Finally, I have comfort time to complete this post after having busy with some surveys that I should fulfil

Finally, I have comfort time to complete this post after having busy with some surveys that I shouldfulfil.Any terms on this post should be refer to previous post Draft Survey: Terms of Conduct.The Draft Survey proceduresand calculationascertained asthe following series :

1. Reading the draftmark of the ship, which consist ofsix (6) points of draftmarks, i.e.; Fore, Midship, and After at both sides of the ship,

2. Sampling and testing thesea water ordock waterdensity at theplace where the vessel floats,

3. Determining of deductible weights by measuringand sounding of ballast tanks, fuel oil, fresh water that existing onboard at the time of survey,

4. Using Hydrostatic Table provided onboard to begin calculation.

Reading the Draftmark of the shipCommonly, all ship are designedwith draftmark for working with Draft Survey to determined their actual weight. The draftmarkcould be findat six (6) pointson the below places:

Forward Port Side (FP),

ForwardStarboard Side (FS),

Midship Port Side (MP),

MidshipStarboard Side (MS),

Aftward Port Side (AP),

AftwardStarboard Side (AS),

Before posting thestep by step Draft Survey Calculation,it is necessary to attachthe popular terms of conduct for Draft Survey for references.

Aft Perpendicular (AP):an imaginary vertical line, at right angles to the keel, passing through the first frame and so located on or nearby the ships rudder post.

Ballast Tanks:tanks aboard the vessel specially designed to receive ballast water or, in the case of tanks vessels, cargo tanks used to contain ballast.

Boiler Feedwater Tanks:tanks provided aboarf the vessel to contain water used for the production of steam.

Bilges:spaces at the bottom of the engine room or pumprooms where water is allowed to accumulate. As the bilges usually also contain waste oil, they may not be discharged within the port limits. For draught survey purposes, the quantity of liquid in the bilges should be controlled/sounded before and after loading or discharge, so that any change in quantity can be detected.

Bunker tanks:tanks intended to contain fuel oil either for stam raising purposes or for the provision of power to the main engines and auxiliaries.

Calibration Tables : (see sounding table).

Centre of Floation :the point around which a ship tips, often called the tipping center. The center of the waterplane area.

Cofferdams fwd and aft:these terms apply more particularly to ocean tankers, coastel tankers and tank barges. They are empty spaces provided in order to separate the cargo tanks from the machinery space aft and from the forward peak and other forwardparts of the ship. Cofferdams frequently contain water, either intentionally or accidentally, and should therefore always be sounded.

Constant:the difference between the light ship weight according to ships documents and the net empty survey displacement after deducting all measurable weights.

Deadweight:the weight of a vessels cargo, fuel, water and stores.

Deckline:a line clearly marked on the port and starboard side of the vessel, amidships as required by International Loadline Regulations.

Deeptanks:tanks situated near to the bottom of the vessel.

Density (true):the mass of a volume unit of a liquid.

Displacement table/scale:a table, specially prepared for each vessel, giving the displacement corresponding to various drafts.

Double Bottom Tanks:tanks situated in the vessels double bottom and used either for bunkers or ballast water.

Draft : depth of water from the water surface down to the bottom of the ships keel.

Draft Marks:a series of figures painted or welded on the vessels hull, usually forward, midships and aft, on both port and starboard sides and indicating the draft of the vessel at the points where the draft marks are situated

Draft (Draught) Survey:a system of cargo measurement based on measuring the draft of the vessel before and after loading or discharge, making into accound any changed in weight other than cargo, which may have taken place during cargo handling operation, i.e. changes in the weight of water ballast, bunkers, stores etc.

Even Keel:when the forward and aft drafts of a vessel are identical, the ship is said to be on an even kee.l

Forepeak Tank:a compartment situated at the extreme forward part of the vessel often used to contain ballast water.

Forward perpendicular (FP) :an imaginary vertical line, at right angles to the keel and passing through the point where the summer loadline intersects the vessels stern.

Freeboard (assignedor statutory):the distance from the upper part of the deckline to the summer loadline as assigned or stated in the Freeboard Certificate relating tho the vessel concerned.

Hogging : the deflection of a cessel loaded in such manner that the draft amiship is less than the mean of the forward and aft drafts.

Hydrostatic Curves :a document specially prepared for each vessel indicating, among other things, the centre of floating or tipping centre at various drafts.

