Guidance 9

G58    Fire dampers

G58.1    Manual control of dampers

G58.1.1    Manual control of a fire damper is to be independent of and capable of overriding any automatic means of control.

G58.1.2    Manual closing is normally by means of a handle linked directly to the damper blade spindle, but may be achieved by local operation of the fire damper by means of a fail-safe electrical switch or pneumatic release (spring loaded, etc.), on both sides of the division, with indication of fire damper status.

G58.2    Automatic closure of dampers

G58.2.1    When a fire damper is required to be closed automatically, the means of operation shall be situated inside the coaming or spigot such that it can be activated by hot gases passing through the ventilation ducting. The MCA is prepared to accept any additional means of operating the damper automatically, subject to compliance with preceding paragraphs.

G58.2.2    The means of operation shall be activated at temperatures within the range of 68°C to 79°C inclusive, except that in exhaust ducts serving spaces with high ambient temperatures such as galleys and drying rooms, the temperature at which the means of operation is activated may be increased to not more than 30°C above the maximum deckhead temperature.

G58.2.3    When the means of operating a fire damper automatically is a spring and fusible link, the link is required to be capable of being released manually from outside the duct by withdrawing the pin over which the link is hooked except that any other effective means of release would be considered.

G58.2.4    A pneumatic or electrical system must be such that the fire damper closes on release of the air or failure of any one of the components or power supply.

G58.3    Manual operation of dampers from both sides of a division

G58.3.1    In order to satisfy the requirements to operate a fire damper from both sides of a bulkhead or deck as indicated in the Regulations, a damper may be fitted on each side of the division within the coaming or spigot, the dampers being operated independently of each other. Only one of the two dampers need be capable of being closed automatically when automatic operation is required by the Regulations.

G58.3.2    Alternatively a single manual or automatic damper as appropriate may be fitted on one side of the bulkhead or deck, arranged for local manual operation, and in addition for manual operation from the blind side of such a division using a suitable linkage. The instructions of this section should be complied with at both operating positions.

G58.4    Open/closed indicator (on damper)

G58.4.1    Each damper is required by the Regulations to be fitted with a visible indicator to show whether the damper is in the open or closed position. The method of indication should be visible from the operating position.

G59    Components clear of coaming

G59.1 The manual and automatic controls, indicator, access panels and any other component should be sufficiently clear of the coaming to enable the coaming to be properly insulated.

G60    Damper controls clear of obstructions

G60.1    Manual and automatic controls of a damper are to be clear of the division, the insulation on the division or any other obstruction when the damper is in the open and closed positions.

G61    Ducts passing through 'A' Class divisions

G61.1    Attention is also drawn to the guidance dealing with Regulations referring specifically to the fitting of fire dampers in ventilation ducts passing through 'A' Class divisions and ventilation systems in general.

G61.2    The other spaces referred to in paragraph 7.2.1 are accommodation spaces, service spaces and control stations.

G61.3    Where the ventilation ducting serving a space or group of spaces fitted with a fixed gas fire-extinguishing system passes through any space not served by the system, the ducting should be of steel and of gas tight construction.

G61.4    The ventilation system serving a space in which gas cylinders are stored should not serve any other space and should be capable of freeing the space of any gas which may leak from the cylinders. Any ducting of such a system which passes through any other space should be of steel and of gas tight construction.

G62    Systems within main zones

G62.1    Wherever practicable the ventilation system leading from each ventilation fan shall be within one main vertical or horizontal zone. The fan room should also be within the same main zone otherwise an excessive number of fail-safe automatic closing fire dampers may be required where ducts penetrate the main zone division.

G63    Smoke control

G63.1    Where the arrangement of ducts and fire dampers in a ventilation system is such that smoke and hot gases may pass from one 'tween-deck to another through the system, a damper should be fitted in the duct on the upper side of the deck separating the 'tween-decks. The dampers may be simple manually controlled steel dampers fitted in a readily accessible position, and need not be of a fire tested type. Alternatively when the ducts are of steel their closure may be achieved by the shutting of punkah louvres or grilles fitted to the openings in the branch trunking within a 'tween-deck.

