4 Operating Limits – Descriptions/Assumptions

  4.1.1 Ship-specific design loading patterns and loading restrictions should be clearly presented in the stability booklet. The following items should be included:

• .1 any required and intended loading conditions (including the ones corresponding to multiple freeboards when so assigned to the ship), i.e. symmetrical/ unsymmetrical, homogeneous/alternating or ballast/ partial/full;

• .2 types (e.g. oil, noxious liquid substances and LNG) of liquid cargo allowed to be carried;

• .3 restrictions to different liquid loads to be carried simultaneously;

• .4 range of permissible densities of liquid loads to be carried; and

• .5 minimum tank filling levels required to achieve compliance with the applicable stability criteria.

  4.1.2 For the verification of damage stability all loading conditions presented in the stability booklet except for ballast, light ship and docking conditions are to be examined.

 In the absence of stability software and KG/GM limit curve(s), in lieu of approved specific loading conditions, a matrix clearly defining any allowable ranges of loading parameters (draught, trim, KG, cargo loading pattern and SG) that the ship is allowed to load whilst remaining in compliance with the applicable intact and damage stability criteria can be developed for the stability booklet when a greater degree of flexibility than that afforded by approved specific loading conditions is needed. If this information is to be used, it should be in an approved form.

  4.3.1 Where KG/GM limit curves are provided, a systematic investigation of damage survival characteristics should be undertaken by making calculations to obtain the minimum required GM or maximum allowable KG at a sufficient number of draughts within the operating range to permit the construction of a series of curves of "required GM" or "allowable KG" in relation to draught and cargo tank content in way of the damage. The curves must be sufficiently comprehensive to cover operational trim requirements.

  4.3.2 The verification of KG/GM limit curves should be conducted without any free surface correction. The actual loading condition uses the free surface correction (see section 6.5) when comparing actual and allowable KG values.

  4.3.3 It is to be noted that any change of filling level, draught, trim, or cargo density might have a major influence to the results of a damage case; therefore the following items should be considered carefully for the calculation of the KG/GM limit curves:

• .1 intact and damage stability criteria applicable to the ship;

• .2 the maximum required damage extent and lesser extents of damage which provide the most severe damage cases;

• .3 draught range of the ship (up to tropical freeboard if required);

• .4 trim range of the ship (see section 6.6);

• .5 full and empty cargo tanks;

• .6 partially filled cargo tanks (consideration of increments as necessary);

• .7 minimum tank fillings in tonnes if required;

• .8 maximum/minimum densities of cargoes; and

• .9 ballast tank filling levels as necessary to achieve compliance.

  4.3.4 Damage stability calculations, on which the KG/GM limit curve(s) is(are) based, should be performed at the design stage. The KG/GM limit curve(s) drawn out taking stability criteria (intact and damage) into account should be inserted in the stability booklet.

 The stability booklet should contain a note for the master to avoid initial heel greater than 1 degree. A steady heeling angle may have a major influence on the stability of the ship especially in the case of damage.

  4.5.1 Any stability software installed on board should cover all stability requirements (intact and damage) applicable to the ship.

  4.5.2 The following types of stability softwares, if approved by an Administration or RO acting on its behalf (according to the 2008 IS Code and MSC.1/Circ.1229), are applicable for the calculation of service-loading conditions for tank ships:

• .1 Type 2: Checking intact and damage stability on basis of a KG/GM limit curve(s) or previously approved loading conditions; and

• .2 Type 3: Checking intact and damage stability by direct application of pre-programmed damage cases for each loading condition, including capability for calculation of intermediate damage stages.

  4.5.3 The software should be approved by the Administration or RO acting on its behalf. The stability instrument is not a substitute for the approved stability documentation, but used as a supplement to facilitate stability calculations.

  4.5.4 Sufficient damages, taking into account lesser damages, and variation of draft, cargo density, tank-loading patterns and extents of tank filling should be performed to ensure that for any possible loading condition the most onerous damages have been examined according to relevant stability criteria.

  4.5.5 The methodologies for determining compliance with relevant stability criteria should be as set out in these Guidelines.