1. Fluid Power Systems Mill Creek High School Power and Energy

2. Objectives  Identify differences between hydraulic and pneumatic systems  Identify advantages of fluid power systems  Understand uses of valves in FPS  State physical characteristics of liquids in FPS  Understand why hydraulic cylinders can increase mechanical advantage

3. Objectives  Discuss examples of various applications of FPS  Understand difference between gauge and actual pressure  Summarize differences between single and double acting cylinders  Interpret a basic Fluid Power Circuit  Calculate Mech. Advantage created using liquids under pressure.

4. Hydraulic System  A system that controls and transmits energy through the use of liquids Hydraulic oil Hydraulic oil Uses cylinders, pumps and lines Uses cylinders, pumps and lines

5. Pneumatic System  Similar to Hydraulic but GASSES are used instead of liquids Air is most commonly used Air is most commonly used Similar in properties to liquid but has some differences Similar in properties to liquid but has some differences

6. Why Fluid Power  The ability to multiply force in order to generate strength  Less wear than other types of systems  Almost unlimited power can be produced  Can transfer power over great distance  Easy to complete and maintain  Gasses (pneumatics) offer cushioning to shock

7. Physics of Fluid Power Systems  Fluids take the shape of the container they are in  Fluids exert pressure  Fluids can freely flow from one container to another

8. Fluids Exert Pressure  Pressure is exerted in ALL directions equally NOT only on the bottoms of the container NOT only on the bottoms of the container  There is more pressure on the lower sides because pressure is a product of weight

9. How Fluids Act  Fluids flow from higher elevation to lower elevation until they are equal  Fluids will flow until both pressures in both areas are equal

10. Effort and Rate  Pressure gauge: measures difference between outside and inside pressure  Measured in Pounds-per-square-inch (psi)  “psi” is the effort in the system  Flowmeter: measures in gallons-per- minute (GPM) or cubic-feet-per-minute (CFM)  “GPM” or “CFM” is the RATE in the system

11. PSIG vs PSIA  PSIG-pounds per square inch gauge The difference between circuit pressure and atmospheric pressure The difference between circuit pressure and atmospheric pressure Most commonly used Most commonly used  PSIA-pounds per square inch actual Accounts for atmospheric pressure Accounts for atmospheric pressure 200psig=214.7psia at sea level 200psig=214.7psia at sea level  What would psig be in Denver, CO  Would psia be higher or lower in Denver. CO

12. Viscosity of Liquids  Viscosity: is a measurement of internal friction of a liquid (resistance to flow)  This is molecular  Higher the viscosity rating the slower a liquid will flow  How long it takes a quart of substance to flow through a specific size opening at a specific temperature

13. Opposition to Flow  Friction: occurs between the substance and the pipe, hose or fitting.  Turbulence: Occurs within the liquid itself  Laminar Flow: stratified layers of motion flow smoothly over one another. At junctions or “t” fittings they become intermixed and all slow down (turbulence) At junctions or “t” fittings they become intermixed and all slow down (turbulence)

14. Hydraulic Pumps  Hydraulic pumps: supply and transmit pressure needed to system…Convert mechanical energy to fluid power Gear pumps: pump in which two gears mesh together inside a housing Gear pumps: pump in which two gears mesh together inside a housing

15. Hydraulic Pumps  Reciprocating pumps: use a piston that moves back and forth (reciprocates) to move hydraulic fluid Check valves keep fluid from moving backwards Check valves keep fluid from moving backwards

16. Hydraulic Pumps  Centrifugal pumps: use centrifugal force to move fluids in a system  Centrifugal force makes objects fly outward when spinning around  Impeller: has many small blades and a central inlet …it draws the liquid out draws the liquid out from center from center

17. Controlling Fluid Power  Flow control valves: (aka: variable flow restrictor) can be used to control the output speed of the fluid can be used to control the output speed of the fluid  Pressure control valves: Pressure reducing valves: reduce pressure Pressure reducing valves: reduce pressure Pressure regulating valves: allow you to adjust pressure coming from compressor Pressure regulating valves: allow you to adjust pressure coming from compressor

18. Controlling Fluid Power  Pressure Relief Valves: used to ensure that pressure in system does not get too high.  Directional Control Valves: (aka: spool valve) to control which path the fluid takes

19. Transmitting Fluid Power  Through devices known as conductors  Hoses and pipes allow high pressure and tremendous movement Hoses flex to absorb shock Hoses flex to absorb shock Pipes may require accumulator for absorbing shock Pipes may require accumulator for absorbing shock

20. Sizing Fluid Power  Factor: Volume that conductor can carry Volume that conductor can carry Velocity at which it can travel Velocity at which it can travel Pressure the conductor is designed to handle Pressure the conductor is designed to handle

21. Flow Rate  Flow rate capacity is determined by the inside diameter of the conductor  Slight increases in diameter increase the flow rate tremendously  A 1” diameter garden hose has 4X the flow rate of a ½” diameter hose

22. Velocity  The rate of motion in a particular direction  Typically measured in Feet-per-second (fps)  As the surface area of the inside of a conductor increases the flow rate decreases because it can hold more  Helen GA

23. Pressure  Working pressure: normal operating pressure that the conductor is designed to handle  Test pressure: maximum pressure that the conductor is designed to withstand  Burst pressure: the pressure at which the conductor will burst  Must anticipate intermittent pressure

24. Making Fluid Power Work  Actuators: device that converts fluid power to mechanical power  Single acting cylinder: force of fluid moves piston in one direction (Returned by load)  Double acting cylinder: Force of fluid can move the piston in both directions

25. Making Fluid Power Work  Fluid motors: device that converts fluid power into rotary mechanical motion Gear motor: Operate like a gear pump Vane motor: fluid pushes against vanes and higher pressure on one side spins it

26. Storing Fluid Pressure  Pressure tank: tank that stores air under pressure in a pneumatic system  Accumulator: a device that stores hydraulic liquid under pressure even when the pump is not running. ABS ABS

27. Blaise Pascal  Pascal’s Law Area X Pressure = Force Of course Area of the cross section of a cylinder = Pi * r 2 cylinder = Pi * r 2