●
A vessel’s remote draught gauge should never be used for surveys, due to lack of the necessary accuracy and the possibility of errors, which may accumulate over the working life of the instrument.
●
When adverse weather conditions are being experienced, access to the offside draught marks may prove difficult or impossible. At these times the draughts on the nearside can be read and the offside draughts calculated using a manometer.
This method should never be used when the offside draughts can be safely observed and accurately read. If, as a final resort, this method cannot be undertaken, the use of a fully calibrated inclinometer, graduated to minutes of arc, is strongly recommended. The type of inclinometer fitted to vessels is not usually of sufficient accuracy to be used.
Density of the water in which the vessel is floating ●
Above: Manometer showing plastic tubing (30-40 m long), fitted at each end with a valve and scale. The valves are to allow the water in the tube to be retained without any air bubbles in it when the device is not in use
Below: Manometer, showing scale and water level. When a scale is fitted and used for the reading care must be taken that the scale is fixed at the same height on each side
●
It is prudent to obtain samples of water in which the vessel is floating at, or very close to, the time at which the draught marks are read. This is particularly relevant when the vessel is lying at a estuarial or river berth when density of the water may be changing, due to the ebb or flow of the tide.
Depending upon the length of the vessel under survey, a number of samples, say between one and three, should be taken. In order to overcome the problem of layering, the samples should be obtained using a closed sampling can at a depth of approximately half the existing draught of the vessel. Alternatively, a slow-filling container can be used to obtain an average sample from keel to waterline.
●
When reading the hydrometer floating in the sample of water, the eye of the observer should be as close to the water level as possible, to avoid parallax errors and also to avoid further errors due to the meniscus.
Ballast water tanks ●
Ballast water tanks including peaks, even those said to be empty, must be carefully sounded or proven to be full by pressing up and overflowing from all air pipes when local regulations permit. If the ballast hold contains ballast water, this compartment must not be fully pressed up but be carefully sounded and the weights of the water carefully calculated.
●
Spaces such as the duct keel and voids – especially those of the lower stools situated at the base of
22
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34