Hydraulics

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Hydraulics
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Hydraulics

• An area of engineering science that deals with
  liquid flow and pressure

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Hydraulic Fluids

• Liquid pumped through a hydraulic system
• Petroleum-based or synthetic oil
• Serve four major functions
• 1. Power transmission
• 2. Lubrication of moving parts
• 3. Sealing of spaces between moving parts
• 4. Heat removal
• Relatively Incompressible!

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Two Types or Conditions of Hydraulic Systems

• Hydrostatic

• Hydrodynamic

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Hydrostatics -a No Flow Scenario

• Static means stationary or non flowing in a
  hydraulic system
• Hydraulic systems are considered static when
  there is no flow
• Pascals Law (for hydrostatics)
• a pressure applied to a confined hydrostatic
  fluid is transmitted with equal intensity
  throughout the fluid
• Same pressure all throughout!

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Hydrodynamics a Flow scenario

• Dynamic means moving or flowing in a
  hydraulic system
• Hydraulic systems are considered dynamic when
  there is flow
• Pascals Law does not apply!
• Pressure does not have equal intensity in a
  flowing dynamic system
• Pressure drops along the length of a hydraulic
  line in flowing systems

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Flow and Pressure

• Flow, Q
• volume flow rate
• amount of fluid moving through system per unit
  time
• Pressure, P
• force per unit area of fluid moving through a
  system

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Mechanical Advantage

• Ideal mechanical advantage (IMA)
• Assumes no frictional losses
• Calculated as ratio of output force to input
  force
• Actual mechanical advantage (AMA)
• always less than ideal
• difficult to calculate

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Application of Pascals Law in a Simple
Hydrostatic System

• How much force must you exert on piston A to
  lift a load on piston B of 500 lbs? What is the
  ideal mechanical advantage of this system?

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Problem Solving

• STEP 2 Use the pressure calculated in STEP 1
  and information about piston A to calculate force
• Known Unknown
• A 1.0 in2 F?
• Equation and algebra
• Substitution Solution

• Step 1 Determine the pressure in the system
  using information about piston B
• Known Unknown
• A 500 in2 P?
• F 500 lb
• Equation No algebra needed
• Substitution Solution

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Problem Solving

• Step 3 Determine the ideal mechanical advantage
  (IMA) of the system using information from STEPS
  1 2
• Known Unknown
• F(input) 1 lb IMA?
• F(output) 500 lb
• Equation No algebra needed
• Substitution Solution

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A Hydraulic System
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Tank/Reservoir

• Storage device which is open and not pressurized

Filter
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Pumps

• Centrifugal pump (Vane Pump) no specific amount
  of fluid flow per rotation flow depends on speed
  of blades

• Positive displacement pump (Gear Pump) a
  specific amount of fluid passes through the pump
  for each rotation

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Accumulators

• Storage device which is closed and is under
  pressure

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Valves

• Check Valve

• Directional Control

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Linear Actuators

• Use hydraulic power to move linearly
• Single Acting Double Acting

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Rotary Actuators

• Use hydraulic power to rotate
• Single-Vane Double-Vane

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Applications

• Robotics
• Oil systems in vehicles (e.g. brakes)
• Presses
• Heavy equipment
• Wood splitter
• Aircraft control systems

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The Hydraulic Trainer
In-line Pressure Gauge
Return line Connections
Supply line Connections
Pressure Regulator
Return line from reservoir
Flow Control Valve
Pressure line
Pump
Check Valve
Actuators
Motor
Inline-Tee
Directional Control Valve