Schwing SPB 28, Operation Manual

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93
Maintenance
SPB Operation Manual
Maintenance
Keeping your machine in good working condition re-
quires regular maintenance. There are two kinds of
maintenance: preventive and scheduled. Preventive
maintenance will help you avoid unnecessary repairs,
but eventually machine parts wear out and require re-
placement.
Scheduled maintenance needs to be done on a time-
ly basis. That may be daily, weekly, monthly, quarter-
ly, semiannually, or annually. It is a good idea to make
a checklist that will tell you what maintenance is due
and when. Keep accurate records of maintenance per-
formed and when the work was completed.
Pressure, Hoses, and Fittings
General information
Most concrete pump hydraulic systems run with fairly
high pressures, in the 2000–5000 PSI range. The maxi-
mum pressure is determined by adjustment of the main
relief valve, and the machines are designed to handle
this pressure safely. Concrete pressure is just a ratio of
the hydraulic pressure.
Specific information
Schwing uses high-pressure fittings and hoses on all
circuits, even if the relief valve for that circuit is set to
low or medium pressure. The fittings and hoses are rat -
ed at a minimum of 5000 PSI working pressure and up
to 15,000 PSI in some fittings. Schwing advises against
changing any circuit to lower rated hoses or fittings.
Schwing uses metric fittings and hoses with metric
threads on the couplings. There are six sizes of tubes
and fittings and six sizes of hoses, all measured by di -
ameter.
All block threads are metric or BSPP.
Hose
Size
Hose ID (mm) Connects with Fitting
and Tube Size
8 8 12
13 13 16
16 16 20
20 20 25
25 25 30
32 32 38
Tube and
Fitting
Size
Tube and
Fitting OD
(mm)
Connects
with Hose
Size
Tube and
Fitting ID
(mm)
12 12 8 8
16 16 13 13
20 20 16 16
25 25 20 20
30 30 25 25
38 38 32 32
Torque specifications
When performing maintenance that requires remov-
al and replacement of bolts, you must adhere to the
torque specifications for those bolts.
The graphs in (Figure 1) demonstrate what happens
to a bolt if it is not properly torqued. The dashed line
represents the prestress or tightness of the bolt. As the
device that uses the bolt goes through its normal func-
tions, the bolt in Example A, which is not tight enough,
gets stretched and relaxed with every duty cycle, be-
cause the bolt is prestressed under the maximum force
of the cycle. In Example B, the torque on the bolt has
been raised to the proper level, which is more than the
maximum force of the duty cycle, so the bolt doesn’t
ever feel the cycle. In this example, bolt B would last
much longer than bolt A. The torque specifications for
bolts used on Schwing equipment are found in the Ap-
pendix section of this manual.
Time
Force
A
Time
Force
B
Figure 1
Effects of proper torque on bolts