Schwing SP 305, Operation Manual

Page: 80 / 104

Appendix
Operation Manual - SP 305 80 revDate
As you can see by the chart in Figure 55, we are
reentering the upper left quadrant through the pressure
scale at about 550 PSI. Remember, we now have to add
the head pressure for our vertical rise. At 1.1 PSI per
foot of level difference and our 70-foot vertical run, we
must now add 1.1
x 70 = 77 PSI to the 550 PSI from
the chart.
550 PSI + 77 PSI = 627 PSI
NOTE!
When calculating the head pressure from
vertical runs, it doesn’t matter if the
pipeline runs straight up and down or if it
runs uphill at an angle. Only the level
difference in feet is needed for the pressure
calculation. If the pipeline is running
downhill, the operator will need special
knowledge, but you don’t need to add any
head pressure to the nomograph.
The nomograph is now complete. The PF of our job
can be calculated like this:
PF = PSI x yd
3
/hr
We need a unit that is capable of 627 PSI and 100 yd
3
/
hr. The PF of this job is:
PF = (627 x 100)
PF = 62,700
The unit must have a PF over 62,700, and it must be
able to pump 100 yd
3
/hr and 627 PSI simultaneously.
Look at the pump shown in our sample nomograph
(Figure 56).
• Can the unit pump at 627 PSI? Yes
• Can the unit pump 100 yd
3
/hr? Yes
• Can the unit pump both simultaneously? No!
This unit will not do the job.
The engine is a little too small. The intersection of 100
yards
3
/hr and 627 PSI has been plotted for visual
representation, but you can see immediately that the PF
of the job (62,700) is bigger than the PF of the unit
(56,650). The curved black line represents the PF of the
unit. If the unit is going to be able to handle the job, the
intersection of pressure and yd
3
/hr will be to the right
and down from the curved line. Anything to the left or
above the line is beyond the power of the hydraulic
pumps. If we could order this same unit with the pumps
set to a higher Kw, the PF of the higher Kw unit would
be 72,600, which would be sufficient.
Plotting the intersection of our hypothetical job again,
you can see that it falls within the power zone of the
hydraulic pumps (Figure 57).
P in PSI
Q in. yd
3
/hr
.
Power factor number (PF)
W
o
rking power (in kW)
For vertical placing,
add 1.105 PSI per foot
of level difference.
56,650
103 KW
English to Metric Conversion Factor is PF 18.966
3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200
200
180
160
140
120
100
80
60
40
20
Example Job
000019.eps
Figure 56
Is this unit sufficient for the job?
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