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Introduction to Hydraulic Systems (15FMCE220)

• Hydraulics is the science of force and movement transmission using liquids.
• It encompasses hydro-mechanics, which includes hydrostatics (pressure times area) and hydrodynamics (mass times acceleration).
• Fluid power is the technology for generating, controlling, and transmitting power using pressurized fluids.
• Fluid power is the driving force behind much of modern industry.
• It is used in virtually all modern machinery for pushing, pulling, regulating, and driving.
• Hydraulics uses liquids like mineral oil or water, while pneumatics uses gases like air.

Fluid Power Advantages

• Ease and accuracy of control: Simple levers and buttons offer precise control of speed and position, even down to a ten-thousandth of an inch.
• Force multiplication: Fluid power systems efficiently multiply forces, allowing significant output from relatively small inputs.
• Constant force/torque: They maintain constant force or torque at varying speeds.
• Simplicity, safety, and economy: Having fewer moving parts simplifies maintenance, enhances safety, and cuts operational costs.

Hydraulic System Components

• Pump: Provides the pressurized fluid.
• Actuator: Linear or angular movement device (e.g., cylinder, motor).
• Lines: Channels for carrying the hydraulic fluid.
• Pressure relief valves: Prevent excessive pressure.
• Directional valves: Direct fluid flow.
• Flow control valves: Regulate flow rate.
• Pressure control valves: Regulate/maintain pressure.
• Tank/reservoir: Holds the hydraulic fluid.
• Filters: Clean the hydraulic fluid.
• Heat exchanger: Controls fluid temperature.

Hydraulic Power Unit (Power Supply Unit)

• Contains the reservoir, drive (often an electric motor), hydraulic pump, pressure relief (safety) valve, filter, and cooler.
• This unit provides the consistent energy and fluid preparation needed in a hydraulic system

Hydraulic Power Unit (Reservoir):

• Used to store hydraulic fluid needed in a system
• Size determined by the actual operational needs of the application

Hydraulic Pumps:

• Externally toothed gear pumps: Move hydraulic fluid by engaging with two meshing gears rotating on a shaft.
• Internally toothed gear pumps: These pumps use a system of interlocking gears to move the fluid.

Hydraulic System Diagrams and Symbols:

• Specific symbols represent various components (e.g., pumps, valves, actuators, and measuring instruments).

Hydraulic Actuators:

• Hydraulic actuators can be a cylinder for linear motion or a motor for rotational motion.

Types of Cylinders

• Single acting: Return occurs through external force.
• With spring return: Returns under spring force.
• Telescopic: Multiple cylinders positioned within others (often for extended strokes).
• Double acting: Movement in either direction using the fluid.
• Differential: Used for different piston sizes offering an advantage of force.
• With adjustable position cushioning: For controlled and smooth movement.

Hydraulic Motors:

• Continuous rotation: Motors providing continuous rotational motion.
• Limited rotation: Motors with specific rotations or limited movement.

Hydraulic Valves:

• 2/2-way valve: Controls the flow between one port.
• 2/2-way valve (by-pass): Uses flow for faster speed by diverting away from the usual route.
• 3/2-way valve: Controls the flow to three ports.
• 3/2-way valve (diverters): Enables a system to switch between various applications.
• 4/2-way valve: Uses two ports for movement, with a tank circuit.
• 4/3-way valve: Provides multiple options (with pump bypass).
• 4/3-way valve (mid-position): Stops the pump flow in its middle or center position. (used as a directional control)
• OR/Shuttle valves: Opens from either side (multiple actions).
• AND/Dual Pressure Line Valves: Opens if both sources are activated.

Valves - Actuation Methods:

• Manual: Operated by hand.
• Mechanical: Operated by components/mechanics.
• Hydraulic/pneumatic: Force applied by hydraulic or pneumatic actuators.
• Electrical (solenoid): Electrically operated valves use a switch/magnet system.
• Combined: Multiple methods of activation.

Pressure Relief Valves:

• Prevents excessive pressure in hydraulic systems.

Pressure Regulators:

• Adjusts system pressure.

Non-return valves:

• Prevent flow in one direction.

Flow Control Valve:

• Controls/regulates flow rate. This can be done by changing the pressure

Brake Valves:

• Prevent pressure spikes.

Unloading Valves:

• Used for high flow/low pressure systems (often in conjunction with high/low pressure circuits).

Sequence Valves:

• Controls the sequences of a system-specific actions.

Circuit Diagrams:

• Represents various components' interconnected configurations.

Symbols:

• Standardized graphical representations of hydraulic components.
• Symbols for hydraulic components

Hydraulic Oil Properties

• Crucial material in hydraulic systems, affecting performance and durability.
• Essential roles are power transmission, lubricant for moving parts, maintaining clearances between components, and dissipating heat.

Additional Notes:

• Further information on hydraulic oil properties, including essential characteristics.
• Many applications, drawings, and diagrams of hydraulic systems enhance understanding.
• Operational principles explained and diagrams/animations further details.