Presentation on theme: "FLUID POWER CONTROL ME604C. Applications FLUID POWER Hydraulic systems are used where large forces are required such as in earth moving equipment, heavy."— Presentation transcript:
Applications FLUID POWER Hydraulic systems are used where large forces are required such as in earth moving equipment, heavy cutting, Pressing and Clamping Pneumatic systems are used for relatively light moving, Clamping and Process operations
Applications FLUID POWER Lifting a car on a Car Ramp does not require high speed or clean control systems. Large forces are required to lift the heavy car. This application is particularly suited to the use of hydraulics.
Fluid Power System Components Push Button Switch Reed Switch Proximity Sensor Solenoid Relay Solenoid Programmable Logic Controller (PLC) FLUID POWER
Hydraulic Fluids FLUID POWER Four Primary Functions: 1.Transmit Power 2. Lubricate Moving Parts 3. Seal Clearance between Mating Parts 4. Dissipate Heat ** Here we examine the physical properties of fluids dealing with the transmission of power. … the single most important material in hydraulic system
Properties of hydraulic fluids Density The density of a fluid is its mass per unit volu me Though liquids are usually considered as incompressible, it is well known that density increases with pressure and decreases with temperature. Density is highly variable in gases nearly propo rtional to the pressure. Note: specific volume is defined as: FLUID POWER
Properties of hydraulic fluids Specific Weight: FLUID POWER NOTE: Density is absolute; and it does not depend on gravitational acceleration which varies with location.
Properties of hydraulic fluids SPECIFIC GRAVITY: FLUID POWER Example ~ 01: A cylinder container has a diameter of 0.5 m and a height of 1 m. If it is to be filled with a liquid having a specific weight of 2000 N/m3, how many kg of this liquid must be added? What is the specific gravity of the liquid.
Properties of hydraulic fluids FLUID POWER pressure depends on the column height and specific weight of the liquid and does not depend on the cross- sectional area of the liquid column. Pressure & pressure Head
Properties of hydraulic fluids FLUID POWER For the fluid power automobile lift system of figure given here, the hydraulic piston has a 250-mm diameter. How much of oil pressure (kPa) is required to lift an automobile of weight 1330 kg? Example ~ 02:
It may also be necessary to model the effect of pressure on viscosity if large fluctuations in pressure are expected. Properties of hydraulic fluids FLUID POWER 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. As the temperature increases, the viscosities of all liquids decrease, whereas the viscosities of all gases increase. VISCOSITY:
Properties of hydraulic fluids FLUID POWER Absolute Viscosity – vs – Kinematic Viscosity VISCOSITY: Point to Note: It has a further advantage in that the viscosity of water at 20.2°C is 1 cP. Thus, the value of viscosity in centipoise is an indication of the viscosity of a fluid relative to that of water at 20.2°C. Unit of Viscosity: Pa S, P, cP, St, cSt
Properties of hydraulic fluids FLUID POWER The moving plate in the figure shown is 0.7m on a side (in contact with the oil) and the oil film is 4 mm thick. A 6 N force is required to move the plate at a velocity of 1m/s. If the oil has a SG of 0.9, find the kinematic viscosity of the oil in unit of cSt. EXERCISE ~ 03
Properties of hydraulic fluids FLUID POWER Bulk Modulus: It is a measure of the compressibility of a liquid and is required when it is desired to calculate oil volume changes for high pressure. Water is about 80 times as compressible as steel.
Properties of hydraulic fluids FLUID POWER EXERCISE ~ 04: A 500 cm3 sample of oil is to be compressed in a cylinder until its pressure is increased from 1 to 50 atm. If the bulk modulus of oil equals 1750 MPa, find the percentage change in its volume.
Energy & Power in hydraulic system FLUID POWER Block diagram of hydraulic system showing major components along with energy input and output terms Why don’t we eliminate hydraulic system and simply couple the load directly to the prime mover?
Energy & Power in hydraulic system The pump head Hp in units of meters FLUID POWER
Energy & Power in hydraulic system Pascal's law: It states that the pressure exerted on a confined fluid is transmitted undiminished in all directions and acts with equal force on equal areas and at right angles to the containing surfaces. FLUID POWER
Energy & Power in hydraulic system Pascal's law ~ contd.: The most useful feature of it is the ease with which it is able to multiply force. FLUID POWER
Energy & Power in hydraulic system Pascal's law ~ contd.: FLUID POWER NOTE: Gain in Force is sacrificed in piston displacement.
Energy & Power in hydraulic system Pascal's law ~ contd.: FLUID POWER Force-Power relation: Force-displacement relation:
Pascal's law ~ applications: FLUID POWER Hydraulic press Energy & Power in hydraulic system
FLUID POWER Hydraulic Jack Energy & Power in hydraulic system
Pascal's law ~ applications: FLUID POWER Hand Operated Hydraulic Jack
Energy & Power in hydraulic system FLUID POWER EXERCISE: 05 The hydraulic jack, shown in the figure, is filled with oil. The large and small pistons have diameters of 75 and 25 mm, respectively. What force on the handle is required to support a load of 8896 N? If the force moves down by 125 mm, how far is the weight lifted?
Energy & Power in hydraulic system FLUID POWER EXERCISE: 06 In the hydraulic device shown in figure, calculate the output torque T2, if the input torque T1 =10 N- cm. Use the following data: radius R1 = 2 cm, diameter d1 = 8 cm, radius R2 = 4 cm, diameter d2 = 24 cm.
Energy & Power in hydraulic system FLUID POWER (a) How much load can be lifted? (b) How many cycles are required to lift the load by 500 mm, assuming no oil leakage? The pump piston has 20 mm stroke. (c) What is the output power assuming 80% efficiency? EXERCISE: 07 : An operator makes 5 complete cycles in 1 s interval using the hand pump shown in figure. Each complete cycle consists of two pump strokes (intake and power). The pump has a piston of diameter 30 mm and the load cylinder has a piston of diameter 150 mm. The average hand force is 100 N during each power stroke.