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Introduction to fluid power

Introduction to fluid power. Fluid power  is a term describing  hydraulics  and  pneumatics  technologies. Both technologies use a fluid (liquid or gas) to transmit power from one location to another. hydraulics, the fluid is a liquid (usually oil),

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Introduction to fluid power

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  1. Introduction to fluid power • Fluid power is a term describing hydraulics and pneumatics technologies. • Both technologies use a fluid (liquid or gas) to transmit power from one location to another. • hydraulics, the fluid is a liquid (usually oil), • pneumatics uses a gas (usually compressed air). • Both are forms of power transmission, which is the technology of converting power to a more useable form and distributing it to where it is needed. • The common methods of  power transmission are electrical, mechanical, and fluid power.

  2. Advantages of fluid power • high horsepower-to-weight ratio — You could probably hold a 5-hp hydraulic motor in the palm of your hand, but a 5-hp electric motor might weight 40 lb or more. • safety in hazardous environments because they are inherently spark-free and can tolerate high temperatures. • force or torque can be held constant — this is unique to fluid power transmission • high torque at low speed — unlike electric motors, pneumatic and hydraulic motors can produce high torque while operating at low rotational speeds. Some fluid power motors can even maintain torque at zero speed without overheating • pressurized fluids can be transmitted over long distances and through complex machine configurations with only a small loss in power • multi-functional control — a single hydraulic pump or air compressor can provide power to many cylinders, motors, or other actuators • elimination of complicated mechanical trains of gears, chains, belts, cams, and linkages • motion can be almost instantly reversed

  3. Application of fluid power system • Construction • Mining • Agriculture • Waste Reduction • Utility Equipment • Marine • Offshore • Energy • Metal Forming • Machine Tools • Military & Aerospace • Other Applications

  4. Types of fluid power systems • Fluid transport system • Transport of water from reservoir using pipe lines • Transport of oil in pipe to two countries. • Fluid power system • Oil used in equipments to acquire desire movement. • Compressed air in pneumatics for crane movements

  5. Properties of hydraulic fluids • Density • The density of a fluid is its mass per unit volume: • Liquids are essentially incompressible  • Density is highly variable in gases nearly proportional to the pressure.  • Note: specific volume is defined as:

  6. Cavitation • Cloud of vapour bubble will form when liquid pressure drops below vapour pressure due to flow phenomenon • Capillarity • Liquid rises into a thin glass tube above or below its general level. • Vapour pressure • Pressure exerted by vapour which is in equilibrium with liquid

  7. Compatibility • Ability of hydraulic fluid to be compatible with the system. • Volatility • The degree and rate at which it will vapourize under given conditions of temperature and pressure. • Corrosiveness • Tendency to promote corrosion in hydraulic system.

  8. Application of pascals law • Hydraulic press

  9. Hydraulic jack

  10. Laminar and Turbulent flow • Laminar • Turbulent

  11. Reynolds number

  12. Darcys equation

  13. Losses in pipes, valves and fittings

  14. UNIT 2: HYDRAULIC SYSTEM COMPONENTS • Sources of Hydraulic Power • construction and working of pumps – Variable displacement pumps • Actuators: Linear hydraulic actuators • Single acting and Double acting cylinders • Fluid motors. • Control Components: • Direction control valve • Flow control valves • Electrical control -- solenoid valves. Relays, Accumulators and Intensifiers.

  15. Basic Pump Classifications • Hydraulic pumps can be classified using three basic aspects: • Displacement • Pumping motion • Fluid delivery characteristics

  16. Basic Pump Classifications • Displacement relates to how the output of the pump reacts to system loads • Positive-displacement pumps produce a constant output per cycle • Non-positive-displacement pumpsproduce flow variations due to internal slippage

  17. Basic Pump Classifications • A non-positive-displacement pump has large internal clearances • Allows fluid slippage in the pump • Results in varying flow output as system load varies

  18. Basic Pump Classifications • Non-positive-displacement pump

  19. Basic Pump Classifications • The basic pumping motions used in hydraulic pumps are: • Rotary • Reciprocating

  20. Basic Pump Classifications • Gear pumpsare rotary pumps Sauer-Danfoss, Ames, IA

  21. Basic Pump Classifications • Piston pumps are reciprocating pumps Reciprocating piston movement

  22. Basic Pump Classifications • In a rotary pump, the pumping action is produced by revolving components • In a reciprocating pump, the rotating motion of the pump input shaft is changed to reciprocating motion, which then produces the pumping action

