Introduction
Hydrostatics Servicing Overview................................................................................................................................................5
General Servicing Instructions.....................................................................................................................................................5
Safety Precautions............................................................................................................................................................................6
Symbols used in Danfoss literature............................................................................................................................................7
General description of H1 family hydrostatic pumps..........................................................................................................7
Design...................................................................................................................................................................................................8
H1 Single Pumps Closed Circuit Pictorial Diagram............................................................................................................10
H1 system schematic....................................................................................................................................................................10
Operation
Pressure Limiter Valves................................................................................................................................................................ 12
Pressure Limiter Sectional View.......................................................................................................................................... 12
High Pressure Relief Valve (HPRV) and Charge Check Valve..........................................................................................12
HPRV/Charge Check Valve Sectional View......................................................................................................................13
Charge Pressure Relief Valve (CPRV)....................................................................................................................................... 13
Bypass Function..............................................................................................................................................................................13
System Schematic for Single Pump................................................................................................................................... 14
Electrical Displacement Control (EDC)...................................................................................................................................14
EDC Operation...........................................................................................................................................................................15
Manual Override (MOR)............................................................................................................................................................... 16
Manual Displacement Control (MDC) ....................................................................................................................................16
MDC Operation..........................................................................................................................................................................17
MDC Torque................................................................................................................................................................................18
Neutral Start Switch (NSS)..................................................................................................................................................... 18
Case Gauge Port M14..............................................................................................................................................................18
Operating Parameters
Input Speed......................................................................................................................................................................................19
System Pressure..............................................................................................................................................................................19
Servo Pressure.................................................................................................................................................................................20
Charge Pressure..............................................................................................................................................................................20
Charge Pump Inlet Pressure.......................................................................................................................................................20
Case Pressure...................................................................................................................................................................................20
External Shaft Seal Pressure.......................................................................................................................................................21
Temperature....................................................................................................................................................................................21
Viscosity.............................................................................................................................................................................................21
Technical Specifications
H1 Pumps General Specification..............................................................................................................................................22
H1P 069—280 Physical Properties...........................................................................................................................................22
Fluid Specification......................................................................................................................................................................... 23
Fluid and Filter Maintenance Recommendations
Filtration System.............................................................................................................................................................................24
Pressure Measurements
Port Locations and Gauge Installation...................................................................................................................................26
H1P Ports Information.............................................................................................................................................................26
Initial Startup Procedures
Unintended Machine Movement.............................................................................................................................................28
Start-Up Procedure........................................................................................................................................................................28
Troubleshooting
High Inlet Vacuum.........................................................................................................................................................................30
Unintended Machine Movement....................................................................................................................................... 30
Fluid Under Pressure............................................................................................................................................................... 30
Electrical Troubleshooting..........................................................................................................................................................30
Integral Filter Bypass.....................................................................................................................................................................30
Neutral Difficult or Impossible to Find................................................................................................................................... 31
Transmission Operates Normally in One Direction Only.................................................................................................31
Service Manual
H1P 069—H1P 280 Axial Piston Single Pumps
Contents
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Danfoss | January 2021 AX152886482551en-000601 | 3
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