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“Invent a New India Using Knowledge”

है”ह”ह

IS 15672 (2006): Flow measurement of natural gas and fluidsby coriolis meters [PGD 26: Weights and Measures]

IS 15672:2006

. Indian Standard

FLOW MEASUREMENT OF NATURAL GAS ANDFLUIDS BY CORIOLIS METERS

ICS 75.160.30; 75.180.30

0 BIS 2006

BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

June 2006 Price Group 8

———. I

Weights and Measures Sectional Committee, PG 26

!

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the Weights andMeasures Sectional Committee had been approved by the Production and General Engineering Division Council.

This standard is used for measuring the gas consumption at the users’ end, when the gas is supplied through thepipelines.

[n preparing this standard considerable assistance has been derived from following publication, 1

1S0 10’790:1999 ‘Measurement of fluid flow in closed conduits — Guidance to the selection, installationand use of Coriolis meters (mass flow, density and volume flow measurements)’.

Annexes A, B, C, and D are for information only.I

For the purpose of deciding whether a particular requirement of this standard is complied with, the final value,observed or calculated expressing the result of a test or analysis, shall be rounded off in accordance with 11S2:1960 ‘Rules for rounding off numerical values (revised)’.

IS 15672:2006

CONTENTS

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

Title

SCOPE

TERMINOLOGY

SELECTIONCRITERIAFORLJSEOFCORIOLISMETER

EFFECTSDUETOPROCESSCONDITIONSANDFLUIDPROPERTIES

PRESSURELoss

CALIBRATIONOFMASSFLOW

SAFETY

TRANSMI~R (SECONDARYDEVICE)

INSPECTIONANDCOMPLIANCE

MASSFLOWMEASUREMENT

FACTORSAFFECTmGMASSFLOWMEASUREMENT

ZEROADJUSTMENT

DENSITYMEASUREMENTI_hDERMETERINGCONDITIONS

VOLUMEFLOWMEASUREWNTUNDERMETERINGCONDITIONS

ADDITIONALMEASUREMENTS

MARKING

ANNEXA

ANNEXB

ANNEXC

ANNEXD

CALIBRATIONTECHNIQUES

SECONDARYCONTAINMENTOFCORIOLISMETERS

CORIOLISMETERSPECIFICATIONS

MASS“FRACTIONMEASUREMENTEXAMPLES

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IS 15672:2006

Indian Standard

FLOW MEASUREMENT OF NATURAL GAS ANDFLUIDS BY CORIOLIS METERS

1 SCOPE

1.1 This standard provides guidance on seIection,installation, calibration, performance and operation ofCoriolis meters for the determination of mass flow,density, volume flow and other related parameters offluids, synonymous for liquids and gases. For gases itspecifies the determination of gas mass flow andstandard volume flow (using pre-determined standarddensity). It also specifies appropriate considerationsregarding the fluids to be measured.

1.2 The primary purpose of Coriolis meter is tomeasure mass flow. Some of the meters offeradditional possibilities for determining the densityand temperature of fluids. From the abovemeasurements, volume flow and other relatedparameters may be determined. The Coriolis meter isused for fluids mixture of solids, gas in liquids andmixture of liquids.

2 TERMINOLOGY

2.1 Coriolis Meter — It is a device consisting of aflow sensor (primary device) and a transmitter(secondary device) which primarily measures the massflow by means of interaction between a flowing fluidand the oscillation of a tube or tubes. It may alsoprovide measurements of the density and the processthe temperature of the liquid.

2.2 Flow Sensor (Primary Device) — It is amechanical assembly consisting of an oscillating tube,drive system, measurement sensor(s), supportingstructures and housing.

2.3 Oscillating Tube(s) — Tube(s) through which thefluid flows to be measured.

2.4 Drive System — It is the means for inducing theoscillation of tube(s).

2.5 Sensing Device — Sensor to detect the effect ofthe Coriolis force and to measure the frequency of thetube oscillations.

2.6 Supporting Structure — Support for theoscillating tube(s).

2.7 Housing — It is the environmental protection ofthe flow sensor.

2.8 Secondary Containment — The housing design

to provide protection to the environment in the eventof tube failure.

2.9 Transmitter (Seccmdary Device) — Itis theelectronic control system providing the drive andtransforming the signals from the flow sensor, to giveoutput(s) of the measured inferred parameters. It alsoprovides corrections derived from parameters such astemperature.

2.10 Flow Rate — It is the ratio of quantity of fluidpassing through the cross-section of the flow sensorand the time taken for the quantity to pass to thissection,

2.11 Mass Flow Rate — Itis the flow rate in whichthe quantity of fluid passes is expressed as mass flowrate.

2.12 Volume Flow Rate — It is the flow rate in whichthe quantity of fluid which passes is expressed asvolume flow rate.

2.13 Accuracy of Measurement — It is the closenessof the agreement betwen the measurement and a true”w-dueof the measurement.

2.14 Simplicity — The mass flow meter is designedto use as a stand-alone device. It can be easily changedthe configuration of the meter without the need forcomputers, complicated software or scripts.

2.15 Repeatability of Results of Measurements —The closeness of the agreement between the results ofsuccessive measurements of the same measurementcarried out under the same conditions of measurement.

In the mass flow meter there are very few moving parts.All of the internal components are fixed in placeresulting in very little physical change inside the massflow meter. Little physical change in the flow cavitymeans higher rates of consistency and repeatability.

2.16 Uncertainty of Measurement — The parameter,associated with the result of a measurement thatcharacterizes the dispersion of the values that couldreasonably be attributed to the measurement.

2.17 Error of Measurement — The result of ameasurement minus true values of the measurement.

2.18 Calibration Factor(s) — Itis the numericalfactor(s) unique to each sensor derived during sensor

IS 15672:2006

calibration which when programme into the sensorsthat the meter performs to its static specification.

2.19 F1ow Calibration -Factor(s) —It is associatedwith the mass flow measurement.

2.20 Density Calibration Factor(s) — It is associatedwith the density measurement.

2.2-1 Zero Offset — It is the measurement of outputindicated under zero flow conditions, usually as a resultof stressed being applied to the oscillating tubes bythe surrounding pipe work and the process conditions.The zero offset can be reduced by means of a zeroadjustment procedure.

2.22 Zero Stability — His the magnitude of the meteroutput of the zero flow after the zero adjustmentprocedure has been completed, expressed by themanufacturer as an absolute value in mass per unit time.This value for zero stability is valid for stable conditions.

2.23 Flashing — It is the (liquids) phenomenon whichoccurs when the line pressure drops to, or below, thevapour pressure of the liquid. This is often due topressure drops caused by an increase in the liquidvelocity. Flashing is not applicable to gases.

2.24 Cavitation — It is the (liquid) phenomenonrelated to and following flashing if the pressurerecovers causing the vapour bubbles to collapse(implode). Cavitation is not applicable to gases.

2.25 Dependability — The mass flow meters arebeing used in process like leak detection, flowmonitoring and atmospheric testing.

It is the term defined that the Coriolis meter is beingused in process like leak detection, flow monitoringand atmospheric testing.

2.26 Relative Humidity — It is the actual amount ofwater vapour contained ima gas as a percentage of themaximum water vapour contained if the gas fullysaturated at metering conditions.

2.27 Choked Flow — It is the maximum flow rate fora particular geometry which can exist for the givenupstream conditions. When choked flow occurs, thevelocity at cross-section is equal to the local value ofthe speed of sound (acoustic velocity), the velocity atwhich small pressure disturbances propagate. Chokedflow can occur either at the inlet or the outlet of aCoriolis meter.

2.28 Shock Wave — It is the discontinuity insupersonic flow across which there is a sudden rise inpressure and temperature.

