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TOTAL OBSERVED
VOLUME (T.O.V.):
The Total Observed Volume of all Petroleum Liquids and
Free Water at observed temperature.
GROSS OBSERVED
VOLUME (G.O.V.):
The Total Volume of all Petroleum Liquids, excluding Free
Water at observed temperature.
G.O.V.
= T.O.V. -
Vfw (at observed temperature)
GROSS STANDARD
VOLUME (G.S.V.):
The Total Volume of all Petroleum Liquids, excluding Free
Water, corrected by appropriate Volume Correction Factor for the observed
temperature and API Gravity 60º F, Relative Density 60º F / 60º F or Density
15º C.
G.S.V.
= G.O.V. X
V.C.F.
FREE WATER
(Vfw):
The volume of water present in a tank which is not in
suspension in the contained liquid at observed temperature.
ONBOARD QUANTITY
(O.B.Q):
Quantity of water, oil, slops, residue, sludge or
sediment, remaining in the tanks prior to loading.
TOTAL CALCULATED
VOLUME (T.C.V.):
It is the Gross Standard Volume plus Free Water.
T.C.V. = G.S.V.
+ Vfw
TOTAL RECEIVED
VOLUME (T.R.V.):
Is equal to the Total calculated Volume minus O.B.Q.
Weight Correction Factor (W.C.F.) is applied to this
Volume to obtain Weight in Metric Tons or Long Tons.
Shore Gross B/L figure is to be compared with this figure.
Whenever Free Water is found in Cargo:
T.R.V. = T.C.V.
- O.B.Q.
LOADED OIL WEIGHT:
Is equal to the Gross Standard Volume minus O.B.Q.
Weight Correction Factor is applied to this Volume to
obtain weight in Metric Tons or Long Tons.
Shore Gross B/L figure is to be compared with this figure
when no Free Water is found in Cargo.
LOADED OIL WEIGHT
= (G.S.V. - O.B.Q.)
W.C.F.
VESSEL’S EXPERIENCE
FACTOR (V.E.F.):
Is equal to the Total of Gross B/L figures divided by the
Total of Ship’s figures over the last 10 voyages.
For the purpose of calculating V.E.F., 10 TO 20 Voyages
may be taken. However all voyages must ‘qualify’. A minimum of 5 ‘qualified’
voyages is needed for some level of V.E.F.
The defination of a “qualified voyage is one that meets
the following criteria:
·
Any voyage that is within +/- 0.0030 of then
average ratio of all voyages listed. (eg.
If the average listed is 1.00105, then all voyages within the range
0.99805 through 1.00405 would qualify)
·
Excludes all voyage prior to any structural
modification which affected the vessel’s cargo capacity.
·
Excludes load or discharge data where shore
measurements were not available.
This Factor is not to be applied to ship’s figure for
assessing Ship / Shore difference.
The Factor may be applied to Ship’s figure to obtain an
approximate B/L figure, only as a counter check where:
SHIP’S FIGURE
X V.E.F = APPROXIMATE B/L FIGURE.
TABLES, VOLUME AND
DENSITY:
API = AMERICAN PETROLEUM INDEX
ASTM = AMERICAN STANDARD OF TESTING MATERIALS
Previously there were 3 versions of ASTM Tables:
·
USA Version
- Giving API at 60º F
·
UK Version
- Giving Specific Gravity at 60º
/ 60º F (Ratio of density of Oil at 60º F to density of Water at 60º F = Specific Gravity)
·
Metric Version
- Giving Density at 15º C (eg. 0.865 kg/m3)
IN PRACTICE:
Volume at observed temperature is calculated by taking
ullages.
Density at 15º C is given by Shore authorities.
Now Volume at 15º C
= Volume at observed
temperature X V.C.F.
And Volume at 15º C
X Density at 15º C = Weight at 15º C (IN VACUUM)
But we want Weight IN AIR, therefore we apply the W.C.F.
W.C.F. = DENSITY AT 15º C -
0.0011
NOTES:
Now all 3 Versions are combined together and made into
total 14 Volumes which contain all calculations regarding CRUDE, LUBE OIL,
DIESEL OIL and all kinds of fluids / liquids.
A particular ship may have selected Volumes only, for the
trade on which she is being run.
HYDROMETER - TO MEASEURE DENSITY OF WATER
PICNOMETER - TO MEASURE DENSITY OF ANY LIQUID OTHER THAN
WATER
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