G63.2    Where individual ducts serve a single 'tween-deck the smoke damper may be at the fan unit or other location providing suitable isolation.

G64    Vertical ducts

G64.1    Paragraph 7.4.3 requires vertical ducts to be insulated as required by the tables in paragraph 2.2.3. Compliance with this Regulation may be achieved in the case of vertical ducts which are fitted with fire dampers, by insulating each damper coaming to the 'A' Class standard of the deck through which the duct passes.

G64.2    Vertical ducts having a cross sectional area not exceeding 0.075m² which pass through 'A' Class decks other than those which are main zone divisions, are not required to be fitted with fire dampers. Such vertical ducts should be insulated to the same 'A' Class standard as the decks through which they pass by continuing the insulation fitted to the deck plating along the ducts for a distance of not less than 450mm from the deck plating.

G64.3    Openings for recirculation of air or balancing a ventilation system may be provided between corridors in separate tween decks provided that they are trunked into the corridors with no openings into the ceiling or lining voids. In addition they should comply with the constructional requirements and the requirements for the provision of fire and smoke dampers of paragraph 7. They should normally be fitted with sliding or hinged steel shutters at their ends.

G64.4    The recommended thickness of the steel coamings incorporating fire dampers for closing openings in ventilation ducts is indicated in the following table:

Table 9.1

G64.5    When any duct not exceeding 0.075m² in cross sectional area, passes through an insulated 'A' Class division the duct or steel sleeve should be insulated for a distance of not less than 380mm from the division with 'A' Class mineral wool insulation having a thickness equivalent to that fitted over the plating of the division.

G64.6    When any duct exceeding 0.075m² in cross sectional area, passes through an insulated 'A' Class division the steel coaming incorporating the fire dampers should be insulated with an 'A' Class mineral wool insulation having a thickness equivalent to that fitted over the plating of the division as indicated in figures 9.21 and 9.22. The insulation is to be attached by means of welded steel pins, wire netting and spring steel washers.

Note: Illustrations of insulation fitted to coamings are on following pages.

G65    Ducts in service trunks

G65.1    Where ventilation ducts are grouped in a service trunk only the service trunk need be insulated at the deck penetration; provided the trunk is closed and has A Class integrity at all points.

G66    Fire resisting ducts

G66.1    Fire dampers are not required to be fitted in a duct which passes through a space surrounded by 'A' Class divisions and has no openings into the space, subject to following main paragraph and provided that the duct:

G66.1.1    has the same thickness as a duct as indicated in paragraph 7.2.1.1.1;

G66.1.2    is adequately supported and stiffened; and

G66.1.3    is insulated to the same 'A' Class standard as the divisions through which it passes or to the higher standard when the divisions have differing 'A' Class standards. This is illustrated by figure 9.23 below.

G66.2    The dispensing of fire dampers in this manner shall not apply when a duct passes through a main zone division, because paragraph 4.1.1.8 still applies.

G66.3    Notwithstanding the preceding main paragraph when a duct serves spaces bounded by 'A' Class divisions and which are situated on each side of another space into which the duct has no openings, fire dampers are still required to be fitted at each end of the 'A' Class ducting in order to maintain the integrity of the two outer spaces from each other. This is illustrated by figure 9.24.

G67    Ducts passing through 'B' Class divisions (paragraph 7.3.2)

G67.1    Ventilation ducts passing through 'B' Class bulkheads, ceilings or linings should be treated as indicated in the following table;

Table 9.2

G68    Ducts from machinery of Category A, galleys etc. (Paragraph 7.2.1)

G68.1    It should be noted that double and single skinned spiroducts are precluded from use in the situations referred to because they are not constructed of steel of the required thickness.

