Electrohydraulic Valves A Technical Look
Electrohydraulic Valves.A Technical Look
ELECTROHYDRAULIC VALVE APPLICATIONSMoog Inc. was the founded in 1951 by William C. Moog,inventor of the Electrohydraulic Servovalve.His creation heralded a new era in precision control. Italso spurred the growth of Moog to become the world leaderin design and manufacture of electrohydraulic control productsand systems. During the past decade the company has extendedits control expertise into Servo-Proportional Valves, ServoElectronics and Direct Drive Valves.Moog products provide precise control of position, velocityand force – so important to the proper operation of a widevariety of industrial machinery.APPLICATIONSFor example: Moog Inc. Servoactuators accurately control the thicknessof steel slabs in continuous casting operations. Moog Inc. ServoJet Servo-Proportional Valves control bothvelocity and pressure in plastic injection molding machinesand wall thickness in plastic blow molding machines. Moog Inc. Direct Drive Valves control the thickness of paperon new “state of the art” paper machines.IndustrialMobile/MarineBasic Metal ProcessingBlow/Injection MoldingEarthquake SimulationEntertainment EquipmentFatigue TestingFlight SimulationGas, Steam & Hydro TurbinesMachine ToolsManufacturing SystemsMaterial TestingPaper MachinesRoboticsRubber ProcessingSaw & Veneer Mill MachinesSteel & Aluminum Mill EquipmentActive SuspensionForestry MachinesMining MachineryRailroadsRemote ControlSeismic ExplorationShipsSubmersiblesVibration ReductionENGINEERING ASSISTANCEThe information contained in this catalog presents typicalproducts offered by Moog; our true expertise is helping you solveyour motion control problems. Our engineering staff is availableto assist you in your efforts to accurately and precisely controlposition, velocity or force in your specific application. Often timesthis results in designing a customized design and product, specifically suited to your need. Moog’s capabilities in this respect areunmatched in industry. So call us and let us know how we canhelp you will be glad you did.Due to our policy of continual research and improvement,we reserve the right to change specifications in this catalogwithout notice.ApplicationsApplicationsEach of these applications involves precise control of a complex structure, which in most cases is subject to varying loadsthat can adversely affect performance. Moog products overcomethe structural and load variation effects through the principlesof feedback. Moog transducers measure the output, which couldbe position, velocity, pressure or acceleration and send signalsto the machine controller.These signals are compared with thedesired output.The sensing and correcting on a continuous basisresults in optimum system performance.2
ELECTROHYDRAULIC VALVE SELECTION GUIDEMoog offers the broadest line of Electrohydraulic Valves onthe market today. Our product line consists of Servovalves(Mechanical and Electric Feedback versions) and ServoProportional Valves (Direct Drive and Two Stage ServoJet versions). Servovalves typically utilize a ISO10372 mountingpattern and are nearly always zero lapped or axis cut (nomechanical deadband). Servo-Proportional Valves utilize anISO4401 mounting pattern and may have a mechanical deadband.Selection of the proper valve involves understanding theperformance requirements of your application.The chart belowattempts to categorize the more popular Moog valve series bytwo very important selection criteria – flow and dynamic 64D66379-20020079-200 HRD662FLOW WITH 1000 psi SERVOVALVE DROP - gpm1007072DDV VALVE5079-100D6614030D63420G761/D765 STDD765 HR107D765 05070100200300 400 500 7001000SERVOJET FREQUENCY OF SERVOVALVE 90 PHASE LAG – Hz(SMALL TO MEDIUM SIGNAL RESPONSE)3
