Flow Control Spools In Oscillating Systems - Danfoss PVG 32 Application Manual

Application Guide
Using flow or pressure control spools

Flow control spools in oscillating systems

6 | © Danfoss | Feb 2017
As mentioned in the beginning of this document, instability is seen in systems that use FC spools in high
inertia systems. An example of such a system is shown in
Natural oscillation example
A
B
Yellow line
Red line
At any given time, the compensator will try to keep the pressure drop across the main spool at the same
level and follow the pressure oscillations from the actuator attached to the valve. When the load pressure
is changing, the compensator will follow this frequency to keep the amount of flow from the valve at the
same level as the pressure.
So an FC spool offers no damping of the system but maintains a constant flow.
Natural oscillation example on page 6.
Pressure
Time
Pl
Pc
AB00000079en-US0101