3 Basic PumpThe basic operating principle that moves fluid through a pump is similar in all pumpsEnlarging the volume of a chamber allows fluid to enter the pumpReducing the chamber volume moves fluid to the systemInlet and discharge valves or ports control fluid movement through the pump
4 How Pumps WorkIn a rotary pump, the pumping action is produced by revolving componentsIn a reciprocating pump, the rotating motion of the pump input shaft is changed to reciprocating motion, which then produces the pumping action
5 Basic PumpIncreasing the size of the pumping chamber moves fluid into the pump
6 Basic PumpReducing the size of the pumping chamber forces fluid into the system
7 Basic PumpThe maximum pressure developed in a hydraulic system is determined by:Resistance to fluid flow in the systemForce the prime mover can exertThe output flow rate of a hydraulic pump is determined by:Volume of the pumping chamberOperating speed of the prime mover
8 Path of least resistance: PressurePath of least resistance:If there is no force (load) on a cylinder there is no pump pressure!PumpWhat will happen to cylinders A & B when power is applied to the pump?Cylinder ADia. = 4” with a load of 2000 lbsCylinder BDia. = 8” with a load of 4000 lbsCylinder ACylinder B
9 Cylinder A Dia. = 4” with a load of 2000 lbs Area = 12.566 in2 P= F/A = psiPumpCylinder ACylinder BCylinder BDia. = 8” with a load of 4000 lbsArea = in2P= F/A = psiCylinder B moves first until it is fully extended and then Cylinder A extends
10 Displacement – The volume of fluid that is discharged per cycle. Cycle – One revolution of the pump shaft.Theoretical Flow Rate - 𝑄 𝑇𝑄 𝑇 = 𝑉 𝑃 ∙𝑁 𝑄 𝑇 = 𝑉 𝑃 ∙𝑁 1000𝑉 𝑝 =𝑝𝑢𝑚𝑝 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡 𝑖𝑛 3 𝑟𝑒𝑣 , 𝑐𝑚 3 𝑟𝑒𝑣𝑁=𝑑𝑟𝑖𝑣𝑒 𝑠𝑝𝑒𝑒𝑑 𝑅𝑒𝑣 𝑀𝑖𝑛
11 EX – A pump has a displacement of 3 𝑖𝑛 3 𝑟𝑒𝑣 and is driven at 1800rpm EX – A pump has a displacement of 3 𝑖𝑛 3 𝑟𝑒𝑣 and is driven at 1800rpm. What is the theoretical flow rate?𝑄 𝑇 = 𝑉 𝑃 ∙𝑁 231 = 3 𝑖𝑛 3 𝑟𝑒𝑣 ∙ 1800 𝑟𝑒𝑣 𝑚𝑖𝑛 𝑖𝑛 3 𝑔𝑎𝑙𝑄 𝑇 =23.4 𝑔𝑎𝑙 𝑚𝑖𝑛
12 Pump Drive and Torque Power Prime mover supplies input power to the pump by driving the pump shaft at a rotational speed.Pressure on the pump resists rotation.Prime mover must generate enough torque to turn the shaft against the resistance.
14 Ex: A hydraulic pump with a displacement of 4 𝑖𝑛 3 𝑟𝑒𝑣 is selected for a system that will operate at a maximum pressure of 5000 psi. What is the required drive torque?𝑇 𝑇 = 𝑝∙ 𝑉 𝑝 2𝜋 = 5000 𝑙𝑏 𝑖𝑛 2 ∙ 4 𝑖𝑛 3 𝑟𝑒𝑣 2𝜋=3183 𝑖𝑛∙𝑙𝑏𝑠
15 Ex: A hydraulic pump with a displacement of 30 𝑐𝑚 3 𝑟𝑒𝑣 is selected for a system that will operate at a maximum pressure of 40,000kPa. What is the required drive torque?Convert to 𝑚 3 𝑟𝑒𝑣30 𝑐𝑚 3 𝑟𝑒𝑣 ∙ 1 𝑚 3 1,000,000 𝑐𝑚 3 = 𝑚 3 𝑟𝑒𝑣𝑇 𝑇 = 𝑝∙ 𝑉 𝑝 2𝜋 = 𝑁 𝑚 2 ∙ 𝑚 3 𝑟𝑒𝑣 2𝜋=191 𝑁∙𝑚
20 EX: A pump has a displacement of 3 𝑖𝑛 3 𝑟𝑒𝑣 and a volumetric efficiency of If it is driven at 1300 rpm, what will its actual flow rate be?𝑄 𝐴 = 𝜂 𝑣 ∙ 𝑉 𝑝 ∙𝑁 231𝑄 𝐴 =0.93∙ 3 𝑖𝑛 3 𝑟𝑒𝑣 ∙1300 𝑟𝑒𝑣 𝑚𝑖𝑛 𝑖𝑛 3 𝑔𝑎𝑙𝑄 𝐴 =15.70 𝑔𝑝𝑚
22 EX: A pump has and overall efficiency of 0 EX: A pump has and overall efficiency of 0.88 and a flow rate of 40 lpm is to be used in a system that has a maximum operating pressure of 20,000kPa. What is the input power require?Calculate the hydraulic power:𝑘𝑊 𝐻 = 𝑝∙𝑄 60,000 = 𝑘𝑃𝐴∙40𝑙𝑝𝑚 =13.33𝑘𝑊Calculate the input power:𝑘𝑊 1 = 𝑘𝑊 𝐻 𝜂 0 = 13.33𝑘𝑊 0.88 =1514𝑘𝑊
25 Hydraulic pumps can be classified using three basic Characteristics: Pump ClassificationsHydraulic pumps can be classified using three basic Characteristics:DisplacementPumping motionFluid delivery characteristics
26 Displacement PumpDisplacement relates to how the output of the pump reacts to system loadsPositive-displacement pumps produce a constant output per cycleA non-positive-displacement pump has large internal clearancesAllows fluid slippage in the pumpResults in varying flow output as system load varies
29 Pumping Motion Classifications The basic pumping motions used in hydraulic pumps are:RotaryGear pumps are rotary pumpsReciprocatingPiston pumps are reciprocating pumpsReciprocating piston movement
