Draught Survey

Draft Survey Cargo Quantificaton

Our competent and diligently trained stuff have always been elemental in conducting the scientific method of quantifying loaded and Discharged Cargo, based on water displaced and density.

What is a Draft Survey?


A draft survey is a calculation of the weight of cargo loaded or unloaded to or from a ship from measurents of changes in water displacement per unit cargo loaded or discharged . The technique is based on Archimedes’ principle. 


Is Draft Survey Procedure Standard?


Draft Survey procedure is standardized by the United Nations Economic Commission for Europe for the measurement of coal cargoes, bulk cargoes and liquid cargo that is known to contain air pockets for example molasses.


How is a Draft Survey accurate?

An accurately performed draft survey has an acceptable error margin of ±0.5%.


What do we do during draft surveys?
A draft survey is performed by reading the ship’s draft on the draft markings at six standard points on the hull: forward, midships and aft on both port and starboard sides. During draft survey we:

  • Read draft marks ( keeping all conditions for reading draft marks in place)
  • Determine density of sea/river water using zeal hydrometer
  • Check and note the quantity water in all ballast tanks, hiding spaces, grey tanks, sewage tanks etc by accurate sounding and gauging
  • Compute all initial and final drafts using ships hydrostatic particulars
  • Carry out trim and list corrections
  • Find out total quantity of ballast, for all sounded tanks and gauged tanks
  • Find out the amount of cargo loaded/discharged/remaining to be loaded/discharged.

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A ships draft mark readings

Why do you need an experienced draft surveyor for your next survey?

Both the image above and below represent a sample of draft mark readings. Note the technical difference in how the two draft marks should be read.

With experience, a draft surveyor can find all the differences in the way data is presented and find all discrepancies; request for corrections of all the unacceptable discrepancies and calculate the right cargo quantities.

Our experienced surveyors are available 24/7 to help you with draft surveys in the most professional and qualified manner.

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Why do we use Zeal Hydrometer in all Our Draft Surveys?
As an international accepted standard, a zeal hydrometer at 15°C should be used in draft surveys.

It is important to use a zeal hydrometer at 15°C to determine the density of water during draft surveys. 

For example, from our experience “where a zeal hydrometer reads 1.022 a hydrometer at the temperature of 20°C is likely to read 1.026 this will usually give the ship higher cargo arrival figures (if the density for the hydrometer at 20°C is used).

If a wrong hydrometer is used at load port, the probability of cargo shortfalls at disport using an internationally accepted zeal hydrometer increases.

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