011_ Fundamentals Meter Provers

8/17/2019 011_ Fundamentals Meter Provers

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FUNDAMENTALS OF METER PROVERS AND PROVING

METHODS

Greg WilliamsFlow Management Devices

5225 South 37th

Street, Suite 400Phoenix, AZ 85040

1. Introduction: This paper will verify thehistory, requirements and operation of allProvers accepted for liquid pipeline meteruncertainty verification in the Liquid Oil/GasIndustry. It will continue with an explanationand the industries wide acceptance of theUni-directional Captive Displacement Prover(UDCDP). This document will supply thereader with information regarding metertypes and the flow volumes that can beused with the UDCDP and will look at the

opportunities for the use of a UDCDP as amass prover. It will also provide theinformation for field verification of proversknown as a water draw.

2. UDCDP History: According to API, FlowProvers must have an uncertainty of lessthan +/-0.01% for all measurements relatingto meter proving including water drawuncertainty, temperature measurementuncertainty on flow proving, pressure

measurement uncertainty, etc.

Prior to the late 1970's in order to achievethe uncertainty of 1 part out of 10,000 usingthe old Prover counters with an uncertaintyof +/- 1 pulse, Provers needed a sufficientvolume to gather at least 10,000 meterpulses between detectors. The doublechronometry technique pulse interpolationtechnique developed and patented by EdFrancisco and precision optical switchesand modern electronics and high speed

timers eliminated the need for the extremelylarge volumes to attain the desireduncertainty. This led to the development ofthe modern Small Volume Prover (SVP)now known as the UDCDP.

Mr. Ed Francisco, the owner of FlowTechnology Inc., in the 1960's wascontacted by NASA to help with proving ofmeters loading rocket fuel in a very short

amount of time. Ed devised the doublechronometry pulse interpolation techniqueto achieve the high accuracy meterproving’s in a very short time period. Doublechronometry for API meter proving asdescribed in API MPMS Chapter 4.6 issimply a method of resolving meter pulsesto a resolution of +/-1 part out of 10,000without the need for actually counting10,000 meter pulses during a meter proving.

3. Developments Allowing Acceptance inthe Industry: Over the years, technologicaladvancements and improvements weremade in the design of the operating systemfor large bore Positive Displacement (PD)Meters and Turbine Meters. As well as agreater understanding of the specificationsof the manufactured pulse output signal forthe Coriolis Mass Flow Meters (CMFM’s)and Liquid Ultrasonic Flow Meters (LUFM’s)meters. The advent of these changes led toimprovements to the ease and the ability to

verify large bore meters with a UDCDP.

Advancements in meter technology alongwith the development of larger UDCDP, withlarger displacement volumes, allows theindustry the opportunity for higher levels ofrepeatability and uncertainty validationsignificantly lower than industry acceptederror limits. The pulse interpolationprocessing solution for capturing less thanten thousand (10,000) total measuredpulses originated in the early 1980’s. This

standardized use of Double ChronometryPulse Interpolation (Verified in API Chapter4 Section 6) inside the flow computerallowed acceptance of UDCDP for theLiquid Oil/Gas Industry.

The double chronometry technique is asimple process. The time for the volumedisplaced and the time period for the wholemeter pulses collected during that timeperiod are timed separately with high


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frequency time bases. The whole meterpulses collected during that time period aremultiplied by the ratio of the times to correctfor differences in the time periods by theformula: (Meter pulse time/Prover volumetime) * number of whole meter pulses.

Modern computer time bases currentlyutilized in flow computers and other doublechronometry devices utilized for flowproving use time bases at least 1 MHzfrequency providing an uncertainty of farbetter than the 1 part out of 10,000 asrequired.

3.1 Pulse Interpolation Process: The firstaction begins with a signal from theupstream detector switch, starting clock one(ET1, displacer elapsed travel time), next

clock two starts with the detection of the firstcomplete pulse (ET2 for the elapsed time tomeasure whole pulses). At the same timethe accumulation of pulses (WP, wholemeter pulses) from the meter being tested isalso started.

