1 TSM363 Fluid Power Systems Fluid Power Introduction and Applications Dr. Tony E. Grift Dept. of Agricultural & Biological Engineering University of Illinois.

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TSM363 Fluid Power Systems

Fluid Power Introduction and Applications

Dr. Tony E. Grift

Dept. of Agricultural & Biological EngineeringUniversity of Illinois

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Agenda

• Energy Transfer Systems• Pascal’s Law• Basic Hydraulic Systems

• Pump• Actuators• Pressure Relief Valve (PRV)

• Applications• Agriculture• Construction/mining• Forestry

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Video: Modern Marvels Hydraulics Ch1: 0-11:03 (11:03)

• Introduction• Power steering• Hydraulic brakes• Thrill rides• Basic fluid power• Jack• History

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Units are irrelevant if everything is kept in Pure SI:

• Distance in m• Area in m2

• Volume in m3

• Time in seconds (s)

• Flow rate in m3/s

• Force in Newton (N = kgm/s2)• Pressure in Pascal (Nm-2)• Work (energy) is Force through a Distance (Nm)• Torque is also Force times a Distance (Nm)• Power is Work per unit of Time (Nm/s)

• Viscosity in Pascal*second (Pa*s)

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Video 1: Introduction (3:20)

• Power supplies cannot directly move loads• Hydraulics can lift large loads in linear fashion (bucket of dump truck)• Conversion into useable form and transmission to work location• Compressed fluid is the energy carrier

• Fluid properties are important• Advantages

• Force can be applied in accurate amounts• Hydraulics have good power/weight ratio (mobile applications)• Precise positioning possible• Hydraulic motion is uniform and speeds are variable• Hydraulic systems can be started under maximum load (platform lift)• Overload protection easily implemented (PRV)

• Forms of hydraulic systems• Stationary systems• Mobile systems

• Construction equipment• Vehicles (Off-road and On-road), ships• Aircraft

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A hydraulic system is nothing more than an Energy Transfer System

• Fluid Power Advantages• multiplies forces• constant torque at all speeds• can work remotely and around

corners• High power density• Easy to implement linear motion• Only two actuators, linear and

rotary

• Disadvantages• Leakages• Sensitive to contamination• Can be dangerous

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Caterpillar 797 Dump Truck (world’s biggest until 2004)

• 3400 HP• 360 Tons capacity• 40 MPH Fully loaded• Mechanical drive

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Liebherr 282B 400 Ton Mining truck (record holder 2005)• 2,700 HP Detroit Diesel • 505,000 lb (229,000 kg)• 267 yd3 (204 m3)• 400 tons (363 tonnes)• Electric AC Drive

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Video 7: Hydraulic system design (1:13)

• Three system components• Power supply unit: external either electric, internal

combustion engine or human (hydraulic jacks)• Power control section (valves, many types,

functions and implementations)• Drive unit (actuators: cylinder and motors)

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Fluid Power Energy Transfer System

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Video 2: Pressure Fluids (2:02)

• Function of hydraulic fluids• Transmit pressure energy• Serve as lubricant• Protect metal from corrosion• Dissipate heat from oil flow• Carry away abraded particles to the filter

• Fluid properties• Viscosity is resistance to flow• Lubricated properties• Mineral or sythetic oils used in hydraulic systems• Additives make oil suitable for certain applications• Only 7% compressible by volume

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Basic Principles

• Liquids form in the shape of the container (like the lines for transmitting fluid power)

• Liquids can be considered incompressible

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Energy Transfer Methods

• Fluid power is one method of energy transmission:• It transfers potential energy in fluid medium to do

desired work.

• Other methods of energy transmission:• Mechanical transmission• Electrical transmission

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Video 3: Pascal’s Law (2:41)

• Pressure determines work output• Pressure applied to surface give Force• Closed system: same pressure is present everywhere • (Pascal’s law)• Operating speed determined by flow rate

• Pressure applied to a confined liquid is transmitted undiminished in all directions, and acts with equal force on equal areas, and at right angles to them.

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Blaise Pascal

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Pascal’s Law: Pressure in static closed system (confined fluid) is the same everywhere

10 N 100 N1 m2 10 m2

10 N/m2

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Video 4: Force transmission (1:35)

• Pressure propagation transmits force• Equal diameters>equal forces• Different diameters> different forces• Force can be transmitted or stepped down• Large masses can be moved with small forces

through cycling pumps (manual jack)

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Conservation of Energy

Energy can be neither created nor destroyed

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Elements of Fluid Power systems

• Power is transmitted by pushing a confined liquid.• Input component is a positive displacement pump.

• Flow from pump is dependent on speed• Flow from pump is independent of system pressure

• Output components are called actuators

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Positive Displacement Pump

• Except for efficiency, pump output is constant regardless of pressure.

• Pump outlet is sealed from inlet.• Fluid at the inlet is forced to the outlet.

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Linear Actuators

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Linear Actuators

• Cylinders

Double actingDifferential area

Double actingDual Rod

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Rotary Actuators

• Motors

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Advantages of Fluid Power

• Variable Speed• Actuators can be driven from a high to low speed using a

flow control valve.

• Reversible• Hydraulic actuators can be instantly reversed in direction of

motion.

• Overload Protection• A pressure relief valve protects a hydraulic circuit from

overload.• Also, a pressure relief valve provides a set clamping force.

• Can Be Stalled• A load can stall a fluid power circuit without damage.

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Where do we find Hydraulics?

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John Deere Utility tractor with dual pumps

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Valtra introduces powerful new hydraulics with output of 160 liters/minute

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Mining & Construction Equipment

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Mining Equipment

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Hydraulics is the Energy Transfer System on most mining equipment

Cylinders

Motors

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Backhoe arm

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Forestry Equipment

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Feller-bunchers fell trees and drop them in a pile

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Cut-to-length feller heads

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Timberjack experimental felling ant?

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Skidders pull trees out of the forest to a collection site

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Forwarders stack trees for transport

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Dept. of Agricultural & Biological EngineeringUniversity of Illinois

TSM363 Fluid Power Systems

Introduction to Hydraulics

The End