G68.2    The automatic closing fire damper required by paragraph 7.2.1.1.3 should be fitted on the opposite side of the boundary penetrated to that of the spaces which it serves. The manual controls of the dampers should be readily accessible and the operating position clearly marked.

G68.3    Care should be taken to ensure that the A-60 standard of the portion of ducting which is required by paragraph 7.2.1.1.4 to be insulated, is not impaired where the ducting passes through a deck or adjoins another structure. It should be borne in mind that the intention of the requirement is to protect the accommodation spaces etc. from a fire in the machinery space of Category A, galley etc.

G68.4    When the measures specified in paragraph 7.2.1.2.2 or 7.2.2.2.2 are adopted and the boundary of the machinery space of Category A, galley, Ro-Ro space or special category space which is being penetrated by the duct is a main zone division, in addition to the duct being insulated for its full length to A-60 standard, paragraph 4.1.1.8 must also be complied with.

G68.5    Similar care with insulation should be taken when the alternative method of protecting accommodation spaces etc. indicated in paragraph 7.2.1.2.1 and 7.2.1.2.2, is adopted.

G69    Ducts from accommodation spaces etc. (Paragraph 7.2.2)

G69.1    See guidance G9.68, which applies in a similar manner.

G70    Galley ventilation

G70.1    The automatic closing fire damper referred to in paragraph 7.5.2.1.2 should be positioned immediately above the grease trap and the fixed means of extinguishing a fire referred to in paragraph 7.5.2.1.4 should be capable of extinguishing a fire situated anywhere above it from the exhaust duct. The fire damper should be provided with manual control operable from an accessible position clear of the equipment which the exhaust duct serves.

G70.2    In all cases when an exhaust duct is fitted with branches serving different items of galley equipment, the requirements of paragraph 7.5.2.1.4 should apply to each branch. In such cases remote control of the fire dampers in the exhaust trunk branches may be necessary; even in those ships which are not required to comply with paragraph 7.5.2.1.2. Where compliance with these standards is not necessary because a galley exhaust duct does not pass through accommodation spaces or spaces containing combustibles e.g. when the duct goes directly to the open air from the galley, then regulations 5.2.1.1 and 5.2.1.2 should be complied with in respect of stopping the fan and providing a means of closure at the duct outlet. It would be sensible in such a case to fit a grease trap in the duct.

G71    Ducts passing through 'A' Class divisions (on cargo ships and tankers)

G71.1    See guidance G9.61 which also applies in a similar manner to cargo ships and tankers.

G72    Fire resisting ducts (on cargo ships and tankers)

G72.1    See guidance G9.66 which also applies in a similar manner to cargo ships and tankers except that paragraph 66.3 does not apply.

G73    Openings for recirculating or exhausting air or balancing systems

G73.1    Paragraph 4.2.3, for cargo ships, paragraph 4.1.2.1, for passenger ships, permits openings in the lower part of 'B' Class doors through which air from cabins or similar spaces and from cabins and public spaces respectively may be taken via the corridors and ducting to the air conditioning machinery room for recirculation or to the atmosphere. 'B' Class bulkheads should not be penetrated by openings other than those in the lower part of the doors or within ducting irrespective of the openings being fitted with shutters or dampers. Open-ended steel coamings should not be regarded as ducting.

G73.2    Air from spaces surrounded by 'A' Class divisions should not be exhausted directly into corridors for recirculating or for return to the atmosphere through openings or open-ended coamings irrespective of the openings or coamings being fitted with shutters or dampers. Such spaces should be fitted with exhaust ducting to the fan room or to the atmosphere. Similarly high risk spaces such as galleys should not be provided with recirculating, balancing or exhaust openings or open-ended coamings into adjacent accommodation spaces.

G73.3    Openings for recirculation of air or balancing a ventilation system may be provided between corridors in separate 'tween decks provided that they are trunked into the corridors with no openings into the ceiling or lining voids. Also, they should comply with constructional requirements (including the provision of fire and smoke dampers) of paragraph 7. They should normally be fitted with sliding or hinged steel shutters at their ends.