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Hydraulic Schematic Symbols Airline Hydraulic's Main PageBasic Symbols Lines -continuous line - flow line -dashed line - pilot, drain -envelope - long and short dashes around two or more component symbols.Circular -large circle -pump, motor -small circle -Measuringdevices -semi-circle -rotary actuatorSquare -one square- pressurecontrolfunction-two or threeadjacentsquares -directionalcontrolDiamond -diamond -Fluidconditioner(filter,separator,lubricator,heatexchanger)Miscellaneous Symbols -Spring -FlowRestrictionhttp://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (1 of 12)11/15/2005 9:44:31 PM

Hydraulic Schematic Symbols Triangle -solid -Direction ofHydraulicFluid Flow -open -Direction ofPnematicflow Pumps andCompressors Fixed Displacement hydraulicpump -unidirectional -bidirectionalVariable displacement hydraulicpump -unidirectional -bidirectionalCompressor Motors Fixed displacement hydraulicmotor -unidirectional -bidirectionalhttp://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (2 of 12)11/15/2005 9:44:31 PM

Hydraulic Schematic Symbols Variable displacement hydraulicmotor -unidirectional -bidirectionalPneumatic motor -unidirectional -bidirectionalRotary Actuator - hydraulic - pneumatic Cylinders Single acting cylinder -returnedby externalforce -returned byspring orextended byspring forceDouble acting cylinders -singlepiston rod(fluidrequired toextend andretract) -doubleendedpiston rodCylinders with cushions - single fixedcushonhttp://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (3 of 12)11/15/2005 9:44:31 PM

Hydraulic Schematic Symbols - doublefixedcushion - singleadjustablecushion - doubleadjustablecushion Directional Control Valves Directional control valve (2 ports /2 positions) -Normallycloseddirectionalcontrol valvewith 2 portsand 2 finitepositions. -Normallyopendirectionalcontrol valvewith 2 portsand 2 finitepositions.Directional control valve (3 ports /2 positions) -Normallycloseddirectionalcontrol valvewith 3 portsand 2 finitepositions. -Normallyopendirectionalcontrol valvewith 3 portsand 2 finitepositions.http://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (4 of 12)11/15/2005 9:44:31 PM

Hydraulic Schematic Symbols Directional control valve (4 ports /2 positions) -directionalcontrol valvewith 4 portsand 2 finitepostionsDirectional control valve (4 ports /3 positions) -directionalcontrol valvewith 4 portsand 3 finitepostions*-(centerposition canhave variousflow paths)Directional control valve (5 ports /2 positions) Normally a pneumaticvalve -directionalcontrol valvewith 5 portsand 2 finitepostionsDirectional control valve (5 ports /3 positions) Normally a pneumaticvalve -directionalcontrol valvewith 5 portsand 3 finitepostionsProportional directional controlvalveElectro-hydraulic servo valve-The spool positions on these valves isvariable allowing for variable flowconditions.http://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (5 of 12)11/15/2005 9:44:31 PM

Hydraulic Schematic Symbols -single-stagedirectoperationunit whichaccepts ananalogsignal andprovides asimilaranalog fluidpoweroutput -two-stagewithmechnicalfeedbackindirectpilotoperationunit whichaccepts ananalogsignal andprovides asimilaranalog fluidpoweroutput Control Methods Manual Control -generalsymbol(withoutshowing thecontrol type) -pushbutton -lever -foot pedalMechanical Control -plunger ortracerhttp://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (6 of 12)11/15/2005 9:44:31 PM

Hydraulic Schematic Symbols -spring -roller -roller(onedirectiononly)Electrical Control -Solenoid(the onewinding)Pilot Operation -pneumatic -hydraulicPilot operated two-stage valve -Pneumatic:Sol firststage -Pneumatic:Air pilotsecondstage -Hydraulic:Sol firststage -Hydraulic:Hyd pilotsecondstage Check valves, Shuttle valves,Rapid Exhaust valves -check valve-free flowonedirection,blocked flowin otherdirectionhttp://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (7 of 12)11/15/2005 9:44:31 PM

Hydraulic Schematic Symbols -pilotoperatedcheck valve,pilot to close -pilotoperatedcheck valve,pilot to openShuttle valve -to isolateone part of asystem froman alternatepart ofcircuit.Rapid exhaust valve/Pneumatic -installedclose to anactuator forrapidmovementof theactuator. Pressure Control Valves Pressure Relief Valve(safety valve)normally closed -linepressure islimited tothe settingof thevalve,secondarypart isdirected totank.Proportional Pressure Reliefhttp://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (8 of 12)11/15/2005 9:44:31 PM

Hydraulic Schematic Symbols -linepressure islimited toandproportionalto anelectronicsignalSequence Valve -when thelinepressurereaches thesetting ofthe valve,valveopenspermittingflow to thesecondaryport. Thepilot mustbeexternallydrained totank.Pressure Reducing valve-pressuredownstreamof valve islimited tothe settingof the valve Flow Control Valves Throttle valve -adjustableoutput flowFlow Control valvehttp://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (9 of 12)11/15/2005 9:44:31 PM

Hydraulic Schematic Symbols -with fixedoutput(variations ininletpressure donot affectrate of flow) -with fixedoutput andrelief port toreservoirwith relief forexcess flow(variations ininletpressure donot affectrate of flow) -withvariableoutput -fixed orifice -meteredflow towardright freeflow to left -pressurecompensatedflow controlfixed outputflowregardlessof load -pressureandtemperaturecompensated -withvariableoutput andrelief port toreservoirFlow dividing valve -flow isdividedequally totwo outputs.http://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (10 of 12)11/15/2005 9:44:31 PM

Hydraulic Schematic Symbols Shut-Off Valve -Simplifiedsymbol Accumulators Filters, Water Traps,Lubricators andMiscellaneous Apparatus Filter or Strainer Water Trap -with manualdrain -withautomaticdrainedFilter with water trap -with manualdrain -automaticdrainAir Dryer refrigerant,or chemicalremoval ofwater fromcompressedair lineLubricatorhttp://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (11 of 12)11/15/2005 9:44:31 PM

Hydraulic Schematic Symbols -oil vapor isindected intoair lineConditioning unit -compoundsymbol offilter,regulator,lubricatorunit -SimplifiedSymbol Heat Exchangers -air or watercooled unitdesigned toremove heatfrom oilreturning toreservoir Hydraulics| Pneumatics| Electro Controls| Marine& Mobile| Fluid Connectors| Safety Systems| Training| Repair & Field Service Contact AirlineIf you would like a Sales Quote, please email Request Sales QuoteIf you have any questions, comments, or suggestionsabout this page please Send E-mail to the WebmasterCopyright 1997 Airline Hydraulics Corporation Legal Disclaimerhttp://www.airlinehyd.com/KnowledgeCenter/Symbols.asp (12 of 12)11/15/2005 9:44:31 PM