Calibration of Liquid Density Meters at Combined Temperature & Pressure

Calibration Stand Update

Tony WrightCustomer Services Manager

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Agenda

• Background• Project requirements• Calibration Process• Current status• Test plan• New equations• Calibration approvals• Calibration of customer’s 7835’s• Summary

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Background for New Calibration Strategy• DECC (Department of Climate Control) in the UK requested all densitometer manufacturers

and Oil companies in the North Sea to launch a project “JIP” (Joint industry project) to understand the behaviour of temperature and pressure effects on Liquid Densitometers and to develop a new calibration strategy.

• TUV NEL ltd, as an independent calibration facility, were contracted to test and validate Liquid Densitometers at combined temperature and pressure. The calibration facility used 4 transfer standard fluids across the temperature range from 20⁰C to 100 C and from ⁰atmospheric pressure to 100 bar.

• From the NEL testing, it was concluded that there is combined pressure and temperature effect during elevated temperature and pressure operating conditions which need to be taken into density calculations.

• DECC then released an instruction stating that Liquid Densitometers should be calibrated at their anticipated operating conditions, i.e. simultaneously at temperature and pressure, using one or more transfer fluids, the density of which has been determined across the required temperature and pressure range with an uncertainty not exceeding 0.01%, directly traceable to national standards.

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Project Requirements

• Objective and Scope– Provide a production calibration stand(s) for combined

temperature/pressure density calibrations.• 3 different fluids:

– Silkospark (current Slough calibration fluid [machining fluid] ~ 825 kg/m3)– Sebacate (~960 kg/m3) – Sodium Bromide – (~ 1400 kg/m3)

• Combined P+T for two fluids (Silkospark, Sebacate) at– 20°C – 0,50,100,150 bar – 80°C – 0,50,100,150 bar

• 20°C at 1 bar A calibration on Sodium Bromide (stand to be capable of combined P+T if required)

• Double capacity of current calibration stands

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Calibration Process FlowSteve/Bob to provide flowchart of calibration steps for various options

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New Stands Schematic Overview

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Current status• Original promise date July 2011

– Slippage due to:• Damage in shipping• Design changes during testing

• Pressure test rig commissioned• Cleaning station commissioned• All calibration stands fully functional

– Modifications completed– Testing and commissioning re-started

• Similar system under test in MMI Boulder

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Pressure Test and Cycle Hydro Stand

• Hydrostatic pressure test rig• Rig will be used on all new and

repair 7835’s to:– Pressure test each sensor to 1.5

maximum operating pressure– Pressure cycle each sensor for 30

times to maximum operating pressure

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Cleaning Station

• Designed to flush out calibration fluids• Up to 3 x 7835’s each cleaning session• 3 stage cleaning process

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Liquid Density Calibration StandsCombined Pressure and Temperature

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Test Plan

• Stability and repeatability tests on distilled water• Change water to calibration fluids

– Repeat stability and repeatability tests– Monitor for cross contamination

• Validate calibration results against– Engineering Dept combined P+T calibration stands– Current production calibration stands– UKAS laboratory (also monitor contamination of fluids)

• Send fluid samples to external UKAS Laboratory to determine effect, if any, of contamination

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New Density Equations• All major flow computer manufacturers contacted• Existing format certificates will continue to be

available for limited pressure and temperature ranges

Dp = Dt * (1+K20*(P-1)) + K21 * (P-1)

K20 = K20A + K20B*(P-1) + K20C*(P-1)^2

K21 = K21A + K21B*(P-1) + K21C*(P-1)^2

Dpt = Dp * (1+K22*(t-20)*(P-1)) + K23*(t-20)*(P-1)

K20A,K20B,K20C, K21A,K21B,K21C Calibrate on new calibration stands on 2 fluids at 20°C for each unit

K22, K23 Calibrate on new calibration stands on 2 fluids at elevated t&P for each unit

Optimum Solution

Equations

New calibration stands

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Calibration Approvals

• Our current ISO17025 (UKAS) calibration laboratory has been in operation since 1981– 20 Deg C and 1 Bar A

• Will apply for ISO 17025 for new stands– Traceability through current UKAS Laboratory– Liquid P+T via 3rd party approved laboratory

• Planned schedule for approval application is 6 months from release of calibration stands

• On receipt of approval, we will apply for MID approval using new stands

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Re-calibration of Installed 7835’s• All installed 7835’s can be re-calibrated on the new stands

to DECC requirements• 7830’s are not supported• Fiscal (Micro Motion business partner) has built and

installed a new 7835 cleaning facility– Operational from December 2012

• Over-check to include air-check and detailed visual inspection prior to despatch to MMI Slough

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Summary• Functional testing of complete system has

started• Calibration stands will be fully commissioned by

mid January 2013– Existing stands will then be decommissioned

• Stands are designed to fully comply with DECC requirements

• Plan to have new calibration stands approved to ISO 17025 by mid 2013

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