2.29 Critical Nozzle — It is the venture nozzle forwhich the nozzle geometrical configuration andconditions of use are such that the flow rate is critical.

3 SELECTION CRITERIA FOR USE OFCOR1OL1S METER

3.1 GeneraI

Coriolis meter shall be selected to measure parameterswithin the required range and accuracy. Considerationshall be taken to the following points when selecting aCoriolis meter:

a)

b)

c)

Accuracy — The accuracy varies dependingon the parameters to which it applies. Specificrecommendations are mass flow, density andvolume flow accuracies respectively. For theother parameters are like multi-componentssystems, immiscible mixture, mass fraction,volume fraction, net mass flow rate, netvolume flow rate, etc.NOTE— Manufacturers’ should specify accuracy forreference condition, if the conditions of use aresignificantly from those of the original calibration; themeter’s performance may be affected.

Installation — The manufacturer shouldspeci~ the preferred installation arrangementand state any instruction of use. Theinstallation arrangement shall be designed toprovide a maximum operating lifetime. Ifneeded, strainers, filters, air and/or vap-oureliminators or other protective devices shallbe placed upstream to the meter for theremovrrl of solids or vapours that could causedamage or provoke errors in themeasurements. Coriolis meter is generallyplaced in the mainstream of the flow but mayalso be placed in a by-pass arrangement fordensity measurements.

lnstallatiun criteria — Consideration shall begiven to the following points:

1)

2)

3)

4)

5)

space required for the Coriolis meterinstallation, including provision forexternal prover or master-meterconnections, should in-situ calibration isrequired;

class and type of pipe connections andmaterials, as well as the dimensions ofthe equipment to be used;

hazardous area classification;

climatic environmental -effects on thesensor, for instance temperature, humidity,corrosive atmospheres, mechanical shock,vibration and electromagnetic field; and

mounting and support requirements.

d) Full-pipe requirement — The.primary deviceshall be mounted such that the oscillatingtube(s) fill completely with the fluid beingmetered; this will prevent the measuringperformance of the instrument from being

2

impaired. The manufacturer should state the

means, if any, required to purge or drain gasesor liquid from the instrument.

e) Orientation — Plugging, coating, trapped gas,trapped condensate or settlement of solidmay effect the meter’s performance. Theorientation of the sensor fully depend on theintended application of the meter and thegeometry of the oscillating tube(s). Theorientation of the Coriolis meter shall berecommended by the manufacturer.

f) Flow conditions and straight length

requirements — The performance of aCoriolis meter is usually not affected byswirling fluid or non-uniform velocity profilesinduced by up-stream or down-stream pipingconfigurations. Although, specials straight-piping”length is normally not required, goodpiping practices shall be observed at alltimes.

g) Valves — Valves up-stream and down-streamto a Coriolis meter, installed for the purposeof isolation and zero adjustment can be of anytype, but should provide tight shut off. Controlvalves in series with a Coriolis meter shall beinstalled down-stream in order to maintain.thehighest possible pressure in the meter and thusreduce the chance of cavitation or flashing.

h) Cleaning — For certain applications (forinstance hygienic services), the Coriolis metermay require in-situ cleaning which may beaccomplished by;

1) mechanical means (using a pig orultrasonically);

2) self-draining by mounting instruments ininclined or vertically upstream lines.

3) hydro-dynamic means:

i) sterilization (steaming-in-place,SIP); and

ii) chemical or biological (cleaning-in-place, CIP).

Care shall be taken to avoid cross-contamination after cleaning fluids have beenused. Also chemical compatibility shall beestablished between the sensor wettedmaterials, process fluid and cleaning fluid.

j) Hydraulic and mechanical vibrations — Themanufacturer should specify the operatingfrequency range of the instrument to enableassessment of possible influences of processor other external mechanically imposedfi-equencies.It is possible that the performanceof the meter maybe influenced by frequenciesother than the operating frequencies. These

k)

IS 15672:2006

effects may largely be addressed byappropriate mounting or clamping of theinstrument.

In environments with high mechanicalvibrations or flow pulsations, considerationshall be given to the use of pulsation dampingdevices and/or vibration isolators and/orflexible connections.

Flashing and/or cavitation — The relativelyhigh fluid velocities which often occur inCoriolis me~ers,cause local dynamic pressuredrops inside the meter which may result inflashing andlor cavitation.

Both flashing and cavitation in Coriolis meters(and immediately up-stream and/or down-stream ofthem), shall be avoided at all times.Flashing and cavitation may causemeasurement errors and may damage thesensor.

m) Pipe stress and torsion — The flow sensorwill be subjected to axial, bending andtorsional forces during operation. Changes inthese forces, resulting from variations inprocess temperature and/or pressure, canaffect the performance of the Coriolis meter.Care shall be taken to ensure that no forcesare exerted on the meter from clampingarrangements.

Measures should also be taken to preventexcessive stresses from being exerted on theCoriolis meter by connecting pipes. Under nocircumstances should the Coriolis meter -beused to align the pipe work.

n) Cross-talk between sensors — If two or moreCoriolis meters are to be mounted closetogether, interference through mechanicalcoupling may occur. This is often referred toas cross-talk. The manufacturer shall beconsulted for methods of avoiding cross-talk.

4 EFFECTS DUE TO PROCESS CONDITIONSAND FLUID PROPERTIES

4.1 General

Variations in fluid properties such as density, viscosityand process conditions such as pressure andtemperature, may influence the meter’s performance.These effects have influences which differ dependingon which parameter isof interest.

4.2 Application and Fluid Properties

In order to identi@ the optimum -meter for a givenapplication, it is important to establish the range ofconditions to which the Coriolis meter will besubjected. These conditions should include:

3

1S 15672:2006

a)

b)

c)

d)

e)

o

~)h)

j)

operating flow rates and the following flowcharacteristics: uni-directional or hi-directional,continuous, intermittent or fluctuating;

range of operating densities;

range of operating temperatures;

range of operating pressures;

pressure on the fluid adequate to preventcavitation and flashing;

permissible pressure loss;

range of operating viscosities;

properties of the meter~d fluids, includingvapour pressure, two-phase flow andcorrosiveness; and

effects of corrosive additives or contaminantson the meters and the quantity and size offoreign matter, including abrasive particlesthat may be carried in the liquid stream.

4.3 Multiphase Flow

Liquid mixtures, homogeneous mixtures of solids inliquids or homogeneous mixtures of liquids with lowratios of gas, may be measured satisfactorily inmost cases. Multiphase applications involvingnon-homogeneous mixtures can cause additionalmeasurement errors and in some cases can stopoperation. Care shall be taken to ensure that gas bubblesor condensate droplets are not trapped in the meter.

4.4 Influence of Process Fluid

Erosion, corrosion and deposition of material on theinside of the vibrating tube(s) (sometimes referred toas coating) can initially cause measurement errors inflow and density, and in the longer term, sensorfailure.

4.5 Temperature Effects

A change in temperature may affect the properties ofsensor materials and thus will influence the responseof the sensor. A means of compensation for this effectis usually incorporated in the transmitter.

4.6 Pressure Effects

Static pressure changes may affect the accuracy of thesensor, the extent of which shall be specified by themanufacturer. These changes are not normallycompensated except in cases of certain precisionmeasurements and certain meter designs and sizes.

4.7 Pulsating F1OWEffects

Corioiis meters generally are able to perform underpulsating flow conditions. However, there may becircumstances where pulsations can affect theperformance of the meter. The manufacturers’

recommendations shall be observed regarding theapplication and the possible use of pulsation dampingdevices.

