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Slops are
oil, oil/water/sediment, and emulsions contained in the slop tanks or
designated cargo tanks. The mixture usually results from tank
stripping, tank washing, or dirty ballast phase separation.
Stop
Gauge is a pre-transfer determination of a specific
volume of cargo represented by a specific tank level,
which, when reached, results in cargo completion of the
transfer. This determination may be done by either shore or
vessel personnel.
Tank
Washing is divided into two types of activities:
Water Washing
involves the use of high-pressure water stream to dislodge clingage and
sediment from the bulkheads, bottom and internal tank structures of a
vessel.
Crude Oil Washing
(COW)
involves the use of a high-pressure stream of the crude oil cargo to
dislodge or dissolve the clingage and sediment from the bulkheads,
bottom and internal tank structures of a vessel during the discharge
operation.
It must
be noted that regulatory agencies (including most ship / facility
internal documented procedures require the tanks to be inerted during
tank cleaning.
Total
Calculated Volume (TCV) (Go to Volumes)
Total
Observed Volume (TOV) (Go to Volumes)
Trim is the
condition of a vessel with reference to its longitudinal position in
the water. It is the difference between the forward and aft
drafts and expressed "by the head" if the forward draft is deeper than
the aft draft or "by the stern".
Trim
Correction is the correction applied to the
observed gauge or observed volume when a vessel is not on an even keel
(equal forward and aft drafts), provided that the liquid is in contact
with all bulkheads in the tank. Correction for trim may be
made by referencing trim tables for each individual tank or by
mathematical calculation.
Ullage
Gauge (Outage) is the measured distance from the cargo liquid
surface to the reference point.
Vessel
Experience Factor (VEF)
is a compilation of the history of the total
calculated volume (TCV) vessel measurements, adjusted for on-board
quantity (OBQ) or remaining on board (ROB), compared with the TCV shore
measurements. Separate VEFs should be developed for loadings
and discharges. The information used to calculate VEF should
preferably be based on documents that follow accepted industry
standards and practices, such as inspection company reports.
It may
be noted that for the purpose of calculating a load or discharge vessel
ratio, the TCV on board the vessel includes all petroleum liquids,
sediment and water, free water and slops found after loading (TCV
sailing volume) or before discharge (TCV arrival volumes).
However, if in the completion of the Sequential Voyage Log, a TCV ratio
(vessel - shore) appears to be in gross error, the ratio may be deleted
with the agreement of both parties. If all qualified voyages
are based on load/discharge data from the same terminal, the
applicability of those VEF data to the loads/discharges at other
terminals should be evaluated.
Vessel
Load Ration (VLR) is the total calculated volume
(TCV) by the vessel measurement upon sailing, less on-board quantity
(OBQ), divided by the TCV by shore measurement at loading -
VLR = (TCV
on sailing - OBQ) / TCV received from shore at loading
Vessel
Discharge Ration (VDR) is the total calculated volume
(TCV) by the vessel measurement on arrival, less remaining on-board
(ROB), divided by the TCV by shore measurement at discharge -
VDR = (TCV
on arrival - ROB) / TCV received from shore at discharge
Volume Correction Factor (VCF)
is the numerical value
determined by laboratory analysis or by standardized computer
arithmetic that when multiplied by the Gross Observed Volume at tank
temperature results in the volume of the product at its standard
temperature (15oC or 60oF).
The factors applicable for bands of API (relative density) and
temperature are available in standard tables booklets or may be
computed using a standardized format. If the VCF is below 1
it is shown accurate to 5 places of decimal otherwise it is shown in 4
places of decimal.
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