how accurate is the shipboard custody transfer ... conferences...how accurate is the shipboard...

How accurate is the shipboard

Custody Transfer Measurement system?

An independent research by SGS.

Gerrit Vermeiren, Manager Oil, Gas & Chemicals – Benelux

Sven Lataire, LNG Business Development Manager

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SGS Survey – LNG Measurement System

� SGS and LNG

� International Developments

� International Standards

� Losses due to Measurement ignorance

� Losses due to Measurement errors

� Losses due to wrong Sampling

� Accuracy of Gas analyses

� Overall in-accuracy of the CTM system

� Conclusions & Guidelines

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� SGS and LNG

� SGS (Societe Generale de Surveillance)

• Head office – Geneva

• 140 countries

• 1300 offices

• 365 laboratories

• 39000 employees

• 150 LNG Inspectors/Measurement engineers

• 120 LNG Chemists

� LNG Competence Center (Belgium-Antwerp)• Training Institute

• Business Development center

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� Cargo value/Measurement errors

� Cargo value

• 138 000 m3

• 64 000 Tons

• 3 300,000 MMBTU

• 20 mio US$

� Measurement error• 0.2-0.3 % (ideal)

• 40-60 k US$

• 3 mio US$/year

• 100 mio US$ – 20 years

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� Cargo value/Measurement errors

� Cargo value parameters

• Level

• Pressure

• Temperature

• Volume calibration

• Sampling

• Gas Testing

• Cargo (vapor/liquid) remainders

• Vapors displaced/Boill-off

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� Long term objective – bilateral contracts• Strategic• Alternative fuel• Political drivers• Same ships/ports-dedicated trades

• Sustainable (low cost) energy source

=> systematic errors - hidden/undiscovered

- time/number balanced

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� Short term objective – spot contracts

• New/alternative energy supply

• Increase in: number-size ofships/terminals/supply/demand

• Commercial trading-spot/short/mid term

• Sustainable growth and profit driventrading

=> systematic errors - visual/significant

- not balanced out

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� International Standards

• NBS Measurement study – 1985

• ISO 13398 LNG procedure for Custodytransfer on board ships

• G.I.I.G.N.L. LNG Custody Transfer Handbook

• ISO – GPA – IP – ASTM

• Klosek Mc Kinley – revised

• Costald

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� Losses due to Measurement ignorance

• Spurious errors

• Systematic errors

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� Spurious errors

• Different standards/edition years

• Same standards – different constants/roundings

• Same methods/standards – different ref. conditions

• Use of different Measurement Instruments – L/T/P

• Wrong set-up/design Sampling station

• Displaced vapors/gasphase/Boil-off/ROB linesystem

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Losses due to Measurement ignorance

• Spurious errors e.g.

• Full or empty liquid lines on board

(before/after-loading/discharge-average 46 tons) → 15935 US$• Vapour phases accounted

(before/after-discharge/loading –diff 192 tons) → 59370 US$• Gas boil off (vapour return) during loading

Est. average 300 tons → 92765 US$• Gas received by LNG carrier when unloading

Est. average 192 tons → 59370 US$---------------------

→ 227440 US$

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� Losses due to Measurement (systematic) errors• Correct measurement

– Calibration– comparison (reference/standard/master)

• Normal Bulk Liquids Measurement:– Dynamic + Static measurement– Calibration Shore tanks / meterproving– Shore/Ship comparison – VEF (0.2-0.5%)– Best practice – Shore 0.2% / Ship 0.3%

• LNG Measurement– Only Static measurement– No shoretank calibration– No ship shore comparison– Best practice – 0.3 � ……..%

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� Calibration tables• Method – ISO 8311/9091 1-2

– Accuracy 0.2%

• Re-calibrations

• SGS calibration tables – ISO 8311/2550 sect.7-8a

– Accuracy 0.05%

� Financial impact on 20 years employment

• 20 mio US$ Loss or Gain

• due to Under or Over–calibration

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� Level – manual/automatic• Industry = > +/- 7.5 mm (1200 US$)

• SGS study => +/- 1 cm (2 cm) – (1400 – 2700 US$)

� Temperature

• Resistance – Pt 100

• Accuracy =>

– Industry : +/- 0.3 degrees Celc.

– SGS study : +/- 0.75 degrees Celc.

– Value : 76 k US$

� Pressure• Insignificant : +/- 1% error on full scale

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� Losses due to wrong Sampling

� True sample

• Independant

• Repeatable

• Reproducible

� True sampling system• Fixed sampling conditions/parameters

• Standard procedures

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� Accuracy of Gas analyses

� GLC methods – ISO6974/GPA2261……

� Total inaccuracy GHV?• +/- 1% - conc. 1-10%

• +/- 10% - conc. 0.1-1%

• Below 0.1% - 30% relative

• Overall inaccuracy =>

– Industry = 0.35%

– SGS study = 0.41%

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± 0.60 %± 0.49 %TOTAL INACCURACY OBTAINED by QUADRATIC COMBINATION OF MEASUREMENTS

± 0.41 %± 0.35 %Overall GCV inaccuracy

± 0.04 %± 0.04 %GCV of the components (NBS)

± 0.1 %± 0.03 %Calibration gas (NBS) (weighting process)

± 0.3 %± 0.3 %Inaccuracy sampling (NBS)

GROSS CALORIFIC VALUE

± 0.31 %± 0.27 %Overall density inaccuracy

± 0.20 %± 0.15 %Temperature measurement

± 0.09 %± 0.09 %Gas analysis (NBS)

± 0.10 %± 0.10 %NBS estimate of LNG measurement

DENSITY

± 0.30%± 0.21%Liquid + vapour boil-off + vapour displaced

VOLUME

SGS SurveyINDUSTRYperception

Inaccuracy of Measurement

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78 mio US$64 mio US$Estimated loss over 20 years contract

130 kUS$107 kUS$Energy value in US$

± 0.60 %± 0.49 %Inaccuracy

SGS Survey (*)INDUSTRYOverall inaccuracy

(*) shipments under SGS supervision

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� Technical/System upgrading

� Ship calibration tables accuracy

� Technical performance CT Measurement system

• SGS LNG vessel data base

� Sampling stations –installation/procedures/verification/maintenance

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� Supervision/Control upgrading

� Independant Inspection

• Monitoring – => brings no value and a wrong expectation of

Independant Inspection

• True Inspection– => true Independant Inspection and corrective

measures

– => Consultancy on total measurement systemaccuracy

We urge the Industry to take drastic measures to increase the overall accuracy of

Shipboard Measurements, to re-define shore based sampling and testing techniques

and to revise the role and importance of Independant Inspection and Certification

SGS and its LNG Competence Center is at your service to achieve this!

So, How accurate is your Shipboard Custody

Transfer Measurement system and Energy Accounting ?

how accurate is the shipboard custody transfer ... conferences...how accurate is the shipboard...

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