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Procedure for measuring quantity of bulk cargo loaded or discharged
A draught survey is frequently used to determine the quantity of bulk cargo loaded or discharged. A comparison of the ship's displacement before loading (or discharging) is made with its displacement afterwards. The difference in displacement gives the quantity of cargo loaded or discharged.
< The following parties are interested in the draught survey:
- Charterer's surveyor
- owner's surveyor
- chief officer
- loading and discharging terminal authorities.
Steps for Draught Survey
- Forward, aft and midships port and starboard draughts.
- List (if any, though all measures should be made to have the vessel upright).
- Soundings of ballast, fresh water and fuel oil tanks.
- Density and temperature (if required) of dock water and liquid in the ship's tanks.
- Total deductibles.
- Mean of all observed draughts.
- FP, AP and midship draught correction.
- Mean of means (MoM) draught.
3. Find value of:
- LCF at MoM from hydrostatic particulars.
- MCTC at MoM (+) 50 cm and at MoM (-) 50 cm.
- TPC at MoM.
- 1st trim correction (in metres).
- 2nd trim correction (in metres).
- Apply 1st and 2nd trim correction to MoM to find draught equivalent or TMD.
5. Find value of displacement at TMD.
6. Calculate list correction (in tonnes) and apply to displacement at TMD to obtain corrected displacement.
7. Calculate density correction and apply to the corrected displacement in step 6 to obtain final displacement.
a. Deductibles from the displacement found in step 7 to find the sum of weight of cargo and lightship, or
b. deductibles and lightship from the displacement found in step 7 to find the weight of the cargo onboard.
9. If both initial and final draught surveys are available for the loading or discharging port, then the difference in displacement found in step 7 for both surveys gives the quantity of cargo loaded or discharged.
Description of various terms that used in cargo calculation are explained here
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Operation of sea going bulk carriers involved numerous hazards . Careful planning and exercising due caution for all critical shipboard matters are important . This site is a quick reference to international shipping community with guidance and information on the loading and discharging of modern bulk carriers so as to remain within the limitations as specified by the classification society.
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