and dampening vibration and sound.

Hydraulic fluid must have the following properties:

  • Having enough temperature viscosity that does not change with temperature changes.
  • Maintain fluid at low temperatures and not change badly easily if used under temperature.
  • Have good oxidation stability.
  • Has anti-rust ability
  • Does not damage (due to chemical reactions) rust and paint.
  • Not compressible
  • Have a good anti-foaming tendency.
  • Having viscosity against fire

Advantages of Hydraulic Systems over other systems


Instrumentation Engineer

Related Articles

Check Also
Back to top button

Adblock Detected

We Noticed You're Using an Ad Blocker Hi there! We understand that ads can be annoying, but they help support our website and allow us to continue providing you with high-quality content. Please consider whitelisting our site or disabling your ad blocker while you visit. Your support means a lot to us! Thank you for understanding!