APPLIED HYDRAULICS AND PNEUMATICS U5MEA23 Prepared by Mr. Jayavelu.S & Mr. Shri Harish Assistant Professor, Mechanical Department VelTech Dr.RR & Dr.SR Technical University UNIT I : FLUID POWER SYSTEMS AND FUNDAMENTALS Introduction to fluid power Advantages of fluid power Application of fluid power system Types of fluid power systems, General types of fluids ◦ Properties of hydraulic fluids ◦ Fluid power symbols Basics of Hydraulics ◦ ◦ ◦ ◦ ◦ Applications of Pascal’s Law Laminar and Turbulent flow Reynolds’s number Darcy’s equation Losses in pipe, valves and fittings Introduction to fluid power Fluid power is a term describing hydraulics and pneumatics technologi es. 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. 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 sparkfree 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 Application of fluid power system Construction Mining Agriculture Waste Reduction Utility Equipment Marine Offshore Energy Metal Forming Machine Tools Military & Aerospace Other Applications 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 Properties of hydraulic fluids Density ◦ The density of a fluid is its mass per unit volu me: ◦ Liquids are essentially incompressible ◦ Density is highly variable in gases nearly prop ortional to the pressure. ◦ Note: specific volume is defined as: Viscosity ◦ Viscosity is a measure of a fluid’s resistance to flo w. It determines the fluid strain rate that is gener ated by a given applied shear stress. Cohesion ◦ Intermolecular attraction between molecules of same liquid Adhesion ◦ Attraction between molecules of liquid and molecules of solid boundary in contact with liquid. 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 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. Application of pascals law Hydraulic press Hydraulic jack Laminar and Turbulent flow Laminar Turbulent Reynolds number Darcys equation Losses in pipes, valves and fittings 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. Basic Pump Classifications Hydraulic pumps can be classified using three basic aspects: ◦ Displacement ◦ Pumping motion ◦ Fluid delivery characteristics 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 pumps produce flow variations due to internal slippage 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 Basic Pump Classifications Non-positive-displacement pump Basic Pump Classifications The basic pumping motions used in hydraulic pumps are: ◦ Rotary ◦ Reciprocating Basic Pump Classifications Gear pumps are rotary pumps Sauer-Danfoss, Ames, IA Basic Pump Classifications Piston pumps are reciprocating pumps Reciprocating piston movement 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 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 Basic Pump Classifications Gear pumps are fixed-delivery pumps Basic Pump Classifications Piston pumps may be designed as variable-delivery pumps 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 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 Pump Design, Operation, and Application Gear pumps are commonly used 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 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 Pump Design, Operation, and Application The gerotor pump design is an internalgear 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 Pump Design, Operation, and Application The gerotor is a common internal-gear design Pump Design, Operation, and Application Gerotor operation Pump Design, Operation, and Application Gerotor operation Pump Design, Operation, and Application Gerotor operation Pump Design, Operation, and Application Gerotor operation 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 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 Pump Design, Operation, and Application Operation of a typical vane pump Pump Design, Operation, and Application Parts of a typical vane pump 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 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 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 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 Pump Design, Operation, and Application Axial piston pumps use two design variations: ◦ Inline ◦ Bent axis 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 Pump Design, Operation, and Application An inline axial-piston pump 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 Pump Design, Operation, and Application A bent-axis axial-piston pump Pump Design, Operation, and Application Radial piston pumps have the highest continuous operating pressure capability of any of the pumps regularly used in hydraulic systems Models are available with operating pressure ratings in the 10,000 psi range Pump Design, Operation, and Application Two variations of radial piston pumps: ◦ Stationary-cylinder design uses springs to hold pistons against a cam that rotates with the main shaft of the pump ◦ Rotating-cylinder design uses centrifugal force to hold pistons against a reaction ring When the main shaft is rotated, each piston reciprocates, causing fluid to move through the pump Pump Design, Operation, and Application A stationary-cylinder radial-piston pump Pump Design, Operation, and Application Large, reciprocating-plunger pump designs were widely used when factories had a central hydraulic power source Today, plunger pumps are typically found in special applications requiring highpressure performance Pump Design, Operation, and Application Screw pumps have pumping elements that consist of one, two, or three rotating screws As the screws rotate, fluid is trapped and carried along to