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***DRAFT***MARINE GUIDANCE NOTE

MGN xxxx(M)DAMAGE STABILITY ASSESSMENT ON OIL, CHEMICALand GAS TANKERS

Notice to Shipowners, Ship masters, Ship officers, Charters, Agents, Terminal Operators, and Surveyors.

Summar

This guidance note advises on the dangers of relying on stability computer programs instead of formallyapproved stability information to carry out stability assessment prior to departure as not all approved stabilitycomputer programs take account of damage stability requirements.

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1.1 Loading computer programs are normally provided for assessing compliance with longitudinal strengthcriteria during loading, and are often additionally approved for assessing intact stability, but not alwaysapproved for assessing damage stability. Surveyors usually check for approved stability books, but rarelycheck correct use of stability computers.

1.2 onditions of loading assessed by using computers approved for intact stability assessment, ratherthan using the approved conditions available in the approved stability book, may appear to ship!s officers togive satisfactory results even though the conditions have not been assessed against the damage stabilityrequirements. "t best this is misleading and at worst could be dangerously unsafe in the event of damage,and ship!s officers may be unaware of these limitations.

1.# " statement that$ alternative conditions must be submitted to the flag "dministration %&r lass ifappropriate' for approval, is often included on the issue of a ertificate of (itness for chemical and gastankers. )owever it appears that such submissions are in general not being made and this safeguard on thecertificate is being circumvented. *ndeed, coping with numerous submissions could present the "dministrationwith a practical problem and is not a very satisfactory situation.1.+ (rom an operators point of view the best solution is likely to be that stability computers are designedand approved to calculate each condition according to all the criteria$ of strength, intact and damage stability."lternatives such as this need to be eplicitly stated on ertificates of (itness.

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2.1 oncern has also been raised on some vessels regarding the practicality of operating to the approvedconditions shown in the stability booklet because there are very small or no margins of residual stability.

2.2 Some cases have been identified where normal operational factors such as part filled tanks, or storesmovements, make a vessel non compliant. There is a increased level of risk where the lack of compliance in

vessels with such low stability margins is being -masked! through assessment of stability prior to departureusing the approved intact stability computer on board.

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#.1 &wners, operators, ships masters, officers and terminal operators are requested to take urgent actionto ensure that all conditions of loading comply with the appropriate requirements for both intact and damagestability and be prepared to demonstrate such compliance.

#.2 hile it may be claimed that ships have had a good safety record with regards to stability, the failingsidentified in this notice would only become apparent when the ship is damaged, which may turn a relativelyminor event into a ma/or catastrophe.

#.# Surveyors and inspectors are requested to pay particular attention to compliance with theserequirements.

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(urther information on the contents of this 0otice can be obtained from

Survey ranchay 13415aritime and oastguard "gencySpring 6laceSouthamptonS&17 189

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