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Hydraulics: Controlling the Transmission of Force and Energy

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Positive Displacement Pumps Resistance of a Positive Displacement Pump Heat Generation in a Hydraulic System Viscosity Friction and Changing Directions Fluid ... – PowerPoint PPT presentation

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Title: Hydraulics: Controlling the Transmission of Force and Energy


1
Hydraulics Controlling the Transmission of
Force and Energy
  • Symbolic Representation of Components Bowling
    Green Presentation
  • July 21, 2009
  • Dave Baker and Paul Turner

2
Prior knowledge assumed to understand this
lecture.
  • Can you guess how many beans are in the Jar?


3
(No Transcript)
4
Carriage Brake System
5
Brake System Components
6
Typical Automotive Breaking System
7
Master cylinder with 2 slaves
8
Hydraulic Multiplication
9
Putting the Stop to a Vehicle
10
Typical Disk Brake
  • Calipers travel a distance of 1/8 to 3/32 of an
    inch per wheel.

11
Fluid Under Pressure
12
Liquid Characteristics
  • Liquid is a substance made up of molecules.
  • Liquid molecules are continuously moving
    (molecular energy)
  • Liquids take on the shape of their container.
  • Liquids are relatively incompressible.

13
Force Transmission Solid vs. Liquid
  • Fluid power systems are capable transmitting a
    static force (potential energy)
  • A force transmitted through a solid is
    transmitted in one direction only.
  • A force applied to a confined liquid is
    transmitted equally in all directions throughout
    the fluid in the form of fluid pressure.

14
Fluid Facts
  • An ideal liquid will not compress at all.
  • Common Hydraulic Oil is compressed approximately
    1 to 1.5 at a pressure of 3000 psi.
  • Blaise Pascal (1623-1662) was a French
    mathematician and philosopher who discovered the
    phenomenon of fluid pressure transmission in
    1653.
  • Pressure is equal to the Force divided by Area
  • P F/A

15
Pascals Law
16
Hydraulic Pressure to Mechanical Force
  • Hydraulic Pressure must be converted to a
    mechanical force before work can be performed.

17
Mechanical Force Multiplication
  • Mechanical forces can be multiplied using
    hydraulics
  • The determining factor for force multiplication
    is the square inch area on which hydraulic
    pressure is applied

18
Hydraulic Horsepower
  • Hydraulic Horsepower GPM or gallons per minute
    X psi or pounds per square inch X .000583
  • Hyd. Horsepower GPM x PSI x .000583
  • 1 Horsepower is 746 watts

19
(No Transcript)
20
Power is the rate of energy change per length of
time.
  • It tells us the quantity of energy that changed
    during a certain period of time.
  • The units of power are chunks of energy per
    amount of time.

21
Why do we need a system?
  • The reason for using hydraulics or any other type
    of energy transmission is to perform work.
  • Accomplishment of work requires the application
    of energy to a resisting object.

22
Positive Displacement Pumps
  • A positive displacement pump you get constant
    flow regardless of pressure.
  • You must have a method to drive the pump (this is
    known as a prime mover)

23
Resistance of a Positive Displacement Pump
  • Resistance to flow comes from the load and liquid
  • There is a direct relationship between pressure
    and resistance
  • Pump applies pressure the load determines how
    much

24
Heat Generation in a Hydraulic System
  • Extra energy which a pump applies to overcome a
    liquids resistance changes to heat.
  • This is inefficiency
  • Heat generation is caused by viscosity, fluid
    friction , and changing direction.

25
Viscosity
  • Viscosity is a measure of the resistance of a
    liquidss molecules to flow or slide past each
    other.
  • Viscosity is affected by temperature.
  • Saybold Universal Seconds (SUS) is a measure of a
    liquids viscosity
  • In many industrial applications, the viscosity of
    oil is 150 SUS at 100 degrees F.

26
Friction and Changing Directions
27
Fluid Velocity
  • Recommend Fluid Velocity in a pump suction line
    is 4 FPS or 4 feet per second.
  • Recommended Fluid Velocity in a system return
    line is 8 FPS.
  • Faster is not always better (cavitation can occur)

28
Pressure Differential
  • Pressure differential is the difference in
    pressure between any two points in a system.
  • Indicates that working energy is present in the
    form of a moving, pressurized liquid.
  • Measures the amount of working energy that
    changes to heat energy between two points.

29
Hydraulic System Design
  • Hydraulic systems are designed to avoid the
    generation of heat.
  • Design should consider oil of the proper
    viscosity, piping of a proper size, and keep
    bends to a minimum.

