Schwing SPB 28, Operation Manual

Page: 70 / 216

GENERAL RULE S
PAGE 40
700+ smgr.fm
S AF ETY M AN U AL
• Foreign matter in the concrete. Pieces of old concrete that break away from
mixer fins, unmixed clumps of cement, mixer fins, hammers, and furry mam-
mals are examples of foreign matter that have caused blockages.
• An inexperienced operator can cause blockages by setting up the job
improperly.
For example, if the placing crew is forced to add hose or pipe to
reach a far point after the pour is already in progress, there is a great chance of
creating a blockage due to the dry conditions inside the pipe or hose. It is for this
reason that the job should be set up so pipe or hose need only be removed (never
added) as the day progresses. If dry pipe or hose must be added, it must be lubri-
cated just like the rest of the pipe was lubricated when you first started.
• An inexperienced or improperly trained placing crew can cause blockages
by kinking the end hose.
This type of blockage can lead to serious accidents
because the hose may unkink by the force of the pump.
• The concrete becomes segregated in the hopper.
a. If the concrete is too wet, the cement and fine material get washed from the
stone and coarse sand. This mix will not pump. It is for this reason that you
should cover the hopper as you wait out a passing storm, never allow a truck
mixer to wash out in your hopper, and never add water to the mix. (Figure
52.)
b. If concrete is over vibrated, it will separate. Turn off the hopper vibrator
when not actively pumping.
8.22 Never try to remove a pipeline blockage by applying high pres-
sure to it, because that will cause the blockage to become a plug. If you have a
blockage, immediately stop the pump. Stroke the pump several times in reverse.
Slowly stroke the pump in forward, and try to dislodge the blockage. If you are
moving the blockage, continue to do so slowly and gently. While attempting to
clear the blockage, remove all personnel from the discharge area, as air may be
introduced into the placing line during this process. If you are unable to move the
blockage after a couple of attempts, stop the pump. Continuing to apply high pres-
sure could create a hazardous condition.
R MnoClean.eps
Figure 52
No water in the hopper
WARNING