Draft Survey: Specimen of Calculation



As 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 to discharge the grain cargo. The Ship’s 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 to Perpendicular (Fd) : 1.70 M, – After Distance to Perpendicular (Ad) : 9.45 M.  See Picture :

marine cargo ship surveyors

The Surveyor came onboard and made Draft Survey to determine the quantity of cargo on arrival. During inspection, she’s draft marks and others data finds 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) : 265.00 Cubic Meter at Density 1.025, – Fresh Water (FW) : 183.00 MT.
– Fuel Oil (FO) :  612.00 MT, – Diesel Oil (DO) : 161.00 MT, – Lub Oil (LO) : 29.00 MT.
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The Draft Survey Calculation is 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).

True Draft and True Trim
– Fore Draft Corrected (Fcd) = Fm + Fc = 10.800 + (-0.004) = 10.796 M.
– Mid Draft Corrected (Mcd) = Mm + Mc = 10.965 + 0.000 = 10.965 M.
– Aft Draft Corrected (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.
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Hydrostatic Table

Refer to the Table, we could obtain :

Displacement (Disp)
– Disp  at 10.970 M :  54,266.860 MT (DISP. FULL).
– Disp at 10.980 M :  54,321.070 MT (DISP. FULL).
– Disp at 10.973 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  at 10.970 M :  54.210 MT (Below TPC on Table).
– TPC  at 10.980 M :  54.220 MT (Below TPC on Table).
– TPC at 10.973 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  at 10.970 M :  1.180 MT (Below LCF on Table).
– LCF  at 10.980 M :  1.190 MT (Below LCF on Table).
– LCF at 10.973 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.
marine cargo ship surveyors
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Moment To Change Trim (MTC)
– MTC = MTC 1 – MTC 2.
– MTC 1 = MMM + 0.5 = 10.973 + 0.5 = 11.473 M.
– MTC 1  at 11.470 M :  709.910  (Below Table).
– MTC 1 at 11.480 M :  710.060 (Below Table).
– MTC 1 at 11.473 M : 709.910 +[ {(11.473 – 11.470) / (11.480 – 11.470)} x (710.060 – 709.910)]
= 709.910 {(0.003 / 0.010) x 0.150} = 709.910 + (0.3 x 0.450) = 709.610 + 0.045 = 709.955.marine cargo ship surveyors
– MTC 2 = MMM – 0.5 = 10.973 – 0.5 = 10.473 M.
– MTC 2  at 10.470 M :  686.460  (Below MTC on Table).
– MTC 2 at 10.480 M :  686.770 (Below MTC on Table).
– MTC 2 at 10.473 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.
marine cargo ship surveyors
So,  MTC = MTC 1 – MTC 2 = 709.955 – 686.553 = 23.402.
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**** From the above results, we collected 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 = 23.402.

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.

Second Trim Correction (STc)
– STc = (TT x TT x MTC x 50) / LBP = (0.400 x 0.400 x 23.402 x 50) / 179.000
= 185.536 / 179.00 = 1. 045899 = 1.046 MT.

Displacement Corrected to Trim (DispT)
– DispT = Disp + (FTc + STc) = 54,283.123 + (14.332 + 1.046) = 54,283.123 + 15.378
= 54,298.501 MT.

Density Correction (Denc) <
– Actual Density (ADen) = Sample Sea Water Density = 1.021
– Denc = DispT x {(ADen – 1.025) / 1.025} = 54,298.501 x {(1.021 – 1.025) / 1.025}
= 54,298.501 x (-0.004 / 1.025)
= 54,298.501 x  (-0.0039024) = -211.89947 = -211.899 MT.

Displacement Corrected to Density (DispDenc)
– DispDenc = DispT + Denc = 54,298.501 + (-211.899) = 54,086.602 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 = 1,256.625 MT.

Displacement Minus to Deductible Weight = Net Displacement (NDisp)
– NDisp = DispDenc – Deduct = 54,086.602 – 1,256.625 = 52,829.977 MT.

Estimated Cargo onboard (EstCOB)
– To estimated quantity cargo onboard, we need to know about Light Ship and Constant. Light Ship and Constant data is provided on the Ship’s Loading Manual. For the new ship, we could refer to the Constant on the Manual, but for the old ship it Constant may vary, please refer to the Chief Officer Constant Declaration or Draft Survey Previous Port, or we could calculate it in the final survey after the Ship completing to discharge her cargoes (empty Ship).
– Light Ship (LS) = 7,780.000 MT, – Constant (CS) = 320.000 MT.
– EstCOB = NDisp – (LS + CS) = 52,829.977 – (7,780.000 + 320.00)
= 52,829.977 – 8,100.000 = 44,729.977 MT.

