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

2. Agenda Energy Transfer Systems Pascal’s Law Basic Hydraulic Systems
Pump
Actuators
Pressure Relief Valve (PRV)
Applications
Agriculture
Construction/mining
Forestry

3. Video: Modern Marvels Hydraulics Ch1: 0-11:03 (11:03)
Introduction
Power steering
Hydraulic brakes
Thrill rides
Basic fluid power
Jack
History

4. 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)

5. 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

6. 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

7. Caterpillar 797 Dump Truck (world’s biggest until 2004)
3400 HP
360 Tons capacity
40 MPH Fully loaded
Mechanical drive

8. 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

9. 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)

10. Fluid Power Energy Transfer System
vo, Fo
P1 Q1
P4 Q4
ni, Ti M
no, To
Energy Level

11. 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

12. Basic Principles
Liquids form in the shape of the container (like the lines for transmitting fluid power)
Liquids can be considered incompressible

13. 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

14. 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.
Blaise Pascal

15. Pascal’s Law: Pressure in static closed system (confined fluid) is the same everywhere
10 N/m2

16. 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)

17. Conservation of Energy
10 m2
1 m2
100 N
1 m
10 m
10 N
10 N/m2
Energy can be neither created nor destroyed

18. 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

19. 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.

20. Linear Actuators A1 A2 F p1 p2

21. Linear Actuators Double acting Differential area Double acting
Cylinders
Double acting
Differential area
Double acting
Dual Rod

22. Rotary Actuators
Motors

23. 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.

24. Where do we find Hydraulics?

25. John Deere Utility tractor with dual pumps

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

27. Mining & Construction Equipment

28. Mining Equipment

29. Hydraulics is the Energy Transfer System on most mining equipment
Cylinders
Motors

30. Backhoe arm

34. Forestry Equipment

35. Feller-bunchers fell trees and drop them in a pile

36. Cut-to-length feller heads

37. Timberjack experimental felling ant?

38. Skidders pull trees out of the forest to a collection site

39. Forwarders stack trees for transport

40. TSM363 Fluid Power Systems Introduction to Hydraulics The End
Dept. of Agricultural & Biological Engineering University of Illinois