Danfoss LDU21C Service Manual page 3

Service Manual
LDU21C Closed Circuit Axial Piston Transmission
Contents
Introduction
General Description
Operation
Operating Parameters
Technical Specifications
Fluid and Filter Maintenance
Pressure Measurements
Initial Startup Procedure
Troubleshooting
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Danfoss | April 2025
Overview..............................................................................................................................................................................................5
Warranty.............................................................................................................................................................................................. 5
General Instructions........................................................................................................................................................................ 5
Remove the unit.......................................................................................................................................................................... 5
Keep it clean..................................................................................................................................................................................5
Lubricate moving parts.............................................................................................................................................................5
Replace all O-rings and gaskets............................................................................................................................................. 5
Secure the unit............................................................................................................................................................................. 5
Safety Precautions............................................................................................................................................................................6
Unintended machine movement..........................................................................................................................................6
Flammable cleaning solvents................................................................................................................................................. 6
Fluid under pressure.................................................................................................................................................................. 6
Personal safety............................................................................................................................................................................. 6
Hazardous material.................................................................................................................................................................... 6
Symbols Used in Danfoss Literature..........................................................................................................................................7
Basic Design........................................................................................................................................................................................8
Key Features....................................................................................................................................................................................... 8
Typical Applications........................................................................................................................................................................ 8
Schematic Diagram..........................................................................................................................................................................9
Check / High Pressure Relief Valve...........................................................................................................................................10
CPRV (Charge Pressure Relief Valve) ...................................................................................................................................... 10
Control............................................................................................................................................................................................... 11
Direct Displacement Control................................................................................................................................................11
Control Handle Requirements............................................................................................................................................. 11
Overview........................................................................................................................................................................................... 13
Input Speed......................................................................................................................................................................................13
System Pressure..............................................................................................................................................................................13
Input Power......................................................................................................................................................................................13
Charge Pressure..............................................................................................................................................................................13
Case Pressure...................................................................................................................................................................................14
Viscosity.............................................................................................................................................................................................14
Temperature.................................................................................................................................................................................... 14
General Specifications..................................................................................................................................................................15
Physical Properties.........................................................................................................................................................................15
Operation Parameters.................................................................................................................................................................. 15
Fluid Specifications....................................................................................................................................................................... 15
Fluid and Filter Recommendations......................................................................................................................................... 17
Port Locations and Gauge Installation................................................................................................................................... 18
Startup Procedure..........................................................................................................................................................................19
Overview........................................................................................................................................................................................... 20
System Operating Hot..................................................................................................................................................................20
Transmission Operates Normally in One Direction Only.................................................................................................20
System will not Operate in Either Direction......................................................................................................................... 20
System Noise or Vibration...........................................................................................................................................................20
Sluggish System Response......................................................................................................................................................... 21
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