Service Manual

MowCircuit
Thetandemgearpumpisdirectlycoupledtothepiston(traction)pump.The
frontgearpumpsection(P2)suppliesuidowtothemowermanifoldandtothe
cuttingreelmotors.Thegearpumptakesitssuctiondirectlyfromthehydraulic
tank.
Mow(machineswithoutbacklap)
Withtheenginerunningandthefunctioncontrolandjoystickleverspositioned
sothereelswillnotturn;refertothetractionunitOperator’sManual,solenoid
reliefvalve(S1)inthemowermanifoldisde-energized.Thede-energized(S1)
by-passesowfromthefrontgearpumpsection(P2)tothehydrauliclterand
backtothetank.Additionally,thepilotoperatedreliefvalve(PRV)inthemower
manifoldwillremainseatedtopreventthereelmotors(andreels)fromrotating.
Withtheenginerunningandthefunctioncontrolandjoystickleverspositionedto
lowerandengagethecuttingunits;refertothetractionunitOperator’sManual,
solenoidvalve(S1)isenergizedtodirectuidowtowardthereelmotors;refer
toFigure24.Mowcircuitpressurewillcausethepilotpistonunderthepilot
operatedreliefvalve(PRV)toshiftandopenthevalve.Theshiftedreliefvalve
allowsuidtoexitthereelmotorsandreturntothetankthroughthemower
manifold,hydrauliclterandoptionalhydraulicuidcooler(ifequipped).Thereel
motorsareconnectedinseries.Fluidowsthroughtheleftfrontreelmotor,then
therightfrontreelmotorandthenthecenterreelmotortoturnthereelmotorsin
themowdirection.Maximumcircuitpressureislimitedto20,684kPa(3000psi)
byreliefvalve(R1)whichislocatedinthemowermanifold.
HydraulicSystem:HydraulicFlowDiagrams
Page4–20
Greensmaster3120
17230SLRevD