LCF:Longitudinal Centre of Floatation.

Length Between Perpendiculars (LBP) : distance between the forward and aft perpendiculars measured parallel to the keel.

List :inclination of the vessel from the vertical position measured at the longitudinal midships axis.

Lightship Weight:the weight of vessel ofter completion of construction but without fuel bunkers, stores, etc.

Mean Forward Draft:average of the forward drafts on port and starboard side.

Mean Midships Draft :average of the midships drafts on port and starboard side.

Midships:longitudinal center of the vessel as indicated on the hull by the Port and Starboard loadline marks.

Moment To Change Trim1 cm (MTC) :the force required to change the trim of a vessel by 1 cm.

Plimsoll Line :another name for summer load mark. The line permanently marked by centre punh, or by welding, on the port and starboard sides of the vessel amidship.

Port Side :the left-hand side of the vessel as seen by an observer facing forward.

Rudder Post:the vertical axis around which the rudder turns.

Sagging :the deflection of a vessel loaded in such manner that the draft amidships is greater than that the mean of forward and aft drafts.

Sounding Pipe:a fixed pipe through which soundings are taken.

Sounding Tables:a table containing the tank volume as taken measured by sounding.

Starboard Side :the right-hand side of the vessel as seen by an observer facing forward.

Stem Correction :correction applied to the mean forward draft when the forward draft marks are not situated at the forward perpendicular.

Stern Correction : correction applied to the mean aft draft when the aft draft marks are not situated at the aft perpendicular.

Summer Loadline:an imaginary line, parallel to the keel passing through the upper edge of the summer mark which corresponds to the maximum draft permitted in the summer zone in sea water.

Ton Per Cm Immersion (TPC) the number of metric tones required to change the mean draft of a vessel by 1 cm.

Trim:the difference between the mean draft and the mean draft forward, both measurements having been corrected to the aft and forward perpendiculars (FP/AP).

Trim Corrections: corrections applied to the displacement of the vessel is not floating on an even keel.

Ullage : the distance between the surface of a liquid in a tank and the top of the tank or corresponding sounding pipe.

Draft Survey: Specimen of CalculationJan 26

SurveyorsSurveyors draft survey, marine survey, marine surveyor 47 CommentsAs I have promised you, I write down this post to explain specimen of Calculation in Draft Survey.Please also refer to the previous post Draft Survey : Procedures and Calculation.

Ok, now we could directly go to the point. The vessel has alongside at the wharf in port todischarge thegrain cargo.The Ships Particulars shown :

Name of Vessel : MV. OCEAN BALL, -Port of Registry (POR) : Panama, Lenght Over All (LOA) : 182.00 M, Lenght Between Perpendiculars (LBP) : 179.00 M, Breath (B) : 32.20 M, Depth (D) : 17.15 M, Gross Tonnage (GT) : 28,342 MT, Net Tonnage (NT) : 17,664 MT, Summer Draft (SD) : 12.163 M, Summer Deadweight (DWT): 52,998 MT, Light Ship (LS) : 7,780 MT, Constant (CS) : 320 MT, Fore Distance toPerpendicular (Fd) : 1.70 M, After Distance toPerpendicular (Ad): 9.45 M.See Picture :

The Surveyor came onboard and made Draft Survey to determine the quantity of cargo on arrival. During inspection, shes draft marks and others datafinds as the followings :

- Fore Draft Port (FP) : 10.79 M / Fore Draft Starboard (FS) : 10.81 M.

-Mid Draft Port (MP) : 10.90 M /Mid Draft Starboard (MS):11.03 M.

-Aft Draft Port (AP) :11.16 M / Aft Draft Starboard (AF) :11.19 M.

- Density of Sea Water Sample (Den) : 1.021.

- Ballast Water (BW) : 265.00Cubic Meterat Density 1.025, Fresh Water (FW) : 183.00 MT.

-FuelOil (FO) :612.00 MT,-Diesel Oil (DO) : 161.00 MT, Lub Oil (LO) : 29.00 MT.

The Draft Survey Calculationis described as below :

Raw Draft Calculation- Fore Mean (Fm) = (FP + FS) / 2 = (10.79 + 10.81) / 2= 21.60/ 2 = 10.800 M.

-Mid Mean (Mm) = (MP + MS) / 2 = (10.90 + 11.03) / 2=21.93/ 2 = 10.965 M.