Clock one stops accumulating based on asignal from the downstream detector switch.Clock two stops accumulation based on thedetection of the first whole pulse signal fromthe downstream detector switch which also

stops the whole pulse accumulation. Thismethod allows for the collection of (ET1)elapsed travel time of displacer, (ET2)elapsed time of whole pulse accumulation,(WP) whole pulse accumulation from meterand (DV) which is the already knowndisplaced or calibrated volume for theprover. Taking these measurementsmultiple times within required repeatabilityvalues allows for the calculation of the newK-Factor.

Figure 1: Double Chronometry Pulse InterpolationFormula and Diagrams

3.2 Multi-Pass Proving: Industryacceptance of multi-pass runs for provingallows for adjustment in repeatability limits

while still meeting ± 0.0027% uncertaintyhelped tremendously in allowing for use ofthe UDCDP in large bore meters.Especially when using the newertechnologies like Coriolis and Ultrasonic andtheir manufactured pulse signals. (APIChapter 4, Section 8, Appendix A andChapter 12, Section 2, Part 3 address theissue of multi-pass uncertainty limits.)

The large bore meter can now be easilyverified to an acceptable repeatability value

more efficiently and faster than using abidirectional pipe/ball prover. Allowingpipeline operators the opportunity to makemultiple proving passes while increasing thelimits of repeatability while still maintainingthe ± 0.0027% uncertainty level required inthe industry.

From API MPMS Chapter 4.Runs at proving repeatability to meet ± 0.00027uncertainty of Meter Factor

ProvingRuns

RepeatabilityLimit

Meter Factor Uncertainty

3 0.02 0.000274 0.03 0.00027

5 0.05 0.00027

6 0.06 0.00027

7 0.08 0.00027

8 0.09 0.00027

9 0.10 0.00027

10 0.12 0.00027

11 0.13 0.00027

12 0.14 0.00027

13 0.15 0.0002714 0.16 0.00027

15 0.17 0.00027

16 0.18 0.00027

17 0.19 0.00027

18 0.20 0.00027

19 0.21 0.00027

20 0.22 0.00027

Table 1: Pulse Average Table from API MPMSChapter 4.8


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4. What is a meter prover? A meter prover is a device used to verifyflow meter uncertainty in order to establish;

the K-Factor (Pulses per unit

volume) of a meter. the Meter Factor of a meter (factor

used with a meter to correctaccuracy for ambient conditions).

the Linearity over the calibrated flowrange for the meter.

the Repeatability for the metersystem.

The meter factor is obtained by dividing theprover test volume by the indicated volumeof the meter. Once the meter factor is

determined it is used as a volume correctionin the calculation for net standard volume ofa receipt or delivery of liquids.

Actual Volume Passed thru Meter

month, every month the meters areleft uncorrected.

It should now be clear how important meterproving is to the petroleum business.

4.2 Classification of Volumetric Proving:

To differentiate between the classificationsof volumetric meter proving the terms staticand dynamic will be defined. The differenceapplies to the way the standard is comparedwith the reading of the flow meter undertest.

In the static scenario the fluid is collected ina test vessel and compared to the grossdelivered amount of the meter under test.

This is normally an open system (will beclosed system when testing with a volatileproduct) and will require interruption of theflow process to perform the meter factor

(Mfg. or Last) Meter Factor XVolume Measured by Prover Test

Figure 2: Meter Factor Formula

= New Meter Factor verification.

4.1 Why companies prove flow meters?The purpose for meter verification or meterproving is to provide accurate measurementwhich then will minimize losses andmaximize profits. The flow meteringsystems are the “cash registers” for allpetroleum operations and this means errorsin meter factors can and will generateenormous financial errors in a company’sinvoicing in a short period of time.

Example:

If we look at the following example isbecomes clear how much money isinvolved.

An 8 inch crude line deliveringproduct to a Refinery, at a flow rateof 2150 Barrels/Hour (BPH).

• The flow meter used in the line,which was proved using a MasterMeter, is found to be inaccurate by0.25% and the crude wholesales for$ 35 per Barrel.