4.8 Viscosity Effects

Higher viscosity fluids may draw energy from theCoriolis excitation system particularly at the start offlow. Depending on the meter design, this phenomenonmay cause the sensor tubes to momentarily stall untilthe flow is properly established. This phenomenonshould normally induce a temporary alarm conditionin the transmitter.

5 PRESSURE LOSS

A loss in pressure may occur as the fluid flows throughto the censor. The magnitude of this loss is a functionof the size and geometry of the oscillating tube(s), themass flow rate (velocity) and dynamic viscosity of theprocess fluid. Manufacturers should specify the lossin pressure which occur under references conditionsand should provide the information necessary tocalculate the loss in p~essure which occurs underoperating conditions. The overall pressure of thesystem should be checked to insure that it is sufficientlyhigh to accommodate the loss in pressure across themeter.

6 CALIBRATION OF MASS FLOW

6.1 Every Coriolis meter shall be calibrated against atraceable National/International Standard by themanufacturer, and calibration certificates for the metershal I be provided. The calibration factors determinedby this procedure shall be noted on the sensor dataplate.

6.2 The calibration of a Coriolis meter is similar tothe calibration of any other flow meter. The calibrationconsists of comparing the output of the meter againsta traceable standard which has a better uncertainty,preferably at least three times better, than that requiredfor the meter under test.

6.3 As the Coriolis meter is a mass flow device, it ispreferable to perform the calibration against a mass orgravimetric reference. Calibration against a volumestandard combined with density determination may beused in situations where mass or gravimetric methodsare not available or not possible, especially whenmaking field calibrations. The errors introduced by thismethod have to be carefully assessed. If a Coriolismaster meter is used, care shall be taken to avoid cross-talk.

6.4 Calibration should, -when possible, be performedusing products and conditions as close as possible tothose for the. intended use. Prior to the start of thecalibration, the zero of the meter shall be checked. The

4

Coriolis meter may need to have a zero adjustment inthe calibration test rig and again in the final installation.Detailed calibration advice, calibration intervals,suggested procedures, calibration levels and anexample of a calibration curve are given in Annex A.

7 SAFETY

7.1 General

The meter should not be used under conditions whichare outside the meter’s specification. Meters shouldalso conform to any necessary hazardous areaclassifications.

7.2 Hydrostatic Pressure Test

The wetted parts of the fully-assembled flow sensorshall be hydrostatically tested in accordance with theappropriate standard.

7.3 Mechanical Stress

The meter shall be designed to withstand all loadsoriginating from the oscillating tube(s) system,temperature, pressure and pipe vibration. The usershould respect the limitations of the sensor at all times.

7.4 ‘Erosion

Fluids containing solid particles or cavitation can causeerosion of the measuring tube(s) during flow. Theeffect of erosion is dependent on meter size andgeometry, particle size, abrasives and velocity. Erosionshall be assessed for each type of use of the meter.

7.5 Corrosion

Corrosion, including galvanic corrosion, of the wettedmaterials can adversely affect the operating lifetimeof the sensor. The construction material of the sensorshall be selected to be compatible with process fluidsand cleaning fluids. Special attention shall be given tocorrosion and galvanic effects in no-flow or empty-pipe conditions. All process-wetted materials shall bespecified.

7.6 Housing Design

The housing shall be designed primarily to protect theflow sensor from deleterious effects from itssurrounding environment (dirt, condensation andmechanical interference) which might interfere withoperation. If the vibrating tube(s) of the Coriolis meterwere to fail, the housing containing the tube(s) wouldbe exposed to the process fluid and conditions whichcould possibly cause housing failure. It is important totake into consideration the following possibilities:

a) pressure within the housing might exceed thedesign limits; and

IS 15672:2006

b) fluid might be toxic, corrosive or volatile andmight leak from housing.

In order to avoid such problems, certain housingdesigns provide:

a) secondary pressure containment (see Annex B);and

b) burst discs or pressure-relief valves, fluiddrains “orvents, etc.

For guidelines on specifying secondary pressurecontainment, see Annex B.

7.7 Cleaning

7.7,1 For general guidelines, see 3.l(h).

7.7.2 Care shall be taken to ensure that cleaningconditions (fluids, temperatures, flow rates, etc) havebeen selected to be compatible with the materials ofthe Coriolis meter.

8 TRANSMITTER (SECONDARY D-EVICE)

Coriolis meters are multi-variable instruments providinga wide range of measurement data tlom only a singlepoint in the process. In selecting the most appropriatetransmitter, consideration should be given to:

a)

b)

c)

d)

e)

o

g)

h)

electrical, electronic, climatic and safetycompatibility;

mounting, that is, integrally or remotelymounted;

required number and tWe of outputs;

ease and security of programming;

outputs demonstrating adequate stability andreasonable response times, and in the case ofan analogue output including the minimumand maximum span adjustments;

output(s) indicating system errors;

required input options, for instance remotezero adjustment, totalizer resetting alarmacknowledgement; and

type of digital communication.

9 INSPECTION AND COMPLIANCE

9.1 As Coriolis meters are an integral part of the piping(in-line instrumentation), it is essential that theinstrument be subjected to testing procedures similarto those applied to other in-line equipment.

9.2 In addition to the instrument calibration andlorperformance checks, the following optional tests maybe performed to satisfj the mechanical requirements:

a) dimensional check,

b) additional hydrostatic test, in accordance witha traceable procedure, as specified by theuser; and

5

IS 15672:2006

c) radiographic and/or ultrasonic examination ofthe primary device to detect internal defects(that is, inclusions) and verifi weld integrity.

Results of the above tests shall be presented in acertified report, when requested.

9.3 In addition to the above reports, the followingcertificates shall be available at final inspection:

a) material certificates, for all pressure-containing parts;

b) certificate of conformance (electrical areaclassifications);

c) certificate of compliance; and

d) calibration certificate and test results.

10 MASS FLOW MEASUREMENT

10.1 Apparatus

10.1.1 Principle of Operation

Coriolis meters operate on the principle that inertiaforces are generated whenever a particle in a rotatingbody moves relative to the body in a direction towardor away from the centre of rotation. This principle isshown in Fig. 1.

A particle of mass ti~slides with constant velocity v ina tube Twhich is rotating with angular velocity w abouta fixed point P. The particle undergoes an accelerationwhich can be divided into two components:

a) a radial acceleration at (centripetal) equal toti.r and directed towards P;

b) a transverse acceleration a, (Coriolis) equal

a, .-

to 2 W.Vat right angles to aiand in the directionshown in .Fig. 1.

To impart the Coriolis acceleration at to the particle, aforce of magnitude 2 w.v.~nis required in the directionof al. The oscillating tube exerts this force on theparticle. The particle reacts to this force with an equalforce called the Corlolis force, AFC,which is definedas follows:

AFC = 2 W.V. dn,

When a fluid of density p flows at constant velocity valong an oscillating tube rotating as shown in Fig. 1,any length A, of the oscillating tube experiences atransverse Coriolis fo~ce of magnitude AFc = 2 w.v.p.A. A, where A is the cross-sectional area of theoscillating tube interior.

Since the mass flow rate q,. can be expressed as:

AFC =,2 w.q,,,.A,

Hence, the (direct or indirect) measurement of theCoriolis force exerted by the flowing fluid on a rotatingtube can provide a measurement of the mass flow rate.This is the principle of operation of a Coriolis meter.

10.1.2 Coriolis Sensor

In commercial designs of Coriolis meters, inertia forcesare generated by oscillating the tube rather than froma continuous rotary motion.

The smallest driving force required to keep the tube inconstant oscillation occurs when the frequency ofoscillation is at, or close to, the natural frequency ofthe filled tube.

at

I

FIG. 1 PRINCIPALOPERATIONOFCORIOLISMETER

6

IS 15672 :“jO06

In most meters the flow tube is fixed between twopoints and oscillated at a position midway betweenthese two points, thus giving rise to opposite oscillatoryrotations on the two halves of the tube. Meters canhave a singIe tube or two parallel tubes which can bestraight or looped.