-Aft Mean (Am) = (AP + AS) / 2 = (11.16 + 10.19) / 2= 22.35/ 2 = 11.175 M.

- Apparent Trim (AT) = Am Fm = 11.175 10.800 = 0.375 M.

- Length Between Mark(LBM) = LBP (Fd + Ad) = 179.00 (1.70 + 9.45)

= 167.85 M

Draft Correction to Distance to Perpendicular.- Fore Correction (Fc) = (Fd x AT) / LBM= (1.70 x 0.375) / 167.85 = 0.003798

= 0.004 M (rounded to 3 Decimals).

-Mid Correction (Mc) = (Md x AT) / LBM= (0.00 x 0.375) / 167.85

=0.000 M (Not Available)

-Aft Correction (Ac) = (Ad x AT) / LBM= (9.45 x 0.375) / 167.85 = 0.021112

= 0.021 M (rounded to 3 Decimals).

TrueDraft and True Trim- Fore DraftCorrected(Fcd) = Fm + Fc = 10.800 + (-0.004)= 10.796 M.

-Mid DraftCorrected(Mcd) = Mm + Mc = 10.965 +0.000= 10.965 M.

-Aft DraftCorrected(Acd) = Am + Ac = 11.175 +0.021= 11.196 M.

-True Trim (TT) = Acm Fcm = 11.196 10.796 = 0.400 M.

Final Draft Calculation- Fore and Aft Mean (FAm) = (Fcd + Acd) / 2 = (10.796+ 11.196) / 2 = 21.992 /2 = 10.996 M.

- Mean of Mean Draft (MM) = (Mcd + FAm / 2) = (10.965 + 10.996) /2 = 21.961 / 2 = 10.9805 M.

- Quarter Mean(MMM)= (MM + Mcd) /2 = (10.9805 + 10.965) /2 = 21.9455 /2 = 10.97275 M

= 10.973 M.

- Or MMM = {(Fcd x 1) + (Acd x 1) + (Mcd x 6)} / 8 ={(10.796 x 1) + (11.196 x 1) + (10.996 x 6)} / 8

= (10.796 + 11.196 + 65.790) / 8 = 87.782 / 8 = 10.97275 M = 10.973 M.

Hydrostatic Table Refer to the Table, we could obtain :

Displacement (Disp)- Disp at10.970 M: 54,266.860 MT (DISP. FULL).

- Disp at10.980 M: 54,321.070 MT (DISP. FULL).

- Dispat10.973 M:54,266.860 +[{(10.973 - 10.970) / (10.980 - 10.970)}

x (54,321.070 - 54,266.860)]

= 54,266.860 {(0.003 /0.010) x 54.210} = 54,266.86 + (0.3 x 54.210)

= 54,266.860 + 16.263 = 54,283.123 MT

Ton Per Centimeter (TPC) -TPC at10.970 M:54.210 MT (Below TPC on Table).

-TPC at10.980 M: 54.220 MT (Below TPC on Table).

-TPC at10.973 M:54.210 +[{(10.973 - 10.970) / (10.980 - 10.970)}

x (54.220 - 54.210)]

= 54.210 {(0.003 /0.010) x 0.010} = 54.210 + (0.3 x 0.010)

= 54.210 +0.003 = 54.213 MT.

Longitudinal Centre Flotation (LCF) -LCF at10.970 M:1.180 MT (Below LCF on Table).

-LCF at10.980 M:1.190 MT (Below LCF on Table).

-LCF at10.973 M:1.180 +[{(10.973 - 10.970) / (10.980 - 10.970)} x (1.190 - 1.180)]

= 1.180 {(0.003 /0.010) x 0.010} = 1.180 + (0.3 x 0.010) = 1.180 +0.003 = 1.183 M.

Moment To Change Trim (MTC)

- MTC = MTC 1 MTC 2.

-MTC 1 = MMM + 0.5 = 10.973 + 0.5 = 11.473 M.

-MTC 1 at11.470 M:709.610 (Below Table).

-MTC1 at11.480 M:710.060(Below Table).

-MTC 1 at11.473 M:709.610 +[{(11.473 - 11.470) / (11.480 - 11.470)} x (710.060 - 709.610)]

= 709.610 {(0.003 /0.010) x 0.450} =709.610 + (0.3 x 0.450) = 709.610 +0.135 = 709.745.

