All internal transfers of cargo
should be completed and all tank valves should be secured prior to
gauging. Loading lines should be vented prior to
gauging. It is common in the case of multi-grade petroleum
product loadings also to seal the individual tank suction valves.
Take gauges, water cuts and
temperatures on all cargo compartments. Inspect for the
presence of petroleum in non-designated cargo spaces, ballast tanks,
cofferdams and void spaces. If petroleum is found, measure it
in the same manner as the petroleum in the cargo
compartments. The data should be recorded on the Vessel
Ullage/Sounding and Capacity Report. Where applicable, show
both the actual ullage as measured and trim and list corrected ullage
on the Vessel Ullage/Sounding and Capacity Report. The report
should indicate whether measurements were manual or automatic and
whether tanks on the vessel were inerted during ullaging. The
observed gauge heights should be recorded in the field work book.
In some instances, it is
impossible to determine the observed reference height, water cut and
innage gauge because of the heavy nature of the product.
Every effort should be made, however, to identify the proper reference
point for ullage measurement as described by the vessel calibration
tables. The location of the reference point should be
recorded in the inspection report.
Vessel measurements taken
through non-slotted standpipes may be inaccurate as a result of
plugging at the base of the pipe, capillary action or pressure
differentials. Additional measurements may be needed from
other locations when this condition exists. Note in the
report, the existence of this condition.
In the case of heavy viscous
materials, air and/or inert gases may be entrained in the
product. An appropriate settling time should be allowed if
possible. If the vessel is gauged immediately after
completion of loading, this fact should be noted on the time log and in
In operations involving
lightering each receiving vessel as well as the delivering vessel
should be gauged prior and upon completion of lightering.
- Water Cut Measurement
Measure free water during the
course of ullaging each compartment. Record the type of
water-finding paste or device that is used to determine the oil/water
interface. Record the interface and any oil emulsion that is
detected. If a sufficient quantity of free water is found,
take a sample of the water.
Products with densities heavier
than water my need to water cut on top of the product. If it
proves impossible to take a water cut measurement, then alternative
sampling measures should be taken.
If free water is detected in
certain products, a protest should be made to the vessel's
representative and to the loading facility and all interested parties
should be notified immediately.
temperatures on the vessel should be taken concurrent with
ullaging. Temperatures should be taken at the upper, middle
and lower mid-point levels and the measurements should be averaged to
determine the temperature of each compartment.
In the case of heated
materials, the portable electronic thermometer (PET) should have a
calibrated range of accuracy that meets the desired temperature range
of the material to be checked.
Caution: Temperatures that are
taken at or near heating elements may distort temperature
profiles. Exercise care when average temperatures are
Sections of text taken from API - MPMS Chapter 17 Marine Measurement