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NORWEGIAN SOCIETY OF CHARTERED ENGINEERS

NORWEGIAN SOCIETY FOR Oil AND GAS MEASUREMENT

NORTH SEA FLOW MEASUREMENT WORKSHOP 1993 26 - 28 October, Bergen

Cariolis Mass Flow Measurement

by

Mr. Stewart Nicholson, NEL, UK

Reproduction is prohtbited without written permission from NIF and the author

J

CDRIOLIS ~ FIOi MFASUREMENr

S Nicholson

NEL, F.ast Kilbride, Glasgow

SUMMARY

This paper describes the work undertaken during a two year consortium fun:ied project at NEL. The consortium consisted of nine members and was established to examine the generic behaviour of Coriolis Mass Flowneters in practical applications.

To this end, eight manufacturers each supplied a one-inch naninal bore meter. The calibration results fran tests on these meters are sumnarised. None of the results discussed are directly attri.l::uted to a particular mmufacturer to preserve confidentiality a.rrangarents .

The tests covered a range of liquid densities, viscosities and tanperatures. Tests were also undertaken to quantify installation and air entrainment ef fect.s on the meters. NEL also undertook gas tests on six of the meters. LPG tests were undertaken by NM.I in The Netherlands.

1

mrRCDr.l'Im

COriolis meters have been used in the market-place for sane years, although ~ it is fair to say that the market has been daninated by a few manufacturers.

Today there are many 11Dre Mass Flcwneter manufacturers and, to provide industry with canprehensive test data, meters fran a range of manufacturers 11111st be teste:l in any evaluation progranme.

?ml.* together with the consortium IIBObers decided that the project should SupfXJrt the testing of eight one-inch meters, which were suwlied for the duration of the tests by the manufacturers listed belCM. This would provide a representative sample of the meters available at the time of the progranme.

It was decided by NEL to form a consortium to fuirl test work on a range of coriolis meters an:::i the nine menber consortiwn ~ised:

CXNSORTIUM MEMBERS

Sta toil Philips Petroleum (UK) Ltd Elf (UK) Ltd Norweqian Petroleum Directorate Total Oil Marine Ltd hooco (UK) Ltd .Amerada Hess Ltd l<OOak Ltd I11'l

Endress and Hauser Schlumberger Rheonik K-Flow Micrarotion Exac Snith Krohne

LEAD LJ.\OORA'IORY: National Engineering laboratory (NEL) LPG TESTS: Netherlands Measuranent Institute (NMI)

The UK Department of Trade and Industry was represented by The National Weights and Measuratents Laboratory.

* The National Engineering laboratory Executive Agency (NEL) is an industrial research establishnent within the Department of Trade and Industry concerned with oost areas of rrechanical engineering research. Within NEL, the Flow Centre is the holder of the United Kinc;Pan National Standards for flow measurenent. Facilities exist for calibration and research into water, oil arrl gas fl<Y meters. All the facilities are fully traceable to the prllnary standards of weight, time, etc, and nost are accredited by The National Measurement and Accreditation service (NAHAS).

2

F.ach meter manufacturer or agent was initially invited to NEL to ensure that their meter was installed to their satisfaction before the first test.

All testing was can-ied out on the NEL low flow test loop. This consists of a gravimetric system using a 300 kg weightank with a pneumatically operated inlet valve which was fitted with switches to enable it to trigger start/stop timers am J;Ulse counters. The tank was weighed using a mechanical weighbridge am the temperature taken using platinum resistance t:hentoleters placed at either end of the test section arxl averaged over the duration of each test point. The test rig is illustrated in Fig. 1.

To enable standardisation, in meter package length, am::mgst all eight meters, an overall gap of 1.5 m was designated for the meters to be fitted into the test line.

Individual pipe lengths were manufactured to suit each package. Pressure tappings were located at either erx:l of the 1.5 m package.

In an effort to gain sane 'hands-on' experience of the neters, they were all given an initial calibration in kerosine at 20°C. This gave manufacturers an OP{X>rtunity to carment on these tests arrl to resolve any initial faults encountered during them.

