Appendix
SP 305
Startup 250:Users:Danny:Desktop:Operation manuals:line pumps:maverick
(P305):Appendix.fm
Operation Manual -
77
less than maximum pressure.
Maximum pressure (abbreviated as max P) is
determined by the size of the differential and material
cylinders and the setting of the main relief valve. To be
sure that the unit will handle the job, be careful to
notice max P and max Q. Here is an example of why
that is important: You contract to pump a job that
requires only 20 yards per hour, but you calculate that
you will need 2100 PSI pressure. The PF of this job is
42,000 (20 x 2100). The pump shown in Figure 51 has
a TK of 72,600, so there is enough power available.
However, the maximum pressure available from the
pump is only 1570 PSI. This pump would not do the
job.
2. Follow the chart in a straight line from required
output into the upper right quadrant until you
come to the size of the pipeline that you will use. A
good rule of thumb for sizing pipeline is to use the
largest diameter pipeline that you can. It takes less
force to move concrete through a 6-inch pipeline
than, for example, a 4-inch pipeline. When
pressure is exerted on concrete in a pipeline, a
paste of water and cement fines coats the inside of
the pipeline and forms a slippery layer on which
the bulk of the concrete slides. While it is true that
a 6-inch pipeline has 49 percent more surface area
to coat than a 4-inch pipeline, the volume of
concrete that can move on the layer is increased by
125 percent, which results in lower velocity of the
concrete (in feet per second), lower friction, and,
therefore, lower pressure. A pump that may not be
capable of completing a difficult job through 4- or
5-inch pipe may be able to do it easily through 6-
inch pipe. Note! Experience has taught us that 5-
inch is the optimum pipeline size for lengthy
vertical runs, such as those found on high-rise
buildings. It is large enough for most aggregate but
small enough that you minimize the amount of
concrete that slides back into the hopper when the
concrete valve cycles, which we call backwash.
You must also consider the people at the point of
placement. Very few hose handlers, if any, can
move 6-inch hose on a slab all day. There is no
provision in the nomograph for mixing pipeline
sizes. For example, if you will be reducing from 5-
inch to 4-inch pipe, you should calculate the chart
as if you were using 4-inch pipe for the entire
distance. This will not be completely accurate, but
you will be safe in your pressure calculation. In our
example, we use 5-inch pipeline (Figure 52).
Q in yd
3
/hr.
Pipeline diameter in inches
6" 5" 4.5"
4"
000023.eps
Make a 90˚ turn when
you intersect with the
pipeline diameter that
applies to your job.
Figure 52
Upper right quadrant—Pipeline diameter
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