• In 1 month the product wasincorrectly invoiced to the amount of:2150 X 24 hours X 30 days X .0025error factor X $35/barrel = $135,450.00, miss invoiced – per

In the dynamic scenario the fluid remains ina closed system whereby the pulseregistration of the meter under test and thepulse registration of the standard proverused are compared directly. There is nointerruption of the normal flow process

during this verification of the meter factor.

4.3 Equipment used for Proving:

There are three types of measurementequipment used for verification in thepetroleum industry today, test measure tankprovers, volume displacement provers,and master meters. Decisions for whichtype of equipment should be used arebased on accuracy requirements, testingflow rates, measurement turndown

requirements, environment, cost to install,cost to maintain, and in some cases localagency approvals.

Prior to the development of the volumedisplacement prover, the volumetric testmeasure tank prover was the best productavailable for volume measurementverification and has been around since theturn of the 20th century. The volume tankprover may be used for the calibration of


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liquid flow meters; but is also approved forperforming a volumetric water drawcalibration of displacement provers per APIMPMS Chapter 4.9. The accuracyuncertainty is specified per tank volumessize. (Note: Tanks over 100 gallons have an

uncertainty of +/- 0.01% or less per NISTuncertainty analysis; tanks 100 gallons orless range from +/- 0.015% for 100 galloncans to 0.3% for 1 gallon cans.)

cans over 100 gallons have anuncertainty of +/- 0.01% or less perNIST uncertainty analysis. Cans 100gallons or less range from +/- 0.015%for 100 gallon cans to 0.3% for 1 galloncans.

The master meter prover solution havingmany possible applications for proving arenoted in API MPMS Chapter 4.5. Althoughused in the industry for some time, it doesnot have total acceptance for custodytransfer approval or for use in weights andmeasures type applications from all local orregional agencies. The required verificationof the master meter’s accuracy must beestablished by using a displacement type ora volumetric tank prover. This should becompleted prior to the start of any meterverification when product characteristics(products, temperature, pressure, density,viscosity) have changed since last mastermeter proving.

The petroleum industry and AmericanPetroleum Institute (API) have accepted theuse of volume displacement provers intwo categories, the conventional pipeprovers (displacement prover with sufficientreference volume to accumulate 10,000whole pulses in a single pass) and the

UDCDP (displacement prover withinsufficient reference volume to accumulate10,000 pulses in a single pass and usespulse interpolation software). In both cases,it will require multiple passes for a provingand to establish a test meter’s new meterfactor. The conventional provers have beenutilized for meter proving since the early1950’s and the captive displacement proverentered the market in the mid 1970’s afterthe acceptance of the double chronometry

pulse interpolation as identified in APIMPMS Chapter 4.6.

Figure 3: The chart above depicts theclassification of each equipment type.

5. Key Components and GeneralOperation of Product used as Provers:

5.1 The volumetric test measure tankprover is covered in the API MPMSChapter 4.4 and was the first product togain acceptance in the industry for meteraccuracy verification in the field. Thisdevice is mechanical in design and is thesimplest to use and operate. The primarytank prover consists of a certified volumetank or test measure (sized by the requiredamount of fluid delivered in 1 minute at theactual maximum flow rate) with graduatedneck and a gauge glass and scale (scale isdesigned for + 0.5 percent of tank certifiedvolume) on the top and possibly the bottomof the tank to measure the tank zero startand stop volume position respectively.There will be temperature measurementlocations on an open or closed type system.On a closed tank system, pressuremeasurement is added as well asinlet/outlet flow connections and drain valve,vapor recovery or release system,overlapping tank side site glasses, andmany other components as illustrated in APIMPMS Chapter 4.4. When moving from astationary tank prover to a portable systemthe additional components needed are avehicle or trailer, leveling equipment, hosesand connectors, and possibly a small liquidpump-off system.

