Schwing SP 750-18 - Filtration and Maintenance Schedule

95
Maintenance
SP 500 / 750-15 / 750-18 / 1000 / 1250 Operation Manual
Filtration
General information
Filtration is the single most important method of keeping
your unit’s hydraulic system operational. Particles that
could damage the components are introduced into the
oil by the di󰀨erential cylinders and the valves, through
the reservoir breather, and by internal wear in the com-
ponents. Additionally, when you change hydraulic oil,
the new oil is not clean enough to be used in a concrete
pump without being pre-ltered. In fact, new hydraulic
oil is only ltered at the renery to 40μ (40 microns).
The oil in your unit needs to be ltered to a MINIMUM of
25μ, and preferably ner than that. Filters are rated by:
• the size of particles they trap, and whether that
size is nominal or absolute
• the dirt holding capacity, in grams
• the clean element pressure drop for a given ow
rate (in PSI and gallons per minute or bar and li-
ters per minute), and
• the ratio of particles of a given size encountered
versus particles passed (referred to as the beta
ratio). An example of a beta ratio would be β25 =
200 (pronounced beta twenty ve equals two hun-
dred). This means that for every 200 particles of
25 microns or larger that hit the lter media, one
makes it through. A ner lter would be, for ex-
ample, β12 = 200. A courser lter example would
be β25 = 75. For concrete pumps, medium to ne
ltration is required.
Specic information
Here are some facts regarding ltration as they relate
to your pump:
• Your unit has a separate oil conditioning circuit,
which includes an oil cooler and a lter. The oil is
pumped from the reservoir, through the cooler and
lter, back to the reservoir.
• As delivered from the factory, your concrete pump
is equipped with a lter that is rated at 10 micron
(shown as 10μ) absolute.
• The beta ratio is β10 = 200. In our case, the beta
ratio means that for every 200 particles of dirt that
hit the lter media that are 10 micron or larger
in size, 1 will make it through. Although we are
not happy about the one particle that is allowed
through, we do not use ner ltration because the
components don’t require it. Additionally, a ner
lter would plug up with dirt too often, resulting in
high maintenance costs to you. We have settled
on a compromise that should a󰀨ord long service
life and minimum maintenance costs. Don’t be
fooled by the one particle that gets through, this
is a high quality element with very good trapping
characteristics.
• The clean element pressure drop is about 3 PSI
at 22 gallons per minute (element only) + 2.5 PSI
for the housing, making a total of 5.5 PSI DP (drop
in pressure) when the element is clean. The pres-
sure drop varies with the viscosity of the oil, which
means pressure in the lter will be high until the oil
is heated to normal operating temperatures. The
lter will hold 55 grams of dirt, when operating at a
ow rate of 27 GPM (gallons per minute). The ow
rate is important, because the lter would hold
more if you operated at a lower ow rate. Good l-
tration is not cheap, but it will save you thousands
of dollars by preventing component failure.
• Your concrete pump is equipped with a recircula-
tion type of ltration system, meaning that there is
a pump that sucks oil from the reservoir, pumps
it through the lter and cooler, and back to the
tank. Whenever the engine is running, oil is being
ltered. The ltration is done with a spin-on lter
assembly (Figure 3). It is equipped with an inte-
gral bypass check valve set at 35 PSI. The bypass
valve protects the lter element from damage, as
explained below. The assembly is equipped with
an anti-back-ow check valve, which prevents oil
from draining out of the tank while you are chang-
ing the spin-on element. There is a dirty lter in-
dicator to tell you when the element is dirty. You
should replace the element whenever the indicator
enters the yellow area and the oil is heated above
20 degrees Celsius. Under normal circumstances,
the element will need replacement about every 6
months. The element has been designed to re-
move all particles large enough to cause undue
wear and jobsite breakdowns (beta 10 = 200). You
can keep the hydraulic system running year after
year by replacing the element when replacement
is due. Do not substitute “will t” elements in this
housing.