HOW TO SELECT A SERVO OR PROPORTIONAL VALVEDETERMINE THE REQUIRED VALVE FLOW RATE ANDFREQUENCY RESPONSEKEY PARAMETERS FOR SERVO OR PROPORTIONALVALVE SELECTIONa) In order to compensate for unknown forces, size the actuatorarea to produce a stall force 30% greater than the desired forceto the supply pressure available.Supply PressureServovalve and ServoJet Valves are intended to operate withconstant supply pressure and require continuous pilot flow tomaintain the hydraulic bridge balance.The supply pressure shouldbe set so that the pressure drop across the valve is equal to onethird of the supply pressure.The flow capacity should include thecontinuous pilot flow to maintain the hydraulic bridge balance.Direct Drive Valve performance is constant no matter what thesupply pressure.Therefore, they are good in systems with fluctuatingsupply pressures.Standard Moog Inc. valves will operate at supply pressuresfrom 200 to 3,000 psi. Optional valves for 50 to 5,000 psioperation are available. Refer to individual valve specifications.A 1.3 FRPSwhere:A actuator area (in2)FR force required to movethe load (lb) at maximumvelocity, ref. key parametersPS supply pressure (psi)Refer to the NFPA standard cylinder bore and rod sizes andselect the area closest to the result of the above calculations.b)From the maximum required loaded velocity and the actuatorarea from the above calculation, determine the valve loadedflow and the load pressure drop.where:QL loaded flow (in3/sec)XL maximum requiredloaded velocity (in/sec)QL AXLPL Type of FluidMoog Inc. valves operate most effectively with fluids that exhibita viscosity of 60 to 450 SUS at 100 F. Due to the Servovalve operating range of -40 F to 275 F, care should be taken to assure fluidviscosity does not exceed 6,000 SUS. In addition, fluid cleanliness isof prime importance and should be maintained at ISO DIS 4406Code 16/13 max, 14/11 recommended. Consult the Moog Inc.Filtration and Valve Series catalogs for recommendations.Fluid compatibility with material used in the constructionof valves must be considered. Contact the factory for specificinformation.where:PL load pressure drop (psi)FRAc) Compute the no-load flow.PSPS - PLQNL QLForce RequirementsIn most applications, a portion of the available supply pressuremust be used to overcome some force. Since valve flow ratings aregiven as a function of pressure drop across the valve, total forcerequirements must be known in order to determine what portionof the supply pressure is available to be dropped across the valve.Total force is the summation of all individual forces that occur dueto the static or dynamic configuration of the system.where:QNL no-load flow (in2/sec)d)Determine the valve rated flow at 1,000 psi valve drop forServovalves and 150 psi valve drop for Proportional Valves.Increase by 10% for margin.10% padQR 1.1(QNL3.8)in3/sec to gpm conversionwhere:QR Servovalve rated flow(gpm) at 1,000 psi dropor Proportional Valverated flow at 150 psi dropFR FL FA FE FSFRFLFAFEFSe) For open-loop control, a valve having a 90 phase lag at 3 Hzor higher, should be adequate.f) For closed loop control of systems utilizing electrical feedback,calculate the load natural frequency using the equations in thisbrochure under “Load Resonant Frequency”.The optimum performance will be achieved if the Servovalve 90 phase point exceedsthe load resonant frequency by a factor of three or more.g) With a calculated flow rate and frequency response, referencethe Valve Selection Table on page 3 for valve selection. AnyServovalve that has equal or higher flow capacity andresponse will be an acceptable choice. However, it is preferable not to oversize the Servovalve flow capacity as this willneedlessly reduce system accuracy.h)Consult individual data sheets for complete valve performanceparameters.where: total required force (lb) force due to load (lb) force due to acceleration (lb) force due to external disturbance (lb) force due to seal friction (lb)Force Due to a LoadForce due to a load FL can be an aiding or resistive component,depending upon the load’s orientation and direction of travel.Consideration has to be taken when computing FL to ensure theproper external friction coefficients and resolved forces are STONRETRACTING
Dynamic ResponseWLWLTYPICAL BODE PLOT OF DYNAMIC RESPONSE4250225FLØFL mWLWL weight of load (lb)m coefficient of frictionFL mWLcosØ (lb)0200175-4150125-8-12-16Force Due to AccelerationThe forces required to overcome inertia become very largein high speed applications and are critical to valve sizing.FA MaVMAXa TaM WL WPgwhere:M mass (lb - sec2/in)a acceleration (in/sec2)WP weight of piston (lb)VMAX maximum velocity (in/sec)Ta time period foracceleration (sec)WL weight of loadCONSTANTKA FEPRESSMAX50100KO KS (lb/in)KO KSThe load resonant frequency for an equal area cylinder is given by:INTERMITTENTƒN Force Due to Seal FrictionMost valves are used on applications which employ some sortof motion device.These motion devices usually utilize elastomerseals to separate the various pressure