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Introduction
6
515 HC04 - 8 June 2007
Limitations of Use
•
USER
- User pre-defined table
as per configuration report
ISO 5167 Limits
The formulae in ISO 5167 can be applied only when the quantities lie within
the limits shown in the table below.
The ISO standard applies only to pressure differential devices in which the
flow remains subsonic throughout the measuring section and is steady or
varies only slowly with time and where the fluid can be considered as single
phase. In addition, each of these devices can only be used within specified
limits of pipe bore size (D) and Reynolds number (Re
D
).
The calculations are based on upstream temperature and pressure values.
However, the ISO standard assumes that the downstream temperature is the
same as the upstream temperature, therefore a downstream temperature
probe is permissible except where very accurate measurements are required.
If the fluid is a gas, the pressure ratio shall be
≥
0.75.
V-Cone Limits
The formulae used, when either of the cone types (V-Cone or Wafer-Cone)
are selected, have been supplied by McCrometer. The accuracy and
applicability of the use of these differential pressure flowmeters should be
confirmed by referring to the manufactures documentation.
Type of device
d (mm)
(in)
D (mm)
(in)
β
Re
D
Orifice plate, corner
or D-D/2 tappings
≥
12.5
≥
0.5
50
≤
D
≤
1000
2
≤
D
≤
40
0.10
≤ β ≤
0.75
Re
D
≥
5000 for 0.10
≤ β ≤
0.56
Re
D
≥
16000
β
2
for
β
> 0.56
Orifice plate flange
tappings
≥
12.5
≥
0.5
50
≤
D
≤
1000
2
≤
D
≤
40
0.10
≤ β ≤
0.75
Re
D
≥
5000 and
Re
D
≥
170
× β
2
D (D in millimetres)
ISA 1932 nozzle
-
50
≤
D
≤
500
2
≤
D
≤
20
0.30
≤ β ≤
0.80
7.0e+04
≤
Re
D
≤
1.0e+07 for 0.30
≤ β ≤
0.44
2.0e+04
≤
Re
D
≤
1.0e+07 for 0.44
≤ β ≤
0.80
Long radius nozzle
-
50
≤
D
≤
630
2
≤
D
≤
25
0.20
≤ β ≤
0.80
1.0e+04
≤
Re
D
≤
1.0e+07
Venturi tube as cast
-
100
≤
D
≤
800
4
≤
D
≤
32
0.30
≤ β ≤
0.75
2.0e+05
≤
Re
D
≤
2.0e+06
Venturi tube
machined
-
50
≤
D
≤
250
2
≤
D
≤
10
0.40
≤ β ≤
0.75
2.0e+05
≤
Re
D
≤
1.0e+06
Venturi tube welded
-
200
≤
D
≤
1200
8
≤
D
≤
48
0.40
≤ β ≤
0.70
2.0 e+05
≤
Re
D
≤
2.0e+06
Venturi nozzle
≥
50
≥
2
65
≤
D
≤
500
2.5
≤
D
≤
20
0.316
≤ β ≤
0.775 1.5e+05
≤
Re
D
≤
2.0e+06
Содержание 515
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