To enable a coriolis meter to perfonn within its specification the meter has to go through a zeroing process before being p.it into operation. This is to enable the meter electronics to establish a datum with which to ccrnpare future readings. To perfonn this duty it is important that the meter is p.irged of all air which may be contained within the neter's tubes. The meter should also be protected to sCJIE degree fran external vibration fran pumps etc, as well as being clanped according to each manufacturer's guidelines. The flow llUlSt then be stoi:p:d before the zero adjustment is urrlert:aken.

Fig. 2 displays calibration results fran a meter with the zero adjustrrent carried out satisfactorily. If the zero adjustment is not satisfactory then a meter will produce a calibration characteristic similar to the one shown in Fig. 3.

All of the meters were calibrated using the p.llse outp.lts. Zero setting took place with the downstream valve closed before a test was urxiertaken, with the exception of the temperature tests. Dlring the first test it was discovered that sare of the meters 'download' pulse counts into a b.J.f fer rrerory which is emptied of J;Ulses sane seco00s later. This allows the generation of 'real' pulses sane seconds after the flCM has been stqp::d. Obviously if these pulses are not counted this can cause errors in the calibration curve similar to that of an incorrect zero.

3

FllJlD VI&DSI'IY AND IEN.5ITY TESTS.

Density was measured 'off-line' using a hydrostatic balance and a first degree equation of density as a function of tanperature was derived. This equation was then used to calculate the density of the liquid at the test tallperature.

Viscosity was measured by a falling ball viscaneter. This was again done off-line with the viscaneter connected to a hydrostatic bath. Water, kerosine, gas oil and glycol were used as test liquids, tlms enabling significant ranges of density arrl viscosity to be covered. This gave a viscosity range of 1.0-29.5 est be~ water and glycol at 20°C arrl a density range of O. 78-1.11 kg/1 for kerosine and glycol at 20°c. Results shoml in Fig. 4 show a iooter that was not affected by changes in viscosity or density, whereas Fig. 5 shows a meter that has a density effect and Fig. 6 a meter that suggests a viscosity effect.

Only one meter performed within the manufacturer's specification OYer the entire range of liquid tests. Two meters gave satisfactory results at high and medium flOfJrates h.lt drifted outside the manufacturers specification towards true lower f lowrates. The renaining neters shO\\led large calibration shifts.

Density ccrnparison readings ranged fran the best meter giving results within 0.001 kg/! and the worst within 0.120 kg/l.

To si..nulate installation effects on the meters, tests were undertaken to investigate the effects of:

- Tensile loading - canpressive loading "':'" Swirling velocity profile - Vibration.

Tensile and canpressive loadings were intrcxiuced using a hydraulically operated expansion piece upstream of the meter package. This was utilised to intrcx:iuce ccnpressive forces of up to 800 kgf arrl tensile forces of up to 350 kgf. None of the rreters was affected by either of those tests.

Swirl was intrc:xiuced by offsetting the meter package by means of a non­coplanar berrl assembly followed by a further 90 degree berrl. This arrangenent was fitted .innedi.ately upstream arrl downstream of the 11Eter package arrl is illustrated in Fig. 7. Pump vibration was isolatsi fran the meter by utilising rubber bellows upstream of the off set pipework. Two of the eight meters showed signs of 2ero drift at law flowrates after swirl was introduced. This is illustrated in Figs 8 and 9. This effect may have been caused by the :installation of this pipeline configuration rather than the fluid swirl as the high flow calibration was unaffected.

Finally, the meter package was vibrated in the vertical axis. This was done by installing an electranagnetic actuator to the upstream pipeo.10rk of the meter package as illustrated in Fig. 10.

4

Acceleration forces of up to 10 m/s 2 \Ere awlied over a frequency range of 30-1000 Hz, although each test was concentrated over that particular meter's tube vibration frequency.

Only one meter s~ an effect fran these forces. This occurred at one particular frequency which was different fran that meter's tube vibration frequency.

The meters were tested at three temperatures between 5 and 40°C. The test liquid in t.his series of tests was water. F.ach meter was zeroed at the datum tanperature, which could have been high or low tatperature depeOOing on the meter sequence in the test schejule. When the initial test was cC1T1plet.ed, the test tenperature was then reset, the systan allowed to settle and the next test coopleted. This was foll<Med by the final test. During these tests, the meters were not rezeroed, switched off or drained of test liquid.