chambers.The frictionbetween these seals and the moving parts acts as opposing force.FS 0.1 F20 30Load Resonant FrequencyOpen loop control consists of a human operator monitoring theparameter (i.e., position or speed) and varying the input of thecontrol valve to obtain the desired result. Closed loop control iscapable of fast, more accurate control and requires a high performance control valve. For optimum performance, the valves 90 phase point should exceed the load resonant frequency by a factorof three or more. Load resonance is determined by the overallstiffness (KA), which is the combination of the hydraulic stiffness(KO) and the structural stiffness (KS), given by:EXTERNALCOMPRESSIONOR TENSILEFORCEDEFORMATIONFORCE10907550250200 300 500HzA valve’s dynamic response can be easily determined by measuringthe frequency at which the phase lag between the input currentand output flow reaches 90 (90 phase lag point).The frequencyresponse will vary with input signal amplitude, supply pressure,and fluid temperature.Therefore, comparisons must use consistent data.The recommended peak-to-peak signal amplitude is 80%of the valve rated current. Servovalve and ServoJet response willimprove somewhat with higher supply pressure, and generallydepreciate at both high and low temperatures. Direct Drive Valveresponse is independent of supply pressure.Force Due to External DisturbancesThese forces can be generated by constant or intermittentsources.FE5Degrees( )FLKO 12¹4s ßAXTwhere:F stall force (lb)MAXs Standard practice involves setting seal friction at 10% ofthe maximum force available, unless absolute values are known.AXmVKOMwhere:ƒN load resonant frequency (Hz)KO hydraulic stiffness (lb/in)where:ß bulk modulus of fluid used (psi)A working area of double endedpiston (in2)XT total piston stroke (in)where:s actuator volumetric efficiencyXm piston stroke used forapplication (in)V total volume of fluid betweenvalve control ports andthe piston (in3)NOTE:Typical bulk modulus (ß) Å 2.0 x 105 psi5
ELECTROHYDRAULIC VALVE PILOT STAGE ANDSPOOL ACTUATION TECHNOLOGIESNOZZLE FLAPPER TORQUE MOTOR DESCRIPTIONAn electrical command signal (flow rate set point) is applied tothe torque motor coils and creates a magnetic force which actson the ends of the pilot stage armature.This causes a deflectionof armature/flapper assembly within the flexure tube. Deflectionof the flapper restricts fluid flow through one nozzle which iscarried through to one spool end, displacing the spool. [Spoolactuation relative to valve operation is detailed on page 17]Movement of the spool opens the supply pressure port (P)to one control port while simultaneously opening the tank port(T) to the other control port.The spool motion also applies aforce to the cantilever spring, creating a restoring torque on thearmature/flapper assembly.Once the restoring torque becomes equal to the torquefrom the magnetic forces, the armature/flapper assembly movesback to the neutral position, and the spool is held open in a stateof equilibrium until the command signal changes to a new level.In summary, the spool position is proportional to the inputcurrent and, with constant pressure drop across the valve, flow tothe load is proportional to the spool hnologyTechnologySERVOJET leBearingThe ServoJet pilot stage consists mainly of torque motor, jet pipeand receiver.A current through the coil displaces the jet pipefrom its neutral position.This displacement, combined with thespecial shape of the jet pipe, directs a focused fluid jet towardsone side of the receiver.The jet now produces a pressure difference across the endsof the spool.This pressure difference causes a spool displacementwhich, in turn, results in control port flow.The pilot stage drain isthrough the annular area around the nozzle to INEAR FORCE MOTOR DESCRIPTIONMoog’s Direct Drive Valves use our proprietary linear forcemotor. A linear force motor is a permanent magnet differentialmotor.The permanent magnets provide part of the requiredmagnetic force.The linear force motor has a neutral mid-positionfrom which it generates force and stroke in both directions. Forceand stroke are proportional to current.High spring stiffness and the resulting centering force, plusexternal forces (i.e. flow forces, friction forces due to contamination), must be overcome during outstroking. During backstrokingto center position, the spring force adds to the motor force andprovides additional spool driving force making the valve lesscontamination sensitive.The linear force motor requires very lowcurrent in the spring centered position.Plug6