The use of a tank prover is simple inoperation; the most important part isselecting the correct size tank for the meterflow rate(s) to be calibrated. Once all pipingconnections are established and tank isverified as empty the inlet flow to the proverbegins and fills the tank to the appropriate


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level. When the tank volume reaches theupper neck gauge glass and the fill line fallswithin determined tank volume scales, theflow is stopped. The technician reads thescale for the exact gross volumemeasurement in the tank and this volume

has a direct relationship with the registeredvolume of the meter under test. Thesevalues are then used to calculate the testmeters new meter factor. If changes aremade, a verification proving is then requiredto assure that any changes applied had thedesired result.

also verify the weight of the product in thetank once a quantity is measured throughthe meter and into the scale tank. Thevolume amount is verified by the equipmentmass weight on the scale. Once the weightof the product is determined, the product

density must be verified and used to convertthe mass measurement to a volumetricmeasurement for comparison to the metersregistered volume.

Gravimetric test measure tank proving in atest lab environment is one way thatdisplacement type prover manufacturersuse to verify the volume of the

measurement area of each size prover.When completing a water draw certificationfor a displacement prover, the weightedamount is determined by the amount of fluidregistered between detector switch one anddetector switch two. Once the weight of thedistilled water is found, the temperature andpressure of the water in the prover body isused to convert to a certified volumeamount. (Refer to API MPMS Chapters,4.9.4, and 12.2.4).

Figure 4: Components in a standardTank Prover

Critical Characteristics of Tank TypeProvers

Using the one minute of flow rule fortank size, prover tank can becomevery large and difficult to maneuverand use

The can needs to be drained aftereach proving – in some casesproduct will have to be pumped to aslop tank resulting in considerableproduct loss.

If used on a loading bay it can stoptruck loading for long period of time.

Particle or heavy viscous product

build-up can cause volume changes Well maintained tanks require little

maintenance costs.

5.2 The gravimetric test measure tankprover is accepted for use in meter proving.When using a gravimetric tank prover, themost significant component is the certifiedweights used to calibrate the scale and thescale(s) itself. The scale is used to weighthe tank empty to establish tare weight, and

Figure 5: ISO 17025 certified gravimetricwater draw test stand – Flow MD –

Phoenix, AZ

Critical Characteristics of Gravimetric TypeProvers

Scales and tank can become verylarge and difficult to maneuver anduse.

Scale is a mass device and requiresprecise temperature and density toconvert to volume


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The can needs to be drained aftereach proving – in some casesproduct will have to be pumped to aslop tank resulting in considerableproduct loss.

Normally used on water test

verification or refined equipment. Particle or heavy viscous product

build-up can cause volume changes Well maintained tanks require little

maintenance costs.

5.3 The master meter proving solution hasbeen applied for years and the operationalrequirements are covered in API MPMSChapter 4.5. A Master meter provingrequires the use of a higher accuracy meter(verified to a higher accuracy level than the

meter under test) installed in series on thepipeline along with the meter being verified.There will be a pulse counter system thatallows the user to gather flow informationover greater time intervals and allows theuser to gather as many pulses as theydesire. The master meter volumeregistered is then compared with the testmeter volume register and a new meterfactor can be calculated from thecomparative totals. A second verification ofthe master meter proving is required to

assure that any changes applied had thedesired result.

Figure 6: Master Meter Test Cart

Critical Characteristics of Master MeterProver

A proving device should preferablybe 10 times more accurate than thedevice being proved. Avoid using anequally or less-accuracy device to“prove” a similar, less-accuracydevice.

Measurement errors form normaloperation of the master meter will betransferred to the test meter

The Master Meter accuracy could beaffected by liquid viscosity, flow rate,temperature or pressure;

Master Meters are usually designedfor a specific fluid type and can’t beused on a range of fluids

5.4 The conventional pipe prover (ball /sphere type) is covered in API MPMSChapter 4, Section 2 and can be designedfor unidirectional or bidirectional operation.The pipe prover was designed for all levelsof flow, but gained the greatest acceptancein the industry in larger pipelines whereother prover types were unable to handle

the higher flow rates. Despite involving amuch larger footprint than other types ofprovers, the pipe prover is very simpledesign. The criterion for a unidirectionalpipe prover is a minimum sphere velocity of1 foot /second and maximum spherevelocity of 5 feet/second. The bidirectionalpipe prover design sphere velocity must bebetween 0.5 feet per second and 10 feet persecond, but in either design the prover mustallow for the counter to accumulate of10,000 pulses between the two required

detector switches. (Check API MPMSChapter 4.2, Appendix B). Pipe proverscome in multiple sizes and designs, flowrates, and sphere velocity calculations thataffect the overall footprint of the individualdevice.

