Function; Pvg 120 With Pvp Open Center; Pvg 120 With Pvp Closed Center - Danfoss PVG 120 Technical Information

Technical Information
PVG 120 Proportional Valve Group

Function

PVG 120 with PVP Open Center

PVG 120 with PVP Closed Center

© Danfoss | March 2017
When the pump is started and the main spools (1) in the individual basic modules are in neutral position,
oil flows from the pump, through connection P, across the pressure adjustment spool (2) to tank.
The oil flow led across the pressure adjustment spool determines the pump pressure (stand-by pressure).
If a reduced stand-by pressure is required, an extra relief valve PVPH or PVPE can be used in PVP.
When the main spools are actuated the highest load pressure is distributed across the shuttle valve
circuit (3) to the spring chamber behind the pressure adjustment spool (2) and completely or partly
closes the connection to tank.
The pump pressure is applied to the right-hand side of the pressure adjustment spool (2). The pressure
relief valve (4) opens when the load pressure exceeds the set value, allowing pump flow to be diverted
back to tank.
In the basic module the compensator (5) maintains a constant pressure drop across the main spool –
both when the load changes and when a module with a higher load pressure is activated.
Shock and suction valves with a fixed setting (7) and the suction valves (8) on ports A and B are used to
protect individual working functions against overload.
In the basic module it is possible to build in an adjustable LS pressure relief valve (6) to limit the pressure
from each working function.
The LS pressure limiting valve saves energy:
•
Without LS pressure limiting valve all the oil flow to the working function will be led across the
combined shock and suction valves to tank if the pressure exceeds the fixed setting of the valves.
•
With LS pressure limiting valve an oil flow of only about 2 l/min [0.5 US gal/min] will be led across the
LS pressure limiting valve to tank if the pressure exceeds the valve setting.
In the closed center version an orifice (9) has been fitted instead of the plug. This means that the pressure
adjustment spool (2) will only open to tank when the pressure in channel P exceeds the pressure relief
valve setting (4).
In load sensing systems the load pressure is led to the pump regulator via the LS connection (10), so the
orifices (11) have been removed, and a plug (12) has been fitted instead of one of the orifices.
In neutral position the pump regulator will set the displacement so that leakage in the system is just
compensated for.
When a main spool is activated, the pump regulator will adjust the displacement so that the set
differential pressure between P and LS is maintained.
The pressure relief valve (4) in PVP is set for a pressure of about 30 bar [435 psi] above maximum system
pressure (set at the pump or an external pressure relief valve).
If the system or the pump regulation has a pressure relief valve, it is possible to use a PVPV pump side
module, without integrated pressure adjustment spool and pressure relief valve.
520L0356 | BC00000040en_US1002 | 9