TYPES OF SERVO SYSTEMSPOSITION SERVO SYSTEMSERVOAMPLIFIERA load positioning servo system is comprised of a Servo, ServoJet or Direct Drive Valve, actuator, position feedback transducer,position command generator, and a Servoamplifier. A typical linearposition servo system using a double-ended piston is shown tothe right (a rotary position servo system can be created bysubstituting the appropriate rotary components).The valve’s two output control ports are connected acrossthe load cylinder. In the Servoamplifier, the command input iscompared to the present position output of the positiontransducer. If a difference between the two exists, it is amplifiedand fed to the valve as an error signal.The signal shifts the valvespool position, adjusting flow to the actuator until the positionoutput agrees with the command input.null– ingand gainsensitivitySERVOVALVEPSC1position feedbackC2RloadICYLINDER– POSITION TRANSDUCERTYPICAL POSITION SERVOVELOCITY SERVO SYSTEMA velocity servo system is comprised of a Servo, ServoJet orDirect Drive Valve, hydraulic motor, tachometer, velocity command generator, and a Servoamplifier whose summing and gainamplifier are configured to also act as an integrating amplifier.Atypical rotary servo system is shown to the right (a linear velocityservo system can be created by substituting the appropriate linearcomponents).The valve’s two output control ports are connected acrossthe hydraulic motor. In the Servoamplifier, the command input iscompared to the present velocity output of the tachometer. If adifference between the two exists, it is integrated over time andsubsequently fed to the valve as an error signal.This signal shiftsthe valve spool position, adjusting flow to the motor until thevelocity output agrees with the command ngand gainsensitivitySERVOVALVEPC1C2Rloadvelocity feedbackGHYDRAULICMOTORTACHOMETERTYPICALVELOCITY SERVOFORCE SERVO SYSTEMA force servo system can be created with a Servo, ServoJet orDirect Drive Valve, actuator, load cell or pressure transducer,and a Servoamplifier (an Adjustable Metering Orifice may beused to improve system performance). A typical force servosystem is shown to the right.The valve’s two output control ports are connected acrossthe cylinder. In the Servoamplifier, the command input is compared to the present force output of the load cell. If a differencebetween the two exists, it is amplified and fed to the valve as anerror signal.The signal shifts the valve spool position, adjustingpressure to the actuator until the force output agrees with thecommand input.SERVOAMPLIFIERnull edriversummingand gainSERVOVALVEPC1AMOC2Rloadforce feedbackLOAD CELLCYLINDERTYPICAL FORCE SERVO7
GENERAL TERMINOLOGYPer SAE ARP 490See Moog Technical Bulletin No. 117 for a complete discussion of Closed Loop and Valve terminology and test techniques.ELECTRICALInput Current – The electrical current to the valve whichcommands control flow, expressed in milliamperes (mA).Rated Current – The specified input of either polarity toproduce rated flow, expressed in milliamperes (mA). Rated currentis specified for a particular coil configuration (differential, series,individual or parallel coils) and does not include null bias current.Coil Impedance – The complex ratio of coil voltage to current.Coil impedance will vary with signal frequency, amplitude, andother operating conditions, but can be approximated by the DCcoil resistance R, expressed in ohms(½) and the apparent coilinductance L, expressed in henrys (H), measured at a specificsignal frequency.Dither – An AC signal sometimes superimposed on the valveinput to improve system resolution. Dither is expressed by thedither frequency hertz (Hz) and the peak-to-peak dither current,expressed in milliamperes (mA).TerminologyTerminologyUnits:Recommended English and Metric units for expressing valve performance include the following:CATEGORYENGLISHMETRICin3/sec (cis)CONVERSIONFACTORSliters/min (lpm)0.98 lpm/cis3.85 cis/gpm3.78 lpm/gpmbarmillimeters (mm)0.069 bar/psi25.4 mm/in25400 µm/in0.454 kg/lbFluid Flowgal/min (gpm)Fluid Pressurelb/in2 (psi)Dimensionsinches (in)Weightpounds (lb)micrometers (µm)kilograms (kg)Torquein-lbNewton meters (N-m)0.113 N-m/in-lbTemperaturedegrees Fahrenheit ( F)degrees Celsius ( C) C 5/9 ( F – 32)8
