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Technical Product Information

VORTEX FLOWMETER WBZ 08

RMG Messtechnik GmbH

VOORTTEX FLLOWWMETTER WWBZZ 08

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VORTEX FLOWMETER WBZ 08Principle, applications, properties, technical data

Principle

A repeating pattern of swirling vortices caused by the unsteady separation of a fl uid stream over bluff bodies is called a “Kármán vortex street” and was discovered by Theodore von Kármán in1878.

Kármán Vortex Street

Vortex shedding in a fl uid following around a body is periodic. The frequency at which the vortices are shed is, in certain range, proportional to the fl uid velocity. Ac-counting for the cross-sectional area of the conduit, the number of vortices is a very exact measure of the fl ow rate and the volume passed through the meter.

Vortex frequency is a function of the fl uid 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/volu-me) 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 forcustody transfer metering.

Applications

Vortex fl ow meters are used for fl uid resp. gas fl ow mea-surement. Gas fl ow at reference conditions is calculated from fl ow at operating conditions pressure and tempera-ture or fl ow 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 ampli-fi er.

The accuracy of the vortex meter is dependent on the length and the condition of the meter run. Upstream fl ow disturbances such as swirl or an asymmetric velocity profi le are eliminated by a fl ow straightener.

The thermistor sensors are accomodated in meter head tubings above the bluff body protecting them against direct exposure to fl ow and the accumulation of conden-sate. 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 amplifi er stabilizes the signals which can be processed by RMG model series ERZ 2000 fl ow computers or the CS 905 counter system.

Properties

• wide range• high accuracy• insensibility to higher loads • no infl uence 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

Pressurestages

PN 10 bis PN 100 / PN 160 / PN 250ANSI 150 bis ANSI 600 / ANSI 900 / ANSI 1500

Measuring ranges

range for custody transfer metering:- calibration at atmospheric pressure 1 : 10/20 - calibration at high pressure max. 1 : 50

Linearity ± 0.5 %

Reproduci-bility ± 0.1 %

Accuracy ± 0.5 %

Fluid standard design for natural gas and non-corrosive gases (other gases upon request)

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VORTEX FLOWMETER WBZ 08Dimensions, measuring ranges

flow straightener inlet straight piping

cover

bluff body

sensor

isolatingvalves

outlet straight pipingvortexflowmeter

1.5 DN 2.5 DN20 DN

A3 DN

B C5 DN

L

PrDN

DIMENSIONS MEASURING RANGES (m3/h)DN A B C** L** C*** L*** Size Qn min Qfl min Qfl max K F

40 1½“ 800 120 630 1.550 -------- --------G 40G 65

40 3/5/1065

10016700 400

50 2“ 1.000 150 800 1.950 1.250 2.400G 65G 100

40 5/10/10100160

8000 365

80 3“ 1.600 240 560 2.400 1.350 3.190 G 250 80 8/13/20 400 2400 350

100 4“ 2.000 300 600 2.900 1.450 3.750G 400G 650

80 20650

10001100 370

150 6“ 3.000 450 750 4.200 1.200 4.650G 1000G 1600

130 5016002500

310 220

200 8“ 4.000 600 1.000 5.600 1.400 6.000G 1600G 2500

160 8025004000

140 260

250 10“ 5.000 750 1.250 7.000 1.550 7.300G 2500G 4000*

200 13040006500

70 130

300 12“ 6.000 900 1.500 8.400 1.700 8.600G 4000G 6500*

320 2006500

1000040 110

400 16“ 8.000 1.200 2.000 11.200 2.000 11.200G 6500G 10000*

320 3201000016000

20 90

500 20“ 10.000 1.500 2.500 14.00 2.500 14.000G 10000G 16000*

500 5001600025000

10 70

600 24“ 12.000 1.800 3.000 16.800 3.000 16.800G 16000G 25000*

800 8002500040000

5 60

Length: A = upstream straight piping, B = meter, C = downstream straight piping, L = total length

*) max. fl owrange 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 fl ow for the vortex meter:

To maintain the range for custody transfer, fl ow may ne-ver drop below the minimum fl ow qfl min tabulated above.

Pressure loss of total meter run:

qfl min: minimum fl ow at fl owing conditionspfl : minimum operating pressure [bar (absolute)]f: signal frequency [Hz], (fmax at qfl max)K: meter factor [pulses/m3]

∆p = pressure loss (mbar)DN = nominal size (mm)ρfl = density at fl owing conditions (kg/m3)

Qn min · pnQfl min = ---------------- (m3/h) pfl

Qfl2

p = 2000 · fl · ------- DN4

fQfl = ----- · 3600 (m3/h) K

Status 12/2008 Vortex Flowmeter WBZ 08We reserve the right for technica changes

WÄGA Wärme-Gastechnik GmbHOsterholzstraße 45D-34123 KasselFon +49 (0)561 5007-0Fax +49 (0)561 5007-207

RMG Gaselan Regel + Messtechnik GmbHJulius-Pintsch-Ring 3D-15517 FürstenwaldeFon +49 (0)3361 356-60 Fax +49 (0)3361 356-836

CANADA

Bryan Donkin RMG Canada Ltd.50 Clarke Street South, WoodstockOntario N4S 7Y5, CanadaFon +1 519 53-98531 Fax +1 519 53-73339

USA

Mercury Instruments LLC3940 Virginia AvenueCincinnati, Ohio 45227Fon +1 513 272-1111Fax +1 513 272-0211

GERMANY

RMG Regel + Messtechnik GmbHOsterholzstraße 45D-34123 KasselFon +49 (0)561 5007-0Fax +49 (0)561 5007-107

RMG Messtechnik GmbHOtto-Hahn-Straße 5D-35510 ButzbachFon +49 (0)6033 897-0Fax +49 (0)6033 897-130

ENGLAND

Bryan Donkin RMG Gas Controls Ltd.Enterprise Drive, HolmewoodChesterfi eld S42 5UZ, EnglandFon +44 (0)1246 50150-1 Fax +44 (0)1246 50150-0

POLAND

Gazomet Sp. z o.o.ul. Sarnowska 263-900 Rawicz, PolenFon +48 (0)65 54624-01 Fax +48 (0)65 54624-08

RMG is your competent partner along the entire chain ran-ging from the exploration to the supply of fi nal consumers. Our reliable products and systems off er to you full control within the range of regulating and measuring technology.

Furthermore we plan and build plants according to your requirements and off er to you reliable and modern soluti-ons also in station automation. Ask us - we look forward to your challenges.

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