Bridge 180 Under Keel Clearance

5/26/2018 Bridge 180 Under Keel Clearance

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BRIDGE MANUAL SHIP PROCEDURE

Card NoBridge-180 Version 01 2013-03-29 Page1 of4UNDER KEEL CLEARANCE

I. Purpose of the document

The following Under Keel Clearance procedure is a standardized mandatory company rule meant to supportmasters in theirs choices for safe and secure navigation.

II. Scope

Such a procedure will prevent groundings; protect our ships, our crews and captains, and our long termcompany global economic interests. It is in line with IMO recommendations (RESOLUTION A.893(21), 25November 1999), good maritime uses and practices.

III. Definitions and abbreviations

Voyage plan

UKC is a paramount and mandatory element of the passage plan. It is calculated for every voyage leg whetherin open seas, confined waters or in ports as soon as depth is under 1.5 vessel draft.

Minimum UKC

Under Keel Clearance isthe distance between the deepest point of the vessel's hull and the sea bed.The company regulation for setting the minimum eligible UKC is as following:

IV. Contents of the procedure

1. When established, Port Cards Company Regulations (PCCR) on minimum UKC / Maximumdraft always prevails. They are checked by Fleet Navigation Center captains when meeting withlocal port authorities. The local agencies are responsible to inform the Fleet Navigation Centerwithout delay in case of any port amendments.

2. National/Local/Port regulations or practices on Maximum Allowable Safe Draft (MASD) are to beused when no PCCR is in force.

However masters are to challenge the MASD using all available information. This informationmust not be limited to the Port Cards: it must consider the attached UKC calculation form andthe ships stability (draft increasing due to the list). In case of doubts, masters must report to theFleet Navigation Center (Nautical Studies Office: [email protected]) and therelevant Line Ops manager.

3. Whenever no regulation exists (Nr 1 or 2), minimum UKC is determined using the attachedcalculation form which is based on good seamanship practices. Some Loading software is alsoable to provide UKC calculation. Only UKC limits from the next table are applicable.


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Calculation form

It provides Dynamic/Net UKC calculations and takes in account the squat effect which is the reduction inunder keel clearance due to the ships forward motion through the water. The squat effect increases with thespeed of the ship and when the channel reduces in depth or width.

The UKC limitations used in the form are as following:

As a result, the form provides Go/No Go situations based on vessels characteristics, channels characteristics,vessels speed, tide and current.

Loading software

The loading software includes a squat sheet which allows to calculate the UKC after taking into account aboveUKC limitations and also perform simulation by varying calculation parameters. This result is viewable on agraph.

Remark: List

Several factors may cause list: Tugs actions, combination of helm and speed, swell, wind, improper loading,...and list causes draft increase.

New draft = 0.5xBeam (m)xsin (list) +Initial draft xcos (list)Draft increase 0.5 xBeam (m)xsin (list)

Ex. Draft Increase due to list

List / Beam 20m 30m 40m 50m1 0.17 0.26 0.39 0.435 0.87 1.30 1.7 2.210 1.7 2.6 3.5 4.3

V. Appendices

-Calculation form according below screen capture and on excel tool in attachment.

LocationMinimum net UKC

20 % staticdraught

15% staticdraught

10% staticdraught

1.0 M 0.6 M or 5%whichever Greater

Coastal waters x x x x

Fairways, channels, restricted water x x x

Moving in port x x

Alongside vessel over 50,000 MT dwt x

Alongside vessel under 50,000 MT dwt


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Vessel: Date :

Length (LBP): Port :

Breadth: Arrival/Departure :

Displacement :

Static Mean Draft :

= Displacement

L x B x D V = Speed in knots

L = Length between perpendiculars

CBx V2

B = Extreme Breadth underwater

100 D = Mean draft corresponding to the Displacement

2 x CBx V2

1,7

100

Squat in Medium waters = Interpollation Open waters / Confined waters for 200 m < channels width


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VI. References

-no references

VII. Modifications of the document

Description of theModification

Date NVersion

Creation 2013-03-29 1

VIII. Validation and Approval

Versionsof the

document

Redactorname andfunction

Date andSignature

ValidationName andfunction

Date andSignature

ApprovalName andFunction

Date andSignature

1

JacquesSubra

Nauticalstudies

2013-03-29

Eric SabrazsMarine

StandardsManager

2013-03-29

FranckMagarianExecutive

VicePresident

CMAShips

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Bridge 180 Under Keel Clearance