Ingangsdatum: 04-06-2008
General1 Fixed gas fire-extinguishing systems for
use in machinery spaces of category A and cargo pump-rooms equivalent to
fire-extinguishing systems required by
SOLAS regulation II-2/10.4
and II-2/10.9 should prove that they have the same reliability which has been
identified as significant for the performance of fixed gas fire-extinguishing systems
approved under the requirements of
the FSS Code, chapter
5. In addition, the system should be shown by test to have the capability of
extinguishing a variety of fires that can occur in a ship's engine-room. Principal
requirements
2 All requirements of
the FSS Code, chapter 5, regulation 2.1, except as modified by
these guidelines, should apply.
3 The
minimum extinguishing concentration should be determined by a cup burner test
acceptable to the Administration.
The design concentration should
be at least 30% above the minimum extinguishing concentration. These
concentrations should be verified by full-scale testing described in the test method,
as set out in the appendix.
4 For systems
using halocarbon clean agents, 95% of the design concentration should be discharged in
10 s or less. For inert gas systems, the discharge time should not exceed 120 s for
85% of the design concentration.
5 The
quantity of extinguishing agent for the protected space should be calculated at the
minimum expected ambient temperature using the design concentration based on the net
volume of the protected space, including the casing.
5.1 The net volume of a protected space is that part of the
gross volume of the space which is accessible to the free extinguishing agent gas.
5.2 When calculating the net volume of a
protected space, the net volume should include the volume of the bilge, the volume of
the casing and the volume of free air contained in air receivers that in the event of
a fire is released into the protected space.
5.3 The objects that occupy volume in the protected space should be
subtracted from the gross volume of the space. They include, but are not necessarily
limited to:
- auxiliary machinery;
- boilers;
- condensers;
- evaporators;
- main engines;
- reduction gears;
- tanks; and
- runks.
5.4 Subsequent modifications to the protected space that
alter the net volume of the space shall require the quantity of extinguishing agent
to be adjusted to meet the requirements of this paragraph and paragraph 6.
6 All systems should
be designed to allow evacuation of the protected spaces prior to discharge. Means
should also be provided for automatically giving audible and visual warning of the
release of fire-extinguishing medium into any space in which personnel normally
work or to which they have access. The alarm should operate for the period of time
necessary to evacuate the space, but not less than 20 s before the medium is
released. Unnecessary exposure, even at concentrations below an adverse effect
level, should be avoided.
6.1 Even at concentrations below an adverse
effect level, exposure to gaseous fire extinguishing agents should not exceed 5
min Halocarbon agents may be used up to the No Observed Adverse Effect Level
(NOAEL) calculated on the net volume of the protected space at the maximum
expected ambient temperature without additional safety measures. If a halocarbon
agent is to be used above its NOAEL, means should be provided to limit exposure to
no longer than the time specified according to a scientifically accepted
physiologically based pharmacokinetic1 (PBPK) model or
its equivalent which clearly establishes safe exposure limits both in terms of
extinguishing media concentration and human exposure time.
6.2 For inert gas systems, means should be
provided to limit exposure to no longer than 5 min for inert gas systems designed
to concentrations below 43% (corresponding to an oxygen concentration of 12%, sea
level equivalent of oxygen) or to limit exposure to no longer than 3 min for inert
gas systems designed to concentrations between 43% and 52% (corresponding to
between 12% and 10% oxygen, sea level equivalent of oxygen) calculated on the net
volume of the protected space at the maximum expected ambient
temperature.
6.3 In no case should a halocarbon agent be
used at concentrations above the Lowest Observed Adverse Effect Level (LOAEL) nor
the Approximate Lethal Concentration (ALC) nor should an inert gas be used at gas
concentrations above 52% calculated on the net volume of the protected space at
the maximum expected ambient temperature.
7 The system and its components should be suitably designed
to withstand ambient temperature changes, vibration, humidity, shock, impact,
clogging, and corrosion normally encountered in machinery spaces or cargo pump-rooms
in ships.
