Operation; T90 Charge Pump Operation; T90 Charge Relief Valve Operation; T90 Multi-Function Valve Operation - Danfoss T90 Series Service Manual

Service Manual
Series T90 Axial Piston Pumps

Operation

T90 charge pump operation

T90 charge relief valve operation

T90 multi-function valve operation

12 | © Danfoss | March 2020
The charge pump is necessary to supply cool fluid to the system, to maintain positive pressure in the
main system loop, to provide pressure to operate the control system, and to make up for internal leakage.
Charge pressure must be at its specified pressure under all conditions to prevent damage to the
transmission.
The charge pump is a fixed-displacement, gerotor type pump driven off the main pump shaft. The charge
relief valve limits charge pressure.
Pump charge system
Case
drain
Charge relief valve
line
Input
PV PF
Charge
pump
Inlet filter
Tank
The charge relief valve on the pump maintains charge pressure at a designated level. A direct-acting
poppet valve relieves fluid when charge pressure reaches a certain level. This level is nominally set
referencing case pressure at 1500 rpm. This nominal setting assumes the pump is in neutral (zero flow). In
forward or reverse, charge pressure is lower. The pump model code specifies the charge relief valve
setting.
Charge pressure relief valve
Charge pressure
The multi-function valve incorporates the system check valve, the pressure limiter valve, the high
pressure relief valve, and the bypass valve in a replaceable cartridge. These functions are described
separately. There are two multi-function valve cartridges in each Series T90 pump to handle functions in
either direction. See corresponding sections for adjustments and repairs.
System
check
valves
P104 121E
P106 157E
AX216086485386en-000101