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

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

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

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)

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

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

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

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

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)

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

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

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

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

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

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

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)

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

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

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.

Linear Actuators A1 A2 F p1 p2

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

Rotary Actuators Motors

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.

Where do we find Hydraulics?

John Deere Utility tractor with dual pumps

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

Mining & Construction Equipment

Mining Equipment

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

Backhoe arm

Forestry Equipment

Feller-bunchers fell trees and drop them in a pile

Cut-to-length feller heads

Timberjack experimental felling ant?

Skidders pull trees out of the forest to a collection site

Forwarders stack trees for transport

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