8/17/2019 How to Prove Your LACT Meter - EmersonProcessXperts

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How to Prove Your LACT Meter

www.emersonprocessxperts.com /2014/04/how-to-prove-your-lact-meter/

Rossella Mimmi Pipeline Oil & Gas Industry Manager

Flow Solutions Group Author: Rossella Mimmi

Lease Automatic Custody Transfer (LACT) units provide a method to transfer the ownership of crude oil from the production facilities to pipelines or trucks. Their use is constantly increasingdue to the many advantages they present compared to tank gauging and other systems: for instance, increased measurement accuracy, better use of labor, better scheduling of runs topipelines, elimination of measurement errors due to tank botom build-up or encrustation, andreduction in investment and maintenance costs. Manual tank gauging also brings up concerns regarding safety.

A crucial component of a LACT unit is the flow meter itself, suitable for custody transfer measurement; meter typesthat are commonly used are turbine , positive displacement , or Coriolis meters. The meter will accurately and

precisely measure the fluid stream volume or mass and accumulate the total throughput.

However, a periodic calibration of the meter is necessary, as its performance can be affected by changes in fluidphysical properties (pressure, temperature, flow rate, density and viscosity), mechanical wear, obstructions in thepipe, or deposits from asphaltenes and paraffin. The performance of the meter must be regularly verified to makesure that repeatable results are consistent and traceable to an external reference. Meter calibration providestraceable evidence of meter performance through on-going trending of meter accuracy and repeatability.

Me ter an d Bi-directional B all Prove r A largely used method to check the performance of the LACT meter is Proving , thatprovides on-site meter calibration. It is based on the principle of comparing a

known volume against the meter output; the ratio between the prover referencevolume and the meter reading is the meter factor, which will be used to correct themeter reading. Provers can be uni- or bi-directional, and use a sphere (ballprov ers) or a piston (piston provers).

Proving sh ould be perf ormed under the same conditions as the meter is normallyexpected to operate. During meter calibration, the prover is connected in series tothe meter to compare the volume r egistered by the meter and the prover whilstliquid is flowing steadily from one to the other.

Compact Prover

Provers are available also in compact configuration; compact provers were developed toanswer the need for a smaller and lighter proving device where space is limited andmobility is desirable. A single prover may be used in multiple locations for proving varioussizes of meters and large volumes.

Another way of calibrating a flow meter on-site is to put it in series with another flowmeter called master meter and compare their readings. The meters that can be used asmaster meters must be compatible with the fluid being tested, be very reliable and repeatable, and give reproducibleresults. Although this method adds one additional step to the calibration chain, so it is considered to have a higher uncertainty than direct volume proving, it has the distinct advantage of speeding up the whole process and givingsatisfactory results. Other advantages of master meters are lower initial investment compared to provers and short

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http://www2.emersonprocess.com/en-us/brands/daniel/flow/turbine-flowmeters/pages/turbine-flow-meters.aspxhttp://en.wikipedia.org/wiki/Positive_displacement_meterhttp://www2.emersonprocess.com/en-us/brands/micromotion/coriolis-flow-density-meters/pages/index.aspxhttp://en.wikipedia.org/wiki/Lease_automatic_custody_transfer_unithttps://www.linkedin.com/pub/rossella-mimmi/11/aa9/2a9http://www.linkedin.com/pub/rossella-mimmi/11/aa9/2a9http://www2.emersonprocess.com/en-US/brands/daniel/metering-systems/provers/Pages/Compact-Prover.aspxhttp://www2.emersonprocess.com/en-US/brands/daniel/metering-systems/provers/Pages/Pipe-Prover.aspxhttp://www2.emersonprocess.com/en-us/brands/micromotion/coriolis-flow-density-meters/pages/index.aspxhttp://en.wikipedia.org/wiki/Positive_displacement_meterhttp://www2.emersonprocess.com/en-us/brands/daniel/flow/turbine-flowmeters/pages/turbine-flow-meters.aspxhttp://en.wikipedia.org/wiki/Lease_automatic_custody_transfer_unithttps://www.linkedin.com/pub/rossella-mimmi/11/aa9/2a9http://www2.emersonprocess.com/en-US/industries/oil-gas/Solutions/Pages/Solutions.aspxhttp://www.linkedin.com/pub/rossella-mimmi/11/aa9/2a9http://www.emersonprocessxperts.com/2014/04/how-to-prove-your-lact-meter/

8/17/2019 How to Prove Your LACT Meter - EmersonProcessXperts

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payback time, reduced maintenance and no need of planned activities; they will also produce better repeatabilitybecause the prove run-time can be as long as desired, or chosen by the batch size rather than defined by thesize/volume of the prover.

Coriolis Master Meter Master meters can be calibrated on-site with a volumetric prover (direct method) under the same operating conditions; that is the preferred method as it reduces theuncertainty. Another acceptable solution is to send the meter to external laboratories that

provide calibration services (indirect method); the 3rd party calibration facility willnormally provide detail of the offset from the reference standard for the meter over thecalibrated flow range. This known offset can then be applied as a meter factor correctionwithin the flow computer.

Proving and validation of LACT meters can be a costly operation, but necessary toensure that the agreed system uncertainty can be achieved. Many challenges are involved in this particular application: frequent changing of operating conditions and fluid quality, compliance to increased standards andregulation requirements, necessity of ensuring measurement system lifecycle sustainability and reliability. Emersoncan provide a range of efficient and cost effective solutions for proving and validations systems to help ensure on-going commercial and standards accountability and avoid fiscal risk.

To connect and interact with other oil & gas and flow measurement professionals, join the Oil & Gas and/or FlowMeasurement tracks in the Emerson Exchange 365 community.

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Posted Wednesday, April 23rd, 2014 under Flow , Oil & Gas .

Tags: ball prover , compact prover , custody transfer , LACT, lease automatic custody transfer , measure & analyze ,mobile prover , oil and gas production , Rossella Mimmi

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