Charge Pressure
An internal charge relief valve regulates charge pressure. Charge pressure maintains a minimum pressure
in the low side of the transmission loop. Charge pressure is the differential pressure above case pressure.
Minimum charge pressure is the lowest pressure safe working conditions allow in the system.
Maximum charge pressure is the highest charge pressure the charge relief adjustment allows, and
which provides normal component life.
Charge flow to transmission must be sufficient to provide adequate charge pressure.
Case Pressure
Do not exceed rated case pressure under normal operating conditions. During cold start, keep case
pressure below maximum intermittent case pressure. Size drain plumbing accordingly.
C
Caution
Possible component damage or leakage
Operation with case pressure in excess of stated limits may damage seals, gaskets, and/or housings,
causing external leakage. This condition may also affect performance since charge and system pressure
are referenced to case pressure.
Viscosity
Maintain fluid viscosity within the recommended range for maximum efficiency and bearing life.
Minimum viscosity should only occur during brief occasions of maximum ambient temperature and
severe duty cycle operation. Maximum viscosity should only occur at cold start. Limit speeds until the
system warms up. Refer to Fluid specifications in LDU20/24 Technical Information Manual
BC152886483777.
Temperature
Maintain fluid temperature within the limits shown in the Technical Specifications section of LDU20/24
Technical Information Manual BC152886483777. Minimum temperature relates to the physical properties
of the component materials. Cold oil will not affect the durability of the components, however, it may
affect the ability of the transmission to provide flow and transmit power. Maximum temperature is based
on material properties. Don't exceed it. Measure maximum temperature at the hottest point in the
system. Refer to Fluid Specifications in LDU20/24 Technical Information Manual BC152886483777.
Ensure fluid temperature and viscosity limits are concurrently satisfied.
Service Manual
LDU20/24 Closed Circuit Axial Piston Transmission
Operating Parameters
©
Danfoss | June 2021
AX152886481311en-000304 | 13
