Ls Connection; Ls Signal - Danfoss PVG 32 Service Manual

Service Manual
PVG 32 Proportional Valve Group
PVG 32 Component Troubleshooting

LS connection

Failure mode
In closed center systems the valve
sections are unstable
Valve operation is slow to respond
or does not respond

LS signal

© Danfoss | February 2017
Description: Port for LS signal for LS (static) option only controller for variable flow pump.
Location: PVP (inlet) module.
Function: Provide a signal to the variable pump controller to create a pressure differential to have the
pump come on stroke for a closed center system.
Cause
Insufficient LS flow to satisfy pump controller
Excessive air entrained in the hydraulic oil
Air trapped in LS line
Insufficient LS flow to satisfy pump controller
Excessive air entrained in the hydraulic oil
Air trapped in LS line
PVG valve is mounted above hydraulic oil reservoir when shut down and sits idle for some time, the valve
could be voided of oil and this would cause the valve to operate erratically and be slow to respond.
Serviceability: Port is serviceable. Need to connect hose to LS port on pump.
LS connection plug
LS Plug
6 mm
35 Nm [308 lbf•in]
Description: The PVG32 uses an internal LS signal network for both Open Center and Closed Center
systems. In Open Center systems the internal LS signal network provides a resolved load sense signal to
the pressure adjustment spool controlling the proper amount of flow and pressure to the operating valve
sections. In Closed Center systems the internal LS signal network provides a resolved load sense signal
directly to the LS pump control which in turn provides the proper amount of flow and pressure to the
operating valve sections.
Location: PVP/PVB Modules.
Corrective action
Ensure that the LS controller on the pump does not have excessive
internal leakage - 0.4 l/min [0.106 gal/min]. Repair or replace the
variable pump controller per pump manufactures specifications
If there is more than one valve in the system ensure that the LS
shuttles are all working properly
Ensure that the oil has enough dwell time in tank, has good anti-
foaming agent, and pump inlet vacuum is within manufacturers
specifications
Bleed air for LS line at highest point
If more than one section, ensure that the LS controller on the
pump does not have excessive internal leakage. Repair or replace
the variable pump controller per pump manufactures
specifications
Ensure that the oil has enough dwell time in tank, has good anti-
foaming agent, and pump inlet vacuum is within specifications
Bleed air for LS line at highest point
P107 740E
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