Fig. 11 illustrates a meter with poor tenperature effect results, with an error of approx.inately 1.5 per cent at mid-flowrange. Fig. 12 shows a meter with a calibration which shows little or no temperature effect.

Of the eight meters, three s~ no effects due to fluid tenperature. 'l\.xl meters s~ calibration shifts in K-factor of 1.5 and 2 per cent. A further one had an increase in K-factor of 0.5 per cent arrl the remrining two had shifts of 1 and 1.5 per cent •

. Temperature sensor location wit.bin the meter housing plays a significant part in how accurately the meter temperature readout reflects fluid temperature. If the sensor is attached to the outside of the tube then the sensor will be affected by the air temperature within the case as well as the tube material and· fluid temperatures.

The variation in results fran all the meter temperature read-outs is illustrated in Table 1.

The differential pressure across each net.er package was IIDilitored throughout the tests using pressure tappings at either end of the package. These were connected to a calibrated Rosenount differential pressure transducer.

The pressure drop across the meter package was between 1.2 arrl 2.0 bar at a flowrate of 4.0 kg/s in kerosine.

'l\.xl of the meters tested gave audible signs of cavitation at 4 kg/s flowrate and their flowrate range was subsequent! y curtailed to prevent damage to those meters.

5

The air entrainment test set-up is illustrated in Fig. 13. The air suwJ.y was taken fran tile NEL 7 bar supply ard was controlled by a pressure regulator upstream of a critical flow nozzle package. This package contained a thentoteter, a 0. 508 nm di.ameter critical flow nozzle cud an upstream pressure gauge. A non-return valve was fitted to prevent test fluid flC7tling back through tile air supply line.

A critical flow rozzle was used to ensure that a constant mass flowrate of air with.in 0 .3 per cent was supplied, providei the upstream pressure and tenperature were rraintained constant.

Air temperature am pressure were rroni:to:red using a platinum resistance thernoneter and TeJcas Instrunents pressure gauge respectively.

Each meter was thoroughly flushed and a mid-range f lowrate set with no air injected. The rreter was 2eroed and an initial test point was uroertaken. An air flowrate of approxirrately 2 per cent by volume was set using the air regulator and the air fla,,v stopped. The meter was pirged of air arrl the liquid flo,..i stopped. 'l'he test point was started by sinultaneously starting the liquid arxi pre-set air flCJ111rate arrl stopped by closing OOt:h flows s.irnultaneausly when the -weightank was full. This method was repeated with air percentages up to 4 per cent by volume.

None of the meters perfoared satisfactorily. '.IWo of them ceased to operate on intrcrluct..ion of the two phase flow. One further meter gave a spread of results of 3 per cent b.lt _the density readings during the test points fluctuated. by 10 per cent. The ranaining meters gave calibration errors of up to SB per cent.

No correlation could be found between volume of air and K-factor error.

These tests w=re carried out in the Gas Flow Measurement Laboratory at NEL using air.

This set of tests can be split into n«> distinct sections: low ard hi<Jh pressure. Three meters had been supplied with 18 bar max pressure flanges and were tested at pressures of 15 bar across a flowrange 0.1-1.0 k.g/s. Three neters 1Nere supplied with f la.n.ges capable of withstarding high pressures. These were tested at 60 bar over a flowrange of 0.1-2.0 kg/s. '1Wo neters 1Nere not tested in air at the manufacturers' requests.

Of the three meters test:ai at low pressure, one gave results having a repeatability of 15 per cent. The ranaining ~exhibited linearities of afProXimatel y O . 6 per cent greater than was achieved fran liquid tests arxi repeatability of, in one case, 1 per cent greater than in liquid tests. In ooth these cases this related to a 10 per cent calibration shift in the K-factor results.

In the high pressure tests one met.er failed to operat.e. The remaining two meters displayed linearities of 1.5 arrl 1.3 per cent arxi repeatability of ±:0.3 per cent greater than their respective liquid tests.

6

Fig. 14 illustrate$ a la,,.r pressure test with zero set at 15 bar and zero set at ambient pressure. This shcMs a typical result in the difference in repeat.ability depending on the pressure at which the meter's zero is set.

Fig. 15 shows a high pressure test result where the neter was zeroed at both 60 bar and ambient pressure and the results are similar, in this case.

