Fluid Power Introduction

Fluid Power Definitions

  • Fluid Power: Use of fluid to transmit power.
  • Hydraulics: Use of liquid under pressure to transmit power.
  • Pneumatics: Use of gas under pressure to transmit power.

Why Use Fluid Power?

  • Multiplication & variation of force.
  • Easy, accurate control.
  • One power source controls many operations.
  • High power / low weight ratio.
  • Low speed torque.
  • Constant force and torque.
  • Safe in hazardous environments.

Basic Fluid Power Components

  • Reservoir / Receiver: Stores fluid.
  • Fluid Conductors: Allows flow between components.
  • Pump / Compressor: Converts mechanical power to fluid power.
  • Valve: Controls direction and amount of flow.
  • Actuators: Converts fluid power to mechanical power.

Work and Power

  • Work: Force times distance (parallel).
  • Power: Work per unit time.

Horsepower

  • power=worktime=force∙distancetimepower = {work \over time} = {force \bullet distance \over time}
  • 1horsepower=180lbs∙180.96ft1min≈33,000ft−lbsmin1 horsepower = {180 lbs \bullet 180.96 ft \over 1 min} ≈ {33,000 ft-lbs \over min}
  • Power (mechanical) = force ∙ distance/time
  • Power (fluid) = pressure ∙ flow rate = psi ∙ gpm
  • 1hp=1,714gal−psimin1 hp = {1,714 gal-psi \over min}
  • # hp = {# gal-psi \over 1714}

Fluid Power Principles

  • Law of conservation of energy: energy can neither be created nor destroyed, but can change form
  • Torque: Twisting force = force x distance (perpendicular).
  • Flow: Makes actuator operation possible; rate of flow determines actuator speed (gpm).
  • Pressure: Overcomes the resistance to flow.

Pascal’s Law

  • Pressure applied on a confined fluid at rest is transmitted undiminished in all directions.

Fluid Power Schematics

  • Line drawing made up of symbols representing components.
  • Symbols emphasize function and methods of operation.