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Definitions
A glossary of terms
used in these procedures is provided in this pages. It incorporates terms
for volumes which have been approved by ISO for use in connection with crude
oil, but excludes those that do not apply to refined products.
Bill of Lading-
A document issued by the cargo supplier which states the quantity of
material delivered to the vessel.
Clingage-
Oil residues which adhere to the surface of tank walls and structures on
completion or discharge.
Note:
This quantity, in practice, can only be estimated.
Critical zone-
The volume close to the bottom or a floating roof tank in which there are
complex interactions and buoyancy effects as the floating roof comes to rest
on its legs. The zone is usually clearly marked on tank calibration tables
and measurements for custody transfer should not be made within it.
Density-
The ratio of the mass of a substance to its volume. Since density is
dependent on temperature and pressure these should be stated.
In-transit loss-
The difference between the Total Calculated Volume on board a vessel after
loading and the Total Calculated Volume on board before discharge.
Note:
In cases where measured quantity is greater before discharge than after
loading, then the terms In- Transit Gain or In-Transit Difference can be
used.
Load
on top (
Meter factor-
The ratio of the actual volume of liquid passed through a meter to the
volume indicated by the meter.
Meter K-factor-
The number of pulses emitted by a meter whilst unit volume is delivered
(usually expressed in pulses/m3).
On board quantity
(OBQ)-
All the oil, water, sludge and sediment in the cargo tanks and associated
lines and pumps on a ship before loading a cargo commences. (This term may
not apply to product movements.)
Outturn-
The quantity of material discharged from a vessel, measured by a shore
terminal.
Outturn
Certificate-
A statement issued by a receiving terminal
and/or cargo surveyor certifying the outturn.
Outturn Loss-
The difference in Net Standard Volume of oil between the quantity shown on
the Bill of Lading and the quantity shown on the Outturn Certificate. The
adjusted loss is the Outturn Loss corrected for the difference between the
OBQ and the ROB. where applicable.
Quantity
remaining on board (ROB)-
AII the oil. water. sludge and sediment in the cargo tanks and associated
lines and pumps on a ship after discharging a cargo has been completed.
excluding vapour but including clingage. (This term may not apply to product
movements.)
Sediment-
Suspended Sediment:
Non-hydrocarbon solids present within the oil but not in solution.
Bottom Sediment:
Non-hydrocarbon solids present in a tank as a separate layer at the bottom.
Total Sediment: The sum
of the suspended and bottom sediment.
Slops-
Material collected after such operations as stripping. tank washing or dirty
ballast separation. It may include oil, water, sediment and emulsions, and
is usually contained in a tank or tanks permanently assigned to hold such
material.
Vessel experience
factor-loading (VEFL)-
The mean value of the qualifying VLRs obtained after several voyages.
Vessel experience
factor-discharge (VEFD) -The
mean value of the qualifying VDRs obtained after several voyages.
Vessel load ratio
(VLR)-
The ratio of the quantity (TCV) or oil measured on board a vessel
immediately after loading less the On Board Quantity (OBQ) to the quantity
(TCV) measured by the loading terminal, i.e.
VLR= Vessel's TCV after loading-OBQ
Shore TCV loaded
Vessel discharge
ratio (VDR)-
The ratio or the quantity (TCV) or oil measured on board a vessel
immediately before discharge less the Quantity Remaining on Board (ROB) to
the quantity (TCV) measured by the receiving terminal, i.e.
VDR= Vessel's TCV
before discharge-ROB
Shore TCV received
Volumes
correction factor-
A factor dependent upon oil density and temperature which corrects volumes
to the standard reference temperature. Such factors shall be obtained from
the latest API-ASTM-IP Petroleum Measurement Tables.
Volumes for
dynamic measurement calculations-
Indicated Volume:
The change in meter reading that occurs during
transfer through a meter.
Gross Volume:
The indicated volume multiplied by the appropriate meter factor nor the
liquid and flow rate concerned, without correction for temperature and
pressure.
Note:
This includes all water and sediment transferred through the meter.
Gross Standard
Volume: The gross volume
corrected to the standard conditions. e.g. 15°C and 1.01325 bar.
Note:
For refined products, dissolved water, suspended water and sediment are not
usually deductible, as limits are commonly prescribed in the quality
specification. For this reason the term NET is not used for products.
Volumes for
static measurement calculations-
Total Observed
Volume (TOV): The volume or oil
including total water and total sediment, measured at the oil temperature
and pressure prevailing. This may be either the volume in a tank or the
difference between the volumes before .and after a transfer.
Gross Observed
Volume (GOV): The volume or oil
including dissolved water, suspended water and suspended sediment but
excluding free water and bottom sediment, measured at the oil temperature
and pressure prevailing. This may be either the volume in a tank or the
difference between the volumes before and after a transfer.
Gross Standard
Volume (GSV): The volume or oil
including dissolved water, suspended water and suspended sediment but
excluding free water and bottom sediment, calculated at standard conditions,
e.g. 15 C .and 1.01325 bar. This may be either the volume in a tank or the
difference between the volumes before and after a transfer.
Total Calculated
Volume (TCV): The gross standard
volume plus the free water measured at the temperature and pressure
prevailing.
Note:
For refined products, dissolved water, suspended water and sediment arc not
usually deductible, as limits arc commonly prescribed in the quality
specification. For this reason the term NET is not used for products.
Dissolved Water:
The water contained within the oil forming a solution at the prevailing
temperature.
Suspended Water:
The water within the oil which is . finely dispersed as small droplets.
Note:
It may, over a period or time, either collect as free water or become
dissolved water depending on the conditions or temperature and pressure
prevailing.
Free Water:
The water that exists in a separate layer.
Note:
It typically lies beneath the oil.
Total Water:
The sum of all the dissolved, suspended and free water in a cargo or parcel
of oil.
Water cut or dip: The measured depth of free water.
Wedge formula:
An equation relating the volume of liquid material in a ship's tank to the
dip, ship's trim, dipping point location and the tank's dimensions when the
ship's calibration tables cannot be applied. To derive the equation,
assumptions have to be made. The major assumption in the derivation is that
the material is free flowing and will accumulate
in the aft end of a tank when the ship is trimmed by the stern.
Weigh conversion
factor- A
factor dependent on the density for converting volume to weight-in-air. Such
factors shall be obtained from the API-ASTM-IP Petroleum Measurement Tables.
Gross Weight-in-Air:
The weight of oil including dissolved water, suspended water and suspended
sediment but excluding free water and bottom sediment.
Net Weight-in-Air:
The weight of oil excluding total water and total sediment.
Weight-in-Air:
The weight or oil excluding free water.