Hydraulic Power

Hydraulics vs. Pneumatics Hydraulic Systems . . . • Use a relatively incompressible liquid• Have a slower, smoother motion• Are generally more precise• Lubricate naturally• Are not as clean as pneumatics when

leakage occurs• Often operate at pressures of 500 - 5000 psi• Generally produce more power

Hydrodynamic Systems

• Fluid is in motion • Force and energy are

transmitted by flow

Water Turbine Propeller

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Hydrostatic Systems• Fluid does not flow quickly or

continuously• Fluid is pressurized• Force and energy transmitted

by pressure• Most common in industrial settings

Liquid FlowFlow Rate

The volume of fluid that moves through a system in a given period of time Flow Velocity

The distance the fluid travels through a system in a given period of time

vQ ( A)Symbol Definition Example Units

Q Flow Rate gpm or gal/min

(gallons per minute)

in.3 / min

v Flow Velocity

fps or ft/s(feet per second)

in. / min

A Area in.2

Mechanical Advantage

out

in

FMA F

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Force at the outputMechanical Advantage Force at the input

Conservation of Energy: An increase in velocity results in a decrease in pressure. Likewise, a decrease in velocity results in an increase in pressure.

Bernoulli’s Principle

Viscosity

The measure of a fluid’s thickness or resistance to flowCrucial for lubricating a systemMeasured in slugs/sec-ft (US) or centistokes (metric)– Hydraulic oil is usually around 1.4

slugs/sec-ft

Decreases as temperature increases

Common Hydraulic System Components

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Cylinder

Transmission Lines

Directional Control Valve

Pump

Reservoir

Filter

Click the lever on the valve to extend and retract the cylinder.

Common Hydraulic System Components

Reservoir Pump

Cylinder

Valve