TM 5-3895-373-20After the hydraulic oil exits the stack valve, the pressureis reduced by a 900 psi (6200 kPa) relief valve. Theexcess hydraulic oil is sent to the return manifold andback to the hydraulic reservoir. The reduced pressurefluid is passed through a check valve.The 900 psi (6200 kPa) hydraulic oil charges a hydraulicaccumulator and maintains pressure to the tracktensioning cylinders. When one or both tracks encounteran obstacle, the track tensioning cylinder is compressed,sending pressure pulsation’s into the track tensioningsystem. The pressure pulsation causes the check valvein the inlet of the track tensioning system to seat. Thisprevents the pressure pulsation from traveling to the restof the hydraulic system. If the pulsation is small, it will beabsorbed by the hydraulic accumulator. Larger pulses,which increase system pressure beyond 1800 psi (12400 kPa), cause a relief valve to lift and vent excesspressure to the return manifold.1.21.ELECTRICALLYCONTROLLEDHYDRAULICCIRCUITS.The paving machine uses electrically controlled hydrauliccircuits for all hydraulic functions. Hydraulic pressure issupplied by two auxiliary pumps and an auxiliary vibrationpump.Hydraulic functions controlled from the operator switchpanel are:1) Screed lift2) Auger/conveyor drive3) Extension screed positioning4) Screed vibrator drive5) Hopper wing liftHydraulic functions controlled from the screed controlpanels are:1) Auger/conveyor drive2) Tow point lift3) Extension screed positioningAuxiliary pumps and auxiliary vibration pump drawhydraulic oil from a common hydraulic reservoir. Pumpoutput is routed through 50/50 flow dividers, pressurerelief valves and flow control and solenoid valves. Theflow control and solenoid valves control the speed ofhydraulic cylinders and motors. Hydraulic oil return isrouted to the return manifold. From the return manifold,the oil is forced through a hydraulic oil cooler and areturn filter before returning to the hydraulic reservoir.Each individual function is explained in the followingparagraphs.1-41
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