Overview
This section defines input speed and pressure operating parameters and limitations for H1 pumps. For
actual parameters, refer to the technical specifications for each displacement.
Input speed
Minimum speed is the lowest input speed recommended during engine idle condition. Operating below
minimum speed limits the pump's ability to maintain adequate flow for lubrication and power
transmission.
Rated speed is the highest input speed recommended at full power. Operating at or below this speed
generally yields 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.
When determining speed limits for a particular application see Danfoss publication BLN-9884
Pressure
and speed limits
.
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 & B and/or C & D. 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 speed and normal operating—or weighted average
—pressure that you can only determine from a duty cycle analysis.
Applied pressure is the chosen application pressure in the order code for the pump. This is the pressure
at which the drive line generates maximum pull or torque in the application.
Rated pressure is the design pressure for the pump. Applications with applied pressures at or below this
pressure should yield satisfactory unit life given proper component selection.
Maximum pressure (peak) is the highest intermittent pressure allowed under any circumstances.
Applications with applied pressures between rated and maximum 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.
Charge pressure
The external charge pump supplies the control with pressure to operate the servo piston and to maintain
a minimum pressure in the low side of the transmission loop. An internal charge relief valve regulates
pressure in the charge circuit.
Minimum charge pressure is the lowest pressure safe working conditions allow in the system loop.
Minimum control pressure requirements are a function of speed, pressure, and swashplate angle, and
may be higher than the minimum charge pressure shown in the technical specifications.
Maximum charge pressure is the highest charge pressure the charge relief adjustment allows, and
which provides normal component life. You can use elevated charge pressure as a secondary means to
reduce swashplate response time.
Service Manual
H1 45/53/60/68 Tandem Closed Circuit Axial Piston Pumps
Operating parameters
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©
Danfoss | June 2018
520L0928 | AX00000103en-US0303
