Table of Contents
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Service Manual
Series T90 Axial Piston Pumps
Contents
Introduction
©
Danfoss | March 2020
Overview..............................................................................................................................................................................................5
Warranty.............................................................................................................................................................................................. 5
General instructions........................................................................................................................................................................ 5
Remove the unit.......................................................................................................................................................................... 5
Replace all O-rings and gaskets............................................................................................................................................. 5
Safety Precautions............................................................................................................................................................................6
Unintended Machine Movement..........................................................................................................................................6
Flammable Cleaning Solvents................................................................................................................................................6
Fluid Under Pressure..................................................................................................................................................................6
Personal Safety.............................................................................................................................................................................6
Symbols used in Danfoss literature............................................................................................................................................7
Design...................................................................................................................................................................................................7
The system circuit.............................................................................................................................................................................9
The basic closed circuit............................................................................................................................................................. 9
Case drain and heat exchanger..............................................................................................................................................9
T90 charge pump operation...................................................................................................................................................... 12
T90 charge relief valve operation.............................................................................................................................................12
T90 multi-function valve operation.........................................................................................................................................12
T90 pressure limiter/high pressure relief valve operation.............................................................................................. 13
T90 system check valve operation...........................................................................................................................................13
T90 bypass valves operation......................................................................................................................................................13
T90 speed sensor operation.......................................................................................................................................................14
T90 filtration options.................................................................................................................................................................... 14
T90 MDC operation....................................................................................................................................................................... 14
T90 MDC solenoid override valve operation........................................................................................................................15
Neutral start switch (NSS) for MDC.......................................................................................................................................... 15
T90 HDC operation........................................................................................................................................................................ 15
T90 3-Position (FNR) electric control operation..................................................................................................................15
High Current Electrical Displacement Control (HCEDC).................................................................................................. 15
HCEDC Principle........................................................................................................................................................................ 15
HCEDC Operation..................................................................................................................................................................... 16
Manual OverRide (MOR).............................................................................................................................................................. 16
T90 Input speed..............................................................................................................................................................................18
T90 system pressure......................................................................................................................................................................18
T90 charge pressure......................................................................................................................................................................18
T90 charge inlet pressure............................................................................................................................................................19
Case pressure...................................................................................................................................................................................19
Temperature and viscosity......................................................................................................................................................... 19
Fluid and filter recommendations........................................................................................................................................... 19
Overview........................................................................................................................................................................................... 21
Features and options....................................................................................................................................................................21
Operating parameters..................................................................................................................................................................21
Fluid specifications........................................................................................................................................................................21
General ..............................................................................................................................................................................................23
Start-up procedure........................................................................................................................................................................ 23
Required tools................................................................................................................................................................................. 24
Port locations and gauge installation.....................................................................................................................................24
Overview........................................................................................................................................................................................... 26
Neutral difficult or impossible to find.....................................................................................................................................26
AX216086485386en-000101 | 3
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