Cylinder/Motor Responds In One Direction Only; Main Valve Spool Moves Without Oil Passing To Cylinder/Motor - Danfoss PVG 32 Service Manual

Service Manual
PVG 32 Proportional Valve Group
System Troubleshooting

Cylinder/motor responds in one direction only

Cause
Verify if fault is mechanical, electrical
or hydraulic
Air in system
Internal leakage
Shock valves
Solenoid actuation
Main spool travel restricted
Remote electrical controller
PVEO connections
Remote hydraulic controller PVRH

Main valve spool moves without oil passing to cylinder/motor

Cause
Insufficient oil supply to valve
Optional pressure compensator in
valve section not functioning
Insufficient load pressure at
compensator spring chamber
Cylinder/motor load too high for
pressure setting of the system
Blocked LS galleries
Shuttle valve faulty
Blocked LS lines to pump controller
Oil bypassing at shock valve/anti-
cavitation check valve
Internal leakage in cylinder/motor
Too much leakage in LS spool in pump
control
Blocked thermal orifice
Load too high for system
Internal leakage in cylinder/motor
Shock valve or anti-cavitation check
valve faulty
System relief valve pressure set too low
for load
16 | © Danfoss | February 2017
Check
Operate manual lever in both directions to confirm if
mechanical or electrical or hydraulic
If operating the manual lever strokes the cylinder/
motor in one direction only, check manual stop screw
adjustment
Check movement of manual lever when electrical
controller is operated
Check movement of manual lever when hydraulic
controller is operated
Entrained air generates heat under pressure
Excessive internal leakage may overheat the system.
Swap and see if problem follows
If power is OK from controller
Stop on manual controller turned in too far
Insufficient signal from electrical controller
Incorrect PVE/PVEO connections
Insufficient pilot oil pressure from remote hydraulic
controller Pressure needs to be 25 Bar [360 psi]
Check
Check the pump per manufacturers procedure
Check compensator spool
LS drilling holes plugged
Check pressure at the valve
Inspect for blockage in LS galleries
Inspect shuttle valve
Inspect LS lines from PCG to pump controller
Check if stuck open or damaged
Inspect for by-passing of oil per cylinder/motor
manufacture per manufactures procedure
Check bleed orifice in LS control
check thermal orifice (blocked)
Check for proper system pressure
Inspect for bypassing of oil per cylinder/motor
manufacturer specification
Inspect for damage and contamination
Install pressure gauge and check pressure
Corrective action
If moving the manual lever operates the cylinder/motor
in both directions check electrical or hydraulic
Back out manual stop on manual controller and torque
the jam not to 8 Nm [70 lbf•in] Do not exceed maximum
torque
If manual lever does not move in one direction check
electrical signal from controller and wiring at the PVE
module
If manual lever does not move in both directions check
hydraulic pressure at the PVG module
Look for foam or bubbles in reservoir. Check for leaks on
inlet side of charge pump.
Install loop flushing defeat option and monitor case flow.
If case flow is excessive, motor may require major repair.
Contact Danfoss Service.
Replace valves
Repair wiring to PVE module
Back out manual stop on manual controller
Repair or replace electrical controller
Connect correct way
Repair or replace remote hydraulic controller
Corrective action
Repair or replace pump per manufacturers procedure
Replace spool
Clean or replace
If pressure is set to spec. per valve lower load on cylinder/
motor
Remove blockage in LS galleries
Repair or replace
Remove blockage in LS lines from the PVG valve to pump
controller
Replace valve
Repair or replace cylinder/motor per manufactures
procedure
Use a LS pump control with no bleed orifice
Replace thermal orifice
Adjust pressure to valve specification
Repair or replace cylinder/motor
Repair or replace cylinder/motor
Adjust pressure to system specification
Lower load
11039167 | AX00000031en-US0301