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UNIT – 1 BASICS OF HYDRAULICS

CE6403 APPLIED HYDRAULICS ENGINEERING Prepared by, Ms. A. SANMUGA VADIVU, AP/ CIVIL, MSEC- KILAKARAI. UNIT – 1 BASICS OF HYDRAULICS. BASIC HYDRAULICS A SYSTEM STUDY. A TALK OVERVIEW. •.

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UNIT – 1 BASICS OF HYDRAULICS

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  1. CE6403 APPLIED HYDRAULICS ENGINEERINGPrepared by,Ms. A. SANMUGA VADIVU,AP/ CIVIL,MSEC- KILAKARAI.

  2. UNIT – 1BASICS OF HYDRAULICS

  3. BASICHYDRAULICS A SYSTEMSTUDY

  4. A TALKOVERVIEW • This talk has been designed to provide instruction on the concept and operation of the basic components of the hydraulicsystem. It also describes the various components of a typical hydraulic system, their construction and functions, and their relationship to each other. However to really appreciate & know abouthydraulics ‘hands on’ experience, is aMUST. •

  5. FluidPower System • Fluid Power Systems are power transmitting assemblies employing pressurised liquid or gas to transmit energy. • Fluid power can be divided into two basicdisciplines • Hydraulics – Employingpressurised liquid • Pneumatics -Employing • Compressedgas

  6. Whatis Hydraulics? • Hydraulics is derived from the Greek word • Hydor meaningWater • Aulos meaning Pipe

  7. Definition ofHydraulics In simple language: Confined liquids under pressure made to dowork. OR Science of transmitting force / motion through medium of confinedliquid

  8. HYDRAULICS DEFINED FURTHER… Fluid Mechanics is the physical science and technology of the static and dynamic behavior offluids. Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluidproperties. •

  9. PASCAL’SLAW Pascal Law – which is the basis for all hydraulic systems, is named after the French Scientist – Blaise Pascal, who established thelaw.

  10. Do you remember Pascal’s Law? It states that “ Pressure exerted anywhere in a confined fluid is transmitted equally in all directions throughout the fluid. • • The basic idea behind all hydraulic system is based upon that principle & can be simply statedas: Force applied at one point is transmitted to another point using an incompressiblefluid.

  11. PASCAL’S LAW ILLUSTRATION

  12. Working Principle of a Hydraulic Press

  13. Functions of HydraulicOil • It transmits power. • Itlubricatesmovingparts • It seals clearances • between moving parts • It dissipates heat

  14. Advantages of oil inHydraulics • • Variablespeed Reversible need direction. Over load protection over- Small package power Can bestalled Simple design Selflubricated Flexible location components. Smooth Acts as coolant Acts as seal matingparts. Noisefree : Possible to control speed throughvalve. : Instant reverse motion is possible. No to stop the system tochange : Protected through relief valvefrom loading. : Components are smaller than other transmittingsystem. : Not possible on direct drive system from Electric motor / Dieselengine. : Pre- engineered componentsavailable. : Hydraulic oil lubricates theparts. : Flexible hoses virtually eliminate the problem of thehydraulic : Incompressible, novibration. : It dissipates heat / cools thecomponent, ; It seals clearances betweentwo : Nonoise. • • • • • • • • • •

  15. Force that is applied at one point is transmittedtoanotherpointusingan • incompressible fluid • In this drawing, two pistons (green) fit into two glass cylinders filledwithoil (blue) and connected to one another with an oil-filled pipe. If you apply a downward force to one piston (the left one in this drawing), then the force is transmitted to the second piston through the oil in thepipe

  16. ForceMultiplication • Assume that the piston on the left is 2 inches in diameter (1-inch radius), while the piston on the right is 6 inches in diameter (3-inch radius). The area of the two pistons is Pi * r2 . The area of the left piston is therefore 3.14, while the area of the piston on the right is 28.26. The piston on the right is 9 times larger than the piston on the left. What that means is that any force applied to the left-hand piston will appear 9 times greater on the right-hand piston. So if you apply a 100-pound downward force to the left piston, a900- pound upward force will appear on theright

  17. HydraulicSystem • Reservoir • Filter • Hydraulic Pump • DirectionalControlValve • Pressure Control Valve

  18. Reservoir-Properties First a tank is needed to store the hydraulicoil Tank /Reservoir Storingoil Compensates difference in volume when actuators areused It dissipatesheat It allows foreign particles to settle down Baffle separates inlet line with the return line and allows the air bubbles toescape

  19. More Properties ofReservoirs • Itallowscondensedwatertosettle atthe bottom of the tank • Breather on the top of the tank allows to • maintainatmosphericpressure andavoid creation of vacuum • Sightglasswillindicate the levelofthe oil. Mercury bulb indicates the oil temperature • Oilfillinginletwillhave a filterforavoiding contamination.