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See the following Draft Survey Report Form..

marine cargo ship surveyors

 

 

 

 

 

 

 

 

 

 

 

 

 

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

Regards,
Surveyors



Author: Faisal Yusuf

Hi, my name is Faisal Yusuf, but you can call me Surveyor. I live in Jakarta, Indonesia and work as a surveyor.

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88 Comments

  1. nice specimen , have any specimens on grain loading calculations . It wud be gr8.

  2. Dear Surveyor,

    Thank you very much for the explanation.

    It was brilliant and proves that you have incredible experience.

    I have used Draft survey Lt which is freely available in google and easily downloadable. Please try it and post your comment on this software.

    Can you please let me know or post a specimen of calculation for
    determining corrected sounding from the one physically observed on the
    tank using a tank capacity table. I have never seen a tank capacity table.

    Best Regards,

    Sadanand

  3. Dear Sadanand,

    The VEF is a compilation of the Total Calculated Volume (TCV) measured on the vessel and adjusted for On Board Quantity (OBQ) or ROB (Remaining On Board), and then compared against the shore TCV.

    The adjusted vessel TCV is divided by the shore TCV to obtain a voyage VEF for each voyage. The sum of all the qualifying vessel VEF’s are averaged to obtain the VEF.

    A VEF(L – Load) should be developed at the load port using only load port TCV’s and discharge VEF(D – Discharge)’s should only use discharge port TCV’s. All voyages should be listed starting with the most current and working backwards.

    Even voyages that do not meet the qualifying voyage criteria should be included. A minimum of five qualifying voyages must be used to obtain a workable VEF.

    Voyages prior to structural changes that affected the vessel’s tank capacity should be excluded. Voyages with no shore side measurements should also be excluded along with any voyage that is not with in +/- 0.3% of the average ratio of all voyages listed.

    I have put downloadable pdf file regards to this matter on the download box.

    Regards,
    Faisal
    Source: John A. “Jack” Szallai – Orion Associates L.L.C.

  4. Dear All,

    Please can anyone brief me about V.E.F.(Vessel Experience Factor) ?

    Regards,

    Sadanand

  5. Still waiting for the draft survey program.

  6. Thanks Phlom,

    You could send any materials related to marine survey and surveyor that you have to my email. I will published it on my blog.

    Regards,
    Faisal

  7. I am back. If is any study material that i can send it to you just mail me and i’ll look for it. They are .pdf and .doc.
    I was to my first draft survey. As observer…cause i am still learning :d But it was really interesting. And i used youre specimen as example and it was very good. So thx!

  8. Dear Phlom,

    Thanks, if you have any related articles you could send me one.

    Best Regards,
    Faisal

  9. Dear Chistian,

    Thanks, Yesterday I have discussed by email with my friend Ronald, he told me that he will launch the New Draft Survey Program. For pre-launching, he will be given the raw program in excel to attach on my blog for reviewing by the blog visitors.

    On the last mail, he said that the download link will submit to me on the next 14 days. Then I will post it here. Hope it could be done.

    Regards,
    Faisal

  10. Dear Joseph,

    Welcome, the Draft survey is the same with others science, where everybody can do it as long as he/she has been wilfulness to learn it.

    Draft survey would be more prefer for seaman or the person who has experienced with ship, cargo and port. Firstly, you should need more effort to learn about basic knownledge of the characteristics, specifications, descriptions and terms among them. Then practising the theory you have got is the best way to improve your skill.

    Is there any feedback for Joseph? Just leave your comments!

    Regards,
    Faisal

  11. Hy there! Thanks for this specimen. It is really useful. Hope it is more to come.
    Ia’su!

  12. Somebody has a basic draft survey programme (in excel for example)?

  13. I am an Accountant. I want to study Draft Survey and Bunkers.
    Any Special Help?

  14. Dear Sadanand, will post it shortly.. Thanks.

  15. Please give specimen report for survey of liquid surveys such as phosporic acid and also explain the derivation for Vessel Experience Factor(V.E.F.)

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