Strand 4 Power Systems (Hydraulics & Pneumatics): Complete Learning Notes

Fluid Power

Using a fluid (liquid or gas) to transmit energy and do useful work.

Hydraulics

Fluid power using mostly incompressible liquids (usually oil).

Pneumatics

Fluid power using compressible gases (usually air).

Pressure

How hard the fluid is pushing on surfaces.

Flow Rate

How much fluid moves per unit time.

Power

How fast energy is transferred.

Pascal’s Principle

A pressure applied to a confined fluid is transmitted throughout the fluid.

Hydrostatic Pressure

Pressure due to a fluid column, given by p = ρgh.

Viscosity

The internal friction of a fluid, affecting flow and pressure loss.

Density

Mass per volume of a substance, denoted as ρ.

Reservoir

Tank that stores fluid, allowing separation of air and contaminants.

Hydraulic Pump

Device that converts mechanical power into fluid power, creating flow.

Directional Control Valve (DCV)

Valves that route flow paths to start/stop motion and reverse direction.

Flow Control Valve

Device that controls the speed of actuators by managing the flow of fluid.

Accumulator

Stores hydraulic energy to supply peak demands and smooth pressure pulsations.

Pressure Control Valve

Manages system pressure limits to prevent overload.

Double-acting Cylinder

Cylinder that can apply force in both extending and retracting directions.

Single-acting Cylinder

Cylinder that applies force in one direction only, with return by spring or external load.

Sequence Valve

Opens to allow flow to the next actuator after a set pressure is reached.

Relief Valve

Limits maximum system pressure by diverting flow back to tank.

Check Valve

Allows flow in one direction while blocking reverse flow.

Throttling

Restricting flow to control speed of actuator movement.

Pump Cavitation

A condition where vapor bubbles form in a liquid due to pressure drops.

Fluid Power System Efficiency

Ratio of useful work output to energy input, often expressed as η = Pout/Pin.

Hydraulic Circuit

System consisting of components that work together to transmit hydraulic power.

Pneumatic Circuit

System that uses compressed air to perform work.

Electro-fluid Power

Control of fluid power systems using electrical signals and components.

Solenoid Valve

Electrically operated valve used to control fluid flow.

Limit Switch

Sensor device used to determine position or state of an actuator.

Fluid Contamination

Presence of unwanted substances in hydraulic or pneumatic fluid affecting performance.

Stored Energy Hazards

Risk associated with stored hydraulic or pneumatic energy, such as in accumulators.

Troubleshooting

Structured approach to identify and fix issues in fluid power systems.

Flow Rate (Q)

Volumetric flow per unit time, calculated as Q = V/t.

Mechanical Power (P_mech)

Power output of a mechanical actuator, calculated as P_mech = F·v.

Hydraulic Power (P_fluid)

Fluid power delivered to a circuit, calculated as P_fluid = p·Q.

Meter-in Control

Restricts flow entering an actuator to control speed.

Meter-out Control

Restricts flow leaving an actuator to control speed and prevent overrunning.

Electromagnetic Actuation

Using electromagnetic fields to operate valves or actuators.

Two-hand Control

Safety feature requiring simultaneous operation of two controls.

AND Pneumatic Logic Valve

Outputs pressure only if both inputs are pressurized.

OR Pneumatic Logic Valve

Outputs pressure if either input is pressurized.

Timed Delay Valve

Pneumatic valve that creates delays in operation by controlling air flow.

Safety and Reliability

Considerations in hydraulic and pneumatic systems to prevent failures and hazards.

Hydraulic Cylinder

Actuator that produces linear motion from hydraulic fluid power.

Pneumatic Cylinder

Actuator that produces linear motion using compressed air.

Rotary Actuator

Converts fluid power into rotary motion.

Flow Measurement

Process of assessing the volumetric flow rate of a fluid in a system.

Pressure Measurement

Assessing the force exerted by fluid on a surface area within the system.

Fluid Power System Components

Key parts of fluid-based systems including pumps, valves, actuators, and reservoirs.

Pump Selection

Choosing a pump based on required pressure and flow for an application.

Pressure Loss

Reduction in pressure due to friction and other resistance in a fluid system.