-MTC2 = MMM- 0.5 = 10.973- 0.5 = 10.473 M.

-MTC2 at10.470 M:686.460 (Below MTC on Table).

-MTC2 at10.480 M:686.770(Below MTC on Table).

-MTC2 at10.473 M:686.460 +[{(10.473 - 10.470) / (10.480 - 10.470)}

x (686.770 - 686.460)]

= 686.460 {(0.003 /0.010) x 0.310} =686.460 + (0.3 x 0.310) = 686.460 +0.093 = 686.553.

So, MTC = MTC 1 MTC 2 = 709.745 686.553 = 23.192.

**** From the above results, wecollected the data as follows: - Disp= 54,283.123 MT, -True Trim (TT) = 0.400 M, -LBP =179.00 M, -TPC = 54.213, LCF = 1.183,- MCT = 23.192.First Trim Correction (FTc) - FTc = (TT x TPC x LCF x 100) / LBP =(0.400 x 54.213 x 1.183 x 100) / 179.000

= 256.35916 / 179.00 = 14.331615 = 14.332 MT.

SecondTrim Correction (STc) - STc = (TT x TT x MTC x 50) / LBP = (0.400 x0.400 x 23.192 x 50) / 179.000

= 185.536 / 179.00= 1.036514 = 1.037 MT.

Displacement Corrected to Trim (DispT) - DispT = Disp + (FTc + STc) = 54,283.123 + (14.332 + 1.037) = 54,283.123 + 15.369

= 54,298.492 MT.

Density Correction (Denc) - Actual Density (ADen) = Sample Sea Water Density = 1.021

- Denc = DispTx {(ADen 1.025) / 1.025} = 54,298.492 x {(1.021 1.025) / 1.025}

= 54,298.492 x (-0.004 / 1.025)

= 54,298.492 x (-0.0039024) = -211.896554 = -211.897 MT.

Displacement Corrected toDensity (DispDenc) - DispDenc = DispT + Denc = 54,298.492 + (-211.897) = 54,086.595 MT.

Deductible Weight (Deduct) - BW = 265.00 x 1.025 = 271. 625 MT, FW = 183.000 MT, FO=612.000 MT,

-DO= 161.000 MT, LO= 29.000 MT.

-Total Deduct = 1,256.625MT.

DisplacementMinus toDeductible Weight = Net Displacement(NDisp)- NDisp =DispDenc-Deduct = 54,086.595 1,256.625 = 52,829.970 MT.

Estimated Cargo onboard (EstCOB) - To estimated quantity cargo onboard, we need to know about LightShip and Constant.Light Ship and Constant data is provided on theShips Loading Manual.

For the new ship, wecould refer to the Constant on theManual, but for the old shipit Constant may vary, please refer to the Chief Officer Constant Declaration orDraft Survey Previous Port, or we couldcalculate it in the final survey after theShip completing to discharge her cargoes (empty Ship).

- Light Ship (LS)= 7,780.000 MT, Constant (CS)= 320.000 MT.

- EstCOB = NDisp (LS + CS) = 52,829.970 (7,780.000 + 320.00)

= 52,829.970 7,100.000 = 44,729.970 MT.

See the following Draft Survey Report Form..

We have completed the Initial Draft Survey, I hope it useful and see you in the next post.

Surveyors.

Use the small boat to go around the ship andget as near as possible to the draft mark for best viewing. The surveyor should be read all above marks clearly, becausereading the draftmark is the first and most essential process. I am not saying that other processses is not essensial, but this processis hard to do and involves manyrules of conduct to gain the correctness and accuracy of Draft Survey itself (I will post it later). The draftmark read is recorded on the surveyor notebook, do not try to remember it or write down in your palm hand. Its useless and un-professional.

Sampling and testing thesea water ordock waterdensityAfter reading the draftmark, directly engage with the sampling of sea water or river water around the ships dock.Why?Because the ship draft will not bethe same at different water densities(at the lower density means the ship more sink andat the higher density means the shipmore float).Where as the water densityissubject tochangeswhich follow withwater tide that carrying different water salinity and temperature on to the ship dock. The sea water density isindeed at density 1.025 and the fresh water at density 1.000. To determine the density of water, we need the instrument named Hydrometer or Density Meter. Inserted the Hygrometer on to the water sample on the Sampling Can or Tube, then we could check the scale pointed on the surface of the sampling water. Records the water dock density as survey data.

