What is the procedure for Draft survey in brief?

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1. Loaded displacement = Light displacement + cargo + ballast + fuel + slops + fresh waster + constant
2. During initial draft survey we obtain the displacement as per the drafts and calculate the constant of the vessel
3. During final draft survey this constant is used to calculate the amount of cargo loaded using the formula given in I above.
4. Obtain visual drafts forward, midship and aft on both sides. Calculate the length between the marks (from stability booklet)
5. Obtain mean of ford, aft and mid draft
6. Calculate correction to all draft as follows
Corr to forward draft = ( trim x distance of ford visual marks from forward perpendicular ) / length between marks
Corr to aft draft = (trim x distance of aft visual from aft perpendicular ) / length between marks
Similarly obtain corrn to mid marks
Apply this correction to ford, mid and aft draft marks and obtain corrected drafts at perpediculars

7. Now calculate the means of means or Quarter Mean draft by following –
( Corr forward draft + Corr aft draft + 6*Corr mid draft ) / 8

8. This draft is called Hydrostatic draft and enter the hydrostatic data tables using this draft to obtain the displacement, TPC, MCTC etc
9. First trim calculation is then calculated by following formula –
(Trim x distance of Centre of floatation from midpoint bet perpendiculars x TPC) / LBP

This trim could be either positive or negative

10. The second trim correction is then obtained by following formula –
(50 x (trim)^2 x (MCTC1-MCTC2))/ LBP
MCTC1 = MCTC at 50 cms greater than True mean draft
MCTC2 = MCTC at 50 cms lesser than Tue mean draft

This correction is always positive.

11.List correction is calculated in tonnes using –
Correction = 6(d1-d2)(tpc1-tpc2)
Where d1 and d2 are the drafts of immersed and emerged sides respectively
And tpc1 and tpc2 are for those respective drafts

12. The result will be Corrected displacement in Salt Water

13. Density correction is then applied to the displacement if the vessel is floating in a water density different than salt water

This displacement is then used in the formula mentioned in point No 1 to calculate the cargo loaded / discharged.

13.

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Asked on May 27, 2021
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1. Loaded displacement = Light displacement + cargo + ballast + fuel + slops + fresh waster + constant
2. During initial draft survey we obtain the displacement as per the drafts and calculate the constant of the vessel
3. During final draft survey this constant is used to calculate the amount of cargo loaded using the formula given in I above.
4. Obtain visual drafts forward, midship and aft on both sides. Calculate the length between the marks (from stability booklet)
5. Obtain mean of ford, aft and mid draft
6. Calculate correction to all draft as follows
Corr to forward draft = ( trim x distance of ford visual marks from forward perpendicular ) / length between marks
Corr to aft draft = (trim x distance of aft visual from aft perpendicular ) / length between marks
Similarly obtain corrn to mid marks
Apply this correction to ford, mid and aft draft marks and obtain corrected drafts at perpediculars

7. Now calculate the means of means or Quarter Mean draft by following –
( Corr forward draft + Corr aft draft + 6*Corr mid draft ) / 8

8. This draft is called Hydrostatic draft and enter the hydrostatic data tables using this draft to obtain the displacement, TPC, MCTC etc
9. First trim calculation is then calculated by following formula –
(Trim x distance of Centre of floatation from midpoint bet perpendiculars x TPC) / LBP

This trim could be either positive or negative

10. The second trim correction is then obtained by following formula –
(50 x (trim)^2 x (MCTC1-MCTC2))/ LBP
MCTC1 = MCTC at 50 cms greater than True mean draft
MCTC2 = MCTC at 50 cms lesser than Tue mean draft

This correction is always positive.

11.List correction is calculated in tonnes using –
Correction = 6(d1-d2)(tpc1-tpc2)
Where d1 and d2 are the drafts of immersed and emerged sides respectively
And tpc1 and tpc2 are for those respective drafts

12. The result will be Corrected displacement in Salt Water

13. Density correction is then applied to the displacement if the vessel is floating in a water density different than salt water

This displacement is then used in the formula mentioned in point No 1 to calculate the cargo loaded / discharged.

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Posted by marinetales
Answered on May 27, 2021