30 Fluid Delivery Classifications Hydraulic pumps are classified as either fixed or variable deliveryFixed-delivery pumps have pumping chambers with a volume that cannot be changed; the output is the same during each cycleIn variable-delivery designs, chamber geometry may be changed to allow varying flow from the pump
31 Fluid Delivery Classifications Gear pumps are fixed-delivery pumps
32 Fluid Delivery Classifications Piston pumps may or may not be variable-delivery pumps
35 Pump SelectionWhen selecting a pump for a circuit, factors that must be considered are:System operating pressureFlow rateCycle rateExpected length of serviceEnvironmental conditionsCost
36 Pump Design, Operation, and Application Gear pumps:positive-displacement,fixed-delivery,rotary unitsexternal or internal gear teeth configurations
37 Pump Design, Operation, and Application Pumping action of gear pumps results from unmeshing and meshing of the gearsAs the gears unmesh in the inlet area, low pressure causes fluid to enter the pumpAs the pump rotates, fluid is carried to the pump discharge areaWhen the gears mesh in the discharge area, fluid is forced out of the pump into the systemFlow outputs from below 1 gpm to 150 gpmPressure rating range up to 3000 psi
38 Pump Design, Operation, and Application The gerotor pump design is an internal-gear pumpUses two rotating, gear-shaped elements that form sealed chambersThe chambers vary in volume as the elements rotateFluid comes into the chambers as they are enlarging and is forced out as they decrease in size
39 Pump Design, Operation, and Application The gerotor is a common internal-gear design
40 Pump Design, Operation, and Application Vane pumps are positive-displacement, fixed or variable delivery, rotary units.Design is commonly used in industrial applicationsDelivery can range up to 75 gpmMaximum pressure of about 2000 psi
41 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 housingRotor is off center in the ring, which creates pumping chambers that vary in volume as the pump rotatesAs chamber volume increases, pressure decreases, bringing fluid into the pumpAs volume decreases, fluid is forced out into the system
45 Pump Design, Operation, and Application A basic piston pump consists of a housing that supports a pumping mechanism and a motion-converting mechanismPumping mechanism is a block containing cylinders fitted with pistons and valvesMotion converter changes rotary to reciprocating motion via cams, eccentric ring, swash plate, or bent-axis designsRotating the pump shaft causes piston movement that pumps the fluid
46 Pump Design, Operation, and Application Piston pump classification is based on the relationship between the axes of the power input shaft and piston motionAxialInlineBent axis
48 Pump Design, Operation, and Application Piston pump classification is based on the relationship between the axes of the power input shaft and piston motionRadialhave the highest continuous operating pressure capability of any of the pumps regularly used in hydraulic systemsare available with operating pressure ratings in the 10,000 psi range
49 Pump Design, Operation, and Application A stationary-cylinder radial-piston pump
50 Pump Design, Operation, and Application RadialReciprocating
51 Pump Design, Operation, and Application Screw pumps have pumping elements that consist of one, two, or three rotating screwsthe screws rotate, fluid is trapped and carried along to the discharge of the pumpscrew pumps operate at a very low noise level
52 Additional Design Features of Pumps Pressure compensation reduces energy consumption
56 Gallons per minute is the number of gallons a pump can force into the system every minute and thus the amount of fluid flow that pump can produce.in3
57 Design & Operating Considerations Cavitation is caused when inlet line pressure drops below the vapor pressure of the fluid and bubbles formReduces lubricity of the system fluidCollapsing bubbles produce severe shock waves that can damage pump partsCollapsing bubbles also produce noisy pump operation
59 Design & Operating Considerations Entrained air is air suspended in fluidEnters the inlet line through leaks on the suction side of the pumpCan produce a result similar to cavitation