the discharge of the pump The design of screw pumps allows them to operate at a very low noise level Pump Design, Operation, and Application A typical screw pump Pump Design, Operation, and Application The lobe pump is a close relative of the gear pump ◦ Two three-lobed, gear-shaped units are often used to form the pumping element ◦ Output flow is larger than a gear pump of comparable physical size because of pumping chamber geometry ◦ Lower pressure rating than gear pumps ◦ Tend to have a pulsating output flow Pump Design, Operation, and Application Operation of a lobe pump Pump Design, Operation, and Application Centrifugal pumps are non-positivedisplacement units ◦ Use centrifugal force generated by a rotating impeller to move fluid ◦ Large clearances between the impeller and the pump housing allow internal pump slippage when resistance to fluid flow is encountered in the system ◦ Typically used in hydraulic systems as auxiliary fluid transfer pumps Pump Design, Operation, and Application Operation of a centrifugal pump Pump Design, Operation, and Application Propeller and jet pumps are non-positivedisplacement pumps ◦ Sometimes used to transfer fluid within hydraulic systems ◦ Propeller pump consists of a rotating propeller-shaped pumping element ◦ Jet pump creates flow by pumping fluid through a nozzle concentrically located within a venturi Pump Design, Operation, and Application Construction of a propeller pump Pump Design, Operation, and Application Construction of a jet pump Directional control valves Check valve Pilot operated check valve Three-way and four-way valves Manually-actuated valve Pilot actuated valve Solenoid actuated valve Center flow path configuration Shuttle valve Directional control valves Pilot operated check valve Three-way valves Four-way valves Manually-actuated valve Pilot actuated valve Solenoid actuated valve Pressure control valves Pressure relief valve Compound pressure relief valve Pressure-reducing valve Pressure relief valve Compound pressure relief valve Pressure-reducing valve Flow control valve/ Needle valve Restrictor needle valve Weight loaded accumulator Spring loaded accumulator Diaphragm type accumulator Bladder type accumulator Intensifier UNIT 3: PNEUMATIC SYSTEM COMPONENTS Pneumatic Components: Properties of air. Compressors. FRL Unit – Air control valves, Quick exhaust valves pneumatic actuators- cylinders, air motors. Compressor construction Types of compressor Piston type reciprocating compressor Fig shows single-acting piston actions in the cylinder of a reciprocating compressor. The piston is driven by a crank shaft via a connecting rod. At the top of the cylinder are a suction valve and a discharge valve. A reciprocating compressor usually has two, three, four, or six cylinders in it. Screw compressor Screw compressors are also belong to the positive displacement compressor family. In screw compressors, the compression is accomplished by the enmeshing of two mating helically grooved rotors suitably housed in a cylinder equipped with appropriated inlet and discharge ports Rotary vane compressor The rotor shaft is mounted eccentrically in a steel cylinder so that the rotor nearly touches the cylinder wall on one side, the two being separated only by an oil film at this point. Directly opposite this point the clearance between the rotor and the cylinder wall is maximum. Heads or end-plates are installed on the ends of the cylinder and to hold the rotor shaft. The vanes move back and forth radially in the rotor slots as they follow the contour of the cylinder wall when the rotor is turning. The vanes are held firmly against the cylinder wall by action of the centrifugal force developed by the rotating rotor. In some instances, the blades are springloaded to obtain a more positive seal against the cylinder wall. Filter Air In Louver Bowl Drain Cock Air Out Filter Element Sight Gauge Regulator Adjustable Locking Knob Main Spring Diaphragm Assembly Air In Valve Assembly Air Out Valve Spring Lubricator 2 Quick Exhaust Valve Port 2 is connected directly to the end cover of a cylinder Port 1 receives air from the control valve Air flows past the lips of the seal to drive the cylinder When the control valve is exhausted, the seal flips to the right opening the large direct flow path Air is exhausted very rapidly from the cylinder for increased speed 2 1 1 2 1 Unit 4: FLUIDICS & PNEUMATIC CIRCUIT DESIGN Fluidics – Introduction to fluidic devices, simple circuits Introduction to Electro Hydraulic Pneumatic logic circuits, PLC applications in fluid power control, ladder diagrams Fluid Power Circuit Design: Sequential circuit design for simple applications using classic, cascade, step counter, logic with Karnaugh- Veitch Mapping and combinational circuit design methods. Fluidics Bistable flip flop SRT flip flop OR/NOR & AND/NAND Fluidic control of pneumatic cylinders PLC Ladder diagram PLC control of hydraulic circuit Cascading circuit UNIT 5: FLUID POWER CIRCUITS Speed control circuits, synchronizing circuit, Pneumo hydraulic circuit, Accumulator circuits, Intensifier circuits. Servo systems – Hydro Mechanical servo systems, Electro hydraulic servo systems and proportional valves. Deceleration circuit, hydrostatics transmission circuits, control circuits for reciprocating drives in machine tools, Material handling equipments. Fluid power circuits; failure and troubleshooting. Speed control circuit Regenerative circuit Pressure intensifier circuit Accumulator circuit Pneumatic motor circuit Regenerative drilling machine Hydraulic fault diagnosis Pneumatics fault diagnosis Thank you.