NIDHIN MANOHARSIZING AND SELECTION OF ACTUATORS FOR VALVESDifferent types of actuatorsAdvantages & DisadvantagesSelection of ActuatorSizing of ActuatorPerformance Tests on ActuatorsForce / Torque Demanded by valvesS.Rammohan, CRE, Fluid Control Research InstituteACTAT!" #A$#% ACTAT!"A powered valve operator used to open or close a valve, energised manually or by pneumatic, electric or hydraulic power source.BASICFUNCI!NS "rovide enough thrust# tor$ue to operate the valve %old the valve gate # plug # disc # ball in re$uired position !perate the valve through its &ull travel at rated speed "rovide &ail sa&e mode in the event o& power &ailure "revent e'cessive &orces under un&avorable conditions #A$#% ACTAT!" ActuatorManual Electric Pneumatic HydraulicLeverHand wheelGear boxMotorSolenoidDiaphragmPistonam!"aneLinear #otary$ail sa%e$ire sa%eP&%'AT(C ACTAT!"Uses compressed air as the source of eer!"Actuator o#p force proportioa$ to air pressureCapacit" decided %"Operatio timeForce demadedSi&e of pipi! re'uired to de$i(er airDiaphra!m)isto CamActuator types & operationAs air pressure increases, the valve opening canbecomes larger or smallerAir-to-open (normally closed, fail close): as the air P increases, the valve opening gets largerAir-to-close (normally open, fail open): as the air P increases, the valve opening gets smallerADVANTAGES Compressed air ecoomica$ ad co(eiet for use Se$f $oc*i! ca %e achie(ed %" a spri! At e$e(ated temperature assist (a$(e operatio E+haust air ca %e (eted to atmosphereDIS ADVANTAGESNo hammer %$o, to useat the (a$(eLimitatio for ho$di! at re'uired positio-ateria$ of costructio is (u$era%$e for heat-aua$ pro(isio create hi!h $oc* i force ,hi$e dec$utchi!Suscepti%$e to sei&ure due to corrosio . dirtAir cosumptio (er" hi!hP&%'AT(C ACTAT!"Comprises an electric motor and a gear arrangementElectrical limit switches or!ue sensor %lectric Actuators"elf loc#ing features- hreaded spindle and nut $ hread of the lead screw should be self loc#ing%anual &peration- 'ormally Provided with hand wheel lever operated clutch(uty cycle%otor will be heated when put in operation)solation- *alve operation +ew times a day,egulating - *alve operation -. - /. starts0hr %odulating - *alve operation /.. - 12.. 0hrADVANTAGES/i!h rotatioa$ speed so hi!h *ietic eer!" Good positioi! accurac" 0 Reductio !eari!Eas" iterfaci! ,ith computersNo dirt or moistureOperate istataeous$" o(er !reat distacesComp$ete s"stem ca %e tested ,#o mo(i! (a$(e positioSe'ueci! of (a$(e operatio is eas"DIS ADVANTAGESVu$era%i$it" to hi!h temperatureVu$era%i$it" to moisture)rec$udes mechaica$ meas of stori! eer!" i the e(et of po,er fai$ure%lectric Actuators)ydraulic ActuatorsUsed for hi!h tor'ue # thrust app$icatiosDifferet mechaisms emp$o"ed Rac* ad piio/"drau$ic motor)isto ad c"$iderRotar" pistoSimi$ar to peumatic actuatioNeeds eer!" source 0 /"drau$ic po,er pac*Tor'ue output deped o f$uid pressureGreater f$e+i%i$it" of eer!" source1ide$" used ,ith the fo$$o,i!Lar!e s$idi! !ate (a$(es Lar!e !$o%e (a$(es)estoc* (a$(esAdvantages #ery *ig* operating torque suitable for large sized valvesFail safe operation is easy + )ydraulic pressure stored(ncompressible+ easy for *ydraulic loc,-ood positional accuracy)ydraulic system is compactDisadvantages Piping pressure drop limits distance of *ydraulic control)ydraulic system is costly&o ,inetic energy for *ammer blo. unseating)ig* t*ermal e/pansion rate + t*ermal insulation requiredClose mac*ining tolerances +susceptible to malfunction)ydraulic ActuatorsDou%$e acti! or ,ith spri! returAir pressures upto 2 %ar o$"Fast respose to si!a$ cha!esStro*e $imited to 345 0 655 mm1ide$" used ,ith cotro$ (a$(esDiap*ragm ActuatorA piece of Fa%ric reiforced e$astomer sad,iched %et,ee casi! coected to a $iear shaftPiston ActuatorA cylinder and a piston .it* an ! ringDouble acting or .it* spring returnAir pressure upto 01 barDifferent mec*anisms to convert linear motion to rotary motionSingle or Double piston(ntegral rac, drivers t*e pinionAvailable for 21 or 0314 rotationTorque output is constantSuitable for plug valves"ac, & PinionDouble piston by a spacer .it* a cam and s*aft bet.een t*em"otational style determined by cam profile'ec*anical stop are not requiredTorque varies .it* profileCam 05Calculation of force requirement 65Selection of Po.er source 75Selection of mec*anism 85Sizing of actuator & components 95Selection of accessories5S%$%CT(!& !F #A$#% ACTAT!"Actuator Selection C*art Sl5&o5 Parameter0 6 7 8 9 0 #alve size and Type :: ::6 Pressure Drop :: ::7 !perating Condition :: :: ::8 Flo. medium :: ::9 Sealing ::; Fire safety :: ::< Fail safe !peration :: = ::3 !perating Temperature ::2 Cyclic Speed & rate :: :: ::01 Stem !rientation ::00Aging ::06 "esponse Time :: :: ::07 Type of Control :: :: ::05 Calculation of force requirement65 Selection of Po.er source75Selection of mec*anism85Sizing of actuator & components95Selection of accessories5Actuator Selection C*art Sl5&o5 Parameter0 6 7 8 9 0 #alve size and Type :: ::6 Pressure Drop :: ::7 !perating Condition :: :: ::8 Flo. medium :: ::9 Sealing ::; Fire safety :: ::< Fail safe !peration :: = ::3 !perating Temperature ::2 Cyclic Speed & rate :: :: ::01 Stem !rientation ::00Aging ::06 "esponse Time :: :: ::07 Type of Control :: :: ::05 Calculation of force requirement65 Selection of Po.er source75Selection of mec*anism85Sizing of actuator & components95Selection of accessories5Actuator SelectionParameters to be considered .*ile selection05#alve Type and size 'he tor(ue ) %orce re(uirement o% the valve65Pressure Drop 'or(ue ) axial %orce & %unction DP75Services & operating condition*hether +n)+%%! #egulating! Modulating duty #egulating duty & based on ,rea- away tor(ue$or part turn! actuator should counterbalancethe %orce due to unbalance

85 Flo. medium Lubrication property o% operating %luid *hether %luid is slurry or contain solid particles Erode the sealing sur%aces *ear and tear depends on the operating %luid Actuator output decreases with time which needsadditional capacity %or actuator95 Sealing + >i directional$orce depends on %low past the valve disc. /01 in case o% ,$" i% seat is placed down streamLess %orce i% the %low is %rom bottom o% discActuator Selection;5 Fire safety$ire sa%ety needs additional metal seat#e(uirement is /0 & 200 1 more normal tor(ue 9;2($(TDDrift08 psi input pressure for 0;3 *ours%ac* 68 *oursG position for 7 & 09 psi to be measuredAccelerated life testSine .ave input .it* mid point at 2 psi and pea, to pac, of ; psi A; + 06 psi@Frequency of 01 cycles per minute 09111 cycles of operationPosition corresponding to 7 & 09 psi to be c*ec,ed before and after t*e testPneumatic Positioner TestingStandard >S 8090DD&A'(C "%SP!&S% T%ST(&-Standard (SA S 6;T.o types of inputa@ Sine .ave + 'id point at arit*metic mean of actualinput Pea, to pea, + 01F of actual inputSignal frequency 15110 + 61 )z'inimum 61 points in 7 decade Amplitude of input and output signalP*ase relations*ip of i/p and o/p signalAt initial frequencyG o/p is same as steady state value .it* same input and no p*ase differenceAt ma/imum frequencyGo/p is 01F of same signal at steady state or t*e p*ase lag is more t*an 7114(nput signal Amplitude0db from 15110 + 61 )z DD&A'(C "%SP!&S% T%ST(&-Standard (SA S 6; DD&A'(C "%SP!&S% T%ST(&-Standard (SA S 6;P*ase s*iftI94DriftI9F of full span in 8 *oursProcedure >lan, "un Static Calibration Actual Testing+ut put 'agnitude Plot + Semi log +Signal freq5 #s -ain P*ase Plot+ Semi log +Signal Freq5 #s P*ase lagb@Step input(nput 01F stepor 21F step of mean!utput 'agnitude Plot + Time #s input signalTime #s output signal