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

Application Guide
Using flow or pressure control spools

Pressure control spools in oscillating systems

© Danfoss | Feb 2017
PC spools are beneficial when they are used with oscillating applications. The spool design applies
dampening to the port because flow from the valve varies with load change. See
example on page 9.
Natural oscillation example
A
B
C
Yellow line
Red line
Dotted line
A certain position of the spool is given leading to a constant pressure, Pc. The load pressure, Pl is
oscillating. Over time, the pressure drop across the main spool (Pc minus Pl) varies, which leads to a
variable flow. The flow out, Ql, is also shown on the graph as a dotted line. The amount of dampening
applied is dependent on the relative difference in pressure between spool set point pressure and load
varying pressure. The relative difference is shown on the graph as ΔP1 and ΔP2.
Natural oscillation
Pressure
Time
Flow
Pl
Pc
Ql
AB00000079en-US0101 | 9