Maintenance
40
8/4/11
Operation Manual - SP 305
MAINTENANCE
Maintenance is what you do to the machine to keep it
in good working condition. There are two kinds of
maintenance: preventative and repairs. Preventative
maintenance is important to avoid unnecessary repairs,
but eventually even well maintained machine parts will
wear out and require repair or replacement.
Some maintenance needs to be done by a time interval
such as daily, monthly, or annually. It is a good idea to
make a checklist that will tell you what maintenance is
due and when it is due. A suggested checklist is
included in this section of this manual. It can be found
on page 57. Keep accurate records of maintenance
performed and when the work was completed. In this
way, you will know that all necessary work has been
completed on time. Complete maintenance records
could also make the machine worth more money when
it comes time to sell or trade it.
There are certain things you should know about the
maintenance of your machine that will not come up on
a timetable of things to do.
We begin the section with some general information
regarding some of these items.
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 differential cylinders and
the valves, through the reservoir breather, and by
internal wear in the components. Additionally, when
you change hydraulic oil, the new oil is not clean
enough to be used in a concrete pump without being
pre-filtered. In fact, new hydraulic oil is only filtered at
the refinery to 40μ (40 microns). The oil in your unit
needs to be filtered to a MINIMUM of 25μ, and
preferably finer 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 flow
rate (in PSI and gallons per minute or bar and liters
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 five equals two
hundred). This means that for every 200 particles
of 25 microns or larger that hit the filter media, one
makes it through. A finer filter would be, for
example, β12 = 200. A courser filter example
would be
β25 = 75. For concrete pumps, medium
to fine filtration is required.
Specific information
Here are some facts regarding filtration as they relate to
your pump:
• Your unit has a separate oil conditioning circuit,
which includes an oil cooler and a filter. The oil is
pumped from the reservoir, through the cooler and
filter, back to the reservoir.
• As delivered from the factory, each SP 305 unit is
equipped with a filter 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 filter 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 finer filtration because the
components don’t require it. Additionally, a finer
filter would plug up with dirt too often, resulting in
high maintenance costs to you. We have settled on
a compromise that should afford 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 pressure
drop varies with the viscosity of the oil, which
means pressure in the filter will be high until the oil
is heated to normal operating temperatures.
The filter will hold 55 grams of dirt, when
operating at a flow rate of 27 GPM (gallons per
minute). The flow rate is important, because the
filter would hold more if you operated at a lower
flow rate. Good filtration is not cheap, but it will
save you thousands of dollars by preventing
component failure.
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