30
Physical World of a Machine
  • Man invented machinery to work for him.
  • All things on earth are surrounded by physical
    elements which hinder the performance of work

31
Force
  • It can cause a body to move.
  • It can retard or stop a body which is moving
  • One unit for measuring force is the pound.
  • A Force is any influence capable of producing
    change in the motion of a body.

32
What is Force
  • The Pound is a unit of force in the English
    system.
  • The Newton is its comparable metric unit.
  • One Newton is equal to 0.2248 pounds

33
Resistance
  • Frictional resistance is always present between
    contacting surfaces
  • Inertia is the reluctance of a body to a change
    in its motion.

34
Inertia (the car or the load doesnt want to
start stop)
  • Inertia as a resistance, is of concern in a fluid
    power system when a load has to be accelerated.
  • Inertia as energy is a concern in fluid power
    systems when a load is required to be decelerated.

35
Overcoming a Resistance
  • In overcoming a resistance, energy changes form.
    For example, when friction is overcome, kinetic
    energy changes to heat energy. When gravity is
    overcome, kinetic energy changes to potential
    energy since it is raised to a higher level.

36
Work, Power, Horsepower
  • The unit of work in the Metric system is the
    Joule
  • The unit of work in the English system is Ft. pd.
  • All work is done within a certain time
  • Power is the Speed that work is done.
  • The unit for measuring power is Horsepower

37
More about Horsepower
  • The first measurement of horsepower was done by
    James Watt (1736-1819) a Scottish inventor.
  • 1 hp 550 ft-lb/sec 33,000 ft-lb/min 42.44
    Btu/min 745.7 watts
  • Metric Horsepower 542.5 ft.lb./sec.
  • A human in good physical condition can output
    1/10 of a horsepower over sustained time
    increments.

38
Effects of Pressure
39
More about Pressure
  • Pressure is force intensity or
    concentration.
  • Fluid pressure is also potential energy.
  • In the measure of pressure is the BAR. One BAR
    equals 14.5 psi.
  • Pressure Force / Area

40
Fluid Power Systems
  • Hydraulic systems operate by means of a liquid
    under pressure. Generally, these are closed
    systems, meaning the liquid is returned to a
    reservoir.
  • Pneumatic system operates by means of a gas under
    pressure. These are open systems the air
    returns to the atmosphere after use. We are
    standing in the reservoir.

41
Why Symbols??
  • Trouble shooting any system with pneumatics or
    hydraulics will be much easier if the Technician
    can understand the flow of power.
  • Reading symbols correctly on a schematic will
    enable the Technician to find a fault and return
    the system to productivity.

42
Fluid System Parts
  • Hydraulic
  • Pneumatic
  • Reservoir (tank)
  • Lines
  • Pump
  • Filters
  • Valves
  • Actuators (hyd. motors and cylinders)
  • Receiver (tank)
  • Lines
  • Compressor
  • Filters
  • Valves
  • Actuators (air motors and cylinders)

43
Drawing Types
  • Assembly drawing
  • Pictorial-shows components in an outline that
    closely resembles the actual shape.
  • Schematic-uses symbols to represent the
    components in a system. Shows the order of
    components but does not indicate size of the
    system.

44
Schematics
  • Hydraulic schematics are often included in
    employment tests.
  • You should be familiar with the most common
    symbols.
  • These will be included on a quiz.

45
Common Symbols
  • Hydraulic Pumps- see arrow direction
  • Hydraulic Motors

46
Arrows
Solid arrows, usually black, indicate hydraulic
components. Arrows that are outlined only
indicate pneumatic components.
47
Common Symbols
  • Electric Motor- M
  • Cylinders-
    Double Acting
  • Single Acting

  • Double Rod

48
Common Symbols
  • Squares indicate a type of valve.
  • Squares are called envelopes
  • The number of squares indicate valve positions

3 position valve 2 position valve
49
Valve Control Methods(Manual)
Look in your text to identify these actuation
methods.
50
Fluid Conditioners
  • Diamonds indicate fluid conditioners
  • Filters
  • Heat exchangers (coolers)
  • Air cooled
  • Water cooled
  • Heaters

51
Common Symbols
  • Pressure Relief Valve

52
Check Valve
53
A simple system
54
A simple system, continued
Can you trace the flow path? Name as many
components as you can.
55
More Symbols
  • We will go over more symbols as class progresses.
  • Next class session will include combining symbols
    to build systems, utilizing symbols to aid in
    troubleshooting.

56
Thats All!
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