Hydraulicshydraulics [h drlliks ] noun study of fluids: the study of water or other fluids at rest or in motion, especially with respect to engineering applications

ObjectivesBehavior of liquids & theory of operationBasic hydraulic system componentsAdvantages & disadvantages of hydraulicsElectrohydraulic systems including speed gears & steering gears

Introduction/UsesHydraulics used in many applications:Steering/control systems (rudder, planes)Deck machinery (anchor windlass, capstans, winches)Masts & antennae on submarinesWeapons systems (loading & launching)Other: elevators, presses

Hydraulic TheoryHydraulics Covers the physical behavior of liquids in motionPressurized oil used to gain mechanical advantage and perform workImportant PropertiesShapelessnessIncompressibilityTransmission of Force

Important PropertiesShapelessnessLiquids have no neutral formConform to shape of containerEasily transferred through piping from one location to another IncompressibilityLiquids are essentially incompressibleOnce force is removed, liquid returns to original volume (no permanent distortion)Transmission of ForceForce is transmitted equally & undiminished in every direction -> vessel filled with pressure

Hydraulic TheoryPascals LawMagnitude of force transferred is in direct proportion to the surface area (F = P*A)Pressure = Force/AreaLiquid properties enable large objects (rudder, planes, etc) to be moved smoothly

Hydraulic Mechanical Advantage

Basic Hydraulic SystemHydraulic FluidUsually oil (2190 TEP)Pressure SourceHydraulic pump (A-end of system)Pressure userHydraulic motor (B-end of system)Piping system (w/ valves, tanks, etc)Get fluid from A-end to B-end

Hydraulic Pump (A-End)Pumps can be positive displacement or centrifugalWaterbury pumpVariable-stroke piston pumpTilting box can tilt fwd/aft while pump rotatesAngle of tilting box determines capacity and direction of oil flow

Hydraulic Pump (A-End)Variable-stroke piston pumpTilting box can tilt fwd/aft while pump rotatesAngle of tilting box determines capacity and dir. of flow

Cylinder/Motor (B-end)Piston/cylinder used if desired motion is linearHydraulic pressure moves piston & ramLoad is connected to ram (rudder, planes, masts, periscopes)PistonCylinderRAMHydraulic Fluid Supply/Return PortsSeal

Cylinder/Motor (B-end)Motor used if desired motion is rotaryEssentially a variable-stroke pump in reverseUsed for capstan, anchor windlass, etc

Piping SystemHas to withstand excessive pressureValves, filters, & HXs all necessaryAccumulatorsHolds system under pressure (w/out contin. pump)Provides hydraulics when pump off/lostCompensates for leakage/makeup volumeTypes: piston, bladder, & direct contact

Accumulator TypesPistonMost commonBladder Gun mountsSteering systemsDirect contactLeast common

AdvantagesConvenient power transferFew moving partsLow losses over long distancesLittle wearFlexibilityDistribute force in multiple directionsSafe and reliable for many usesCan be stored under pressure for long periodsVariable speed controlQuick response (linear and rotary)

DisadvantagesRequires positive confinement (to give shape)Fire/explosive hazard if leaks or rupturesFiltration critical - must be free of debrisManpower intensive to clean up

Electrohydraulic Drive SystemUses hydraulics to transfer power from electric motor to loadRotary: Waterbury pump connected to rotary piston hydraulic motor (speed gear)Tilting box of A-end controls direction/speed of B-endAdv: high starting torque, reversibility, high power-to-weight ratio ex: Electrohydraulic Speed Gear or Steering Gearcapstan, anchor windlass, cranes, elevator, ammo hoist

Electrohydraulic Speed Gear

Electrohydraulic Steering GearSame as speed gear except B-end is a hydraulic cylinder to produce linear motionWaterbury pumps connected by piping to hydraulic ram cylinderVarious methods for connecting rams to tillersTwo pumps for redundancy & reliabilityMovement of steering wheel through hydraulic system moves rudder

Electrohydraulic Steering Gear

Control of SystemRemote controlNormal methodControl from bridgeEmergencyTake local controlManually position control surface/rudder

Questions?