Draft Survey: The Accuracy and Factors Effecting

Sometimes the accuracy of Draft Survey is a big question, especially when the cargo loaded or discharged from the vessel shown extremely different weight with the references Weight Scale or Counter Weight. Unfortunately, the parties concerns would be doubt on to the weight resulted by Draft Survey, as they have been relying upon the mentioned scales for many years.

Draftmark

Draught Survey UN ECE: Code of Uniform Standards and Procedures

UN ECE was published the Factors Affecting Draft Survey as follows :

1- Incorrect hydrostatic information or draft marks: Investigations carried out in specially performed draft surveys have indicated that there can be significant errors in the determination of displacement due to typographical errors or arithmetical errors in the ship’s hydrostatic tables. This could be improved if the tables furnished to the surveyor bore an approval stamp by the flag government or the classification society. A number of years careless re-painting of draftmarks, especially if they have not been permanently marked on the hull, can cause erroneous readings. If there is any doubt, the draft marks should be re-sited at the next dry-docking.

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Bunker Survey Calculation

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The bunker calculation is simple and needs the following:
– Tank Sounding data and Tank Capacity Table. The Corrected Sounding means below is the sounding after correcting with vessel’s trim and list.
– Temperature of Oil on Tanks,
– Oil Density @15*C,
– Table ASTM 54B (VCF) and Table ASTM 56 (WCF).

Now we could go with sample of 1 tank to test the calculation.

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How to Conduct Bunker Survey

What is Bunker Survey? The survey is carried out to measure and ascertain the quantity of Bunker on board at the specific time. This survey is produced the report that states the amount of bunker, usually Fuel Oil (FO) and Diesel Oil (DO), and sometimes Lubricating Oil (LO) is included.

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If you stucked here, moving is the best idea to improve your performances

Good Day All..

Thanks for you all that has been accessed and comments given during the time.

In this good time, I am announced that www.surveyors.wordpress.com has just moved to the new address at www.sevensurveyor.com. Eventhough, you could access it form the both addresses.

Hope marine cargo surveyor could find this site more attractive and readable. Your contribution to improve this site is highly appreciated.

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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 :

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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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Draft Survey: Procedures and Calculation

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marine cargo ship surveyors

The Draft Survey procedures and calculation ascertained as the following series :

  1. Reading the draftmark of the ship, which consist of six (6) points of draftmarks, i.e.; Fore, Midship, and After at both sides of the ship,
  2. Sampling and testing the sea water or dock water density at the place where the vessel floats,
  3. Determining of deductible weights by measuring and sounding of ballast tanks, fuel oil, fresh water that existing onboard at the time of survey,
  4. Using Hydrostatic Table provided onboard to calculation.

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Draft Survey: Terms of Conduct

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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 ship’s 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.
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