When no flow is present, the phases of the relativedisplacements at the sensing points are identical, butwhen flow is present Coriolis forces act on theoscillating tube(s), causing a small displacement/deflection or twist which can be observed as a phasedifference between the sensing points.

Coriolis forces (and hence distortion of the tube) onlyexist when both axial motion and forced oscillationare present. When there is forced oscillation but no

Repeatability is otlen given as a separate parameter,expressed as a percentage of the reading. It is calculatedin a similar way to accuracy.

Accuracy and repeatability statements are usually madefor reference conditions which are specified by themanufacturer. These reference conditions shouldinclude temperature, pressure, density range and flowrange.

11 FACTORS AFFECTING MASS FLOWMEASUREMENT

11.1 General

See also Annex “Cfor further details.

11.2 Density and Viscosityflow, or flow with no oscillation, no deflection will

Density and viscosity usually have a minor effect onoccur and the meter will give no output.

measurements of mass flow. Consequently,The sensor is characterized by flow calibration factorswhich are derived during manufacture and calibration.These vaIues are unique for each sensor and arenormally recorded on a calibration certificate and/or adata plate secured to the sensor housing.

10.”1.3 Corio[is Transmitter

A Coriolis meter requires a transmitter to provide thedrive energy and to process the subsequent signals. Itis necessary to match the transmitter to the sensor byentering the calibration factors from -the sensor dataplate.

The mass flow rate is usually integrated over time inthe transmitter to give the total mass.

The transmitter may contain application softwarewhich can be used to evaluate additional parametersbut their requi~ements necessitate the entry of othercoefficients into the sofiware. All outputs are usuallyscaled separately.

10.2 Acmwacy

The term accuracy, expressed as a percentage of thereading, is often used by manufacturers and users as ameans of quantifying the expected error limits. Formass flow, the term accuracy includes the combinedeffects of linearity, repeatability, hysteresis and zerostability.

Linearity, repeatability and hysteresis are combinedand expressed as a percentage of the reading. Zerostability is given as a separate parameter in mass perunit time. In order to determine the complete accuracyvalue, it is necessary to calculate zero stability as apercentage of the reading at a specified flow rate, andadd this value to the combined effects of linearity,repeatability and hysteresis.

compensation is not normally necessary. However, forsome designs and sizes of meters, density changes mayinduce an offset in the meter output at zero flow and/or a change in the meter calibration factor. The offsetcan be eliminated by performing a zero adjustmentunder operating conditions.

11.3 Multiphase Flow

Liquid mixtures, homogeneous mixtures of solids inliquids, and homogeneous mixtures of liquids with alow ratio of gas maybe measured satisfactorily in manycases. Multiphase applications involving non-homogeneous mixtures can cause additionalmeasurement errors and in some cases can stopoperation. Care shall be taken to ensure that gas bubblesor condensate droplets are not trapped in the meter.Special attention shall be given under thesecircumstances to the zero-adjustment procedure.

11.4 Temperature

Temperature changes affect the flow calibration factorof the sensor and compensation is necessary.Compensation for this effect is usually performed “bythe transmitter. However, large differences intemperature between the oscillating tube(s) and theambient temperature can cause errors in thetemperature compensation. The use of insulationmaterials can minimize these effects. Temperaturevariations mayalso induce an offset in the meter outputat zero flow. Thus, it is-necessary to check the meterzero at the process temperature.

11.5 Pressure

Pressure usually has a minor effect on measurementsof mass flow and compensation is not normallynecessary, However, for some designs and sizes ofmeters, pressure changes can affect the flow calibration

7

IS 15672:2006

factor and, in this case, compensation is necessary.Pressure changes may also induce an offset in the meteroutput at zero flow. This effect can be eliminated byperforming a zero adjustment at the process pressure.

11.6 Installation

Stresses exerted on the sensor from surrounding pipework can introduce an offset in the meter output atzero flow. This offset shall be checked after the initialinstallation or after any subsequent change in theinstallation. Another zero adjustment shall beperformed, if the offset is unacceptable.

12 ZERO ADJUSTMENT

Once the meter installation is complete, a zeroadjustment is usually necessary to overcome the effectsdescribed above. To check or adjust the zero flow, themeter shall be full and all flow stopped by turning offthe down-stream valve first followed by the up-streamvalve. It is recommended that the meter zero is firstchecked, and adjusted if the offset is unacceptable. Zeroadjustment shall be made under process conditions oftemperature, pressure and density. It is essential thatthe fluid remain stable and that there are no bubbles orheavy sediment and no movement. Zero adjustment isusually initiated by pressing a zero button in thetransmitter or by remote control.

The level of the zero adjustment can be checked byobserving the meter output at zero flow. However,before viewing the output, it is essential that the lowflow cut-off setting in the transmitter be set to zero oralternatively, an output unaffected by the Iow flow cut-off setting be used. If appropriate, the hi-directionalfunction may need to be activated. .It is advisable tocheck the zero the meter periodically.

13 DENSITY MEASUREMENT -UNDERMETERING CONDITIONS

13.1 General

Coriolis meters can provide in-line densitymeasurement under metering conditions. This clauseoutlines how density and relative density measurementsare made on fluids under metering conditions. It alsoincludes recommendations for density calibration.Density-based inferred measurements such as standarddensity and concentration are dealt with in 8.

13.2 Principle of Operation

Coriolis meters are normally operated at their naturalor resonant frequency. For a resonant system there is avery close relationship between this frequency and themoving mass. With good approximation, the naturalfrequency ~f a Coriolis meter viewed as a resonantsystem can be written as:

with

m=mt+mfl

where

f = resonant or natural “frequency;

CR = mechanical stiffhess or the spring constantof the measuring tube arrangement;

m = total oscillating mass;

m, = oscillating mass of the measuring tube(s); ‘

mfl = oscillating mass of the fluid within thetube(s);

Vfl= volume of fluid within the tube(s); and

Pfl = density of the fluid.

The mechanical stiffhess or the spring constant of themeasuring tube arrangement depends on the design ofthe meter and the Young’s modulus of elasticity of thetube material.

The density of the fluid, pfl can be determined.

‘fl=[vfl(;fR)2]-t

and after simplification it “becomes:

where

K, and Kz are coefficients for the densitymeasurement, determined during the calibrationprocess.

The fi-equency can be determined by measuring theperiod of the tube oscillation, TPor by counting cycles,NCduring a time window (gate), tW:

fR =+- or fR~f w

K1 and Kz are temperature dependent and should beautomatically by means of an integral temperaturemeasurement.

13.3 Relative Density

Dividing the fluid density under process conditions bythe density of pure water under reference conditions,results in the relative density, d, under processconditions, as follows:

d- I%P.,&

8

where

P“ = density of fluid under metering conditions;and

PW,,~= density of water under reference conditions.

13.4 Accuracy

The term accuracy is often used by manufacturers andusers as a means of quantifying the -expected errorlimits. For density, the accuracy includes the combinedeffects of linearity, repeatability and hysteresis. Densityaccuracy is expressed as an absolute value in mass perunit volume (that is, g/cn# or kg/m3).

Accuracy and repeatability statements are usually givenfor reference conditions which are specified by themanufacturers. These reference conditions shouldinclude temperature, pressure, density range and flowrange. If properly installed, the meter should measuredensity within these accuracy limits.

13.5 Factors Affecting Density Measurement

13.5,1 General

See also Annex C for further details.