  20. PUMPS • HydraulicPumpisthe mostimportant component in the hydraulic system. • Functionofthe HydraulicPumpistoconvert Mechanical Energy to Hydraulic Energy • HydraulicPumpare classifiedintwo categories: • Hydro-dynamic • Hydro-static

  21. Pump • Now we need a pump to createflow • Tank • Pump • Two types of hydraulic pumps are most commonlyused: • RotaryPumps • ReciprocatingPumps

  22. ROTARY & RECIPROCATING TYPES • Common Pumps in Rotary type are: • Gear Pumps • Vane Pumps • CommonPumpsinReciprocatingtype are: • Axial Piston Pump RadialPistonPump

  23. ACTUATORS • An actuator is a mechanical device for moving or controlling a mechanism or system. An actuator typically is a mechanical device that takes energy & converts it to a desirable form for usage or application. Actuator Tank Pump

  24. ACTUATORSContd… • There are mainlytwotypesof Actuators: • Linear actuators (single acting • cylinders, double actingcylinders) • Rotaryactuators(vane motors, gear motors, piston motors etc.)

  25. Types ofValves • There are three maintypesof Valves: • Pressure Control Valves (relief • valves, pressure regulatingvalve, pressure reducing valve etc.) • Directional Control Valves (check valve, axial spool valve, ball valve etc.) • FlowControlValves (needle valve, throttle check valve etc.)

  26. Hydraulic System – some applications of the basic components Actuator Hoses to connectthe components Piston reverse movement isnot possible We need a direction control valve to change the direction of flow as perrequirement Pump Tank

  27. HydraulicSystem Actuator There are mainlytwo design principles for valves - Spool valves Direction ControlValve - Poppet valves Pump Tank

  28. HydraulicSystem Actuator Direction ControlValve The control valve is at neutralposition Pump Tank

  29. HydraulicSystem Actuator Now the control valve is shifted toleft Direction ControlValve Pump Tank

  30. HydraulicSystem Actuator Direction ControlValve To change the piston movement in opposite direction the control valve is now shifted to right Pump Tank

  31. HydraulicSystem Actuator Is it a complete circuit? OR Direction ControlValve We need some thingmore Pump Tank

  32. HydraulicSystem Actuator Piston atend -No roomto move Pressure Direction yes increases ControlValve We need some thingmore We need to control the systempressure Pump Tank

  33. HydraulicSystem Actuator Direction ControlValve Pressure reliefvalve Pump Tank

  34. HydraulicSystem Actuator Direction ControlValve Pressure reliefvalve Pump Tank

  35. HydraulicSystem Actuator Direction ControlValve Pressure reliefvalve Stops pressure increasing beyond the presetvalue Pump Tank

  36. HydraulicSystem Actuator Now wehave asystem which canwork But is this systemprotected from dirt? Direction ControlValve Pressure reliefvalve Pump Tank

  37. HydraulicSystem Actuator We need to protect the system from dirt by installing a FILTER in thesystem Direction ControlValve Pressure reliefvalve We have a system nowwhich can worksafely Pump Filter Tank

  38. FILTERS • There are basicallythree types of Filters • Suction line filters • Pressure line filters • Return line filters

  39. Why is filtrationnecessary? • Impurities in the Hydraulic • systemaffectthe components of the hydraulic system and • shorten their service life. • Reductioninservice life ofthe components occurs in two • ways: • Wear and Tear • Breakdown of component • Filtersare usedtoremove the smallest insoluble particles • andkeepthe hydraulicsystem clean

  40. HydraulicSystem Actuator Now we know: • A Reservoir containsoil • Filter cleans thesystem • Pump createsflow • Resistance createspressure • Actuators perform thework Direction ControlValve • Hoses transmit theoil • D.C. Valves change direction of oilflow • Relief valves control the maximum systempressure. Pressure reliefvalve Pump Filter Tank

