26
D_FB-D_1FB 5715-669 UK.indd CM
Prop. Directional Control Valve
Series D*FB / D*1FB
Operation Manual
Parker Hannifin GmbH
Hydraulic Controls Division
7. Trouble Shooting
Basis of troubleshooting is always a systematic
approach. At first the following questions have to
be checked:
• Are there practical experiences with similar
failures?
• Have system adjustments been changed?
Afterwards starting of troubleshooting by means of
a priority list of the most likely reasons.
For suspect of a sluggish spool the valve may
be flushed with clean pressure fluid.
Troubleshooting in a hydraulic system requires
in either case a systematic approach. The work
may exclusively be performed by qualified
personnel, as it requires detailed knowledge
about function and construction of the system.
Reversals or dissassemblings may not be
taken imprudently! Prior to the works it has to
be clarified, if the system has been operated
properly until the failure occured.
malfunction at hydraulic load runtime
- generally no function
- high frequent oscillation
- low frequent oscillation
- one way operation only
- speed variations at unchanging command
- different speeds depending on travel direction
- speed too low
- drifting without command
possible reasons for malfunction
corrective actions
x
hydraulic pump resp. motor defective
replace hydraulic pump resp. motor
x
x x x x x
drive overloaded
reduce pressure resp. speed, increase valve size
x
x x x x x x valve contaminated
clean pressure fluid, filter / flush valve
x
x
hydraulic fluid too viscous / too cold
change fluid grade, provide operational temperature
x
x x
too low oil level within tank
refill pressure fluid
x x x
filter contaminated
clean resp. replace filter
x
x
x x supply voltage too low
keep supply voltage range
x
supply voltage carries too much ripple
reduce ripple
x
x
x
command signal too low
increase command signal
x
command signal carries too much ripple
reduce ripple
x
dither signal amplitude too high
reduce parameter P5
x
dither signal amplitude too low
increase parameter P5
x x
x
x x central connector contact failure
clean contacts resp. replace connector
x
feed cable interrupted
fix feed cable
x x x x x
x x wiring sequence incorrect
correct wiring sequence
x
x feed cable without shielding
change cable grade
x
*)
pilot flow configuration incorrect
correct pilot flow configuration
*)
only for D*1FB
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