RE 30011-B, Edition 10.2021, Bosch Rexroth AG
Product description |
Pressure and flow control system SYDFE1 series 2X, 3X
25/96
To vary the displacement for the pump combination from 0 % to 100 %, swivel
angle command values b1.5 V and +10 V must be provided.
5.5
OPERATING PRESSURE LIMITS
WARNING
Overpressure!
Risk of severe injury!
▶ Make certain that the maximum operating pressure is not exceeded.
At a pressure of ≥ 250 bar the following restrictions must be observed for SYDFE1:
• The pressure transducer must be located downstream of a pulsation damper or
the high-pressure hose.
• When a standard pilot valve spool is used (version “A”), the pressure controller
P-gain (see page 69) may have to be reduced. This has an influence on the
accuracy and dynamics of the closed pressure control loop.
• The loop gain can also be reduced by installing a pressure transducer of a higher
pressure rating (e.g. 400 bar).
The minimum operating pressure depends on the pilot oil supply and is explained
in more detail in the following chapter.
5.5.1 Internal/external pilot oil
If the operating pressures of the application are always > 20 bar, the version with
internal pilot oil supply should be selected, because no cavitation due to too small
command values can occur with this version.
Operation is also possible at pressures higher than approximately 12 bar, but
dynamics is restricted within the range below 20 bar.
This minimum (pilot) pressure level ensures that the pump can respond to the
electrical swivel signal at any time. When the consumer line is blocked, the
smallest achievable steady-state swivel angle is the zero stroke angle.
For applications, in which lower operating pressures occur or are to be controlled,
a pre-load valve (SYDZ for SYDFE1) can be used. For this solution, the minimum
pressure is ≥1 bar
The advantage of the pre-load valve is that the pilot oil pressure of the pump
cannot fall below the value preset on the pre-load valve and that pressures
≤10 bar on the output side can be continuously controlled.
Being equipped with a pre-load valve the pump cannot permanently swivel back
over zero, irrespective of electrical actuating signals or any control errors. The
smallest achievable swivel angle during steady-state operation therefore is the zero
stroke. This is not valid for applications, in which, for example, a suspended load
can cause operating pressures ≥12 bar. In such cases the pump can also be used
in motor operation (for lowering the load). A check valve integrated in the pre-load
valve permits, within certain limits, a reversal of the direction of oil flow.
Maximum operating
pressure
Minimum operating
pressure
Internal pilot oil supply
Pre-load valve