The measurement of density can be influenced bychanges in process conditions. In certain applications,these influences may be significant and manufacturersshall be able to quantify the effect, or give guidanceon the likely impact on the performance of the meter,for instance could be expressed as a density shifl perdegree change.

13.5.2 Temperature

Temperature changes can effect the density calibrationfactor of the sensor. Therefore, compensation for thesechanges is necessary and is performed automatically bythe transmitter. However, due to non-linearity of thedensity equation, the effect may not be entirelyeliminated. In order to minimize this effect in pensionapplications, it may be necessary to calibrate at theoperating temperature. Large differences in temperaturebetween the oscillating tube(s) and the ambienttemperature can errors in temperature compensation. Theuse of insulation materials can minimize these effects.

NOTE— In certain applications, for instance cryogenic liquids,there may be a transient temperature influence, resulting froma step change in process temperature (thermal shock) whichwill momentarily influence the density measurement, This mayalso need to be taken into account,

13.5.3 Pressure

Pressure usually has a minor effect on measurementsof density and compensation is not normally necessary.However, for some design and sizes of meters, pressurechanges can affect the density calibration factor. Inthis case, compensation is necessary and it may be

necessary to performoperating pressure.

13.5.4 Multiple Phases

IS 15672:2006

the calibration at process

The density of liquid mixtures, homogeneous mixturesof solids in liquids or homogeneous mixtures of liquidswith a low.ratio of gas maybe measured satisfactorily.[n some circumstances, multiphase applications(particularly gas bubbles in liquids) mean causeadditional measurement errors and even stop op-eration.The degree to which bubbles or suspended solids can-be tolerated without influencing the densitymeasurement will depend on their distribution in andcoupling with the carrier fluid. For example, largepockets of air in water are more troublesome thanhomogeneously distributed bubbles in a highly viscousliquid. The suitability of a Coriolis meter for densitymeasurement of a multiphase system will depend onits intended use. The choice of an appropriate metershould only be made after careful consideration andconsultation with the manufacturer.

13.5.5 Flow

Density calibration is usually carried out under staticconditions, that is, without any fluid flowing. However,when in operation on a flowing flui-d,hydraulic noisemay influence the density measurement. Fluidvelocities which may given rise to such an effect willvary depending on the sensor size and geometry. Forprecise densitymeasurements at velocities withirilheseranges, it is advisable to perform the density calibrationunder flowing conditions. Some manufacturers offerautomatic compensation for flow effects on densitymeasurement.

13.5.6 Corrosion, Erosion and Coating

Corrosion and erosion will decrease the mass of themeasuring tube; conversely, coating will increase themass of the tube. Both of these effects will induce errorsin the density measurement. In applications where theseeffects are likely, care shall be taken in specifyingsuitable materials, selecting the most appropriate metersize (limiting) velocity, and where necessary, applyingregular cleaning.

By monitoring the density measurement trend, it maybe possible to diagnose excessive corrosion, erosionor coating within the measuring tube(s).

13.5.7 Installation

Installation stresses do not influence the densitymeasurement. For certain sensor designs there may bea minor orientation effect. In precision densityapplications, it maybe necessary to calibrate the meterin is intended final orientation or alternatively performa field adjustment.

9

1S 15672:2006

13.6 Calibration and Adjustment 14.2 Volume Calculation

13.6.1 General

Coriolis meters maybe calibrated during manufactureand/or by field adjustment. Only single-phase, cleanliquids shall be used for calibration or adjustment. Themeasuring tubes shall be clean and fi-eeof coating ordeposits and shall be flushed immediately prior tocat ibration. Arty deviation from these requirementsmay result in significant measurement errors.

13.6.2 Manufacturer’s Calibration

Coriolis meters should .be calibrated by themanufacturer for density measurement, usually air andwater as reference fluids. The density calibrationfactors determined by this procedure shall be as givenby the manufacturer, usually noted on the sensor dataplate. If a precision density measurement is required,a special calibration may be necessary using multiplefluids of similar densities, temperatures and pressuresfor the final use. In these circumstances, a densitycalibration certificate for the meter shall be availableon request.

13.6.3 Fie[d A~usttnent

The advantage of field adjustment is that it can beperformed by the user with the process fluid in themeasuring tubes. It is essential that the densitymeasurement from the Coriolis meter remain stablebefore the adjustment is made. The user should knowthe density of the fluid within the meter to the requireduncertainty.

The transmitter shall be equipped with facilities tosupport a field adjustment with the meter filled withone or more liquids. Field adjustment is recommendedif installation effects, for instance meter orientation,are to be eliminated.

The procedure necessary to accomplish a field adjustmentshall be outlined in detail in the instruction manual.

NOTE — The Coriolis meter density measurement may oftenbe used as an indication of the stability of the system whichmay be helpful in diagnosing potential application and/orinstallation problems.

14 VOLUME FLOW MEASUREMENT UNDERMETERING CONDITIONS

14.1 General

Coriolis meters directly measure fluid mass flow rateand density under metering conditions. They aregenerally used -where measurements of either, or both,of these parameters are of key importance. There areapplications where the advantages of a Coriolis metermay be very beneficial, but the desired measurementis volume under metering conditions. Coriolis metersmay be effectively used for volume flow measurement.

Volume may be calculated from mass and density asfollows:

v=;

where

V = volume under metering conditions;

p = density under metering conditions; and

m = mass.

Above equation may be incorporated directly into thetransmitter software provided the Coriolis meter is ofa type that may measure both mass and density. Themass part of the above equation is measured as afunction af time (mass flow rate) and therefore thevolume calculated is.also a function of time.

9“=+where

q = volume flow rate under metering conditions;v

and

q. = mass flow rate.

The Coriolis meter may then provide the volume flowrate calculated from above equation as an outputsignal. The calculated volume flow rate may also beintegrated with respect to time to obtain the totalvolume.

The calculated volume flow is based on dynamic massflow and dynamic density measurements made underprocess conditions. Volume flow in this form is adynamic measurement under process conditions, notunder reference conditions.

14.3 Accuracy

The manufacturer should specify the expected accuracyfor volume measurement. If this information is notavailable, the expected accuracy for volume flowmeasurement may be-calculated from:

&v = -&;+&;

where

c, = accuracy of the volume measurement;

c. = accuracy of the mass measurement; and

EP= accuracy of the density measurement,

NOTE— All the above values of accuracy are expressed interms of* pereent of the reading.

14.4 Special-Influences

14.4,1 General

Coriolis meters may only give a computed value ofthe volume and as such, the reliability can be only as

10

good as the data entered into the volume equation. Onthis basis, any variation in the fluid or in processparameters which may have an influence on thereliability of mass flow and density measurements mayhave a combined effect on the reliability of thecalculated volume measurement. For specific effectsof variations in process conditions on mass flow anddensity measurements, see 5 and 6.

14.4.2 Emp& P@e Effect

A Coriolis meter measuring liquid flow may respondto tubes becoming empty or liquid being displaced byvapour by a drop in the density reading falling closeto zero. If this were to occur while there was still asmall indicated mass flow present, the calculation ofthe liquid volume would be erroneously high (see 14.2).This problem may be avoided by incorporating asuitable low-density cut-offsetting, designed to inhibitany flow measurement being performed unless themeter is properly filled with liquid. Manufacturer mayprovide alternative methods for eliminating thisproblem.

14.4.3 Multiphase Fluids

Liquid volumes cannot be measured reliably, if thereis more than one phase present.

14.5 Factory Calibration

14.5.1 Mass Flow and Densi@

When comparing a Coriolis meter volume output witha known volume standard, it is impossible todistinguish between the inaccuracy of the instrument’smass flow measurement and the inaccuracy of thedensity measurement. Therefore, for calibrationpurposes, Coriolis meters should always be consideredas mass flow and density measuring devices.

