Schwing SPB 28, Operation Manual

Page: 80 / 216

GENERAL RULE S
PAGE 5 0
700+ smgr.fm
S AF ETY M AN U AL
12.6
When blowing out a vertical line, a shutoff valve is required to
prevent the following scenario.
1. (See diagram A in Figure 67.) Without a shutoff valve installed, the pipeline is
disconnected from the pump. Immediately, the concrete drains out of the ver-
tical sections of pipe, leaving concrete in both horizontal sections, and air
trapped in between.
2. (See diagram B in Figure 67.) The ball is inserted, and pushed with com-
pressed air. This also compresses the air that is trapped in the vertical sections
of pipe. The trapped air will be violently expelled when it reaches the end of
the pipe, but the pipe will not yet be empty.
A shutoff valve installed at the bottom of the vertical run will prevent this hazard-
ous situation. The shutoff valve must be capable of handling the maximum con-
crete pressure of the pump and, of course, must be installed before the pour
begins. Several different styles are available, ranging from a manually operated
flat gate that is put into place with a hammer to fully hydraulic types that will also
divert the concrete to a different pipeline. With a shutoff valve installed, you can
proceed as indicated below.
12.7
Blowing out vertical sections of pipe (for example on a high-
rise building) requires additional safety precautions
.
1. Know where the discharge area for blowing out will be before the pour
begins.
Ready the area and accessories before the pour begins so you will not
waste time when pumping is completed.
2. Blowing out with compressed air requires two qualified persons.
3. The persons at both ends of the pipeline must be able to communicate
without delays,
which means you must establish communications (for exam-
ple, with a radio).
hosepop9.eps
Figure 66
Never use air to blow out hoses or short pipelines
WARNING
WARNING