Determining of deductible weights by measuringand soundingDeductible Weightcould measure by sounding the tanks which used the Sounding Tape or gauging the tank level by visual inspection.Any deductible weight such as Ballast Water, Fresh Water, Fuel and Diesel Oil, and Bilges is notify to check. Records all in the survey book includes withthe densityfor Ballast and Bilges, and forOil complete it with density and temperature .The Fresh Water was at density 1.000.

View the Sounding Pipe:

Using Hydrostatic Table provided onboard to begin calculation, I think all necessary datawas completed,so we could do calculation.The calculation isuses Displacement Table or usually called Hydrostatic Table. This table is included all data that we need to complete the calculation.

Raw Draft Calculation; Fore Mean or Fm = (FP+FS)/2,Mid Mean or Mm = (MP+MS)/2, and Fore Mean or Am = (AP+AS)/2. while Apparent Trim or AT =Am Fm. the Apparent Trim is the Trim that visually find.

Draftmark posision and correctionto perpendicular.As the ship draftmarkis not placed at the perpendicular,the Fore and After draft should be corrected with distance from the draftmark to perpendicular.The correction rules is: if the Trim byStern, the Fore correction should be minus and After correctionplus, and if the Trim byHead (stem),the Fore correction should be plus and After correctionminus. The Midship correction is parallel with the fore correction with the same pattern.SomeHydrostatic tableprovided with these correction result. But if not the reference pattern is for Fore Correction or Fc = (Fd x AT) : LBM and AfterCorrection or Ac = (Ad x AT)/ LBM. Where Fd = Fore distance to perpendicular, Ad =After distance to perpendicular, and LBM = Length Between Markor Length between Fore and After draftmarks or LBM= LBP (Fd + Ad).

True Draft Calculation / Draft Corrected; Fore draft corrected or Fcd = Fm+ Fc,Mid draft corrected or Mcd = Mm+ Mc, andAfter draft corrected or Acd = Am+ Ac.

True Trim or TT : Actual Ship Trim after draft corrected or TT = Acd Fcd.

Fore and After Mean Draft or FAm = (Fcd + Acd)/2, Mean of Mean Draft or MM = (FAm + Mcd)/2, and Mean of Mean of Mean Draft or MMM or Quarter Mean = (MM + Mcd)/2.

The above calculation is similar with : MMM = {(Fcd x 1) + (Acd x 1) + (Mcd x 6)}/8.

Coresponding to the MMM or Quarter Mean result,the surveyor could check thevalue of needed parameters on Hysdrostatic table like; Displacement, TPC, LCF, and MTC. Records them accurately.

Get the Displacement or Disp.

First Trim Correction or FTc = (TTx LCF x TPC x 100) / LBP. Could be plus or minus depend on LCF.

Second Trim Correction STc = (TT x TT x MTC x 50) / LBP. The result always plus (+).

Displacement corrected by Trim or DispT = D (FTc + STc).

Density Correction or Denc = DispT x {(Aden 1.025) / 1.025}.where theAden is Actual Densitythatsurveyor has taken sampling and testingpreviously. The density correction commonly in minus (-), due totheActual Density is usually lower than1.025 (fresh sea water). In case of at some port where the water salinity is high, thedensity correctioncould be plus (+).

And we have got the Displacementcorrected by Density or DispDenc = DispT + Denc. (after corrected by density we willget the actual ship weight as per shown by Draft Survey)

Deductible Calculation. The same as draft, the deductible also need to corresponding to the table thatnamed Tank Table / Tank Capacity Table. Refer to the sounding records that done before, the surveyor could be calculate the total deductbile existing onboard. Total Deductible or Deduct= Ballast Water + Fresh Water + Bilges + Fuel Oil + Diesel Oil,this total should be minus to the Displacement corected by Density.

The Net Displacement or NDisp = DispDenc Deduct.

The Net Displacement is the actual ship weight afterminus with deductible weight. For Unloading, toestimate thequantity of cargo onboard, the Net displacement should be minus with Light Ship and Constant.

I think difficult for the amateur writer like me to describe the complex narration of draft survey calculation,butto make it clear, the sample of Draft Survey Calculation will be post sooner or later..

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