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Electromagnetic Flowmeter BFM921
7.5 Flowrate versus diameter
The choice of flowrate for an electromagnetic flowmeter depends on the diameter of the sensor. The higher
pipe diameter, the higher flowrate can be measured. A determining parameter for flowrate is maximum
velocity of the liquid. Maximum velocity is the speed, where the flow of liquid inside pipe is still laminar. In
M921 it is limited to 10m/s (with 125% overload). Speed over 10 m/s is usually too high for industrial
applications. Such diameter of pipe is usually selected, where expected flowrate is between Q
In the table below applicable flowrates for various diameters is displayed in units l/s and m
DN
Q
Q
0.3%
5%
15
0,005
0,09
20
0,009
0,16
25
0,015
0,25
32
0,024
0,40
40
0,04
0,6
50
0,06
1,0
65
0,10
1,7
80
0,15
2,5
100
0,24
3,9
125
0,4
6
150
0,5
9
200
0,9
16
250
1,5
25
300
2,1
35
350
2,9
48
400
3,8
63
500
5,9
98
600
8,5
141
700
12
192
800
15
251
Q
- minimum applicable flowrate (minimum flowrate with guaranteed accuracy)
0.3%
Q
- recommended minimum flowrate (minimum flowrate with best accuracy)
5%
Q
- recommended nominal flowrate (expected working flowrate)
N
Q
- recommended maximum flowrate (maximum flowrate for industrial use)
50%
Q
- maximum applicable flowrate (maximum flowrate with guaranteed accuracy)
100%
Q
- maximum applicable overload (Q
MAX
Table 2: BFM921 flowrates
A sensor diameter should be chosen to keep real flowrate between Q
flowmeter has the best accuracy.
64
Flowrates [ l/s ]
Q
Q
Q
N
50%
100%
0,50
0,88
1,77
0,90
1,57
3,14
1,40
2,45
4,91
2,20
4,02
8,04
4,0
6,3
12,6
6,0
9,8
19,6
9,0
16,6
33,2
14,0
25,1
50,3
20,0
39,3
78,5
30,0
61
123
50,0
88
177
100
157
314
150
245
491
200
353
707
300
481
962
400
628
1257
600
982
1963
800
1414
2827
1000
1924
3848
1200
2513
5027
Table 19 : Applicable flowrates for various diameters
) (flowmeter is still measuring)
125%
Flowrates [ m3/h ]
Q
Q
Q
MAX
0.3%
5%
2,21
0,06
0,32
3,93
0,11
0,57
6,14
0,18
0,88
10,05
0,3
1,5
15,7
0,5
2,3
24,5
0,7
3,5
41,5
1,2
6,0
62,8
1,8
9,0
98,2
3
14
153
4
22
221
6
32
393
11
57
614
18
88
884
25
127
1203
35
173
1571
45
226
2454
71
353
3534
102
509
4811
139
693
6283
181
905
and Q
5%
and Q
5%
3
/hr.
Q
Q
Q
N
50%
100%
2,00
3,18
6,36
3,20
5,65
11,31
5,00
8,84
17,67
8,00
14,5
29,0
13,0
22,6
45,2
20,0
35,3
70,7
35,0
59,7
119,5
50,0
90,5
181,0
80
141
283
150
221
442
200
318
636
300
565
1131
500
884
1767
800
1272
2545
1000
1732
3464
1300
2262
4524
2000
3534
7069
3000
5089
10179 12723
4000
6927
13854 17318
5000
9048
18096 22620
, because in this range the
50%
Operation manual
BASI
.
50%
Q
MAX
7,95
14,14
22,09
36,2
56,6
88,4
149,3
226,2
353
552
795
1414
2209
3181
4330
5655
8836
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