Hydraulic Systems: Principles and Applications in Fluid Power

Hydraulic Systems: Principles and Applications

Introduction: The hydraulic method is chosen for tasks that involve the transmission of large forces. This method is used to create and control forces and movements with pressurized fluid.

Advantages of Hydraulic Systems

• Great Efforts: Ability to transmit substantial forces.
• High Power-to-Weight Ratio: Efficient performance relative to system weight.
• Precision: Accurate positioning of heavy loads.
• Smooth Movement: Regular and smooth operation.
• Accurate Speed Control: Precise control over operational speeds.
• Starting Under Maximum Load: Capability to start under full load conditions.
• Easy Overload Protection: Simple mechanisms to protect against overload.

Oil Hydraulic Fluid Circuit

Oil Hydraulic Fluid Circuit: Fluid Pressure

Requirements for Hydraulic Fluids

1. Withstand High Pressures: Ability to operate under high pressures.
2. Lubricate: Provide lubrication to moving parts.
3. Protect Against Corrosion: Prevent corrosion within the system.
4. Remove Heat and Abrasive Particles: Carry away heat and particles that can cause wear.

Additives are used to improve fluid properties and separate air.

Pressure and Flow

Pressure (P) determines the workforce, while flow (Q) determines the speed of work.

Pascal's Principle: P = F / A, where P is pressure, F is force, and A is area. Units: N/m² (Pascals, Pa), where 1 bar = 100,000 Pa = 10 kPa.

Q = V / t, where Q is flow rate, V is volume, and t is time. Units: m³/s, where 1 m³/s = 1000 l/s = 60,000 l/min.

Fluid Handling and Pressure Loss

Fluid is transported in steel or rubber tubes. If the velocity of fluid through a narrow section is 4 to 6 m/s, it can lead to turbulence. A sharp decrease in pressure can cause a partial vacuum and the formation of bubbles. If pressure increases sharply, it can lead to cavitation, where material particles are dislodged. This can cause a sudden increase in temperature, leading to a micro-diesel effect (combustion).

Purification and Filtration Techniques

When fluid flows, resistance creates pressure. The maximum available pressure (system pressure) is set using a pressure-limiting valve to prevent equipment damage from excessive pressure when the actuator stops. The tank serves to store and condition the oil. It should have sufficient dimensions to hold the oil and allow enough time for sedimentation and cooling.

Physical Principles: Pressure Transmission

Pressure (P) is applied to an area (A) to generate a force (F). This force is transmitted to a second plunger with a different surface area. This generates a different pressure in the second plunger: P₂ = F / A₂.

Force and Displacement Transmission

Any force applied at a point in a hydraulic system can be utilized anywhere else because the fluid acts as a plunger. A force is applied to a plunger, and the resulting pressure is transmitted to a second piston with the same surface area. If we apply the same load to the second piston, the forces will balance. However, if the same pressure is transmitted to a piston with double or triple the surface area, the plunger can withstand the pressure (Pascal's Principle). If one plunger moves a certain distance, the other will also move the same distance. If the surface area of the second plunger is three times larger, it will only move one-third of the distance.