Farr HD8625 - Valve Operation; Illustration 2.G.1: Tong Rotation Control Valve

Technical Manual
hD8625 8-
5
/
8
” 35K Tong
2.15
IMPROPERLY SECURED HYDRAULIC CONNECTIONS WILL INTERRUPT HYDRAULIC FLUID FLOW, AND
COULD RESULT IN THE FOLLOWING FAILURES:
•
Arestrictioninthepressuresupplyhosewillresultinhighpressurewithinthepowerunithydraulicsystem,which
willactivatethehydraulicgovernorandincreasetheenginespeedtoashighasmaximumRPM.
• Arestrictioninthereturnlinewillresultinhighpressurewithinthepowerunitandthetonghydraulicsystem,caus-
ingenginespeedsashighasmaximumRPM,andpossiblefailureofthemotorseal.
Followinginspectionofthehoses,starttheengineandallowittoidleuntilwarm.Allowhydraulicfluidtocirculateforapproximately10
minutes,thenslowlyclosetheBypassValvetoallowhydraulicfluidtocirculatethroughthehosesandtothetong(circulatingpres-
sureshouldnotexceed200psi).Placethetonggearshifterinlowgearandrotatethetongslowlyforwardandthenreversewiththe
throttlevalvecontrollever.Oncethishasbeendoneandthepropersizejawshavebeeninstalled,thetongisthenreadytorunpipe.
2. Valve Operation
4-wayproportionalvalvescontroloperationofhydraulicdevicesonthetongassemblysuchashydraulicmotorsandcylinders.When
anyonevalveis“centered”orinthedetentposition,thereisnohydraulicoutputfromthevalve.Whenthevalveispushedforward
thereisaneffect,andwhenthevalveispulledback,thereisanoppositeeffect.Thesevalvesfeatureproportionalcontrol,which
meansthatfurtherextensionofthevalvehandle(therebyfurtheropeningthevalveorifice)resultsinproportionallyhigherhydraulic
outputtothecontrolleddevice.
Thefollowingillustrationdemonstratesthetypeandeffectofthehydraulicvalveswithwhichthistongismaybeequipped.
TONGMOTOR
Thisisaproportionalvalve.Pushingthevalvehandleforwardwillcausethetongmotortorotateinaclockwisedirection(asseen
fromthetopofthetong).Thisisthedesireddirectionofrotationformakingupajoint.Pullingthevalvehandleintheoppositedirec-
tionresultsincounter-clockwiserotation,whichisthedesireddirectionofrotationforbreakingoutajoint.
IllustratIon 2.g.1: tong rotatIon Control valve
Ensureadequatelubeoilandhydraulicoillevelsbeforestartingengine.Usestartupproceduresasrecommendedbythepowerunit
engineoperator’smanual.OpentheBypassValveonthehydraulicsystem,andinspectallpressureandreturnlinehoseconnections
toensurecorrectandsecureinstallation.
seTup & operaTion