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Published byGuy Codner Modified over 4 years ago

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**INTERTANKO A Final Report upon Crude Oil Cargo Measurement Control**

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

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**CRUMECON Project Objectives 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)

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**CRUMECON Project Developed Dilemma**

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 %. Nearly every voyage reported vapour releases during the voyage.

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**CRUMECON Project Developed Cargo 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.

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**CRUMECON Project Density 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

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**CRUMECON Project The 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”

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**CRUMECON Project The Perceived Problem**

Background -the Basis Equations for the Crude Oil Tables “Alpha” - the calculated expansion coefficient K0 - a Constant/function used to calculate “Alpha” (kg/m3)/deg C Where: a = K0/rt2 The VCF Equation - VCF = EXP(-a*Dt*( (a*Dt))

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**CRUMECON Project Findings from Density Modeling**

Initial Boiling Point = deg C Cloud Point = 7.5 deg C

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**CRUMECON Project Findings from Density Modeling**

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**CRUMECON Project Findings**

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

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**CRUMECON Project Findings**

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 $ US$ 25/bbl

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**CRUMECON Project Findings**

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.

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**CRUMECON Project Findings**

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

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**CRUMECON Project Findings**

Based upon the % VOC Loss Equation and the mean Crude Oil TVP quoted in the CRUCOGSA report – 14.7 psia – the annual loss of VOC to atmosphere is calculated to be 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

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**CRUMECON Project Interim 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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