Danfoss H1P 280

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The schematic above shows the function of a hydrostatic transmission using an H1 axial variable displacement pump with electric

proportional displacement control (EDC) and an H1 bent axis variable displacement motor with electric proportional control (L*) and

integrated loop flushing device.

Service Manual

H1P 069—H1P 280 Axial Piston Single Pumps

Introduction

Danfoss | January 2021 AX152886482551en-000601 | 11

Main Page

Table of Contents3
Hydrostatics Servicing Overview5
General Servicing Instructions5
Safety Precautions6
Symbols Used in Danfoss Literature7
General Description of H1 Family Hydrostatic Pumps7
Design8
H1 Single Pumps Closed Circuit Pictorial Diagram10
H1 System Schematic10
Operation12
Pressure Limiter Valves12
Pressure Limiter Sectional View12
High Pressure Relief Valve (HPRV) and Charge Check Valve12
Hprv/Charge Check Valve Sectional View13
Charge Pressure Relief Valve (CPRV)13
Bypass Function13
System Schematic for Single Pump14
Electrical Displacement Control (EDC)14
EDC Operation15
Manual Override (MOR)16
Manual Displacement Control (MDC)16
MDC Operation17
MDC Torque18
Neutral Start Switch (NSS)18
Case Gauge Port M1418
Operating Parameters19
Input Speed19
System Pressure19
Servo Pressure20
Charge Pressure20
Charge Pump Inlet Pressure20
Case Pressure20
External Shaft Seal Pressure21
Temperature21
Viscosity21
Technical Specifications22
H1 Pumps General Specification22
H1P 069-280 Physical Properties22
Fluid Specification23
Fluid and Filter Maintenance Recommendations24
Filtration System24
Pressure Measurements26
Port Locations and Gauge Installation26
H1P Ports Information26
Initial Startup Procedures28
Unintended Machine Movement28
Start-Up Procedure28
Troubleshooting30
High Inlet Vacuum30
Unintended Machine Movement30
Fluid under Pressure30
Electrical Troubleshooting30
Integral Filter Bypass30
Neutral Difficult or Impossible to Find31
Transmission Operates Normally in One Direction Only31
System Operating Hot31
System will Not Operate in Either Direction32
System Noise or Vibration32
Sluggish System Response32
Adjustments34
Standard Procedures34
Charge Pressure Relief Valve Adjustments34
Pressure Limiter Adjustment35
Engaging the Bypass Function37
Displacement Limiter Adjustment for Single Pumps37
Control Neutral Adjustment38
Mechanical Neutral Adjustment40
Unintended Machine Movement40
Minor Repair43
Control Solenoids Repair45
MDC Control Repair46
Angle Sensor on EDC Repair49
EDC with Angle Sensor Repair50
Automotive Control Repair51
Shaft, Seal and Bearing Repair55
External Filter Repair57
Filter Bypass Valve and Switch Repair58
Charge Pump Repair (Removable Auxiliary Pad)58
Charge Pump Repair (Integrated Auxiliary Pad)59
High Pressure Relief Valve Repair61
Charge Pressure Relief Valve Repair62
Pressure Limiter Repair62
Torque Chart64
Fasteners and Plugs64
Fastener Size and Torque Chart65
Plug Size and Torque Chart66

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