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Flow channel and intake system
Figure 19. System No. 10: Relationship between pump discharge and frequency of the motor controller
TR-01-22
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(Point
No.
3) on
the
second
characteristic
pipe
curve.
To
obtain
lower
flow
conditions,
the
pump
discharge
can
again
be
reduced
until
Point
No.
4 is
reached,
corresponding
to 30 percent of
the
nominal
speed.
At
Point
No.
4,
the
discharge
through
the
piping
system
is
approximately
7.5
ℓ
/sec,
which
is 10 percent of
the
maximum
discharge of 75 ℓ
/sec,
at
Point
No.
1.
The
20
pump-and-piping
systems
were designed to have
this
same
functional
capability.
30
1800
RPM
1440
RPM
1080
RPM
540 RPM
25
FS = 100 mm
FS = 50 mm
20
3
15
1
10
1
5
4
2
0
0
10
20
30
40
50
60
70
80
90
100
Flow
Rate
(litres/sec)
Figure
18.
System
No.
10:
Pump
performance
and
characteristic
pipe
curves
Calibration
and
Testing
Relationship
between
pump
discharge
and
frequency
After
the
recirculation
system
was
constructed,
tests
were conducted to
develop
a
relationship
between
pump
discharge
rates
and
frequency
of
the
motor
controllers
for
each
of
the
20
pump-and-piping
systems.
The
discharge
from
each
system
was
measured
using
the
factory
calibration
equations
supplied
with
each
of
the
40
in-line
flow
sensors.
Tests
were conducted
starting
with
low-flow
conditions
by
closing
the
valve
in
the
larger
pipeline
and
allowing
the
flow
to
pass
through
the
smaller
pipeline.
Each
system
was
evaluated
for
the
full
range
of frequencies of
the
motor
controllers
starting
at 15 Hz and
increasing
up to 60
Hz in increments of 5
Hz,
for
a
total
of 10
data
points
per
calibration
curve.
Each
data
point
represents
the
average
flow
rate
measured
for
500-sec
duration
and
sampled
at 20
Hz.
This
series
of 10
tests
was
repeated
for
the
high-flow
conditions
by
closing
the
valve
in
the
smaller
pipeline
and
allowing
the
flow
to
pass
through
the
larger
pipeline.
31
Chapter
3
Longshore
Current
Recirculation
System
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