BRAYBALLVALVETECHNICALBULLETINNO.1006
V-CONTROLBALLVALVESELECTIONGUIDE
V-CONTROLBALLVALVESELECTION
Thecontrolvalveisthemostimportantsingleelementinanyfluidhandlingsystem.Thisisbecauseit
regulatestheflowofafluidinthesystem.Theautomatedvalveisoftenreferredtoasthefinalcontrol
element,andiscertainlythemostimportantpartofanypipingsystem.Thesystemwillnotoperateat
anefficientlevelwithoutaproperlysizedvalve.Forvalvesthataretoooversized,theresultsarepoor
controllabilityofthesystemandmaycausethevalvetohuntorcycle.Valvesthataretooundersized
willrequirealargerpressuredropacrossthevalvetomaintainadequateflowandmaynotprovide
therequiredcapacity.Undersizingavalvecancausethepumptoworkharderandmakethevalve
susceptibletotheeffectsofcavitation.
Toproperlyselectacontrolvalve,itishelpfultohaveageneralknowledgeoffluidmechanicsandofthe
componentsofthepipingsystem.ToselectaV-PortorRoundPortcontrolvalveformodulatingservice,
youwillneedtohavethefollowingcustomersuppliedinformation.
Generaldescriptionoftheapplication
Media
InletPressure
Temperature
FlowRate(maximum,normal,minimum)
PressureDroporOutletPressure(maximum,normal,minimum)
LineSize
SpecificGravityofMedia
CriticalPressureofMedia
Thekeytorememberisthatvalvesizingisnotanexactscienceandthatoftenyoumustselectfromthe
bestoptions.
CALCULATETHEVALVESIZE
Withtheaboveinformation,thefollowingstepsareusedtocorrectlysizeavalveinapipingsystem.
1.CvvalueisobtainedbyusingtheappropriateANSI/ISA–75.01.01flowsizingformulaorcomputer
aidedflowcontrolsizingprogramthatisbasedontheseformulas.
2.CavitationischeckedbyusingtheFLvalue(LiquidPressureRecoveryFactor),andtheexpansion
factorneededforcompressible