These two parameters should first be calibrated inaccordance with the recommendations given in 10and 11, before the meter can be used for volumetricmeasurements. Once the meter has been calibrated formass flow and density, a theoretical prediction of thevolume accuracy can be determined.

14.5.2 Volume Check

The expected value of accuracy for volumemeasurement may be checked by performing avolumetric test against a known volume standard. Inaddition to the standard calibration certificate onrequest manufacturers shall be able to provide test datashowing volume flow rates and correspondingvolumetric errors. These errors can be determined usingthe mass flow calibration data and the precisecalibration fluid density. The volume determinationcan also be checked by means of a field test, which

IS 15672:2006

shall be performed using the Coriolis meter in itsoperational installation using the process fluid.

15 ADDITIONAL MEASUREMENTS

15.1 General Considerations for Multi-ComponentSystems

The density measurement made by a Coriolis meter isa finction of the composite density of the process fluidof the tube(s). If the fluid contains two componentsand the density of each component is known, the massor volume fraction of each component can bedetermined.

By combining the (independent) mass flow rate anddensity (or concentration) measurements, the net massflow each component ~f a two-component mixture canalso be calculated. Net flow measurements are 1imitedto two-component systems for instance oil and water,and are useful in a wide variety of applications. Forexample, flow rates of each component of-two-component systems such as water-and-oil mixturesliquid-and-solid slurries, sugar measurements and othertwo-component systems can be determined using aCoriolis meter.

Theoretically a Coriolis meter will measure the averagedensity ofmulti-component fluids, including two-phasesystems. This is generally true in the case of slurries(solids carried by a liquid). However, measurements ofa gas phase in a liquid stream or conversely, a liquid ina gas stream, can be difficult to make due to structural;influenc~s within the sensing element. Consult themanufacturer, if two-phase flow is to be measured.

15.2 Immiscible Mixtures

15.2.1 General

An immiscible liquid is a liquid containing twocomponents which do not mix. The total volume is thesum of the individual volumes under meteringconditions.

15.2.2 Mass Fraction

The relationship between component A and componentB respectively, as a mass fraction w expressed as apercentage.

PB(PA - p~,~.., ) ~ , ~.WB =

memum, (PA -a)P

where

WAand w~ = respective mass fractions ofcomponent A and component B inrelation to the mixture;

11

IS 15672:2006

f. and f, = respective densities of componentand component B; and

P = measured density of the mixture.,ncasured

15.2.3 Volume Fraction,

The relationship between component A and componentB, as a volume fraction p expressed as a percentage.

PmmsuredVA =

-F% XlooPA–fi

where

9Aand % = respective volume fractions ofcomponent A and component B inrelation to the mixture.

15.2.4 Net Mass Flow Rate

By combining the total mass flow rate and the massfraction measurements, the net mass flow rate of eachof two-components may be calculated as follows:

~ A = qm.T x ‘AIll 100

~, B=!?m.TxwBn 100

where

qm~ = total mass flow rate of the mixture;and

q~,Aand q. * = net mass flow rate of components Aand B, respectively.

15.2.5 Net Volume Flow Rate

By combining the total volume flow rate and volumefraction measurements, the net volume flow rate ofeach of two-components maybe calculated as follows:

qv.T x 9A

qvA = 100

qvTx~B

q,B=100

where

qv,~ = net total volume flow rate;

qv.A and qv.B= net volume flow rate of components

A and B, respectively; and

~. and % = respective volume fractions ofcomponents A and B in relation tomixture (see 15.2.3).

15.3 Miscible Liquids Containing Chemically Non--interacting Components

A miscible liquid consists of two components which

mix completely or dissolve together and the totalvolume of the liquid maybe different from the sum ofthe individual volumes .at metering conditions.

When two liquids are completely miscible, such asalcohol and water, the mass fi-action (of either liquidcomponent) versus density is usually read fi-om tablevalues. It is not possible to obtain general equation validfor all miscible liquids due to the non-linear relationshipbetween mass fi-action and density. It is necessary toderive an equation for each mixture (see Annex D).

15.4 Solutions Containing Chemically-InteractingComponents

The relationship between two soluble liquids whichreact chemically is complex, see Annex D.

15.5 Special Consideration for Temperature andPressure

The previous equations and discussions (as well as thosein Annex D) assume constant temperature and pressureconditions. In any mixture, temperature and pressurewill affect the density of each of the two componentsdifferently. Therefore, corrections are required.Typically, pressure has a small influence on the densityand can be considered negligible, particularly if thepressure is almost constant. Any influence can becharacterized.by making a calibration. Temperature hasa much larger influence and on-line corrections arenecessary. Coriolis meters provide temperaturemeasurement for material property corrections of thesensing element. This is a convenient measurement touse for liquid prbperty corrections within the transmitter,however, it may be necessary to make a separatetemperature measurement for precision applications.

16 MARKING

The meter shall be marked with at least the followinginformation:

a) Manufacturer’s name or trade-mark,

b) Serial number;

c) Maxim~ flow rate, q~= in actual volumeunits; and

d) Maximum allowable operating pressure.

16.1 BIS Certification Marking

The product may also be marked with the StandardMark.

16.1.1 The use of the Standard Mark is governed bythe provisions of Bureau ofIndian Standards Act, 1986and the Rules and Regulations made thereunder. Thedetails of conditions under which the licence for theuse the Standard Mark may be granted to manufacturersor producers may be obtained from the Bureau ofIndian Standards.

12

IS 15672:2006

ANNEX A

(Clause 6.4)

CALIBRATION TECHNIQUES

A-1 1NTRODUCTION

Coriolis meters are calibrated in the same manner anany other flow meter. Calibration involves comparingthe output of the meter under test with a suitablestandard of adequate certainty. There are two levels ofcalibration, described in detail in A-2, as follows:

a) Type 1 standard calibration — the details ofwhich are specified by the manufacturer; and

b) Type 2 special calibration — the details ofwhich are specified by the user.

Ideally, Coriolis meters shall be calibrated usingg-avimetric techniques. However, volumetric methodscan also be used, provided the overall uncertainties ofthe mass flow measurement include the uncertainty ofboth volume and density measurements. C.oriolismeters measure mass, therefore, quantities of fluidmeasured during a gravimetric calibration, shouidultimately be expressed in units of mass that iscorrected for buyoyance.

NOTE — Calibration strictly refers to the procedure by whichthe flow meter is checked against a traceable reference anddoes not include adjustment to the calibration factors.

A-2 CALIBRATION METHODS

A-2. 1 General Considerations

When calibrating Coriolis meters, it is advisable tocollect data from the transmitter output(s) which is (are)independent of any damping settings. A sufficientnumber of pulses shall be counted during the test toestablish an acceptable calibration uncertainty.

There are three main methods for calibrating flowmeters: gravimetric, volumetric and by use of a master-meter. In each case, two operational techniques can beused.

a) Dynamic flying) start/stop — data collectionstarts and stops while the fluid is maintainedat a stable flow rate. The transmitter-signalprocessing time may result in a delay in thepulsed output. This shall be taken intoconsideration when using a dynamic methodin which small amounts of liquid aremeasured, for instance small volume _proversand diverter-based test facilities.

b) Static start/stop — data collection starts andstops at zero flow conditions. In this case, therun time shall be sufficiently long to accountfor errors induced by flow rate variations at

the start and end of the run. The transmitter-signal processing time may result in a lag inthe pulsed output. Therefore, even after thevalve has been closed and the flow hasstopped, the meter’s electronics may cent inueto indicate flow. Errors due to this delayedpulse output shall be accounted for.

