No voyages shall be excluded beyond the reasons given above, unless specifically agreed to by all interested parties.
1. These shall be the most recent voyages available and listed in chronological order. Do not use the current voyage. b) Quantities should be combined for multiple grades on the same voyage, unless a compartmental VEF is being calculated.
A VEFD should be used to compare discharge port transferred quantities. The VEFD should be used to compare the shore’s TCV received with the vessel’s VEF corrected TCV delivered.
14.2.4.2 Alternate Method - Calculation of a VEF The alternate method provides a statistical outlier rejection technique and uses an average of qualifying ratios.
In essence what this is stating is:
- When a load operation takes place the VEFL must be used i.e. a Vessel’s Experience Factor (VEF) compiled using Loadport data. - When a discharge operation takes place the VEFD must be used i.e. a Vessel’s Experience Factor (VEF) compiled using Discharge data. It is a fact that in many, if not most cases, the data needed to establish a VEFD is simply not available at the time and place of the subject discharge, as vessels tend to depart before an outturn is fully established. Individual companies/clients have taken a variety of approaches to how this issue is best addressed. These are: 1. To stick with the wording in the standard 100% and expect it to be followed in full. 2. To ask that it be followed where possible (not often) and to be consulted whenever it is not. 3. To allow the “custom and practise“ approach that has been the norm for years, of deviating from the requirement in the text and use the VEFL at the discharge.
c) Do NOT include both load and discharge information on the same form.
d) Data from different voyages do not need to be in consistent units and can be mixed, i.e. some voyages measured in barrels and some in tons. However, vessel and shore data for each individual voyage must be in consistent units and cannot be mixed. f) Calculate the individual ratio for each voyage, rounding to five decimal places.
The actual calculation process is quite complex and does not lend itself to field applications.
If when calculating a VEF, the primary method does not produce a VEF, then contact Technical Governance (ogc.tgteam@sgs.com) to explore using the alternate method to calculate a VEF.
g) Report the final VEF to four decimal places.
14.3 Load and Discharge VEF
14.2.4.1 Alternate Method - Rejected Voyages
The current revision of “API MPMS Chapter 17.9 / EI Hydrocarbon Management HM 49: Vessel Experience Factor (VEF) Third Edition, July 2019” contains within its text some wording that has caused debate, and in some cases confusion. Specifically, as follows: A VEFL should be used to compare load port transferred quantities. The VEFL should be used to compare the shore’s TCV delivered with the vessel’s VEF corrected TCV loaded .
a) Voyages where only vessel tank measurements were available (i.e. vessel-to-vessel transfers, active shore tanks); except where quantities are determined onboard FPSOs using meters in accordance with globally recognized standards. b) All voyages prior to any changes to measurement equipment, table, vessel’s structure, or other changes.
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