8 The system and its components
should be designed and installed in accordance with international standards
acceptable to the Organization2 and manufactured and
tested to the satisfaction of the Administration. As a minimum, the design and
installation standards should cover the following elements:
- safety:
- toxicity;
- noise, nozzle discharge; and
- decomposition products;
- storage container design and arrangement:
- strength requirements;
- maximum/minimum fill density, operating temperature range;
- pressure and weight indication;
- pressure relief; and
- agent identification and lethal requirements;
- agent supply, quantity, quality standards;
- pipe and fittings:
- strength, material, properties, fire resistance; and
- cleaning
requirements;
- valves:
- testing requirements;
- corrosion resistance; and
- elastomer compatibility;
- nozzles:
- height and area testing requirements; and
- corrosion and elevated temperature resistance;
- actuation and control systems: - testing requirements; and - backup power
requirements;
- alarms and indicators:
- predischarge alarm, agent
discharge alarms as time delays;
- abort switches;
- supervisory
circuit requirements; and
- warning signs and audible and visual alarms
should be located outside each entry to the relevant space as appropriate;
- agent flow calculation:
- approval and testing of design calculation
method; and
- fitting losses and/or equivalent length;
- enclosure integrity and leakage requirements:
- enclosure leakage;
- openings; and
- mechanical ventilation interlocks;
- design concentration requirements, total flooding quantity;
- discharge time; and
- inspection, maintenance, and testing
requirements.
9 The nozzle type, maximum nozzle spacing, maximum height
and minimum nozzle pressure should be within limits tested to provide fire
extinction per the proposed test method.
10Provisions should be made to ensure that escape routes which
are exposed to leakage from the protected space are not rendered hazardous during
or after discharge of the agent in the event of a fire. In particular, hydrogen
fluoride (HF) vapour can be produced in fires as a breakdown product of the
fluorocarbon fire extinguishing agents and cause health effects such as upper
respiratory tract and eye irritation to the point of impairing escape. Control
stations and other locations that require manning during a fire situation should
have provisions to keep HF and HCl below 5 ppm at that location. The
concentrations of other products should be kept below concentrations considered
hazardous for the required duration of exposure.
11 Where agent containers are stored within a
protected space, the containers should be evenly distributed throughout the space
and meet the following provisions:
- a manually initiated power release, located outside the
protected space, should be provided. Duplicate sources of power should be
provided for this release and should be located outside the protected space, and
be immediately available;
- electric power circuits connecting the
containers should be monitored for fault conditions and loss of power. Visual
and audible alarms should be provided to indicate this;
- pneumatic, electric or
hydraulic power circuits connecting the containers should be duplicated and
widely separated. The sources of pneumatic or hydraulic pressure should be
monitored for loss of pressure. Visual and audible alarms should be provided to
indicate this;
- within the protected space, electrical circuits essential for the
release of the system should be fire resistant according to standard IEC 60331
or other equivalent standards. Piping systems essential for the release of
systems designed to be operated hydraulically or pneumatically should be of
steel or other equivalent heat-resisting material to the satisfaction of the
Administration;
- each pressure container should be fitted with an automatic
overpressure release device which, in the event of the container being exposed
to the effects of fire and the system not being operated, will safely vent the
contents of the container into the protected space;
- the arrangement of
containers and the electrical circuits and piping essential for the release of
any system should be such that in the event of damage to any one power release
line or container valve through mechanical damage, fire or explosion in a
protected space, i.e. a single fault concept, at least the amount of agent
needed to achieve the minimum extinguishing concentration can still be
discharged having regard to the requirement for uniform distribution of medium
throughout the space; and
- the containers should be monitored for
decrease in pressure due to leakage and discharge. Visual and audible alarms in
the protected area and on the navigation bridge or in the space where the fire
control equipment is centralized should be provided to indicate this
condition.
12 A minimum agent hold time of 15 min should be provided.
13 The release of an extinguishing agent may produce
significant over and under pressurization in the protected space. Measures to limit
the induced pressures to acceptable limits should be provided.
14For all ships, the fire-extinguishing system design manual
should address recommended procedures for the control of products of agent
decomposition, including HF vapour generated from fluorocarbon extinguishing
agents which could impair escape. Clearly, longer exposure of the agent to high
temperatures would produce greater concentrations of these types of gases. The
type and sensitivity of detection, coupled with the rate of discharge, should be
selected to minimize the exposure time of the agent to the elevated temperature.
The performance of fire-extinguishing arrangements on passenger ships should not
present health hazards from decomposed extinguishing agents, for example on
passenger ships, the decomposition products should not be discharged in the
vicinity of muster (assembly) stations. Other mitigating steps include evacuation,
and donning masks.
1Refer to document FP 44/INF.2 - Physiologically based pharmacokinetic model to
establish safe exposure criteria for halocarbon fire extinguishing agents.2Until international standards are developed, national standards acceptable to the
Administration should be used. Available national standards include, e.g., Standards
of Australia, the United Kingdom and NFPA 2001.