14B.2.1 Structure

  Purpose

The purpose of this section is to contain a fire in the space of origin. For this purpose, the following functional requirements should be met:

• the ship should be subdivided by thermal and structural boundaries;
• thermal insulation of boundaries should have due regard to the fire risk of the space and adjacent spaces;
• the fire integrity of the divisions should be maintained at openings and penetrations.

  14B.2.2.1 The hull, superstructures, structural bulkheads, decks and deckhouses should be constructed of steel or other equivalent material.

  14B.2.2.2 However, in cases where any part of the structure is of aluminium alloy, the following should apply:

• .1 Insulation of aluminium alloy components of "A" or "B" class divisions, except structure which, in the opinion of the Administration, is non-load-bearing, should be such that the temperature of the structural core does not rise more than 200°C above the ambient temperature at any time during the applicable fire exposure to the standard fire test. This insulation is to be applied on all sides except for the upper sides of decks and the outside of the vessel.

• .2 Special attention should be given to the insulation of aluminium alloy components of columns, stanchions and other structural members required to support lifeboat and liferaft stowage, launching and embarkation areas, and "A" and "B" class divisions to ensure that for members:

  • (a) supporting lifeboat and liferaft areas and "A" class divisions, the temperature rise limitation specified in .1 above should apply at the end of one hour; and

  • (b) supporting "B" class divisions, the temperature rise limitation specified in .1 above should apply at the end of half an hour.

• .3 Aluminium alloy components of divisions that are required to be equivalent to steel (identified by an * in tables 1 and 2) should be insulated with 25mm of mineral wool approved for use in A class divisions or with an equivalent insulation acceptable to the Administration.

  14B.2.2.3 For composite structures, the insulation is to be such that the temperature of the laminate does not rise more than the minimum temperature of deflection under load of the resin at any time during the specified fire exposure. The temperature of deflection under load is to be determined in accordance with the requirements of a recognised international standard. This insulation is to be applied on all sides except for the upper sides of decks and the outside of the vessel.

• .1 Special attention should be given to the insulation of composite components of columns, stanchions and other structural members required to support lifeboat and liferaft stowage, launching and embarkation areas, and "A" and "B" class divisions to ensure that for members:

  • (a) supporting lifeboat and liferaft areas and "A" class divisions, the temperature rise limitation specified in .1 above should apply at the end of one hour; and

  • (b) supporting "B" class divisions, the temperature rise limitation specified in .1 above should apply at the end of half an hour.

Special attention should be given to the fixing of fire door frames in bulkheads constructed of materials other than steel. Measures are to be taken to ensure that the temperature of the fixings when exposed to fire does not exceed the temperature at which the bulkhead itself loses strength.

  14B.2.2.4 Crowns and casings of a machinery space of category A should be A60 divisions and openings therein, if any, should be suitably arranged and protected to prevent the spread of fire.

  14B.2.2.5 For structures in contact with sea-water, the required insulation should extend to at least 300mm below the lightest waterline.

  14B.2.2.6 Fire divisions using steel equivalent, or alternative forms of construction may be accepted if it can be demonstrated that the material by itself, or due to non-combustible insulation provided, has the fire resistance properties equivalent to the A or B class standard required.

  14B.2.2.7 Insulation required by 14B.2.2.6 is to be such that the temperature of the structural core does not rise above the point at which the structure would begin to lose its strength at any time during the applicable exposure to the standard fire test. For 'A' Class divisions, the applicable exposure is 60 minutes, and for 'B' Class divisions, the applicable exposure is 30 minutes.