60 Design & Operating Considerations Testing inlet line pressure can help indicate which condition existsHigh negative pressure (vacuum) indicates cavitationPressure closer to 0 psi may indicate entrained air
61 Design & Operating Considerations The inlet line of the pump must be carefully sized and configured to eliminate cavitation and air entrainmentFluid velocity in the line should not exceed feet per secondLines should be no smaller than the diameter of the pump inlet fittingStrainer and inlet line filters must not restrict fluid flow
62 Design & Operating Considerations Pump Flow RateQ (gpm) = (V * N)/231Q (lpm) = (V * N)/1000Q – flow rate (in3/min, cm3/min)V – pump displacement (in3/rev, cm3/rev)N – drive speed (rpm)Horsepower required for a given flow rate and pressureHP = (P*Q)/1714P in psi; Q in gpm; HP in hpkW = (P*Q)/60,000P in kPa; Q in lpm; kW in kW
63 Glossary Application information Axial piston pump Information supplied by a manufacturer describing conditions and limits of operation in which a product may be expected to successfully operate.Axial piston pumpA hydraulic pump using a design in which the reciprocating motion of the pistons is parallel to the power input shaft.
64 Glossary Balanced-vane pump A hydraulic vane pump using a design with two inlet and outlet chambers that balance the load forces on the bearings of the pump rotor shaft.
65 GlossaryCavitationThe formation of gas within a liquid stream that occurs when pressure drops below the vapor pressure of the liquid; may result in excessive noise and pump damage. The condition in a hydraulic pump can result from restricted inlet flow or excessive oil viscosity.
66 Glossary Dual pump Fixed-delivery pump A design in which two pumps are built into a single case. The pumps may be rated at different pressures and flow outputs to provide additional flexibility.Fixed-delivery pumpAny hydraulic pump design that has a nonadjustable fluid delivery rate.
67 GlossaryGear pumpA hydraulic pump design that uses gears to move fluid through the pumping chamber of the component. Gears may have internal or external teeth.
68 Glossary General hydraulic horsepower A computed figure used in hydraulic systems based on fluid flow and pressure. Equal to fluid flow weight in pounds per minute multiplied by the pressure in feet of head divided by 33,000 foot pounds per minute.
69 Glossary Gerotor design A common internal-gear pump or motor design. The pumping chamber of these units has two gear-shaped elements that form varying-size chambers as they rotate.
70 GlossaryImpellerThe rotating component of a dynamic compressor or impeller pump. Energy is increased in the fluid as centrifugal force causes flow through the unit.
71 Glossary Mechanical efficiency Non-positive-displacement pump The theoretical horsepower needed to operate a pump or compressor divided by the actual horsepower required.Non-positive-displacement pumpA pump that does not have a variable-volume pumping chamber. An impeller or other device is used to move the fluid. The inertia of that fluid movement produces pressure when flow is resisted.
72 GlossaryPower unitThe unit in a hydraulic system that provides energy for the system, moves fluid through the system, provides a safe maximum limit of system pressure, and maintains desired system temperature and fluid cleanliness.
73 Glossary Radial-piston pump A positive-displacement piston pump design in which the pistons are located in a cylinder block or housing that is perpendicular to the power input shaft.
74 Glossary Reciprocating pump One of a variety of pump designs using reciprocating pistons to move fluid. The drive mechanisms vary, but a reciprocating piston moves the fluid against resistance from the system actuator.
75 GlossaryScrew pumpA pump unit that uses intermeshing screws to form chambers that linearly move hydraulic oil through the pump. The design provides a continuous, positive displacement of the oil.
76 Glossary Stationary-cylinder design Swash plate A radial-piston hydraulic pump design in which a cam operates pistons located in a fixed cylinder block.Swash plateAn inclined disk in a hydraulic axial-piston pump or motor that causes the pistons to reciprocate.