Parker - Series PVP Variable Volume Piston Pumps - Siebert ...

Catalog HY28-2662-CD/USControl OptionsHi/Lo Power Control (HLM)(Available with PVP41 and PVP48 Only)The graph shown below represents the flow-pressurecharacteristics of a Hi-Lo control for PVP pumps. Thereare up to four separate adjustments that must be madewith the pump controls to get a particular setting, all ofwhich influence the shape of the curve. To get theproper settings, it is very important that all pertinentinformation is supplied with each Hi-Lo pump ordered.As you can see from the graph below, there are twopeak power points. Our intention is to have the samemagnitude of power required for both peaks. Of coursemany combination of settings are possible butspecification of the settings becomes very difficult. Tomake factory settings, we need to know the requiredflow (applicable if pump has a maximum volumestop), the shaft speed, the required Power limit, andthe compensation pressure. Based on theserequirements, we will adjust the low pressure set pointand the reduced flow set point of the Hi-Lo control tobest match the requested parameters called out onthe order.Important note: As with power controls, not allcombinations of flow, power, pressure, etc. are possible.The first rule is that the settings must conceptually beachievable (i.e. power out is ALWAYS less than powerin). Be careful in assuming efficiencies when estimatingthe Out/In relationship, since a pump operating at lowVariable Volume Piston PumpsSeries PVPpressure or in a de-stroked condition can have a muchlower overall efficiency than expected. The other thingto keep in mind is that the pump will require the peakpower at only two points. All other operating pressureswill require less than maximum power and thereforethe pump will deliver less hydraulic power in theappropriate ratio based on the actual pump efficiencyat those conditions.Typical Hi-Lo ControlFlow/Pressure CharacteristicsOutlet FlowLOW FLOW SETTINGADJUSTMENTCONSTANT POWER CURVELOW PRESSUREADJUSTMENTSystem PressureMAX. PSIADJUSTPVP SERIESPRESSURE & POWER COMPENSATORCONTROL OPTION "HLM"OUTLET PORTREMOTE PORTLOW PHIGH PINLET PORTCASE DRAINPORTSERVO PISTONOUTLETPORTINLETPORTPISTONhpm102-1.p65, lw, jkFIGURE 711Parker Hannifin CorporationHydraulic Pump DivisionMarysville, Ohio USA