Hydraulic System

I. BASIC PRINCIPLES OF HYDRAULIC SYSTEM.

In a hydraulic system fluid flow serves as a successor force. Mineral oil is a common type of fluid used.
The nature of the liquid:- Does not have a fixed shape, always adjust the shape they occupy.- Liquids can not be compressed.- Continuing pressure in all directions.

Hydraulics can be expressed as a means of transferring power by pushing a number of specific liquids. Component called a pressurized fluid flow generator pumps, and hydraulic pressure converter components into mechanical motion (straight / rotation) are called the working elements (cylinders / motors hidroulik).
The advantages of hydraulic systems:
- Flexibility in the placement of power transmission components.- Style is very small can be used to transport a large force.- Successor style (oil) also serves as a lubricant.- Expenses can be easily controlled using the pressure regulator valve (relief valve).- Can be operated at varying speeds.- Direction of operation can be reversed immediately.- It's safer if operating at overload.- Power can be stored in the accumulator.
The weakness of the hydraulic system:
Hydraulic systems require an environment that really clean. Its components are very sensitive to the damage caused by dust, corrosion and other impurities, and the heat affects the properties of hydraulic oils.


II. EQUATION / FORMULA BASIC.

Pressure is the force per unit cross-sectional area.In the equation expressed as:

P =, where P = Pressure / Pressure (Pascal).F = Force / force (Newton).A = Area / area (meter 2)
Capacity is the amount of flow per unit time.In the equation expressed as:

Q =, where Q = Capacity / Debit (m3/sec).V = Volume of Fluid (M3).t = Time (sec).
Or, Q = A x V, where A = Area (Meter 2).V = Fluid velocity (M / dt).
Boyle equation:
P1 x V1 = P2 x V2, where P = PressureV = Volume
Continuity equation:
Q1 = Q2 A1 x V1 = A2 x V2

Conversion unit:
- 1 Pascal = 1 Newton / meter2 (Pa = N/m2)- 1 bar = 105 Pa = 100 kPa= 14.7 psi (lbf / in2)= 1 Kgf / cm2- 1 m3/sec = 60 M3/menit- 1 M3/menit = 1000 LPM (liters / min).


Example:

Two related vessel, Style in vessel 1 (F1) = 1000 N.The diameter of the vessel 1 (d1) = 10 cm2Diameter of vessel 2 (d2) = 40 cm2Style on vessel 2 (F2) = ... ... ... ... .. ?


Completion:
- On Vessel 1:
Pressure 1 (P1) =

F1 = 200 N
A1 =; d1 = 10 cm 2 = 10 x 10-2 m2= 0.1 m
A1 = = 7.85 x 10-3 m2

P1 = = = 127.388 x 103 N/m2

= 1.27388 x 105 N/m2
= 1.27388 x 105 Pascal = 1.27388 Bar
- The vessel 2:
According to the law of Pascal 'Pressure in a closed vessel will be forwarded all directions with the same great'.- The pressure in vessel 1 (from calculation) = 1.27388 N/m2- In accordance with the laws of pascal the pressure on the vessel 2 will be equal to the pressure on the vessel 1.- Pressure in the vessel 2 (P2) = P1 = 1.27388 x 105 N/m2.
- Style on bejana2 (F2)
P2 =, then F2 = P2 x A2

P2 = 1.27388 x 105 N/m2
A2 = d2 = 40 cm = 40 x 10-2 m2= 0.4 m2
A2 = = 0.1256 m2

F2 = P2 x A2= 1.27388 x 105 N/m2 x 0.1256 m2= 16,000 N
So by using the principle of hydraulics can be concluded that with a small force F1 (1000N) to produce a much larger force F2 (16,000 N).

Valve Type

Below are brief explanations for the common types of valves used in today's industrial flow control industry. To view diagrams of each valve type, visit the Valve Photo Gallery.

MULTI-TURN VALVES OR LINEAR MOTION VALVES

The Gate Valve: The gate valve is a general service valve used primarily for on - off, non-throttling service. The valve is closed by a flat face, vertical disc, or gate that slides down through the valve to block the flow.

Directional Control Valves

Bang-bang is the term often used to describe basic directional-control valves. It refers to how the valves shift - from fully open to fully closed. This usually occurs in an instant, causing fluid to rapidly accelerate and decelerate. Under certain conditions, this can cause fluid hammer, which sounds like a hammer striking the hydraulic system from inside. Hence, shifting the valve from one position to another can produce a bang-bang sound.

Fig. 1. Basic check valve allows fluid to flow in one direction, in this case from bottom to top. Shown are ISO symbol and cross-sectional photo of spring-loaded check valve. The spring keeps fluid from flowing unless downstream pressure acting on the poppet overcomes spring force. 

A less informal term to describe these components is discrete valves. This term refers to how the valves operate: they shift from one discrete position to another, such as extend, retract, and neutral. Proportional valves, on the other hand, control direction and speed. In addition to shifting into discrete positions, they can shift into intermediate positions to control actuator direction, speed, acceleration, and deceleration.
Even more basic than the discrete directional-control valve is the digital valve. As in digital electronics, digital valves operate either on or off. Whereas discrete valves generally use a spool to achieve two, three, or more positions, discrete valves use a plunger, poppet, or ball that seals against a seat. The advantage to this type of operation is that it provides a positive seal to prevent cross-port leakage.
Perhaps the simplest of all directional-control valves is the check valve, a specific type of digital valve. Basic check valves allow fluid to flow in one direction, but prevent fluid from flowing in the opposite direction. As with all fluid power components, directional-control valves can be represented by standard symbols published in ISO 1219. Figure 1 shows a cross-section of a spring-loaded check valve and its ISO 1219 representation.

Ports and positions