Maintenance
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S
P Rock Valve Model
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Operation Manual -
101
operated at a lower flow rate. Good filtration is not
cheap, but it will save you thousands of dollars by
preventing component failure.
The return filter is equipped with an integral bypass
check valve, with a spring force of 50 pounds. That
means that when the filter is clogged with dirt and oil is
having a hard time making it through, the pressure
difference between the filter inlet and the tank raises.
This pressure difference (commonly referred to as a
pressure differential
) is called delta P, and is shown as
Δ
P. When the
Δ
P reaches 50 PSI, the check valve opens
and the oil returns to the tank unfiltered. If the filter did
not have the bypass check valve, it would simply break
apart when it was clogged. That would put all of the
dirt that it ever trapped directly into the system, plus
the element itself would become a contaminant.
The pumps are equipped with a medium pressure filter
assembly that has been manufactured especially for us
(Figure 42). It is equipped with an integral bypass
check valve, set at 50 PSI. The bypass valve protects
the filter element from damage due to running with a
clogged filter or cold starts. The assembly is equipped
with an anti-back flow check valve, which prevents oil
from draining out of the tank while you are changing
elements. There is a delta P indicator to tell you when
the element is dirty (set at 35 PSI). You should replace
the element whenever the indicator pops out and the oil
is above 20 degrees Celsius. Under normal
circumstances, the element will need replacement
about every 6 months. The element has been designed
to remove all particles large enough to cause undue
wear and job site breakdowns (beta 12 = 200). You can
keep the hydraulic system running year after year by
replacing the element when replacement is due. Do not
substitute “will fit” elements in this housing.
To change the element:
a. Make sure the engine is shut off.
b. Position a pan or bucket under the filter
housing to catch drips.
c. Use a filter wrench to remove the old filter.
The type of filters installed on your unit are the result
of years of experience and testing. We recommend that
you DO NOT change the housing or element to some
other type. You may learn that, in the long run,
sometimes cheaper is more expensive.
oilfilter.eps
Figure 42
The main return filter
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