Figure 7: Examples of Pipe/Ball Provers

The key components of a pipe prover arethe U shaped smooth lined uniformcircumference pipe, the four way divertervalve system, the inflatable prover ball ordisplacer sphere, the ball launchingchamber(s), the two detector switches and ameter pulse generating proving counter.


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Figure 8: Standard components inPipe/Ball Prover

Before the proving operation starts, a

required proving flow rate must beestablished. The proving pass is startedwhen the four way valve actuates to launchthe prover sphere into the flow pipe. It thentravels through the pre-run area until itreaches the u shape measuring section ofthe pipe. When the sphere contacts the firstmechanically actuated detector switch, thecounter is started and the sphere continuesto travel until the second detector switch isactivated, at which time the counter isstopped signaling a complete pass in a

unidirectional prover. The sphere continuesto travel until it reaches the other launchchamber where it remains until the start ofthe next proving pass. If bidirectional, thefour way valve will again actuate to start thepass in the opposite direction and whenconcluded will be a single pass registration.The flow pulses accumulated from the testmeter are then compared with the pulsesgenerated from the accumulated volumebetween the detector switches on theprover. The proving passes are continued

until sufficient passes are completed andthe multiple pulse totals can be comparedwith sufficient repeatability to satisfy therequirements as specified in API MPMSChapter 4.8, Chapter 9.3, and Chapter 13.2.

Critical Characteristics of Conventional PipeProver

Ball provers requires launch andreceive chambers and long pre-rundistance;

Possible high pressure drops withBall Provers;

More difficult calculations to correct

for temperature and pressure; Appreciable uncertainties due to

mechanically activated detectionswitches;

Large in size and expensive toinstall.

Sphere materials must becompatible with product, ball changewith product change

Appreciable uncertainties due tomechanically activated detectionswitches and detector switch might

be sensible to vibrations; Difficult to maintain and service

5.5 The Uni-direction CaptiveDisplacement Prover or small volumeprover is a device that is also covered in

API MPMS Chapter 4.2. This type of proverwith insufficient reference volume toaccumulate 10,000 pulses in a single runrequires pulse interpolation software tocalculate the 10,000 pulse requirement tosatisfy a proving pass. One of the most

significant design changes compared to apipe prover was relocating the detectorswitches to the outside of the measurementpipe and installing them on a switch bar.This allows for higher quality switchactivation and easier access for service.The most significant advantage of thedesign is the ability to verify meter accuracyfaster over a larger flow range with a 1200to 1 turndown and considerably reducedfootprint for installation. The majorcomponents of the UDCDP are the prover

body, prover frame, piston assembly, opticswitches, puller assembly, drive system,drive shaft, and controller. For the completeproving operation there is also a need for aflow computer or proving software that takesin raw data from the prover and meter undertest and per API MPMS Chapter 12.2requirements calculates all data andgenerates a proving report automatically.

Another tremendous advantage ofUDCDP's has when used for dry LPG's


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meter proving is the low friction sealsallowing for smooth operation duringproving. With the LPG’s, the Pipe/BallProver is susceptible to squealing andlunges in the moving of the ball due tominimal to no lubrication capabilities of the

product.

