A SURVEY PRESENTATIONA SURVEY PRESENTATION

Coils Stowed in warehouseCoils Stowed in warehouse

Coils stowed in shedded warehouseCoils stowed in shedded warehouse

Coils stacked in rows of 2 tiersCoils stacked in rows of 2 tiers

Label marking on coilLabel marking on coil

Storage AreaStorage Area

General view of vessel holdGeneral view of vessel hold

Hold Inspection in progressHold Inspection in progress

Wooden dunnagesWooden dunnages

Marking on wooden dunnageMarking on wooden dunnage

Coils delivered alongside vesselCoils delivered alongside vessel

Coils ready for loadingCoils ready for loading

Loading in progressLoading in progress

Loading by shorecraneLoading by shorecrane

Survey in vessel holdSurvey in vessel hold

Coils stowed in vessel holdCoils stowed in vessel hold

Coils stowageCoils stowage

Cover tornCover torn

Cover crushedCover crushed

Strapping LoosenedStrapping Loosened

Cover tornCover torn

Telescopic rollTelescopic roll

Coils lashed to secure for voyageCoils lashed to secure for voyage

Rust on coilRust on coil

Scratched and rolling markScratched and rolling mark

Rust and loosened outer edgeRust and loosened outer edge

Survey under deficient lighting situationSurvey under deficient lighting situation

Steel BilletsSteel Billets

Steel BilletsSteel Billets

Scrap MetalsScrap Metals

Scrap MetalsScrap Metals

Scrap MetalsScrap Metals

Pig IronPig Iron

Pig IronPig Iron

Iron Ore PelletsIron Ore Pellets

Iron Ore PelletsIron Ore Pellets

Iron Ore PelletsIron Ore Pellets

Steam CoalSteam Coal

Steam CoalSteam Coal

Steam CoalSteam Coal

Aluminium IngotAluminium Ingot

What is Draught Survey?

Definition

Draught Survey methodology is based on the recommendations contained in the United nations "Code of Uniform Standards and procedures for the performances of Draught Surveys of Coal Cargoes" published by the Economic and Social Council of the U.N. under the reference ECE/Energy/ 19 dated 03-02-1992. 

Draught Survey is by definition -

A METHOD OF CARGO MEASUREMENT TO DETERMINE THE WEIGHT OF CARGO ON BOARD THE VESSEL BY USING SHIP’S DISPLACEMENT CALCULATION (I.E. EMPTY VERSUS LOADED CONDITION) TAKING INTO ACCOUNT ALL VARIABLES BEFORE AND AFTER LOADING.  The purpose of a draught survey is to determine the weight of cargo that has been loaded on board the vessel or will be discharged from the vessel. Loads which are acting on ship’s hull structure when ship is floating and are associated with draught survey calculation are:

1.Actual weight of the ship ( include fittings, equipment and machinery)2.Cargo load (weight)3.Bunkers plus other Consumable loads (weight)4.Ballast load (weight)5.Hydrostatic pressure (sea water pressure)

Having read the draught at the forward, midship and after marks, port and starboard, determining the density of the dock water and measuring the deductible weights the draught survey calculation can commence.

  First step is to perform correction and calculation of 6 draughts to

obtain a single correct mean draught (corrected for the placement of the draught marks, effect of trim, list and hull deformation).

           

Shearing action of the Hull Girder in still water.

When the ship is floating in still water, the weight of ship’s structure and its machinery (lightweight) and other weights like the cargo, bunkers, ballast and provisions (deadweight) will be supported by global buoyancy up thrust acting on the exterior of the hull.

    

Bending action of the Hull Girder “Sagging” in still water 

Bending action of the Hull Girder “Hogging” in still water

Corrections of draughts to the perpendicular and for “Hogging & “Sagging” On completion of draught reading the figures are corrected to the perpendiculars.

On most of the vessels draught marks are not sited at the perpendiculars and corrections are applied to the observed draughts.

The mean fore and aft mean draught shall be calculated and compared with amidships draught to establish whether the ship is hogged or sagged.

The forward and aft mean draught will rarely be the same as the amidships draught due to deformed hull and will be either hogged or sagged.

The three draughts shall be now reduced to one draught which is corrected for the hull deformation. This is done by averaging the draughts, giving greater weight to the amidships draught where the ship is “wider”.

Fore & Aft Mean = Forward draught mean + Aft draught mean2

 M/M = Fore & Aft Mean + Amidships Mean

2  M/M/M = Mean of Mean + Amidships Mean

2 By using the corrected mean draught the surveyor will calculate the displacement which should be extracted from the ship’s approved hydrostatic tables.

The displacement must now be corrected for errors due to trim. a.) First part of the trim correction simply called the layer correction which allows for the LCF (longitudinal center of floatation) not being amidships.

This correction corrects the draught amidships to the true mean draught, at the Center of Flotation.

Trim correction = Trim x TPC x LCF x 100LBP

Second part of the trim correction, called “Nemoto’s” formula is intended to allow for the LCF movement with change of trim. Trim correction = (Trim)² x (MCTC2 – MCTC1) x 50

LBPDisplacement corrected for trim correction shall be corrected for a density of the water in which the ship is floating. Conventionally, density 1.025 was used to compute the displacement table. Density correction= Displacement x (1.025 – observed density)

1.025 Finally to get a net displacement, the deductible weights (bunker, ballast and fresh water) shall be deducted from displacement corrected for errors in draught, hull deformation, density and trim.

The difference between the loaded net and the light net displacement is the cargo weight.

 

Obstacles 

• The theory is often complicated in practice, as the ship bends and twists.

• Draught readings accuracy depends on the sea condition.

• Because of the ship condition knowing the actual weights of liquids and stores can be difficult tocalculate.

• Density can also be difficult to measure accurately.

• Ship’s crew can deliberately or by mistake adjust the ballast or bunkers during the survey.

Obstacles

• Incorrectly painted draught marks.

• Closing or opening of hatch covers during draught survey readings.

• Blocked sounding pipes.

• Incorrect documentation on board. (incorrect hydrostatic tables or incorrect tank calibration)

• Original light ship’s weight was changed due to some ship’s modification. (No evidence of ship’s weight modification could be found)

• Other obstacles which will affect the accuracy of draught survey calculation.

The End

Thank you

End of Presentation