Valve Pressure Drop ÆPV – The sum of the differentialpressure across the control orifices of the valve spool, expressedin psi or bar.Valve pressure drop will equal the supply pressure,minus the return pressure, minus the load pressure drop,[ÆPV (PS – R) – ÆPL].HYDRAULICControl Flow QV – The flow through the valve control ports tothe load expressed in in3/sec (cis), gal/min (gpm), or liters/min (lpm).Rated Flow QR – Servovalves are typically rated at 1,000 psidrop, while Proportional Valves are rated at 150 psi drop.Theflow under no-load condition, QNL, will vary with supply pressureas shown in Figure 1.The relationship can be calculated by:PERFORMANCELinearity – The maximum deviation from control flow from thebest straight line of flow gain, expressed as percent of rated current.where:QNL no-load flowPÆPSQ QNLRSymmetry – The degree of equality between the flow gain of onepolarity and that of reversed polarity. Measured as the differencein flow gain for each polarity, expressed as percent of the greater.PS supply pressureQR Servovalve rated flowat 1,000 psi drop, P.V.rated flow at 150 psi dropÆP valve drop, typically 1,000 psifor Servovalves and 150 psifor Proportional ValvesHysteresis – The difference in valve input currents requiredto produce the same valve output as the valve is slowly cycledbetween plus and minus rated current.FIGURE 1CHANGE IN RATED FLOW WITH PRESSUREThreshold – The increment of input current required to producea change in valve output.Valve threshold is usually measured as thecurrent increment required to change from an increasing output toa decreasing output, expressed as percent of rated current.200100ID0 PS100IDm@SpPg060100Dm @ 00 PSIpg0140
Moog Inc.was the founded in 1951 by William C.Moog, inventor of the Electrohydraulic Servovalve
Siemens Electrohydraulic actuators for valves CM1N4566E Building Technologies 08.06.2010 Third-party valves with strokes between 12 40 mm can be motorized, provided they are «closed with the de-energized» fail-safe mechanism and provided that the necessary mechanical coupling is available. For SKC32. and SKC82. actuators the Y1
4 Section Pages Argus Atomac Automax Deutsche Audco Durco McCANNA 3-Piece Ball Valves 6 - 9 One Piece Threaded Valves 9 Flanged Ball Valves 10 - 14 One-Piece Butt Weld Valves 15 Top Entry Valves 15 Butterfly Valves 16 Non-lubricated Plug Valves 17 - 19 Lined Valves and Accessories 20 - 24 Check Valves 25 Gate Valves 25 Rotary Contro
MANUAL VALVES PVC-U The PVC-U manual valves line consists of a comprehensive range of ball valves, butterfly valves, diaphragm valves, check valves, sediment strainers, air release valves, foot valves and angle seat valves for use in the construction of process and service lines fo
FC & FL valves, WKM type valves, Shaffer type valves, Flocon type valves, check valves, cup testers, pulsation dampeners: www.mcmoiltools.com o’Drill / mCm Centrifugal pumps, cyclone pump, skid packages, gate valves, shear relief valves, reset relief valves, float valves, butterfly valves, plug
1 subject page bronze gate valves 6-17 bronze globe valves 18-25 bronze swing check valves 26-29 engineering data 58-68 iron swing check valves 39-40 iron gate valves 31-36 iron globe valves 37-38 the wm.powell company—profile 2-3 terms and conditions 69-71 iron ul and fm gate valves 42-51 iron ul and fm check valves 52-55 figure number cross comparison table 57 bronze and iron valve index 4
1. Control Valves for General Service 2. Control Valves for Severe Service, Including 'OMEGA' Trim Valve 3. Steam Let-down Control Valves 4. Anti-surge Valves 5. Control Valves with Butterfly, Ball, Segment Ball (V-Notch, Eccentric) 6. Control Choke Valves 7. Pressure Regulating Valves 8. Retrofit Kit(Trim, Actuator, Instruments) for Up-grade
50 80 100 150 200 250 300 350 400 450 500 550 600 . (API 624/ ISO 15848), cryogenic valves (-196 C) and valves in exotic metallurgies. Valves in other sizes and ASME classes available on demand. 4 Compliance Standards Parameter Standard Design Gate Valves API 603, ASME B16.34 Globe Valves ASME B16.34 Check Valves ASME B16.34 Ends Face-to-face/ End-to-end Dimensions ASME B16.10 End Flange .
1 P a g e An Idiot's Guide to Lust Epidemic by cooperlee77 This guide follows the Normal version but {Hard} options are included. Maps are included and pictures of locations can be found at the end of this
