Annex 4, page 1 ANNEX 4 ALTERNATIVE TEXT FOR OPERATIONAL GUIDELINES FOR VERIFICATION OF DAMAGE STABILITY REQUIREMENTS FOR TANKERS GUIDELINES FOR VERIFICATION OF DAMAGE STABILITY FOR TANKERS PART 2 OPERATIONAL GUIDELINES Introduction 1 These Guidelines are intended to provide additional information and guidance on the methods used to verify tanker compliance with the applicable damage stability requirements. 2 It is the responsibility of the master to ensure the ship is loaded in accordance with the applicable damage stability requirements during all operational conditions where cargo is carried. It is critical to verify a ship's damage stability characteristics before departing port because, in the unlikely event that damage does occur during a voyage, there may be insufficient time for the crew to take effective action to restore the ship's stability. Familiarity with the ship's damage stability characteristics will help the master and crew to determine whether or not to abandon ship, and to decide what measures are required to mitigate the effects of damage and, where possible, improve the situation. Definitions 3 The stability and buoyancy characteristics of a ship typically include, but are not limited to, the draft, trim, heel, height of the centre of gravity (KG), righting arm (GZ) and metacentric height (GM). 4 The term intact stability refers to the stability and buoyancy characteristics of an undamaged ship in a static condition, which are evaluated during approval of the ship's stability information and must also be verified prior to the ship's departure from port. 5 The term damage stability refers to the residual stability and buoyancy characteristics of a damaged ship in a static condition, which are evaluated during approval of the ship's stability information and must also be verified prior to the ship's departure from port. Damage stability compliance assures that the ship has sufficient reserves of intact stability to withstand a specified extent of damage. Damages of varying size and layout are applied during evaluation of damage stability, up to the maximum extent of damage defined in the applicable Regulations, and confirm whether or not the ship has adequate residual stability characteristics to meet specified minimum criteria after flooding. 6 The term stability in the damaged condition refers to the residual stability and buoyancy characteristics of a ship after an actual damage to its structure has occurred, the initial contents of any damaged compartment have been lost and flooding of all damaged compartments is completed.
Annex 4, page 2 7 A stability instrument is an instrument installed on board a particular ship by means of which it can be ascertained that stability requirements specified for the ship in the stability booklet are met in any operational loading condition. A stability instrument comprises hardware and software. General 8 Compliance with basic intact stability criteria does not ensure compliance with damage stability requirements. In a particular loading condition, a ship may need intact stability characteristics well in excess of the statutory minimum to ensure compliance with damage stability. 9 Compliance with damage stability requirements does not ensure stability in the damaged condition shall be sufficient to ensure survival following any case of damage, but only damages up to the maximum extent considered by the applicable Regulations. The actual extent of damage and flooding must be determined during an incident in order to compare this with the standard damage cases used to confirm regulatory compliance in accordance with these Guidelines. If the actual case of damage exceeds the maximum extent applied by the Regulations, then the case must be specially evaluated prior to taking remedial action. Information on the actual extent of damage will also be required to determine whether a ship has sufficient structural integrity in the damaged condition. 10 It should be noted that damage stability is normally calculated for individual loading conditions based upon the ship's specific draft and trim, the specific gravity and level of liquids in each tank, and value of the condition KG or GM. The result is also dependent upon maintenance of the watertight and weathertight boundaries of the buoyant hull. If any of these factors change, or the boundary of the hull is not maintained watertight or weathertight, the calculations are no longer valid and the ship may not meet the survival criteria. Regulatory requirements 11 The regulations which require tankers to verify compliance with damage stability requirements are contained in various instruments developed by the IMO, as follows: Ship Type Cargo ships of 80 m in length and upwards *, keel laid on or after 1 Jan 2009 Cargo ships over 100 m in length*, constructed on or after 1 Feb 1992 & Cargo ships 80 m in length and up, but not over 100 m*, constructed on or after 1 Jul 1998 Oil tankers of 150 gross tonnage and above, delivered after 31 Dec 1979 Ships carrying dangerous chemicals or noxious liquid substances in bulk, keel laid on or after 1 Jul 1986 Ships carrying liquefied gases in bulk, keel laid on or after 1 Oct 1994 1 July 1998 BG Code??? Regulation SOLAS 2009, chapter II-1, regulation 5-1 SOLAS 90, chapter II-1, regulation 25-1 MARPOL Annex I, regulation 28 IBC Code, Chapter 2, regulation 2.2.5 IGC Code, Chapter 2, regulation 2.2.5 * If a cargo ship is shown to comply with subdivision and damage stability regulations in another IMO instrument, the ship is not required to comply with the SOLAS damage stability requirements.
