Hydraulic Systems: Working Principle, Design, Calculations and Industrial Applications
HYDRAULIC SYSTEMS
Working Principle, Design, Calculations and Industrial Applications
Hydraulic systems are power transmission systems that use incompressible fluid (usually oil) to provide high force and precise control. Due to advantages such as high power density, stable motion and precise control, they are widely used in heavy industry, mobile machinery and industrial automation.
In this guide, we will examine hydraulic systems in detail using an engineering approach.
1. How Does a Hydraulic System Work?
Hydraulic systems are based on Pascal’s principle:
Pressure applied to a confined fluid is transmitted equally in all directions.
Basic energy conversion:
Mechanical → Hydraulic energy → Mechanical force
2. Main Hydraulic System Components
Hydraulic pump
Hydraulic cylinder / motor
Directional control valve
Pressure control valve
Flow control valve
Hydraulic oil tank
Filtration system
Hoses and fittings
3. Hydraulic Force Calculation
Formula
F = P × A
F → Force (N)
P → Pressure (Pa)
A → Piston area (m²)
Force Table (150 bar)
| Cylinder Diameter | Force (kN) |
|---|---|
| 40 mm | 18.8 |
| 50 mm | 29.4 |
| 63 mm | 46.8 |
| 80 mm | 75.4 |
| 100 mm | 117.8 |
4. Flow and Speed Calculation
Q = A × V
Q → Flow rate (L/min)
V → Cylinder speed
Flow determines pump selection and system speed.
Flow Table
| Cylinder Diameter | Speed | Flow |
|---|---|---|
| 50 mm | 0.1 m/s | 12 L/min |
| 63 mm | 0.1 m/s | 19 L/min |
| 80 mm | 0.1 m/s | 30 L/min |
5. Hydraulic System Design Steps
Determine force requirement
Size the cylinder
Calculate flow
Select pump
Select valves
Calculate pressure loss
Design cooling and filtration
6. Hydraulic vs Pneumatic Comparison
| Feature | Hydraulic | Pneumatic |
|---|---|---|
| Force | Very high | Low |
| Precision | High | Medium |
| Speed | Medium | High |
| Cleanliness | Low | High |
| Cost | High | Low |
7. Energy Efficiency
Losses in hydraulic systems:
15% pump loss
10% pressure loss
5% leakage
8. Industrial Applications
Press machines
CNC machines
Injection molding machines
Construction machinery
Heavy lifting systems
9. Engineering Recommendations
Oil temperature should be 40–60°C
Filtration <10 micron
Pressure spikes must be controlled
Leakage must be prevented
CONCLUSION
Hydraulic systems are one of the most efficient power transmission methods for applications requiring high force and precise control. Proper design, correct component selection and regular maintenance maximize system performance.
To understand the differences between pneumatic and hydraulic systems, read What is a Pneumatic System. For detailed design principles, see Hydraulic System Design.