2 X vessel’s trim

Y

P1

P

The corrected sounding can be calculated by the following approximate formula:

Corrected sounding (P) = observed sounding (P1) + distance (y) x trim/LBP

Where the distance “y” is the distance from the sounding position to the end bulkhead.

Mixtures

When conducting a bunker survey and the vessel loads bunkers, this could be mixed with bunkers already on board. The relative density (RD), or density, of the mixture must be used to calculate the total quantity of the oil in the tank. The final RD of the mixture can be found by the following formula:

RD of mixture = (original volume x original RD) + (loaded volume x loaded RD)

Original volume + loaded volume

RESIDUE IN COMPARTMENTS

Tanks of liquids, particularly ballast tanks, are subject to the build up of residues and scale. The quantity of sediment is difficult to assess without entering the tank. Leaving a measurable quantity of water in the tank instead of pumping it completely dry can minimize the effect on the ballast calculations. The calculations then use a known amount of water, which can be deducted from the displacement. The error due to the unknown weight of sediment is reduced to the difference between the density of water and the density of the sediment. This accumulation of sediment will reduce the deadweight capacity of the vessel and therefore should not be allowed to accrue indefinitely. Inspect ballast tanks if in any doubt about the quantity of sediments. There are patent chemicals available to put the mud into suspension, so that it may be disposed of with the water in an appropriate and safe manner, when a suitable opportunity allows. However, these may not always be effective; when a hard crust has developed on the top of the mud, it can sometimes only be removed by hand.

Anchors and cables

The anchor may be in the housed position, where they contribute to the lightship, or they may have been used in the mooring of the ship. Then the anchors will be on the seabed along with a given length of cable. The loss of weight due to its removal is weight taken from the light displacement; this amount should therefore be added to the quantity of cargo. There should be information available onboard to enable the surveyor to establish or calculate the weight of the missing anchor and cable. In the case of the chain cable, it can be calculated with reasonable accuracy by the following formula:

Weight per shackle (tones) = 15 x (link diameter in cm) 2 x 3,87

1000

The link diameter is the diameter of the steel rod, which makes up each individual link. In the case of the anchor itself, this will vary from ship to ship, but this information should be available on board. This anchor weight should be rounded to the nearest half tones.