Annex 4, page 3 Assessment of a ship's loaded condition 12 The first step in verifying damage stability compliance is to make a careful assessment of the ship's actual condition, once it is loaded and/or ballasted for departure. As a minimum, the assessment of the ship's actual condition should include the following steps: 1. determine the ship's forward and after drafts, along with the midships draft, if available; 2. confirm that the cargo measuring devices (gauges) are working and accurate; 3. gauge the levels of all cargo and ballast tanks; 4. confirm the specific gravity of the loaded cargo(es); and 5. record the above information. 13 Once the data above is obtained and recorded, it should be used to calculate other variables required to verify damage stability compliance, such as trim, GM or KG. There should be instructions available to assist in calculating any necessary variables. 14 There are various methods available to verify compliance with damage stability regulations, as described in the four sections below. If a ship is not in full compliance with the damage stability regulations, then the loading of the ship must be adjusted to ensure compliance is achieved prior to departure from port. Use of approved loading conditions 15 The stability information supplied to the master will include various loading conditions which have been verified by the Administration (or recognized organization acting on its behalf) as complying with stability requirements, including damage requirements, and have been approved for use in service of the ship. It is important to confirm that the approved loading conditions cover both intact stability and damage stability requirements. 16 At any time the operator of a ship may request the Administration (or recognized organization acting on its behalf) to approve additional loading conditions for use in service of the ship and to append these approved conditions to the stability information. 17 If a ship is loaded in accordance with one of the approved conditions provided in, or appended to, the stability information, the ship complies with the damage stability requirements. 18 Any variation from an approved loading condition will reduce the accuracy of the approval and may result in non-compliance with the damage stability requirements. However, it is accepted that the probability of such non-compliance occurring is low when the differences in loading are very small, and minor variations from an approved loading condition are permissible to allow for small variations in loading. 19 A ship may be considered to be loaded in accordance with an approved condition provided none of the following limits are exceeded:
Annex 4, page 4 <<The recommended method proposed in Section 9 of Annex E of the report of the Correspondence Group is recommended for insertion here, directly or by reference.>> 20 A ship may not exceed the variations discussed in this section unless the revised condition is verified as compliant with damage stability using a method from one of the following three sections Use of curves or tables of minimum operational GM versus draft or maximum allowable KG versus draft 21 The stability information supplied to the master may also include simplified stability data, such as curves or tables of minimum operational GM versus draft or maximum allowable KG versus draft, which has been verified by the Administration (or recognized organization acting on its behalf) as complying with stability requirements, and has been approved for use in service of the ship. It is important to confirm that any such simplified stability data covers both intact stability and damage stability requirements prior to using it to verify a loading condition other than an approved loading condition. 22 Simplified stability data establishes limits for some of the ship's stability characteristics. Once the ship is loaded and/or ballasted for departure, it complies with damage stability requirements if its stability characteristics fall within the limits specified in the simplified stability data. Depending on the ship, simplified stability data may be defined by a single curve or table, but in other cases there may be many curves or tables to address each damage case as these apply to a single loading condition. There should always be specific instructions describing how to use simplified stability data and to interpret the results. 23 If any restrictions were assumed or applied in the development of the simplified stability data, then those restrictions also apply to the ship's actual loading condition (e.g. minimum ballast filling in voids outboard of an empty cargo tank). Any restrictions associated with use of the simplified stability data should be clearly stated in the stability information, and any use of the simplified stability information should include a process to ensure that any such restrictions are met in the loading condition being assessed for compliance. 24 In the case of parcel tankers for which curves of minimum operational GM or maximum operational KG are approved, it is recommended that stability verification using this data is undertaken using an approved stability instrument of Type 2 as provided for in the 2008 IS Code, part B, Chapter 4. Use of a stability instrument 25 A stability instrument may be used to verify compliance with damage stability regulations, provide the instrument has been verified by the Administration (or recognized organization acting on its behalf) as complying with stability requirements and its use has been authorized in service of the ship. It is important to confirm that any authorization for the stability instrument covers both intact stability and damage stability requirements. 26 There should be specific instructions describing how to check the accuracy of the stability instrument, and how often this must be done (e.g. prior to use, once a week, once a month).
Annex 4, page 5 27 Once the ship is loaded and/or ballasted for departure, the ship's actual stability characteristics can be entered into the stability instrument to verify that the ship complies with the damage stability requirements. There should be specific instructions describing how to use the stability instrument, the tolerances used by the software, and how to interpret the results. 28 Stability instrument calculations may be less conservative than those made during approval of loading conditions or simplified stability data. [If necessary, there should be specific instructions describing the required level of accuracy for tank gauges, and describing whether additional underway calculations are needed to verify continued compliance with the damage stability requirements.] Use of shore-based support 29 Once the ship is loaded and/or ballasted for departure the ship's actual stability characteristics may be sent to a company support office ashore or the classification society for remote verification of compliance with damage stability requirements, where this is authorized, or sent to the Administration (or recognized organization acting on its behalf) for direct approval of the loading condition. Where this type of verification is employed, the ship should not sail until a copy of the damage stability approval has been received. Documentation 30 Verification of compliance with damage stability requirements should be documented in accordance with the company's operating procedures and the company's safety management system. This should include a method of retaining manual calculations and/or stability instrument printouts used to verify compliance, so that this information can be provided to third parties, such as company auditors, surveyors or port State control inspectors. It is recommended that records are retained on board for a minimum of three years to ensure they are available at the next SMC audit. ***