Xylem Parshall flumes - Manual

Installation Instructions
MJK Automation A/S
Byageren 7
DK-2850 Nærum
Denmark
Tel.: (+45) 45 56 06 56
Fax: (+45) 45 56 06 46
[email protected]
www.mjk.dk
MPARGB0204 As our products are developed continuously,
we reserve the right to make any changes without prior notice.
Parshall flumes
It is very important for the overall measuring
accuracy to comply with the installation
instructions on the next page.
At free flow, only the level h
a
is measured.
The location of the sensor is important and
must be carried out as illustrated below. It is
important to have a laminar flow (horizontal
streaming calm water with no whirls) at the
outlet and inlet from the flume, and the outlet
must be unobstructed.
The flume must extend upstream at least ten
times the width of the inlet section of the
flume. On the outlet side the only demand is
that the water should run freely.
The flow is calculated from the formula:
Q = k × h
a
n
where: Q = flow in m 3
b = throat width
h
a
= water level before the throat [m]
h
b
= water level in the throat [m]
L = distance to the sensor = 3 to 4 × h
a max
The factor k and exponent n are constants. The
formula complies to free flow, h
b max
< 0,7 × h
a max
General
Table for determination of the constants k, n and the distance
to the sensor.
b b b b b k k k k k n n n n n L L L L L
2" 425 1,548 0,27
3" 630 1,548 0,30
6" 1310 1,574 0,41
9" 1851 1,528 0,58
12" 2407 1,519 0,89
Q/h diagram for Parshall flumes, the height h
a
is
shown as a function of the flow Q.
Specifications
Size Q
min
Q
max
H
max
Weight
2 inch 50 mm 10 m 3 /h 100 m 3 /h 393 mm 10.3 kg
3 inch 75 mm 27,5 m 3 /h 275 m 3 /h 591 mm 16.5 kg
6 inch 150 mm 60 m 3 /h 600 m 3 /h 609 mm 33.0 kg
9 inch 225 mm 12 m 3 /h 1200 m 3 /h 753 mm 43.5 kg
12 inch 300 mm 20 m 3 /h 2000 m 3 /h 885 mm 100.0 kg
Material Fibre glass
pH range pH 3 - 10
Temperature range - 20 … +30 °C, for short periods up to 90 °C
1” 2”
3” 6” 9” 12”
24”
36”
Note!