Six meters were sent to NMI in The Netherlands for testing at the Shell Pernis plant using LPG to give an extreme value of density.

The meters 'IEre all reconf igunrl to st.airlardise the pulse outpits alla,,.ring calibration by a crnpact meter prover.

Fig. 16 illustrates a typical meter calibration where the LPG results have been re-calculated and superi.np:lsed onto a graph of the previous test liquids. There is a shift in K-factor of approx:inately 0.5 per cent. Overall the LPG results prcx:iuced linearities of 0.05-1.0 per cent and repeat.ability of similar order to those of the respective meters in other liquid calibrations.

cnons1rns

Fran the results found the meters can be separated into four gruups.

One meter performed within the manufacturer's specification in all test phases.

'IWo meters performed to the manufacturers' specifications after initial teething problens had been overcane.

A further two meters, although not meeting the manufacturers' specification, indicated that the specif icatian could be obtained wit.h further upgrading.

The renaining three meters provided erratic test results throughoot the test series.

It is obvious fran the above that while a minority of m:mufacturers' meters perform satisfactorily, the majority showed significant roan for improvement.

It is encouraging to note that since the inception of th.is project many manufacturers have cane into the market with new products and ITDst of the manufacturers whose meters were tested in this report have already developed new meters or upgraded the meter electronics.

7

TABLE 1.

ltlldnal l3°C 20°C 45°C tanperat:ure

Meter NEL Meter NEL Meter NEL Meter Ref

oc Ge oc oc oc oc

l 12.18 10.60 19.95 19.00 45.29 44.50

2 12.24 11.22 19.86 18.96 46.14 45.24

3 12.75 NIA 19.94 NIA 45.34 NIA

4 12.29 12. 70 19.96 20.10 45.10 43.90

s 12.34 13.JO 19.93 21.00 44.69 NIA ~

6 12.74 12.60 20.16 20.00 45.74 45.00

7 12.3~ 15.00 20.04 23.00 44.91 47.00

8 12.85 14.10 20.40 21.20 46.28 44.50

Note: Meters 3 and 5 net tested at all 3 tauperatures

TEST METER TEMPERATURE COMPARISO

8

p T ,. METER PACKAGE 1.5m

Test Section 3m long

Supply Tonk

_,Flow

Cooling Circuit

FIG.1. TEST RTG I AYOllT

T

Bypass Control

VI

Pump

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.... 0 0 ii

I 1998 ~ ~

1988.

1970 I I I I • _J I I I 0 .s t 1.5 2 2.5 3 3.5 '4 4.5 s FLOWRATE.(kg/s)

• • • • FIG.2. SATISFACTORY ZERO CALIBRATION

-···- -·~-- --- - ---------- ·---·--- --·--· .. ----···-----· ·-----··--· ---·- '-----··-- .. -- -----· ·-·-···

20.2

Oi .::s::. 20.1 ...._ (I)

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0: 20 a l!I 0 a I-0

..... <{ LL ..... I 19.9 a ~

19.B

19 • 7 0._~ --.....J. L-5 --~-· -l~~---2-•5---· -~---··3·L----L _ __...._ _ _.. . . .5 4 4.5 5

FLOWRATE.(kg/s)

FIG.3. UNSATISFACTORY ZERO CALIBRATION

•

2020

1999 I-

ALL T£9TI HITlt ZERO AT H DtG,C:, 0---Btl!l.fll KtRO, 14152 Hlo- 6 Jf- ---1419l' G,OIL. 84194 Cl..YCOL- 0

B

1970 '--'-'1'------"1---L--..1_-- .I I

0 .S 1.5 2 2.S 3 I I --'·----3.5 4

I LOWHATE .(kg/s) . 4.S 5

• • • FIG.4. NO DENSITY OR VISCO~TTV ~~~~r.T~

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ALL TESTS MITH ZERO AT H Dta.c. 0-1418,,18 ICl:AO. 14112 H20-- {).

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se.s---~~...._• ____ ...._. __ ~~·---~---·~~_._• ____ _.... __ ~--·------__.•..__~__.·.__~__. 0 .s 1 1.s 2 2.s 3 3.s .. 4.5 s ·

FLOWRATE.(kg/s)

FIG.5. DENSTTY FFFFr.T

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• FIG.6.