Figure 9: Standard Components for FlowMD UDCDP

The operation of the UDCDP is nearly fullyautomated. Once the valves are aligned todirect flow through the prover and therequired flow rate is set, the flow computeroutputs a signal to the UDCDP controller tobegin the proving run. That signal engages

the drive system drawing the piston shaft tothe upstream position in front of the firstoptical switch. Once the electronic clutchreleases the piston the product flow velocitywill close the piston and begin the traveldownstream through the certifiedmeasurement section of the prover’s flowtube. The certified measurement forcalibration begins when the optic flagmounted on the external portion or the driveshaft, activates the first optical switch andcontinues the travel downstream until the

second optical switch is contacted signalingthe end of the first pass. Simultaneously,when the first optical switch is contacted, asignal is transmitted to the flow computer tostart the interpolated signal prover counterand the counter for the meter under test.This begins the pulse accumulation from themeter and the controller. When the secondoptical switch is activated a signal is sentstopping the pulse counters, signifying theend of the next pass. This processcontinues until the set quantities of required

passes are complete. During this processthe flow computer is receiving pressure andtemperature information from transmittersinstalled downstream as well as thetemperature of the switch bar on the proverand also upstream by the meter in the pipe

line. Once the multiple pass information isprocessed it will be compared for sufficientrepeatability to satisfy the requirements asspecified in API MPMS Chapter 4, Section8; Chapter 9.3; and Chapter 13.2. The APIproving reports can then be generatedautomatically as required.

Critical Characteristics of Uni-DirectionalCaptive Displacement Prover

Can be used in situations where

it is possible to collect less than10,000 meter pulses in a proverpass, by utilising “DoubleChronometry” or pulseinterpolation.

Designed with an internal pistonto displace the volume andexternally mounted opticaldetector switches.

Precise external optical switchesare easily serviced.

Small amount of liquid required

for a volume water draw test. Piston and Poppet assemble is

designed for fail safe operationnot to disrupt flow.

Prover allows for accuratemeasurement of flow meters witha wide variety of fluids. Therepeatability of a prover will bebetter than 0.02% as stated inthe API guidelines.

Has a turndown ration of 1200 to1 allowing for use on multiple

size meters. UDCDP pulse interpolation is

completed in the flow computeror other type of computingdevices that is part of the provingsystem.

6 The Industry Acceptance of theUDCDP: With a smaller certified volumeand faster operational sequence the


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UDCDP attained the highest level ofacceptance for meter verification in theliquid oil and gas industry. As the industrycontinues to grow, the UDCDP has keptpace with the growth by offering larger sizeswith a maximum flow ranges to 24,500 GPM

(35,000 BPH or 5,564 M³H). With thestandard of 1200 to 1 turndown each proversize can be used to calibrate multiple sizemeters making it a very economical choice.With higher flow rate proving capabilitiesand significantly smaller certified volumes,the UDCDP can usually complete a multi-pass proving of a meter in the same amountof time it takes to make a single pass withits predecessor the Pipe/Ball prover.

The other major changes to the UDPDP arethe higher (450ºF or 232ºC) and lower (-262ºF or 162 ºC) operational temperaturespecification to continue to meet industryneeds. The design for high temperatureand cryogenic temperature UDCDP is nowa reality.

Another advantage the UDCDP over itspredecessors is the installation footprint thatcan be 10-30 time smaller in area. Thelarger footprint when comparing the overallcapital expense of total installation andcommission cost makes the UDCDP a

better economical choice especially withlarger meters from 6” through 16” meterswith high flow rates.

Table 3: Comparison of Pipe/Ball Provervs. UDCDP 12,500 BPH (1,897 M³H)

Figure 10: UDCDP sized for 28,800 BPH(4,500 M³H) compared to 4 way valve forthe same flow rate in a Pipe/Ball Prover.

The other major developments in theUDCDP is the design changes to theelectronics that now have the ability tocontinuously verify the certified volume aftereach prover pass, and a continuous self-diagnostics of the health of the completeprover system.

7 UDCDP Designed for Mass Proving Asthe use of Coriolis Meters (designed tomeasure mass first and density second)continue to expand in the liquid oil and gasmarket, the required volumetric proving canbecome a challenge. First the CoriolisMeters have very little influence formeasuring mass, since the movement of thefluid inside the tube causes the time phaseshift from the inlet to the outlet electronic

measurement coils which are a directrelationship to mass flow. Since the densitymeasurement is derived by the vibrationalfrequency of the tube, changes in weight ofthe tube will change the density of theoutput. When using the Coriolis meter forvolume measurement the standardcalculation of mass / density = volume isutilized. Therefore if product buildup on thewalls of the tubes occurs, this productusually has a different density than theproduct in liquid state inside the tube during

flow causing possible errors in the volumeoutput.

