flow compensator pressure exceeds 15 bar [210 PSI].Use a gauge that is dampened or glycerine filled. Withthe gauge installed and the load sensing valve in theclosed position, start the systemand observe the flowcompensator pressure. If thereading is other than 13 to 15bar [190 to 210 PSI],readjustment of the flowcompensator may be required.

3) To change setting, remove the adjustment screw coverfrom the flow compensator valve. Loosen the flowcompensator adjustment screw lock nut with a 7/16 inchopen end wrench.

4) With the system running andsystem control valve in theclosed position, use a 1/8 inchAllen wrench to turn theadjustment screw to the properor desired flow compensatedpressure. Clockwise rotation of the adjustment screw willincrease the pressure setting and counter-clockwiserotation will decrease the pressure setting. Important: Anyreadjustments exceeding the 31 bar [450 PSI] maximumfactory setting must have priorapproval from Eaton HydraulicDivision or the warranty of thepump will be void.

5) After adjustments arecomplete, hold the adjustmentscrew stationary and tightenthe locknut to (torque 8 to 11Nm [6 to 8 lbfft]).

6) After turning system off, installthe compensator screw coverand check pressurecompensator settings.

This procedure is used to adjust the compensator on theEaton model 70122, 70422, 70423, and 70523compensated controlled piston pumps.

Model 70422

Left hand rotation shown

1) Pump model 70122 incorporates two gauge ports. Themodels 70422 and 70423 may or may not have gaugeports, its an optional feature. The pump model 70523does not incorporate gauge ports.Gauge port size is 3/8-24 UNF-2B. One gauge port is tocheck system pressure and the other to check inletvacuum. To check system pressure on models withoutgauge ports a tee fitting must be installed in the pumpsoutlet port. Always adjust flow spool first and thanpressure spool.

Gauge Port

Adjustment end of compensator valve Pressure SpoolTo check or readjust flow compensator valve setting:2) Install pressure gauge into gaugeport using a 1/2 inch open end wrenchand remove the plug furthest awayfrom adjustment end of thecompensator valve. A recommendedpressure gauge for checking the flowcompensator is 0 to 21 bar or 0 to 41bar [0 to 300 PSI or 0 to 600 PSI] if the

May, 1997EatonMedium Duty Piston Pump

Pressure or Pressure-Flow CompensatorControl Adjustment Procedures

Flow Spool

Flow SignalLine Port

To check or readjust pressure compensator valvesetting:7) Install pressure gauge into gauge port use a 1/2inch open end wrench and remove the plug furthestaway from adjustment end of thecompensator valve.

8) Install a pressure gauge into thegauge port. A recommendedpressure gauge for checkingsystem pressure is 0 - 670 bar [0 -10,000 PSI]. The gauge usedshould also be dampened orglycerine filled. With the gaugeinstalled, actuate the directionalcontrol valve so that the dischargeof the pump is blocked by thesystem load, observe the readingon the pressure gauge. If the reading is other than the207 to 214 bar [3000 to 3100 PSI] maximum factorysetting, readjustment of the pressure compensatorvalve may be necessary. A lower setting for specialapplications may be possible and permissible.

9) To change the compensatorsetting, you must first use asmall screwdriver or similartool to remove the adjustmentscrew cover from the pressurecompensator cap. Note: Thepresent covers are plastic andif carefully removed may bereused. Prior caps were made of aluminum and in mostcases when removed are not reusable.

10) To readjust the pressurecompensator you must firstuse a 7/16 inch open endwrench to loosen thecompensator adjustment screwlock nut.

11) Next start the pump andactuate the directional control valve so that the dischargeof the pump is blocked by the system load. Observe thepressure gauge and use a 1/8 inch Allen wrench andslowly turn the adjustment screw to obtain the desiredpressure setting. Clockwise rotation of the adjustmentscrew will increase the pressure setting and counter-clockwise rotation will decrease the pressure setting.Important: Any readjustments exceeding the 207 to 214bar [3000 to 3100 PSI] maximum factory setting musthave prior approval from Eaton Hydraulic Division or thewarranty of the pump will be void.

12) After readjustment of thepressure compensator iscompleted, hold theadjustment screw stationaryand tighten the locknut(Torque 8 to 11 Nm [6 to 8lbfft]). Remove the load andinstall the compensatorscrew cover. Remove pressuregauge and replace the gaugeport (torque 8 to 11 Nm [6 to8 lbfft]).

BA

C

B

A

Test Circuit Set Up forPressure-Flow Compensators1) Do not connect the flow signal line to the unit andleave the flow compensator signal port open.For 1.16, 2.32, and 2.77in3/r pumps: Block flow frompump using shut - off valve B and set flowcompensator to produce pressure range specified atpoint A.For 4.21 in3/r pumps: Set flow compensator for rangespecified at an output flow of 5-7 gal/min.2) Connect flow compensator port downstream ofshut-off valve B with the flow signal line.3) Open shut-off valve B. Block flow from pumpusing shut-off valve C which is downstream from theflow signal line. Set pressure compensator to producea pressure range at point A as specified.Note: For 1.16 in3/r pumps, and 2.32 in3/r pumps withnon A-pad backplate, add the inlet pressure to thepressure setting tolerance.

Test Circuit Set Up forPressure Compensators1) Block flow from pump using shut-off valve B. Setpressure compensator to produce a pressure range (atZero flow).Note: For 1.16 in3/r pumps, add the inlet pressure tothe pressure compensator setting tolerance. For allother units, add the case pressure to the pressuresetting tolerance.

Low Pressure Standby

Pressure FlowCompensator

Spool

Orifice

High PressureCompensator

Spool

High Pressure Standby

Operation of SystemHigh Pressure Standby

Eventually, the piston in the cylinder (actuator) reaches the end ofits travel. When it does, flow past the lands of the directional controlspool stops. Pressure equalizes on both sides of the directional controlspool and pressure also equalizes on both ends of the pressure-flowcompensator spool. The 200 PSI spring forces the pressure flowcompensator spool all the way to the left. When pressure reaches 3000PSI, the high pressure compensator spool moves to the right and directsoil to the camplate control piston. The piston moves the camplate tonear zero angle and the pump stops producing flow. This is called thehigh pressure standby mode.

Low Pressure StandbyHere the spool in the directional control valve has been returned to

neutral. The pressure that was directed to the right end of the pressure-flow compensator spool is now drained through the orifice in the controlvalve. The pump will stroke back to near zero displacement andpractically no flow is produced. The 200 PSI acting on the left end of thepressure-flow compensator spool will be offset by the 200 PSI springacting on the right end of the spool. The spool will modulate back andforth to maintain 200 PSI in the discharge circuit of the pump.

2008 Eaton CorporationAll Rights ReservedPrinted in USADocument No. E-PUPI-TS008-ESupersedes 02-604November 2008

EatonFluid Power GroupHydraulics Business USA14615 Lone Oak RoadEden Prairie, MN 55344USATel: 952-937-9800Fax: 952-294-7722www.eaton.com/hydraulics

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