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A Final Report upon Crude Oil Cargo Measurement Control (CRUMECON) Project

INTERTANKO International Association of Independent Tanker Owners Safe Transport, Cleaner Seas, Free Competition. A Final Report upon Crude Oil Cargo Measurement Control (CRUMECON) Project. CRUMECON Project Objectives and Deliverables.

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A Final Report upon Crude Oil Cargo Measurement Control (CRUMECON) Project

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  1. INTERTANKO International Association of Independent Tanker Owners Safe Transport, Cleaner Seas, Free Competition A Final Report upon Crude Oil Cargo Measurement Control (CRUMECON) Project

  2. CRUMECON ProjectObjectives and Deliverables • Analise the Cargo quantity figures in the CRUCOGSA database to establish the extent of intransit losses. • Examine and correlate the extent of intransit loss with the average True Vapour Pressure of the cargo for the voyage and its Reid Vapour Pressure. • Establish, if available, a cause for the transit loss with reference to the volatility of the cargo (an inherent vice)

  3. CRUMECON ProjectDevelopedDilemma • An analysis of the CRUCOGSA cargo figures revealed no loss of cargo from the load and discharge port comparison • An intransit gain was found - very similar to the average reported by the PM-L4A statistic of + 0.03%. • Nearly every voyage reported vapour releases during the voyage.

  4. CRUMECON ProjectDevelopedCargo Calc. Procedure • Instead of using the conventional tables for TCV/GSV calculations, a calculation procedure to MASS with correction to TCV/GSV was selected. • Procedure required the modeling of the Density profile for each crude oil type for application of Observed Temperature to calculate MASS from TOV.

  5. CRUMECON ProjectDensity Data available • CRUCOGSA Database • Approx 330 Crude Oil Voyages • with approx 330 Crude Oil Samples from both the load and discharge ports • representing 67 crude oil types • each sample analysis supplies a density profile of 10 data points over the observed carriage temperature range

  6. CRUMECON ProjectThe Perceived Problem • An error caused by a systematic error in the cargo calculation method • The 1980 Volume Correction Factor Tables • derived from a data base of 124 samples and 690 data points • “The sample was chilled to 50 deg F, settled and the upper portioned siphoned off. This step removed any wax that formed at 50 deg F and the assorted solids in the original sample”

  7. CRUMECON ProjectThe Perceived Problem • Background -the Basis Equations for the Crude Oil Tables • “Alpha” - the calculated expansion coefficient • K0 - a Constant/function used to calculate “Alpha” - 613.9723 (kg/m3)/deg C Where: a = K0/rt2 • The VCF Equation - VCF = EXP(-a*Dt*(1.0 + 0.8(a*Dt))

  8. CRUMECON ProjectFindings from Density Modeling Initial Boiling Point = 26.33 deg C Cloud Point = 7.5 deg C

  9. CRUMECON ProjectFindings from Density Modeling

  10. CRUMECON ProjectFindings • Assumption - The Cargo temperature on loading is significantly above 15 deg C (standard temperature) and approximated to 30 deg C • Given this assumption the Cargo figures at loading port are understated by approx 0.25% - i.e. more cargo onboard than calculated

  11. CRUMECON ProjectFindings • Assumption - During the voyage the Cargo temperature cools and approaches 15 deg C - Zero Error at 15 deg C - VCF = 1.00 • Given the foregoing assumption, there is an average intransit loss of approx 0.2% rather than an intransit gain of 0.03% • 0.2% of VLCC cargo = 580 m3 = 3650 bbls = US $ 91,200 @ US$ 25/bbl

  12. CRUMECON ProjectFindings • A statistical review of the recalculated “in-transit” difference population derived a standard deviation of +/- 0.21%. • The derived standard deviation is the value attributed in literature for the scope of measurement error for two independent measurements.

  13. CRUMECON ProjectFindings • After application of the “Ideal Gas Law” relationship, the equation best modelling the data population is: Predicted % VOC Loss = 0.4367 * Ln(1/TVP) + 1.0111 • No VOC Loss will occur when the TVP is below approx. 10 psia.

  14. CRUMECON ProjectFindings • Based upon the% VOC Loss Equationand the mean Crude Oil TVP quoted in the CRUCOGSA report – 14.7 psia – the annual loss of VOC to atmosphere is calculated to be 4.973 million tonnes. • Using the UKOOA loading loss percentage (0.1%), the total VOC loss per annum from the transportation of crude oil is estimated to be 8.686 million tonnes

  15. CRUMECON ProjectInterim Conclusion • As a result of reports from vessels operating using either the VOCON procedure or valve the in-transit releases are nearly eliminated. • It is also believed that the use of the VOCON valve will reduce the extent of losses of VOC gases during loading

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