This is where the UDCDP with the option foran installed Densitometer and aPycnometer can be used as a completeMass Prover solution. This system allowsthe verification of all of the parameters ofthe measurement uncertainty for a Coriolismeter. Also note the temperature andpressure of the measurement is verified as


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part of the required parameters as with allproving calculations.

Figure 11: Standard Mass prover design

8 Groups and Agencies that Govern theProving Processes: The AmericanPetroleum Institute (API), InternationalOrganization of Legal Metrology (OIML),and National Institute of Standards andTechnologies (NIST) oversee the meterproving process generally. There are globalrequirements and regional requirements tobe aware of and the specific regulations orstandards for each country, providence,state or city where measurement equipmentand measurement verification devices areused must be taken into account. Notedbelow in the reference sections aredocuments that should be evaluated whenproving meters and for the operation anddesign of verification equipment andsystems.

8.1 Where does a Prover Device fallwithin the Agency Approvals?

• Level 1. Primary standards involvemass, volume, and/or densitystandards developed and/ormaintained by National Institute ofStandards and Technology (NIST)and/or other national laboratories to

calibrate secondary workingstandards.

• Level 2. Secondary workingstandards include mass, volume,density, and/or weighing systemsmaintained by NIST and/or othernational laboratories to calibrate fieldtransfer standards conforming toChapter 4.7. Secondary workingstandards may also be maintainedby state and other certifiedmetrology laboratories to calibrate

field transfer standards. Theseadditional secondary workingstandards, however, increaseuncertainty in the final custodytransfer quantities.

• Level 3 . Field transfer standardsconforming to API MPMS Chapter4.7 are devices used to calibratemeter provers in compliance to APIMPMS Chapters 4.2, 4.3, and 4.4.

• Level 4 . Meter provers incompliance to Chapter 4 can be

used to determine meter factors thatcorrect the indicated volumes ofmeters.

Traceability Pyramid of Standards

Within API MPMS Chapter 4 there is notedan overview of Hierarchy in provingproducts.

Liquid metering systems designed andoperated in conformance with API’s Manualof Petroleum Measurement Standards

typically have one or more of the followinglevels of hierarchy as shown below.

Figure 12: Pyramids of Traceability forWorking and Operational Standards.

These traceability standards (Listed inFigure 12) can be used for all liquidmeasurements in the global market.Starting with the meter on the bottom to theSI weights on the top. Each level requires aminimum of 2x better capability ofcertification.

InternationalComparison of

Measurements


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The Captive Displacement Volume Proveslies in the middle of the TraceabilityPyramids illustrated above. What thismeans is the prover devices that havehigher uncertainty can and are used toverify each other. In the world of Captive

displacement Provers, the Volume Can andthe Scale Can Provers are used forVolumetric and Gravimetric Proververification respectively. Certification of aProver is noted in the API MPMS Chapter 4and OIML R119 documents and is requiredevery 1, 2 or 3 years depending on theservice.

With the field use of a master meter used involume certification of a ball prover theUDCDP becomes in most cases a critical

part that the Pipe/Ball Prove fieldcertification as noted in Figure 12.

Figure 13: Field Water Draw UDCDP in 3Step Process or Ball Prover is 5 Step

Process

Although capable of being certified by avolumetric can for the water draw, one ofthe greatest advantages of the UDCDP isthe ability to be field certified gravimetricallywith the use of electronic high precisionbalance (scale). The largest UDCDPdesigned at this time has a 4 BBL certified

volume which can be gravimetric waterdrawn with a scale and a tank that canhandle a weight of 1500 lbs. Manufacturersof UDCDP have recognized the importanceof accurate volume calibrations, and haveemployed the gravimetric method in their

final acceptance testing for years. There isdocumentation in an ISHM Paper(Reference 13 below) that the comparisonindicates the gravimetric method has asignificant improvement (decrease in value)in uncertainty over volumetric water draws.The values also show an improvement thatis much greater than an order of magnitude(a factor of 10) better than the volumetricmethod.