  41. HydraulicSystem Actuator • Few morefacts: • Pressure increases the system capacity • Flow increases the system speed Direction ControlValve Pressure reliefvalve Pump Filter Tank

  42. ThisExcavatorweighsover28 tons, but has swift movements. The bucket can effortlesslyscoopoutmore than a cubic meter of rock weighing about 2.0T

  43. Transmission ofHydraulic Power • The engine is connected to a pair of pumps that can generate 140 gallons per minute at 4,500 psi. You can see from the picture that the arm has a pair of pistons working in unison at the "shoulder" -- one at the "elbow" and then one to rotate thebucket.

  44. Transmission of Hydraulic Power • These pistons, along with the two track motors and the rotating motor, are all controlled by two joy sticks and four pedals in the cab. These controls send electrical signals to an electrically-operated valve block located next to thepu mpp..

  45. Transmission of Hydraulic Power From the valve block, high-pressure hydraulic lines make their way to the cylinders & they get activated whereby the bucket can be moved as desired from the cabinwith the touch of abutton.

  46. Some BasicCalculations • A 4-inch piston has an area of 12.56 square inches. If the pump generates a maximum pressure of 3,000 pounds per square inch (psi), the total pressure available is 37,680 pounds, or about 20tons. Another thing you can determine is the cycle time of the piston. To move a 4-inch-diameter piston 24 inches, you need 3.14 * 22 * 24 = 301 cubic inches of oil. A gallon of oil is about 231 cubic inches, so you have to pump almost 1.5 gallons of oil to move the piston 24 inches in onedirection. These form the basic criteria while selecting the hydraulic pump. For example the actual engine, pump & sump details for this excavator is: Engine Cummins 6CT 8.3-C 8,270 cubiccentimeters 340 horsepower at 1,900rpm Pump Maximum pressure: 5,000 psi (4,500 psi) Oil flow: 2x270 liters per minute Capacities Fuel: 530 liters Engine oil: 22liters Hydraulic oil: 320liters •

  47. DUMP TRUCKS orTIPPERS • DUMPERS WITH TELESCOPIC CYLINDERS & HYDRAULICSTEERING

  48. What exactly is "full hydraulicsteering?" • The expression refers to any steeringsystem • configurations where a vehicle is steered solelyby • means of a hydraulic circuit comprising, as aminimum, a • pump, lines, fluid, valve, and cylinder (actuator). that is to say, the vehicle is steered (usually via the frontwheels) • purely by a hydraulically powered steeringcylinder. This • is an important distinction from "hydraulicallyassisted" • steering, where hydraulic power serves only to assista • mechanical steering system (as is the case withthe • hydraulically assisted power steering on virtually every light car / truck on the road today). It indicates thatthe • vehicle is steered ONLY by hydraulics, with no other system (mechanical linkage) inplace.

  49. Whyuse hydrostaticsteering? • Because there are a number of distinct advantages: • Power - depending on system design parameters (flow, pressure, cylinder size,etc.) hydrosteeringcandevelopsteeringforceFARinexcessofanyothermechanical, electrical, or hydraulically boosted system.This is a must for massive construction equipment. It is also extremely advantageous to 4x4s with big tires,locker differentials, low tire pressures, the must negotiate and be steered inextremely challenging terrain. For a given amount of steering input effort, no other system can match the power output of a hydro steeringsystem. Flexibil ity - the very nature of fluid power (hydraulics) allows for great flexibilityin system design and mounting. The steering need not be constrained by the requirements for mechanicallinkages. Operator comfort - because of the power generated, required operator input levels are very low in hydro steeringsystems. Control - depending on system design and tuning, precise, custom steering canbe arranged, (for example, a system with very few turns of the steering wheel from lock tolock) Weight - the power to weight ratio of hydrostatic systems generally far outstrips traditionalhydraulicallyboostedmechanicallyactuatedsteeringsystems. Smoothness - hydro steering systems are smooth and quietin operation. Vibration is kept to a minimum. kickback, bump steer, and operator fatigue are all but eliminated. Overload protection - when properly designed, automatic valves can guard the system against a breakdown fromoverloading • • • • • •

  50. The component in the top right of the picture is the hydraulic steering directional control valve/ meteringsection;andistheheartofthesystem

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