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Section V – Service and Maintenance
A. Inspection
Periodic inspection of the fluid condition and tube or piping
connections can save time-consuming breakdowns and un-
necessary parts replacement. The following should be
checked regularly.
1. All hydraulic connections must be kept tight. A loose
connection in a pressure line will permit the fluid to leak out.
If the fluid level becomes so low as to uncover the inlet pipe
opening in the reservoir, extensive damage to system
components can result. In suction or return lines, loose
connections permit air to be drawn into the system resulting
in noisy and/or erratic operation.
2. Clean fluid is the best insurance for long service life.
Therefore, the reservoir should be checked periodically for
dirt or other contaminants.
If fluid becomes contaminated, the system should be drained
and the reservoir cleaned before new fluid is added.
3. Air bubbles in the reservoir can ruin system compo-
nents. If bubbles are seen, locate the source of the air and
seal the leak.
B. Adding Fluid To The System
When hydraulic fluid is added to replenish the system, it
should be pumped through a 10 micro (absolute) filter.
It is important that the fluid be clean and free of any
substance which could cause improper operation or wear.
C. Adjustments
See Test Procedure – Section VII.
D. Lubrication
Internal lubrication is provided by the fluid in the system.
E. Replacement Parts
Reliable operation through the specified operating range is
assured only if genuine Vickers parts are used.
Sophisticated design processes and materials are used in
the manufacture of our parts. Substitutions may result in
early failure. Part numbers are shown in the parts listing –
reference Figure 3.
F. Product Life
The longevity of these products is dependent upon
environment, duty cycle, operating parameters and system
cleanliness. Since these parameters vary from application to
application, the ultimate user must determine and establish
the periodic maintenance required to maximize life and
detect potential component failure.
G. Troubleshooting
Table 3 lists the common difficulties experienced with FCGT
electrically modulated flow control valves. It also indicates
probable causes and remedies for each of the troubles
listed.
TROUBLE
PROBABLE CAUSE
REMEDY
External leakage
Back pressure in drain line and/or
defective seals.
Drain directly to reservoir. Replace seals.
Stiction
Contamination and/or metering spool
misalignment. Insufficient dither.
Clean valve. See alignment noted in test
procedure Section VII.
Feed rate variations
Hydrostatic pressure compensator
inoperative and/or sticking hydrostat.
Clean valve and flush system. Polish
hydrostat and metering spool or replace
with new parts.
Maximum flow not obtainable
Contaminants in throttling orifice. Metering
spool binding and not shifting fully or
insufficient voltage to torque motor.
Clean valve. Check torque motor coils and
input current. Realignment may be neces-
sary. If this does not correct trouble, valve
should be returned to Vickers for overhaul.
Check valve inoperative
Dirt lodged between mating faces, or finish
faces scored.
Disassemble and flush thoroughly. Check
filter element. Filter bypass may be open.
Table 3. Troubleshooting Chart
