Principles of Power Hydraulics

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Fluid Power

• Chapter 1 and 2
• Principles of Power Hydraulics

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Terms

• Hydrostatic system--transfers energy by pressure
  Pushing on a confined liquid
• Head--a term for pressure
• Atmospheric pressure--14.7 psi at sea level
• 29.92 inches of hg (30 inches hg) 14.7 psi
• 1 atm 14.7 psi
• 30 inches hg 1 atm
• Absolute pressure --gage pressure 14.7

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Head

• Torricelli discovered that in a tank with a hole
  near the bottom, the fluid would run out slower
  as the level in the tank decreased.
• Feet of head--amount of liquid above the outlet.

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Flow Velocity

• Flow--the volume of fluid passing a point in a
  given time Generally in gpm or cubic inches per
  minute
• 1 gpm 231 cubic inches per minute
• Cubic inches/minute (gpm)x(231)
• Velocity--average speed of the fluid past a given
  point Generally in fpm or inches per second

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Flow Types

• Laminar flow
• straight smooooooth flow
• minimal friction between fluid piping

• Turbulent flow
• jumbled flow, white water
• increases friction between fluid piping
• caused by high velocity, sharp bends, changes in
  pipe diameter

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Laminar Flow
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Turbulent Flow
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Bernoulli

• Discovered that if the flow rate is constant
  then the sums of the kinetic energy the
  pressure energy must be constant
• FE ke pe
• if ke ? then pe ?
• if ke ? then pe ?
• A venturi is an example of Bernoulli's law

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Bernoulli's Law
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Venturi
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Symbols

• Different companies will use different types of
  symbols.
• Pictorial.
• Cutaway.
• Graphical (schematic).
• You need to be able to read these symbols,
  especially the schematic symbols.
• Why???????

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Lines (Piping)

• Working lines, shown schematically by a solid
  dark line, carry the main stream of fluid.
• Pilot lines (long dashes) carry control fluid to
  components.

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Lines (Piping)

• Drain lines (short dashes) return fluid to tank.
• Return lines (shown like working lines) return
  fluid back to the tank.

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Rotating Components

• Convert fluid flow to a circular motion.
• Drawn with 1 or 2 triangles inside a circle.
• Position of triangle(s) will indicate a pump or a
  motor.
• The number of triangles will indicate a single
  direction or a reversible unit.

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Cylinders

• Coverts the fluid flow into a linear motion.
• The schematic will indicate single action, double
  action, double rod, single rod, etc.
• Drawn as a rectangle, it will show connections,
  rod piston head.

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Hydraulic Valves

• Many options, styles.
• Drawing will show connections, possible
  positions, flow path, spool type and actuating
  method.

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Hydraulic Tanks

• Drawings show many tank symbols.
• Why???
• Tanks are either vented or pressurized.
• Symbol will show what kind of tank and how the
  return lines are connected.

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Schematic Drawings

• The schematic will show you the order of the
  system, what components are used and the
  functions of the system.

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Schematic Drawings

• The drawing will not show the actual size, shape,
  location or construction of the components in the
  system.
• The drawing is a tool to aid you in construction
  and trouble shooting.

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Typical schematic
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Sources

• http//en.wikipedia.org/wiki/Hydraulic_machinery

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The End!!!!!!!!!