DRAFT SURVEY-repaired

Surveyors and ship's officers should discuss the ship's documentation details, the location and state of all compartments, tank capacities, stability information book, calibration tables, measurement bases, reference points, units, and sign conventions. They should also note the full sounding depths of tanks, the summer draught and freeboard, and the record of recent tank soundings.

1. Correct observed draughts to the centreline. 2. Correct centreline draughts to the correct position of the perpendiculars. 3. Allow for hog or sag and obtain the correct draught midships. 4. Enter the corrected draught into hydrostatic tables for uncorrected displacement. 5. Correct displacement for trim, list, and density.

It is important to verify the units and sign conventions because there can sometimes be a mixture of units and sign conventions within the same documentation, which can affect the accuracy of calculations and corrections.

To achieve consistency of results.

Accuracy to within 0.5%.

Samples should be taken from half draught depths from at least two positions on the offshore and onshore side, avoiding discharges, stagnant water, and outfall areas. Use a sample bucket, rinse it and the sample jar with the first sample, and take density readings promptly. Use a hydrometer, ensuring it floats freely, and read where the liquid surface meets the graduated stem, avoiding parallax.

A survey where the weights of all measurable non-cargo elements on the vessel are determined and added to the light displacement to produce the approximate weight of cargo on board.

A draught survey determines the vessel’s displacement before and after loading or discharging, and the difference between these two displacements is the weight of cargo loaded or discharged. Its primary purpose is to determine the amount of cargo loaded or discharged for the benefit of all interested parties.

The most accurate time to take draughts and densities is at slack water, although this may not always be practicable. Draughts and densities should be obtained at nearly the same time to ensure accuracy, as tidal changes can affect the sample density.

It may be necessary to assume a small percentage (1% or 2%) of the tanks’ total capacity as additional weight to cover all remaining drainings if residual water is indeterminable.

The sample should be taken at the bottom of the pipe using a suitable sampling can which can be opened at the appropriate depth.

Variations could be caused by the ballasting taking place at different times and locations.

Staff, documentation, and equipment should be ready on the arrival of the ship. It is important for the vessel to arrive with a safe trim suitable for navigation to enter port and within the limits of trim covered by the trim corrections of the sounding tables.

Every compartment should be carefully inspected and sounded multiple times, and the average value assumed to be correct. Ensure the tape reaches the bottom of the tank and check the consistency of the depth of different tanks, considering the vertical tank height and the length of the sounding pipe.

Calculations should deal only with the acquired facts and not introduce any unsubstantiated constants.

To take into account all the prevailing circumstances and ensure accuracy, as an inaccurate survey may result in considerable expense to several parties.

If a bunker survey is not conducted, the chief engineer’s bunker figures for fuel oil, diesel oil, and lubrication oil are required, along with the daily port consumption quantities. Any bunkers or stores delivered during the stay should be recorded, and the delivery notes must be sighted for inclusion in the final survey.

Residual water may remain in ballast tanks due to poor drainage and liquid left in pipes, which is difficult to detect. Ensuring that the empty tanks are actually clear of ballast remains a major issue.

They should be recorded on the survey report.

There should be no movement of ballast, fresh water, bunkers, or cargo, and no operation of hatches, cranes, and moorings.

Additional samples should be taken and this factor included in the report. Errors due to vessel movement at an exposed berth can be minimized by taking several soundings and assuming the average value to be correct.

Overflowing ballast water can wet cargo waiting to be loaded, soak electric power boxes on the quayside, or wash debris and pollutants over the side.

Sections 3, 4, and 5 should be repeated for the final survey, and adequate preparation is required again for the final survey.

The purpose of the UN ECE draught survey code forms is to achieve uniformity and consistency in draught surveys, avoiding discrepancies that give rise to commercial disputes. They can be freely downloaded from the UN ECE website at http://www.unece.org/energy/se/coal/code.html.

The master must decide whether to delay the ship to complete the draught survey properly, balancing careful preparation to minimize delays.

Ballast holds should be visually inspected to ensure they are empty of ballast, as poor tank calibrations and hull deformation can cause problems.

The ballast tank dipper or hand pump down the sounding pipe may be used to obtain a sample where the water is well mixed.

All parties should work together for a unanimous result, and facts should be established by inspection and not by verbal agreement.

Recording bilges pumped during the ship’s stay can provide useful evidence to explain any apparent loss of cargo between successive surveys.

For a stern trim, the position of the forward air pipe relative to the forward tank bulkhead should be checked to determine any possible remaining void spaces.

Invoice figures for the weights should be verified and a check made that nothing has been landed.

Well-documented draught surveys can be used as evidence to successfully defend shortage claims on bulk cargoes, which often involve significant sums of money.