Specifications

9. How often do I change the fluid?
Fluid change frequency depends on whether the filtration
quality is high, oil temperature is maintained at reasonable
levels, moisture condensation is low, and the oil is not breaking
down. Regular observations of oil color in the sight glass are
sufficient for monitoring the condition of the fluid. If it remains
clear and machine operation is normal, do not change the
fluid.There is no firm and fast rule for fluid change. Hydraulic
system fluids are not like the oils in engines, as they are not
subject to continuous chemical contamination. If the fluid is
scheduled to be changed at a time when filters are not
showing indication of contamination, then leave the old filter
elements in for one or two days before changing them for
new elements.Where the hydraulic power unit is dedicated
to the valve alone, it may be several years before an oil
change is necessary.Where the valve is fed from a larger
power unit which services other functions, a more frequent
change will be necessary.
10. Adjusting the Null on a Valve.
As stated in section 3, no other field adjustment exists on a
valve other than the null adjustment.This is set at the factory
and should not normally be disturbed. If a valve is indicating
an excessive null drift, it may be indicative of contamination.
The null adjustment allows the spool to be centered and thus
limit any actuator motion when the valve electrical signal is
zero. It is preferable to disconnect the valve connector when
carrying out this adjustment.With critical axis cut spools, the
null may drift slightly with temperature change and valve age.
One to two percent drift is permitted as it will be corrected
with the closed loop control in operation. For instructions on
how to adjust the null of a valve, see individual valve series
data sheets.
11. Test Equipment.
It is difficult to troubleshoot a closed loop system to isolate
which components are faulty.The simplest way to check a valve
is to use a valve tester. Moog offers valve testers for its valves.
Model M040-119 is for Mechanical Feedback Valves, while
our M040-104 Series is for both Electrical Feedback Valves
with integrated electronics and Mechanical Feedback Valves.
These testers allow the valve to be driven with a controlled
command signal, either positive or negative, from an independent
source. It allows the Servoactuator to be positioned or moved
about its stroke length and to observe proportionality between
command and speed. Measurement of the position feedback
signal can be carried out at any point along the stroke.
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