D-160TS-7-E
47
How to Determine Minimum Flow Rate
Example 1 A 200mm (8
″
) size meter is to be used for air having a pressure of 0.74MPa [gauge] at 20
℃
. Find the minimum flow rate.
[Solution] Finding the minimum flow rate for nominal size 200mm (8
″
) in Table A corresponding to 0.74MPa [gauge] air in Table B,
we obtain:
where accuracy is ±1% of reading: 94.5m
3
/h, where accuracy is ±1% of full scale: 51m
3
/h.
Example 2 A 250mm (10
″
) size meter is to be used for city gas having a pressure of 0.5MPa [gauge] at 20
℃
with an accuracy of ±1% of
reading. Find the minimum flow rate.
[Solution] Finding the minimum flow rate for nominal size 250mm (10
″
) in Table A corresponding to 0.305MPa [gauge] and
0.577MPa [gauge] of city gas in Table B are 191m
3
/h and 161m
3
/h, respectively. Hence, at 0.5MPa [gauge] we obtain from the rule
of proportion:
0.577 − 0.5
Qmin= 161 +
× (191−161)
≒
170m
3
/h
0.577 − 0.305
Example 3 A 200mm (8
″
) size meter is to be used for butane gas having a pressure of 0.301MPa [gauge] at 80°C with an accuracy of 1% of
reading. Find the minimum flow rate.
[Solution] Although the minimum flow rate in Table A corresponding to 0.301MPa [gauge] is 94.5m
3
/h, the minimum flow rate should
increase by the amount of decrease in specific weight due to elevated temperature (80
℃
) as follows:
0. 0.301
273.15
Sp. weight of butane at 80
℃
= 2.703 ×
×
≒
8.3kg/m
3
0.101325
273.15 + 80
The minimum flow rates for the nominal size 200mm (8" ) corresponding to specific weights 7kg/m
3
and 10kg/m
3
in Table A are
107m
3
/h and 94.5m
3
/h, respectively. Hence, the minimum flow rate of butane at 80
℃
(sp. weight 8.3kg/m
3
) can be obtained from the
rule of proportion:
10 − 8.3
Qmin= 94.5 +
× (107 − 94.5)
≒
102m
3
/h
10 − 7
Nom. size
mm
Sp. weight kg/m
3
Accuracy
Minimum flow rate m
3
/h [actual]
Max. Flow rate
m
3
/h
0.5
0.8
1
1.2
3
5
7
10
20
40
60
20
(
3
/
4
″
)
±1% of reading
—
—
—
—
3.42
2.06
1.47
1.03
0.59
0.42
0.34
12.5
±1% of full scale
—
—
—
—
2.05
1.23
0.99
0.83
0.59
0.42
0.34
25
(1
″
)
±1% of reading
—
—
—
—
4.35
2.61
1.87
1.34
0.95
0.67
0.55
25.5
±1% of full scale
—
—
—
—
2.61
1.89
1.6
1.34
0.95
0.67
0.55
32
(1
1
/
4
″
)
±1% of reading
—
—
17.1
14.2
5.68
3.41
2.72
2.28
1.61
1.14
0.93
56.5
±1% of full scale
—
—
10.2
8.5
4.16
3.22
2.72
2.28
1.61
1.14
0.93
40
(1
1
/
2
″
)
±1% of reading
—
49.5
39.6
33
16.6
14
12.5
11.1
8.78
6.97
6.09
87
±1% of full scale
—
14.8
11.9
9.87
5.6
4.34
3.67
3.07
2.17
1.54
1.26
50
(2
″
)
±1% of reading
102
63.3
50.7
42.2
22.3
18.8
16.8
14.9
11.9
9.38
8.19
185
±1% of full scale
30.3
19
15.9
14.5
9.16
7.1
6
5.02
3.55
2.51
2.05
80
(3
″
)
±1% of reading
151
93.8
75.1
62.6
41.6
35.1
31.4
27.9
22.1
17.6
15.4
530
±1% of full scale