  23. Basic Pump Classifications • Hydraulic pumps are classified as either fixed or variable delivery • Fixed-delivery pumps have pumping chambers with a volume that cannot be changed; the output is the same during each cycle • In variable-delivery designs, chamber geometry may be changed to allow varying flow from the pump

  24. Basic Pump Classifications • Gear pumps are fixed-delivery pumps

  25. Basic Pump Classifications • Piston pumps may be designed as variable-delivery pumps

  26. Basic Pump Classifications • When selecting a pump for a circuit, factors that must be considered are: • System operating pressure • Flow rate • Cycle rate • Expected length of service • Environmental conditions • Cost

  27. Pump Design, Operation,and Application • Gear pumps are positive-displacement, fixed-delivery, rotary units • Gear pumps are produced with either external or internal gear teeth configurations

  28. Pump Design, Operation,and Application • Gear pumps are commonly used

  29. Pump Design, Operation,and Application • Pumping action of gear pumps results from unmeshing and meshing of the gears • As the gears unmesh in the inlet area, low pressure causes fluid to enter the pump • As the pump rotates, fluid is carried to the pump discharge area • When the gears mesh in the discharge area, fluid is forced out of the pump into the system

  30. Pump Design, Operation,and Application • Gear pumps are available in a wide variety of sizes • Flow outputs from below 1 gpm to 150 gpm • Pressure rating range up to 3000 psi

  31. Pump Design, Operation,and Application • The gerotor pump design is an internal-gear pump • Uses two rotating, gear-shaped elements that form sealed chambers • The chambers vary in volume as the elements rotate • Fluid comes into the chambers as they are enlarging and is forced out as they decrease in size

  32. Pump Design, Operation,and Application • The gerotor is a common internal-gear design

  33. Pump Design, Operation,and Application • Gerotor operation

  34. Pump Design, Operation,and Application • Gerotor operation

  35. Pump Design, Operation,and Application • Gerotor operation

  36. Pump Design, Operation,and Application • Gerotor operation

  37. Pump Design, Operation,and Application • Vane pumps are positive-displacement, fixed or variable delivery, rotary units. • Design is commonly used in industrial applications • Delivery can range up to 75 gpm • Maximum pressure of about 2000 psi

  38. Pump Design, Operation,and Application • Vane pump consists of a slotted rotor, fitted with moveable vanes, that rotates within a cam ring in the pump housing • Rotor is off center in the ring, which creates pumping chambers that vary in volume as the pump rotates • As chamber volume increases, pressure decreases, bringing fluid into the pump • As volume decreases, fluid is forced out into the system

  39. Pump Design, Operation,and Application • Operation of a typical vane pump

  40. Pump Design, Operation,and Application • Parts of a typical vane pump

  41. Pump Design, Operation,and Application • Vane pump may be pressure unbalanced or pressure balanced • Unbalanced has only one inlet and one discharge, which places a side load on the shaft • Balanced has two inlets and two discharges opposite each other, creating a pressure balance and, therefore, no load on the shaft

  42. Pump Design, Operation,and Application • Piston pumps are positive-displacement, fixed- or variable-delivery, reciprocating units • Several variations • Many provide high volumetric efficiency (90%), high operating pressure (10,000 psi or higher), and high-speed operation

  43. Pump Design, Operation,and Application • A basic piston pump consists of a housing that supports a pumping mechanism and a motion-converting mechanism • Pumping mechanism is a block containing cylinders fitted with pistons and valves • Motion converter changes rotary to reciprocating motion via cams, eccentric ring, swash plate, or bent-axis designs • Rotating the pump shaft causes piston movement that pumps the fluid

  44. Pump Design, Operation,and Application • Piston pump classification is based on the relationship between the axes of the power input shaft and piston motion • Axial • Radial • Reciprocating

  45. Pump Design, Operation,and Application • Axial piston pumps use two design variations: • Inline • Bent axis

  46. Pump Design, Operation,and Application • Inline has the cylinder block and pistons located on the same axis as the pump input shaft • Pistons reciprocate against a swash plate • Very popular design used in many applications

  47. Pump Design, Operation,and Application • An inline axial-piston pump

  48. Pump Design, Operation,and Application • Bent axis has the cylinder block and pistons set at an angle to the input shaft • Geometry of the axis angle creates piston movement • Considered a more rugged pump than inline • Manufactured in high flow rates and maximum operating pressures

  49. Pump Design, Operation,and Application • A bent-axis axial-piston pump

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