Draught surveys

Corrections check list

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OBSERVED DRAUGHTS:

Forward...P & S aft...P & S midships...P & S

Mean values, ie. draughts at centreline, forward, aft and midships.

Correct from marks to perpendicular and midships positions.

Misplacement opposite to trim, then positive (+)

Misplacement same as trim, then negative (-)

Hog/sag correction (mean of mean of means, or similar).

negative (-) for hog positive (+) for sag

CORRECTED MEAN DRAUGHT ... to enter hydrostatic tables.

Displacement from displacement table.

First trim correction or Correction for layer (in tonnes).

LCF same as trim, then positive (+)

LCF opposite to trim, then negative (-)

Second trim correction (in tonnes).

Always positive (+)

List correction (in tonnes).

Always positive (+)

Correction for density.

Less than salt water density, then negative (-)

CORRECTED DISPLACEMENT.

Information check list

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GENERAL INFORMATION

Ship's name Call letters Port of registry

Flag Year built Master

Owners Owner's address Owner's agent

Manager/operator Charterer Charterer's agent

Shipper Chief Officer Chief Engineer

Surveyor/s P&l correspondent Ship's location

Survey requested by: Survey on account of: Type of cargo

Weather conditions Date and time of arrival

THE STABILITY INFORMATION BOOK

Length between perpendiculars

Extreme and moulded breadth

Overall and moulded depth

Summer draught and freeboard

Summer displacement and deadweight

Misplacement of draught marks from perpendiculars and midships

Lightship displacement with lightship constant

Hydrostatic particulars:

Displacement, TPC, MCTC, LCB, LCF

Capacity plans and tables

Correction tables:

Trim

Position of marks

List

Hull deflection

PLANS

General arrangement plan

Profile plan indicating each space in the ship

OTHER SOURCES

Sounding tables and corrections for trim

Quantity of bunkers

Check list of reservations

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(Not an exhaustive list)

Height of waves / swell	Clarity of draught marks
State of tide - underkeel clearance	Squat effects
Variations in density	Daytime / night-time
Anchors moved, in or out	Ice / snow on deck
Quantity of bilges pumped	Residue in tanks
Suspect calibrations	Ship movements

Documentation and information

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Surveyors and ship's officers should discuss documentation details and the location and state of all compartments. The instruction pages of the stability information book and calibration tables should be studied and a check made of the tank capacities with the capacity plan. It should be remembered that the port and starboard tanks may not be the same and consequently have separate calibration tables.

The base for measurement of vertical heights, the reference point for longitudinal measurements, the units and the sign conventions used in the tables must all be verified. The units used in the correction tables should also be carefully noted because there is sometimes a mixture of units and sign conventions contained within the same documentation. The whole survey should be conducted using the units of the ship and the final result changed to a suitable unit, if necessary. When feet and inches are the standard unit, convert to feet and decimals of a foot for the convenience of a calculator.

The full sounding depths of tanks, the summer draught and freeboard and the record of recent tank soundings should be noted.

If a bunker survey is not to be carried out, the chief, engineers bunker figures (fuel oil, diesel oil and lubrication oil) are required, also the daily port consumption quantities. Should any bunker or stores be delivered during the stay then the delivery notes must be sighted for the additional quantities to be included in the final survey. The draught survey is only interested in changes in the bunkers on board, that is consumption and deliveries.

The position of the anchors should be checked, should any alterations be proposed during the stay then the weight of the anchors and cables should be determined.

Equipment check list

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Sample jar and water sample bucket with line

Ballast tank dipper with line

Small hand pump with hose for taking samples

Draught survey hydrometer with certificate

Steel sounding tape with graduations in metres and feet

Water finding paste

Draught/freeboard measuring device

Manometer if some draughts are impossible to read, plus a long measuring tape

Plastic tube with plug, to act as sounding pipe extension

Boat available to read inaccessible draughts

Pilot ladder on board ready for obtaining draughts

Documentation

Pocket computer with draught survey program or calculator

Prior to arrival

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Sounding tape

The ship should be asked to prepare for the draught survey.

The ballast tanks should be adjusted to a level covered by the sounding tables.

It should be remembered that full tanks can be pressed up but still retain air pockets and also it can be difficult to establish that a tank is completely empty without visual inspection.

Ballast holds, (main cargo holds used for ballast) should be empty of ballast on arrival at the loading port, if possible.

The vessel should arrive with a safe trim, suitable for the navigation to enter port and within the limits of trim covered by the trim corrections of the sounding tables. The vessel should arrive in an upright condition.

Staff, documentation and equipment should be ready on the arrival of the ship. There should be no movement of ballast, fresh water, bunkers or cargo and hatches, cranes and moorings until all measurements are taken and agreed by surveyors and ship's officers. The prudent surveyor will have observed the shore side draughts before boarding as these can

be used to indicate any changes.

Surveyors tools

Practical procedure

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It is impossible to cover every conceivable problem likely to be encountered when carrying out a draught survey. Ships and ports vary so much that there will always be the unforeseen circumstances which will require an on-the-spot decision. These notes and steps to be taken, give only a broad approach to the subject. There is however, no substitute for experience.

An inaccurate survey may result in considerable expense to several parties, therefore it should be conducted carefully and accurately. Being well prepared and having sufficient time will allow the survey to be conducted correctly. It may not appear expedient to delay the ship in order to complete the draught survey properly, but it could save money in the long term. This decision must lie with the Master, however careful preparation could reduce these delays to a minimum.

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

UN/ECE draught survey code forms

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They are the work of the United Nations Economic Commission for Europe, the Coal Working Party of the Energy Committee, which produced the Code of uniform standards and procedures for the performance of draught surveys of coal cargoes. The Working Party recommend the use of the forms in order to achieve uniformity and consistency in draught surveys, so avoiding the discrepancies which give rise to commercial disputes.

The forms have been freely given, so that all surveyors and ship's officers may photocopy and use them as a standard format throughout the industry.

Deadweight survey

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Under certain circumstances, the surveyor or ship's officer may have no choice but be restricted to carrying out a deadweight survey. The weights of all measurable non-cargo elements on the vessel are determined; bunkers, fresh water, ballast, stores etc. These are then added to the light displacement (including any lightship constant). This total is then deducted from the present displacement to produce the approximate weight of cargo on board.

Draught survey

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The draught survey is the "before and after" survey, which determines, by measurement, the vessel's displacement before and after loading or discharging. The difference between these two displacements is the weight of cargo loaded or discharged.

Introduction

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The purpose of a draught survey is to determine the amount of cargo loaded or discharged for the benefit of all the interested parties. A well-conducted draught survey of a large vessel should achieve accuracy to within 0.5%.

The survey must be conducted meticulously, taking into account all the prevailing circumstances. The final report should incorporate every aspect and difficulty which has been encountered in order to convey all aspects of the survey.

While draught surveys may be carried out by professional surveyors, the ship's officers should also perform a draught survey to the same degree of accuracy. It is hoped that this guide will assist in achieving the required standards.