2 2.5 l 3.5 FL nwRA TE .(kg/s) • VTSr.OSTTY Fl='l='F~T

4.5 5

•

• • •

1•1·• NB

\ Pipe clamplno lo lloor

FIG.7. SWIRL EFFECT TEST . PTPE LAYOllT

------·---------··-------------------.

20.2 •

~

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(f)

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B m Ii a: 20 .. l5J l5J l5J 0

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TEST IN ICEROBINE. H.JJEa.c. c:za..oJ

19.7 I I I I • I I I -0 .5 I I. 5 2 2.5 3 3.5 4 4.5 5 FLOWRA TE .(kg/s)

• • • • FIG.8. ZERO DRIFT DURING SWIRL TEST

..... l..J

103 -------·---------------·------------. 1

102.5

ci 101.5 0 1-u Lt_ I ~ IBI

100.s

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5 FLOWRATE.(kg/s)

FIG. 9. ZERO nRT FT nt I~ TM~ ~IAr rr:::u Tt:'CT

l.5m lcsl mclcr pockogc

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FLOW

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180.5

A A A A Oi A .:Y. 180 - A A A A A -- El (/) B

Cl> El El B

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El ::l m -Q-gs 99.5 • • f-

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TEST 14111.GLYCOL 149.Ct 0

99 0 .s I. 5 2 2.5 3 3.5 4.5 5

FLOWRATE.(kg/s)

FIG.11. POOR TEMPERATURE EFFECT CALIBRATION

"' 0

Oi ..:x:: --(/J (J) (/)

:::J

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2050 ----·----·---­-----~------

2030 ,..

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1990 ,_

1970,..

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FLOW RA TE .(kg/s)

• FIG.12. GOOD9r-EMPERATURE EFF!cr CALIBRATION. ,,

. "' ......

BBER BELLOWS .

.. IR PRESS. REGUL!-\TOR WITH GAUCE

R TEfvlP. PR0BE

NOZZLE PACKA··:.

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PRESSURE GAUG ·

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FIG.13. AIR ENTRAINMENT TEST. PIPE LAYOUT

Ol ::J:. --(/) Ql (/)

::J

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::::(

•

x ZERO SET HtTH NO rLOW RT ·~ AnR 0 ZERO SCT HITH NO ~LOH AT AMHl[NT PR(SSURE

1900r--=-~~~~T,~...;....~-..:~-=-=;,r-..:...:....:...~.:...:..:.:_..:..:::_:_:_:__T1:___:::~~~~--,,,-~~~~--.

1850

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1800 fl II ll ... II II

IC II ll JI M • M

M • • IC •ll

1750

FLOWRATE.(kg/s)

FIG. 14. tow PRESSURE GA' TEST RESULT •

1.ee

1.97

a.es

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::i .8- 1.e3

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• 99

* METER ZEROED AND TESTED AT 60 BAR ~~:..::::E::..1.-..i::-.u..R Z ROED AT AMBIE T AND

..

.e

• • II • • • • • II

1.2 1.4 1.6

FLOW RATE .(kg/s)

• •

1.8

FIG.15. HIGH PRESSURE GAS TEST RESULT

• •

• I

2

Oi .::t:. -.... CJ)

<l> CJ)

::::l _g. a: ..,, 0 ,,.. I-u <( LL

I ~

•

2030 ,---·--·-··--------- ---------- ·-------------------­---------l

2020 ~

2e1e -0

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1998 ,_

1989 ,_

0 0 0 e e

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ll'G ttBT.ca.cu.ma. - 0 D - •• 11 ... 11 tao. 1419'1! tmo - ll l - 14111n' 8.0IL. 8411"4 GLYCOL ~ 0

1970------a.•-------·------·~---·~----~·L-----Ll _____ .__. ____ i. ____ ~·~ ----~ 0 .5 I I .S 2 2.5 3 3.5 4 4.5 5

FLOWRATE.(kg/s)

FIG .11 . LPG AND LIOU!~ TEST RESULT •

References

[1] Paper presented at the North Sea Flow Measurement Workshop, a workshoparranged by NFOGM & TUV-NEL

Note that this reference was not part of the original paper, but has been addedsubsequently to make the paper searchable in Google Scholar.