Overview
This section defines the operating parameters and limitations for LDT21/24/32 with regard to input
speeds and pressures. For actual parameter data, refer to the
Specifications section.
Input / Output 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. An
independent braking system is required, redundant to the hydrostatic transmission, which is sufficient to
stop and hold the vehicle or machine under all conditions of operation in the event of hydrostatic drive
power loss.
System Pressure
System pressure is the differential pressure between system ports A & B. It is the dominant operating
variable affecting hydraulic unit life. High system pressure, which results from high load, reduces
expected life. Hydraulic unit fatigue life depends on speed and normal operating—or weighted average
—pressure that you can only determine 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 (peak) is the highest intermittent pressure allowed under any circumstances.
Applications with applied pressures between maximum working and maximum intermittent require
factory approval with complete application, duty cycle, and life expectancy analysis.
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.
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.
Service Manual
LDT 21/24/32 Closed Circuit Axial Piston Transmission
Operating Parameters
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Danfoss | June 2022
AX417167456877en-000101