A-2.2 Gravimetric Methods

The test fluid shall be collected in a weighing vessel.rhe mass of the vessel shall be recorded before thetest starts and after the test is completed. The differencebetween these two readings is the collected mass andin the case where air or gas is displaced, the collectedmass shall be corrected for buoyant y. Care shal 1 betaken to avoid evaporation and the formation ofcondensation on the tank walls. Calibration is madeby comparing the transmitter totalizer with thecollected mass.

A-2.3 ‘Volumetric

The Coriolis meter can be calibrated using anestablished volumetric method, for instance collectingthe test fluid in a certified vessel or using a volumeprover. However, the collected quantity (volume) mustbe converted into mass by multiplication by the fluiddensity. The density can be measured dynamicallyusing an on-line densitometer or, if the fluid density isconstant, by sampling methods. If the properties of thefluid are well known, the density can also bedetermined by measuring the fluid temperature andpressure within the vessel.

A-2.4 Master-Meter (Reference Meter)

A master-meter can also be used to calibrate a CorioIismeter using established methods. The stability andaccuracy of the master-meter shall be fully documentedand should provide adequate uncertainty in mass units.If the master-meter is a volumetric device, itsmeasurement shall be converted to mass using thedensity. The density can be measured dynamicallyusing an on-line densitometer or, if the fluid density isconstant, using sampling methods. If the properties ofthe fluid are well known, the density can -also bedetermined by measuring the fluid temperature andpressure during the test.

If the master-meter is a Coriolis device, care shall betaken to avoid cross-talk. The manufacturer shall beconsulted for methods of avoiding cross-talk.

13

“’ # I

IS 15672:2006

A-2.5 Calibration Frequency

A Ccmiolis meter should not drift, if it is correctlyinstalled and used with clean, non-abrasive fluids. Thefrequency of calibration of the meter is governed bythe criticality and nature of the operating conditions.It may be appropriate to reduce or increase thefrequency of calibration as data isgathered. For fiscaland/or custody transfer applications, this frequencymay be prescribed by regulation, or agreed betweenthe relevant parties, and may be once or twice peryear.

If the meter installation conditions vary, for instanceas a “resultof pipe work modification in the vicinity ofthe meter, it is likely that the meter zero offset will beaffected. This can be corrected by conducting a zeroadjustment. A zero adjustment is needed if the meteroutput at zero flow conditions is greater than the meterzero stability specified by the manufacturer.

A-3 CALIBRATION PROCEDURES

The procedures adopted for all meter calibrationmethods should ensure that:

a)

b)

c)

d)

e)

f)

meter is installed in accordance withmanufacturer’s recommendations;

meter under test, and the test facility itself, istilled completely with test fluid before andafter the test to prevent any effect fi-omair;

calibration is preceded by an appropriatewarm-up period and hydraulic run-in time;

all transmitter configuration data is recordedprior to the start of.the test;

meter output is monitored at zero flow beforeand atler the test; and

test flow rates are selected to cover theoperating flow range of the meter when it isin service.

A-4 CALIBRATION CONDITIONS

A-4. 1 Flow Stability

The flow must be kept stable to within +5 percent ofthe selected flow rate for the duration of the calibrationtest at that flow rate.

A-4.2 Zero Adjustment

First, a zero flow condition shall be established (andchecked) in the test rig. If the meter output at zero flowconditions is within the zero stability value specifiedby the manufacturer, a zero adjustment will not benecessary. However, if the output at zero flowconditions is seen to be unsatisfactory, a single zero

adjustment shall be made only at the start of thecalibration and not between runs. It is recommendedthat the fluid conditions be recorded as part of the zeroadjustment.

A-4.3 Temperature and Pressure

Variations in fluid temperature and pressure shall beminimized during the calibration process. For a singlerun, the temperature shall be held constant towithin 1‘C, and to within 5°C for the entire durationof the calibration. The fluid pressure within the testrig shall be kept sufficiently high to avoid flashing orcavitations in the meter and/or in the vicinity of themeter. Ideally, proving shall be performed under thenormal operating pressure and temperature conditionsof the intended use,

A-4.4 Density and ‘Viscosity

Depending on, the, Cori,olis meter design, theperformance may be affected by variations in fluiddensity and viscosity. In these cases, test fluids shallbe used having properties that are the same or similarto the process fluid for which the meter is intended.

A-5 -CALIBRATION CERTIFICATE

The following data shall be included on a metercalibration certificate:

a)

b)

c)

d)

e)

0

g)

h)

j)k)

m)

n)

P)

@

unique attribute certificate number, repeatedon each page along with the page number andthe total number of pages;

certificate date of issue and the test date if itdiffers from the certificate date of issue;

identity of the party commissioning the test;

name and location of the test laboratory;

test fluid data such as product name or density;temperature pressure;

unique identification of meter under test;

traceability of the test facility and itsprocedures;

uncertainty statement and calculation method;

relevant ambient conditions;

relevant test data and the results of thecalibration, including meter output at zeroflow at start and finish of calibration;

calibration data shall be presented inchronological order;

orientation of the Coriolis meter;

configuration data within the transmitter atwhich the calibration is performed; and

authorized signature.

14

.

A-6 TYPICAL<ALIBRATION CERTIFICATE

A typical calibration certification format is given below:

‘certificateNo.: .................................................................................... Page .........OF..............

upplier: .........................................................................................................................

ensor: Type number .....................................................................................................

Serial number ...................................................................................................

Sensor calibration factor ..................................................................................

ransmitter: ..........................................................................................................................

ensor: Type number ....................................................................................................

Serial number ...................................................................................................

mA-pulsed-density etc .....................................................................................

)Utputcalibrated:’ ...........................................................................................

‘est Conditions

alibration fluid (product name) ...........................................................................................

‘iscosity ................................................. at ................................. ‘C

)ensity ................................................. at .................................°C

‘temperature of test fluid ...................................................................................... “c‘ressure at inlet to the meter ..................................................................................... bar

)utput at zero flow before calibration .....................................!.....................................................

)utput at zero flow after calibration ...........................................................................................

orientation .........................................................................!...... ...........

‘acility traceable to ...........................................................................................

Uncertainty of test facility ...........................................................................................

91h Percent of Indicated Mass Observed Error Spec$cation

ScaIe Mass Reference (%) (’??)

. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . ..

. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . ..

. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . ..

. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . ..

3bserved i--

:rror I I I I I I I I I I I I I I I I I

(0/0)\

r-

50% 100% at fullscale reading ‘

Flow range minimum ..................................maximum ........................................

Pressure drop at maximum flow ...........................................................................................................

Configuration data at which calibration was performed

(may be printed on separate sheet, belonging to this certificate)

15

IS 15672:2006

ANNEX B

(Clause 7.6)

SECONDARY CONTAINMENT OF CORIOLIS METERS

B-1 SAFETY GUIDELINES FOR THE SELECTIONOF-COR-1OL1S METERS

B-1.l General Considerations

When the Coriolis meter is used in critical applications,such as in offshore oil and gas production and in theImetering of flammable or toxic substances, care shallbe taken to verifi that the integrity of the meter can bemaintained up to test pressure over the expectedlifetime under true process “conditions.

It is generally thought that because Coriolis meters havethin-walled vibrating tubes, they are vulnerable to stressfatigue resulting in tube failure. This is commonmisconception and has often led to a gross over-specification of these meters or in some cases, theiravoidance altogether.

Experience amongst manufacturers demonstrates thatwhen used in normal operation, the stresses inducedwithin a Coriolis meter are too small to instigate fatigue.

When Coriolis meters are specified for a particularapplication, special attention shall be given to thefollowing specific areas.