9. Summary: There was a great deal ifinformation provided in this paper. The ideawas to supply enough information thatwould substantiate the use of a UDCDP asan acceptable and viable proving devicefrom both an economical and qualitativeperspective for the liquid Oil and GasIndustry. As the industry changes from theoriginal technology (Turbine and PD) to thenewer technologies (Coriolis and Ultrasonic)for metering liquid products the UDCDP willcontinue to be the operative choice for thefuture. There are many options for using aproving device and all influences likeaccuracy, flow rates, measurementturndown, environment, installation andoperational costs, local agency acceptanceshould be part of that decision. There areapplications for every type of proving deviceand hopefully the information provided herehas supplied guidance to help make thosedecisions.


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References:

1) American Petroleum Institute, “Manual of Petroleum Measurement Standards,” Chapter 4,“Proving Systems”, Section 1, “Introduction”, Section 2, “Displacement Provers”, Section 4,“Tank Provers”; Section 5, “Master-meter Provers”, Section 6, “Pulse Interpolation”, Section 7,“Field-standard Test Measures”, Section 8, “Operation of Proving Systems”Section 9,“Calibration of Provers”.

2) American Petroleum Institute, “Manual of Petroleum Measurement Standards Chapter 9—“Density Determination”, Section 3—“Standard Test Method for Density, Relative Density, and

API Gravity of Crude Petroleum and Liquid Petroleum Products by Thermohydrometer Method”

3) American Petroleum Institute, “Manual of Petroleum Measurement Standards Chapter” 12“Calculation of Petroleum Quantities”, Section 2—“Calculation of Petroleum Quantities UsingDynamic Measurement Methods and Volumetric Correction Factors “, Part 4—Calculation ofBase Prover Volumes by the Waterdraw Method”.

4) American Petroleum Institute, “Manual of Petroleum Measurement Standards”, Chapter 13 –Statistical Aspects of measuring and Sampling”, Section 2—“Methods of Evaluating MeterProving Data.”

5) International Organization of Legal Metrology, OIML-R119,” Pipe provers for testingmeasuring systemsfor liquids other than water” 1996, www.oiml.org

6) Lee, Diane G., “Series 1 – Small Volume Provers: Identification, Terminology andDefinitions,” March 2005; www.nist.gov/owm.

7) Lee, Diane G., “Part 2 – Small Volume Provers: History Design and Operation,” June 2005;www.nist.gov/owm.

8) Lee, Diane G., “Part 3 – Small Volume Provers: Mathematical Determination of MeterPerformance Using SVPs,” August 2005; www.nist.gov/owm.

9) Lee, Diane G., “Small Volume Provers (SVP) Proving Reports ‘March 2006”;www.nist.gov/owm.

10) APLJaK Ventures Kelowna, BC, Canada, Website “Volumetric Calibration”

11) Alex Ignatian, ASGMT 2013, “Small Volume Captive Displacement Provers For Natural GasLiquids.”

12) ISHM Paper OPERATIONAL EXPERIENCE WITH SMALL VOLUME PROVERS

Class #4110.1 Steve Whitman; Coastal Flow Liquid Measurement, Inc.

12) ISMH 2007 ----Theory and Application of Pulse Interpolation to Prover SystemsClass#4140.1-2007Galen Cotton; Cotton & Co. LP

13) 27th International North Sea Flow Measurement Workshop 20 – 23 October 2009,Tønsberg, Norway--Realistic Pipe Prover Volume Uncertainty--Paul Martin, IMASS (formerlySmith Rea Energy Limited).

14) ISHM 2013 Paper 4200 The Uncertainty of a Water draw Calibration vs. GravimetricCalibration on Small Volume Provers --- Gary Cohrs, Flow Management Devices

Documents

011_ Fundamentals Meter Provers