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Service Manual
Operating parameters
Overview
Input speed
System pressure
Charge pressure
16
Series 90 Pumps
This section defines the operating parameters and limitations for Series 90 pumps with regard to input
speeds and pressures. For actual parameters, refer to the operating parameters for each displacement.
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.
Continuous 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.
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 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. System pressure must remain at or below continuous pressure during normal operation to
achieve expected life.
Continuous pressure is the average, regularly occurring operating pressure. Operating at or below this
pressure should yield satisfactory product life.
Maximum pressure is the highest intermittent pressure allowed. Maximum machine load should never
exceed this pressure. For all applications, the load should move below this pressure.
All pressure limits are differential pressures referenced to low loop (charge) pressure. Subtract low loop
pressure from gauge readings to compute the differential.
An internal charge relief valve regulates charge pressure. The charge pump supplies the control with
pressure to operate the swashplate and to maintain a minimum pressure in the low side of the
transmission loop.
Minimum charge pressure is the lowest pressure allowed to maintain a safe working condition in the low
side of the 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 operating
parameters table.
Maximum charge pressure is the highest charge pressure allowed by the charge relief adjustment, and
provides normal component life. You can use elevated charge pressure as a secondary means to reduce
the swashplate response time.
The charge pressure setting in the order code is the set pressure of the charge relief valve with the pump
in neutral, operating at 1800 min-1 (rpm), and with a fluid viscosity of 32 mm2/sec (150 SUS). The charge
520L0818 • Rev 0101 • August 2015
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