B-1,2 Materials

Care shall be taken to establish that suitable wettedmaterials re-selected for compatibility with the processfluid(s) being metered including cleaning fluids.Material incompatibility is the most common sourceof Coriolis-tube fracture and-can be totally avoided atthe sensor selection stage. Standard material guidesdo not necessarily apply to thin-walled, vibrating tubes.Manufacturers’ recommendations shall be consideredas well as standard material guides.

B-1.3 Velocity

Care shall be taken to ensure that no erosion takes placewithin the sensor when measuring the flow of abrasiveproducts. Thinning of the measuring tube througherosion crm eventually lead to catastrophic failure.Manufacturers shall be able to specifj the maximumflow velocity not subject to erosion for a given sensorsize.

B-1.4 Tube Pressure Rating

In order to guarantee conformance for the tube pressurerating, the manufacturer should provide the followinginformation:

a) ASME Codes to which the tubes have been

designed (or a recognized equivalentstandard); and

b) design calculations pertaining to the codesmentioned in (a) for the wail thickness,pressure ratings, etc.

B-1.5 Flange Pressure Rating

Similarly, appropriate ASME design Codes shall beavaitable for checking the suitability of the connectionsto the Coriolis sensor.

B-1.6 Pressure Testing

Evidence shall be available from the manufacturer toconfirm that the full-assembled sensor has passed anappropriate pressure test. This evidence shall beavailable in terms of a certificate or a test procedure.

When the above criteria can be fidfilled for any givenuse, secondary containment should not be necessary.

B-2 SECONDARY CONTAINMENT

B-2. 1 Appropria-te Use

While the principles laid down in B-1 serve as safetyguidelines for meter selection, there may be situationswhere all of the above-mentioned criteria cannot besatisfied. For example, if some concern remainsregarding material compatibility due to the unknownnature of the process fluids which will pass throughthe meter, then secondary containment may berequired. In this case, the following issues shall beaddressed regarding the integrity of the secondarycontainment offered.

B-2.2 Design Integrity

Evidence shall be available from the manufacturerdemonstrating ,that the containment vessel has beendesigned specifically for the given purpose and inaccordance with a recognized standard.

B-2.3 Pressure Testing

In addition to the provision of design calculationsdemonstrating the suitability of a containment vessel,it may be necessary for manufacturers to-perform teston the fully assembled containment vessel. Suchpressure tests shall be conducted using suitable purgeconnections in the containment case. Test shouldconform to an established procedure and shall %esupported by the necessary documentation and testcertificates.

I

I

16

IS 15672:2006

B-2.4 Selection of Appropriate Secondary-Containment Pressure Ratings

General guidelines for specifying the pressure ratingof secondary-containment vessels are as follows:

a) Maximum continuous containment pressure>Process relief pressure; and

b) Containment burst pressure > Plant designpressure.

The secondary-containment of a Coriolis meter will onlybe subjected to p~essureunderabnormal conditions (tubeti-acture), which would, fi-omnecessity, be for a limited

duration and a single occurrence. On this basis, it maybe possible to accept a pressure specification for thecontainment vessel of the Coriolis meter which is lessrigorous than that of the rest of the pipe work. Suchcompromises should only be made within design and/or test code requirements.

In cases where the process design pressure is higherthan that of the secondary cmtainment pressure, thesafety of the Coriolis meter installation can be enhancedby installing a pressure switch in the secondarycontainment for use as a trip alarm. Alternatively, abursting disc or relief valve can be used.

ANNEX C

(Clauses 11.1 and 13.5.1)

CORIOLIS METER SPECIFICATIONS

C-1 The following is the minimum amount ofinformation to be specified by the manufacturer for aCoriolis meter:

Identification

Primarymeasurements

Output signals

Performance

ManufacturerModel number (Measuringprinciples)

Mass flowldensityltemperatureRanges of above

AnaloguePulseDigitalDisplayDiscrete

Accuracy for specified conditionsZero stabilityRepeatabilityOperating influences ontemperatureOperating influences on pressure

Operating limits

Mechanical

Electrical

Certification

Operating influences on gas ratioby volumePressure drop under specifiedconditions

DensityPressureTemperatureViscosity

Tube geometryMaterials of constructionTube dimensionsOverall dimensionsWeightProcess connectionsSecondary containment

Power supply

Safety approvalsFiscal approvalsSecondary containmentGeneral documentation

1S 15672:2006 .-.

ANNEX D

(Clauses 15.3, 15.4 and 15.5)

MASS FRACTION MEASUREMENT EXAMPLES

D-1 MISCIBLE LIQUIDS CONTAININGCHEMICALLY NO-N-INTERACTINGCOMPONENTS

D-1.1 Relationship Between -Density and MassFraction

Figure 2 is an example of the relationship betweendensity and mass fraction for two miscible liquids,water and ethanol at 20°C.

Pure water and pure ethanol have the followingdensities:

a) Water = 0.999823 gtcm’

b) Ethanol = 0.78934 g/cm3

For example, a density of 0.78934 g/cm3 is given fora mass fraction of 100 percent ethanol and a densityof 0.999823 g/cm3 for a mass fraction of Opercentethanol (or 100 percent water) in Fig. 2. Otherintermediate values of density can be determined fromthe non-linear curve given in Fig. 2.

D-1.2 Mass Fraction

The value of mass fraction, expressed as a percentage,is determined directly from table values or the curvefit of a graph similar to Fig. 2,

D-1.3 Volume Fraction

The net volume of two components that are soluble isdificult to quantify in absolute terms. If a volume ofcomponent A and a volume of component B are mixed,the resulting volume does not equal the sum of volume-A and volume B. This results from a change in theinterstitial occupancy of solute molecules in themixture. In practice, users may need to know thevolume fraction before mixing for better volume-flowcontrol.

~

PA = PA

()Xloo

‘A ‘B—+—

PA PB

yrl_

~, = ~B

()

Xloo‘A—+5

PA ~B

where

P. =

% =

MIA, WB =

PAand p, =

volume fraction of component Aexpressed as a percentage,

volume fraction of component, Bexpressed as a percentage,

respective mass fractions ofcomponent A and component B inrelation to the mixture, and

respective densities of component Aand component B.

D-1.4 Net Flow Calculation

Once the mass or volume fractions are known, net massand volume flow calculations are identical to thoseindicated in 15.2.4 and 15.2.5.

D-2 SOLUTIONS CONTAINING CHEMICALLY-INTERACTING COMPONENTS

D-2.1 Relationship Between Density and MassFraction

The relationship between two soluble liquids whichchemically interact is complex. An example is sulphuricacid and wate~ the acid ionization changes the solutiondensity. As shown in Fig. 3, the relationship betweenconcentration and density is not defined by a simplecurve that is a single density value can correlate to twodifference values of mass fraction. In such cases, it isimportant for the user to understand the relationshipbetween density and mass fraction and to work within asufficiently narrow range of mass tlaction in order tocorrelate a single value curve for density.

D-2.2 Mass Fraction

The value of mass fraction, expressed as a percentage,is read directly from table values or the curve fit of agraph similar to Fig. 3.

D-2.3 Volume Fraction

The determination of volume fraction, expressed as apercentage, before mixing is calculated in the samemanner as described in D-1.3.

D-2.4 Net Flow Calculation

Once the mass or volume fractions are known, net massand volume flow calculations are identicaI to thosegiven above.

18

IS 15672:2006

>

100

0.75 0,8 0.85 0.9 0.95 1

DENSITY (g/crn3)

FIG. 2 MASS FRACTIONP’ER,S(LSDENSITYCURVEFORETHANOLANDWATER

8

100 1

9896 )94

92

-90/

8886848280 .

1.72 1.74 1.76 1.78 1.8 1.82 1.6

DENSITY (glcm3 )

FIG. 3 MASS FRACTIONOF SULPHURICACID nmsus DENSITY

19

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Amend No. Date of Issue Text Affected

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