Overview
This section defines the operating parameters and limitations for LDU20/24 with regard to input speeds
and pressures. For actual parameters, refer to Operating Parameters in the Technical Specifications
section.
Input Speed
Minimum speed is the lowest input speed recommended during engine idle condition. Operating below
minimum speed limits pump’s ability to maintain adequate flow for lubrication and power transmission.
Rated speed is the highest input speed recommended at full power condition. Operating at or below
this speed should yield satisfactory product life.
Maximum speed is the highest operating speed permitted. Exceeding maximum speed reduces product
life and can cause loss of hydrostatic power and braking capacity. Never exceed the maximum speed
limit under any operating conditions.
Operating conditions between rated speed and maximum speed should be restricted to less than full
power and to limited periods of time. For most drive systems, maximum unit speed occurs during
downhill braking or negative power conditions.
W
Warning
Unintended vehicle or machine movement hazard.
Exceeding maximum speed may cause a loss of hydrostatic drive line power and braking capacity. You
must provide a braking system, redundant to the hydrostatic transmission, sufficient to stop and hold the
vehicle or machine in the event of hydrostatic drive power loss.
System Pressure
System pressure is the differential pressure between system ports A and B. It is the dominant operating
variable affecting hydraulic unit life. High system pressure, which results from high load, reduces
expected life. Hydraulic unit life depends on the speed and normal operating, or weighted average,
pressure that can only be determined from a duty cycle analysis.
Maximum working pressure - is the highest recommended application pressure. Maximum working
pressure is not intended to be a continuous pressure. Propel systems with application pressures at, or
below, this pressure should yield satisfactory unit life given proper component sizing.
Maximum pressure is the highest allowable application pressure under any circumstance. Application
pressures above maximum working pressure will only be considered with duty cycle analysis and factory
approval. Minimum pressure must be maintained under all operating conditions to avoid cavitation.
All pressure limits are differential pressures referenced to low loop (charge) pressure.Subtract low loop
pressure from gauge readings to compute the differential.
Input Power
Maximum continuous input power is the highest recommended input power to HST excluding PTO
output power.
Service Manual
LDU20/24 Closed Circuit Axial Piston Transmission
Operating Parameters
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©
Danfoss | June 2021
AX152886481311en-000304
