Danfoss PVG 32 Service Manual

PVMF
P B F
(Standard assembly)
P A F
(Optional assembly)
PVBS, main spools for flow control (standard)
When using standard flow control spools, the pump pressure is determined by the highest load pressure.
This is done either via the pressure adjustment spool in open center PVP (fixed displacement pumps) or
via the pump regulator (variable displacement pumps).
In this way the pump pressure will always correspond to the load pressure plus the stand-by pressure of
the pressure adjustment spool or the pump regulator.
This will normally give optimum and stable adjustment of the oil flow.
PVBS, main spools for flow control (with linear characteristics)
PVBS main spools with linear characteristic have less dead band than standard spools and a completely
proportional ratio between control signal and oil flow in the range beyond the dead band.
W
Warning
PVBS with linear characteristic must never be used together with PVEM electrical actuators.
The interaction between the small dead band of the spools and the hysteresis of the PVEM actuator of
20% involves a risk of building up a LS pressure in neutral position.
PVBS, main spools for pressure control
In a few systems load sensing pump pressure may result in unstable adjustment of the oil flow and a
tendency towards system hunting. This may be the case with working functions that have a large
moment of inertia or over-center valves. In such systems main spools for pressure control can be
advantageous. The spools are designed in such a way that the pump pressure is controlled by the spool
travel. The main spool must be displaced until the pump pressure just exceeds the load pressure before
the working function is applied.
If the main spool is held in this position, the pump pressure will remain constant – even if the load
pressure changes – giving a stable system.
The use of pressure control spools, however, also means that:
•
the oil flow is load dependent
•
the dead band is load dependent
•
the pump pressure can exceed the load pressure by more than is usual.
Service Manual
PVG 32 Proportional Valve Group
Operation
12 |
©
Danfoss | February 2017 11039167 | AX00000031en-US0301

Danfoss PVG 32 Specifications

General

Brand	Danfoss
Model	PVG 32
Category	Control Unit
Language	English