SERVING THE GAS INDUSTRY WORLDWIDE
Technical Product Information
VORTEX VO ORTTEX FL FLOWMETER LOW WMETTER W WBZ BZZ 08
RMG Messtechnik GmbH
VORTEX FLOWMETER WBZ 08 Principle, applications, properties, technical data
Principle A repeating pattern of swirling vortices caused by the unsteady separation of a fluid stream over bluff bodies is called a “Kármán vortex street” and was discovered by Theodore von Kármán in1878.
2
The accuracy of the vortex meter is dependent on the length and the condition of the meter run. Upstream flow disturbances such as swirl or an asymmetric velocity profile are eliminated by a flow straightener. The thermistor sensors are accomodated in meter head tubings above the bluff body protecting them against direct exposure to flow and the accumulation of condensate. This arrangement also allows an inspection of the sensors without taking the meters out of service. The arrangement creates ideal conditions for signal generation. A downstream amplifier stabilizes the signals which can be processed by RMG model series ERZ 2000 flow computers or the CS 905 counter system.
Kármán Vortex Street
Vortex shedding in a fluid following around a body is periodic. The frequency at which the vortices are shed is, in certain range, proportional to the fluid velocity. Accounting for the cross-sectional area of the conduit, the number of vortices is a very exact measure of the flow rate and the volume passed through the meter. Vortex frequency is a function of the fluid velocity, the geometry of the bluff body and the ratio between the bluff body size and the diameter of the conduit. The geometric data determine a meter factor (pulse/volume) which is independent of pressure and temperature, density and viscosity. The vortices produced by the bluff body in the meter are the cause of velocity and pressure oscillations. These oscillations are picked up by a thermistor sensor whose resistance varies in response to the pressure oscillations. The measurement is duplicated for high accuracy for custody transfer metering.
Applications Vortex flow meters are used for fluid resp. gas flow measurement. Gas flow at reference conditions is calculated from flow at operating conditions pressure and temperature or flow at operating conditions and density data. The vortex meter consists of a meter body, a bluff body and a meter head with thermistor sensors and an amplifier.
Properties • • • • • • • • • •
wide range high accuracy insensibility to higher loads no influence of meter position insensibility to vibrations high reproducibility twin signal generation maintenance without taking meter out of service insensibility to dirt explosionproofed
TECHNICAL DATA Diameters
DN 40 bis DN 600
Pressure stages
PN 10 bis PN 100 / PN 160 / PN 250 ANSI 150 bis ANSI 600 / ANSI 900 / ANSI 1500
Measuring ranges
range for custody transfer metering: - calibration at atmospheric pressure - calibration at high pressure
Linearity
± 0.5 %
Reproducibility
± 0.1 %
Accuracy
± 0.5 %
Fluid
standard design for natural gas and non-corrosive gases (other gases upon request)
1 : 10/20 max. 1 : 50
VORTEX FLOWMETER WBZ 08 Dimensions, measuring ranges sensor cover flow straightener
isolating valves
inlet straight piping
Pr
DN
bluff body
2.5 DN 20 DN A
1.5 DN
outlet straight piping
vortex flowmeter
3
5 DN C
3 DN B L
MEASURING RANGES (m3/h)
DIMENSIONS DN
A
40
1½“
50
B
C**
L**
C***
L***
Size
Qn min
G 40 -------G 65 G 65 2.400 G 100
800
120
630
1.550 --------
2“
1.000
150
800
1.950 1.250
80
3“
1.600
240
560
2.400 1.350
3.190 G 250
100
4“
2.000
300
600
2.900 1.450
3.750
150
6“
3.000
450
750
4.200 1.200
4.650
200
8“
4.000
600 1.000
5.600 1.400
6.000
250
10“
5.000
750 1.250
7.000 1.550
7.300
300
12“
6.000
900 1.500
8.400 1.700
8.600
400
16“
8.000 1.200 2.000 11.200 2.000 11.200
500
20“
10.000 1.500 2.500
600
24“
12.000 1.800 3.000 16.800 3.000 16.800
14.00 2.500 14.000
Length: A = upstream straight piping, B = meter, C = downstream straight piping, L = total length *) max. flowrange of 1:50 feasible **) 2 pockets for densitometer and drier or G¾ taps for PT 100 resistance thermometer (taps spaced at 230 mm) ***) 4 densitometer + drier pockets or more than 5 taps Physics require the following minimum flow for the vortex meter: Qn min · pn Qfl min = ---------------- (m3/h) pfl To maintain the range for custody transfer, flow may never drop below the minimum flow qfl min tabulated above.
G 400 G 650 G 1000 G 1600 G 1600 G 2500 G 2500 G 4000* G 4000 G 6500* G 6500 G 10000* G 10000 G 16000* G 16000 G 25000*
Qfl min
40
3/5/10
40
5/10/10
80
8/13/20
80
20
130
50
160
80
200
130
320
200
320
320
500
500
800
800
Qfl max 65 100 100 160 400 650 1000 1600 2500 2500 4000 4000 6500 6500 10000 10000 16000 16000 25000 25000 40000
K
F
16700
400
8000
365
2400
350
1100
370
310
220
140
260
70
130
40
110
20
90
10
70
5
60
Pressure loss of total meter run: Qfl2 p = 2000 · fl · ------DN4 qfl min: minimum flow at flowing conditions pfl: minimum operating pressure [bar (absolute)] f: signal frequency [Hz], (fmax at qfl max) K: meter factor [pulses/m3] f Qfl = ----- · 3600 (m3/h) K ∆p = DN = ρfl =
pressure loss (mbar) nominal size (mm) density at flowing conditions (kg/m3)
SERVING THE GAS INDUSTRY WORLDWIDE
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ENGLAND
CANADA
Bryan Donkin RMG Gas Controls Ltd. Enterprise Drive, Holmewood Chesterfield S42 5UZ, England Fon +44 (0)1246 50150-1 Fax +44 (0)1246 50150-0
Bryan Donkin RMG Canada Ltd. 50 Clarke Street South, Woodstock Ontario N4S 7Y5, Canada Fon +1 519 53-98531 Fax +1 519 53-73339
POLAND
USA
Gazomet Sp. z o.o. ul. Sarnowska 2 63-900 Rawicz, Polen Fon +48 (0)65 54624-01 Fax +48 (0)65 54624-08
Mercury Instruments LLC 3940 Virginia Avenue Cincinnati, Ohio 45227 Fon +1 513 272-1111 Fax +1 513 272-0211
We reserve the right for technica changes
Status 12/2008
Vortex Flowmeter WBZ 08