49.3
39
34.9
31.8
20.2
15.6
13.2
11.1
7.79
5.51
4.5
100
(4
″
)
±1% of reading
197
123
98.3
81.9
56.1
47.3
42.3
37.5
29.8
23.7
20.7
900
±1% of full scale
58.8
42.3
37.8
34.5
21.9
16.9
14.3
12
8.45
6.8
6.8
150
(6
″
)
±1% of reading
291
182
146
131
96.2
81.2
72.5
64.4
51.1
40.6
35.5
2100
±1% of full scale
117
92.1
82.4
75.2
47.6
36.9
31.2
26.1
22
22
22
200
(8
″
)
±1% of reading
385
241
204
192
142
120
107
94.5
75
59.6
52
3400
±1% of full scale
205
162
145
132
83.4
64.6
54.6
51
51
51
51
250
(10
″
)
±1% of reading
479
299
275
258
191
161
144
128
101
98
98
5200
±1% of full scale
317
251
224
205
130
101
98
98
98
98
98
300
(12
″
)
±1% of reading
573
377
350
329
243
205
183
168
168
168
168
7500
±1% of full scale
454
359
321
293
186
168
168
168
168
168
168
400
(16
″
)
±1% of reading
779
616
551
503
378
378
378
378
378
378
378
12000
±1% of full scale
779
616
551
503
378
378
378
378
378
378
378
500
(20
″
)
±1% of reading
1230
966
864
789
741
741
741
741
741
741
741
19000
±1% of full scale
1230
966
864
789
741
741
741
741
741
741
741
Type of Gas
Sp. weight kg/Nm
3
Pressure of Gas MPa (gauge) Temperature 20°C
Acetylene
1.175
—
—
—
0
0.176
0.361
0.547
0.824
1.75
3.60
5.45
Argon
1.785
—
—
—
0
0.081
0.203
0.325
0.508
1.12
2.34
3.55
Carbon Monoxide
1.250
—
—
—
0
0.160
0.334
0.508
0.726
1.64
3.38
5.12
Ethane
1.357
—
—
—
0
0.139
0.299
0.460
0.700
1.50
3.10
4.71
Ethylene
1.264
—
—
—
0
0.157
0.329
0.501
0.759
1.62
3.34
5.06
Air
1.293
—
—
—
0
0.151
0.319
0.487
0.740
1.58
3.26
4.94
Oxygen
1.429
—
—
—
0
0.121
0.279
0.431
0.660
1.42
2.94
4.46
Hydrogen
0.0899
0.503
0.866
1.11
1.35
3.53
5.95
—
—
—
—
—
Carbon Dioxide
1.977
—
—
—
—
0.064
0.174
0.284
0.449
1.00
2.10
3.20
Nitrogen
1.251
—
—
—
0
0.159
0.333
0.507
0.768
1.64
3.38
5.11
City Gas
0.802
—
0
0.034
0.061
0.305
0.577
0.848
1.25
2.61
5.32
—
Natural Gas
0.828
—
—
0.030
0.056
0.293
0.555
0.818
1.21
2.53
5.15
7.78
Propane
2.020
—
—
—
—
0.060
0.168
0.276
0.437
0.975
2.05
3.13
Butane
2.703
—
—
—
—
0.019
0.100
0.180
0.301
0.703
1.51
2.31
Methane
0.717
—
—
0.050
0.081
0.354
0.657
0.960
1.42
2.93
5.97
—
Table A
Table B
Find the value closest to the pr
essur
e of gas
to be used (lower value) in T
able B and
determine the minimum
flow rate in T
able A.
（
3
）
Flow ranges
The OVAL VORTEX FLOWMETER measures actual flow rate (m
3
/h[actual]) under pressure. If flow rate
information is given under the standard conditions (0
℃
, 1 atmospheric pressure) (m
3
/h[normal]), it must be
converted into an actual flow rate before you refer to the flow range table below.
1. Flow ranges listed in above table is calculated based on temperature 20
℃
and viscosity 0.017mPa•s.
2. If it is necessary to determine the minimum flow rate precisely, contact OVAL.
NOTE
：
