MSC.1/Circ.1270
REVISED GUIDELINES FOR THE APPROVAL OF FIXED AEROSOL FIRE-EXTINGUISHING SYSTEMS
EQUIVALENT TO FIXED GAS FIRE-EXTINGUISHING SYSTEMS, AS REFERRED TO IN SOLAS 74,
FOR MACHINERY SPACES
(4
June 2008)
1.
The Maritime Safety Committee, at its seventy-fourth session (30 May to 8 June
2001), approved the Guidelines for the approval of fixed aerosol
fire-extinguishing systems equivalent to fixed gas fire-extinguishing systems,
as referred to in SOLAS 74, for machinery spaces (MSC/Circ.1007).
2.
The Sub-Committee on Fire Protection, at its fifty-second session (14 to 18
January 2008), reviewed the Guidelines for the approval of fixed aerosol
fire-extinguishing systems equivalent to fixed gas fire-extinguishing systems,
as referred to in SOLAS 74, for machinery spaces (MSC/Circ.1007) and revised
the Guidelines.
3.
The Committee, at its eighty-fourth session (7 to 16 May 2008), after having
considered the above proposal, approved the Revised Guidelines for the approval
of fixed aerosol fire-extinguishing systems equivalent to fixed gas
fire-extinguishing systems, as referred to in SOLAS 74, for machinery spaces,
as set out in the annex.
4.
Member Governments are invited to apply the Revised Guidelines for the approval
of fixed aerosol fire-extinguishing systems equivalent to fixed gas
fire-extinguishing systems, as referred to in SOLAS 74, for machinery spaces on
and after 9 May 2008 and bring them to the attention of ship designers, ship
owners, equipment manufacturers, test laboratories and other parties concerned.
5.
This circular supersedes circular MSC/Circ.1007.
Annex.
REVISED GUIDELINES FOR THE APPROVAL OF FIXED AEROSOL FIRE-EXTINGUISHING SYSTEMS
EQUIVALENT TO FIXED GAS FIRE-EXTINGUISHING SYSTEMS, AS REFERRED TO IN SOLAS 74,
FOR MACHINERY SPACES
1.
Fixed aerosol fire-extinguishing systems for use in machinery spaces of
category A equivalent to fire-extinguishing systems required by SOLAS
regulation II-2/10.5 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 International
Code for Fire Safety Systems (FSS Code), chapter 5. In addition, the system
should be shown, by testing according to appendix 1 to these Guidelines, to
have the capability of extinguishing a variety of fires that can occur in
machinery spaces.
2.
Aerosol fire-extinguishing systems involve the release of a chemical agent to
extinguish a fire by interruption of the process of the fire.
There
are two methods considered for applying the aerosol agent to the protected
space:
.1 condensed
aerosols are created in pyrotechnical generators through the combustion of the
agent charge; and
.2 dispersed
aerosols that are not pyrotechnically generated and are stored in containers
with carrier agents (such as inert gases or halocarbon agents) with the aerosol
released in the space through valves, pipes and nozzles.
3.
Aerosol is a fire-extinguishing medium consisting of finely divided solid
particles of chemicals released into a protected space as either condensed
aerosol or dispersed aerosol.
4.
Generator is a device for creating a fire-extinguishing medium by pyrotechnical
means.
5.
Efficiency coefficient is the percentage (%) of aerosol forming composition
actually discharged from a specific aerosol generator. It is determined by
comparing the mass loss of a generator after discharge to its beginning mass.
6. Design application density
(g/m³) is the mass of an aerosol forming composition per m³ of the
enclosure volume required to extinguish a specific type of fire, including a
safety factor of 1.3 times the test density.
7.
Agent medium for the purpose of these guidelines, these words are
interchangeable.
8.
The design application density should be determined and verified by the
full-scale testing described in the test method, as set out in appendix 1.
9.
The delivered density for each type of generator should be determined and
verified by the test method set out in appendix 2.
10.
The system discharge time should not exceed 120 s. Systems may need to
discharge in a shorter time for other reasons than for fire-extinguishing
performance.
11.
The quantity of extinguishing agent for the protected space should be
calculated at the minimum expected ambient temperature using the design density
based on the net volume of the protected space, including the casing.
11.1 The net volume of a protected space is that part of the gross
volume of the space, which is accessible to the fire-extinguishing agent.
11.2 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 may
be released into the protected space.
11.3 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:
.1 auxiliary
machinery;
.2 boilers;
.3 condensers;
.4 evaporators;
.5 main engines;
.6 reduction
gears;
.7 tanks; and
.8 trunks.
11.4 Subsequent modifications to the protected space that alter
the net volume of the space should require the quantity of extinguishing agent
to be adjusted to meet the requirements of this paragraph and paragraphs 10.1,
10.2, 10.3, 10.4, 12.2, 12.3, 12.4 and 12.5.
12.
No fire suppression system should be used which is carcinogenic, mutagenic or
teratogenic at application densities expected during use. The discharge of
aerosol systems to extinguish a fire could create a hazard to personnel from
the natural form of the aerosol, or from certain products of aerosol generation
(including combustion products and trace gases from condensed aerosols).
Other
potential hazards that should be considered for individual systems are the
following: noise from discharge, turbulence, cold temperature of vaporizing
liquid, reduced visibility, potential toxicity, thermal hazard and potential
toxicity from the aerosol generators, and eye irritation from direct contact
with aerosol particles. Unnecessary exposure to aerosol media, even at
concentrations below an adverse effect level, and to their decomposition
products should be avoided. All aerosols used in fire-extinguishing systems
should have non-ozone depleting characteristics.
12.1 All systems should be designed to allow evacuation of the
protected spaces prior to discharge through the use of two separate controls
for releasing the extinguishing medium. Means should also be provided for
automatically giving visual and audible warning of the release of
fire-extinguishing medium into any space in which personnel normally work or to
which they have access. The alarms should operate for the period of time
necessary to evacuate the space, but not less than 20 s before the medium is
released.
12.2 Condensed aerosol systems for spaces that are normally
occupied should be permitted in concentrations where the aerosol particulate
density does not exceed the adverse effect level as determined by a
scientifically accepted technique* and any combustion products and trace gases produced by the
aerosol generating reaction do not exceed the appropriate excursion limit for
the critical toxic effect as determined in acute inhalation toxicity tests.
_____________
* Reference
is made to the United States' EPAs Regional Deposited Dose Ratio Program
"Methods of Derivation of Inhalation Reference Concentrations and
Application of Inhalation Dosimetry" EPA/600/8-90/066F. October 1994.
12.3 Dispersed aerosol systems for spaces that are normally
occupied should be permitted in concentrations where the aerosol particulate
density does not exceed the adverse effect level as determined by a
scientifically accepted technique. Even at concentrations below an adverse
affect level, exposure to extinguishing agents should not exceed 5 min. If the
carrier gas is a halocarbon, it may be used up to its No Observed Adverse
Affect Level (NOAEL) calculated on the net volume of the protected space at the
maximum expected ambient temperature without additional safety measures. If a
halocarbon carrier gas is to be used above its NOAEL, means should be provided
to limit exposure to no longer than the corresponding maximum permitted human
exposure time specified according to a scientifically accepted physiologically
based pharmacokinetic** (PBPK) model or
its equivalent which clearly establishes safe exposure limits both in terms of
extinguishing media concentration and human exposure time.
_____________
**
Refer to document FP 44/INF.2 (United States) Physiologically based
pharmacokinetic model to establish safe exposure criteria for halocarbon
fire-extinguishing agents.
12.4 If the carrier is an inert gas, 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.
12.5 In no case should a dispersed aerosol system be used with
halocarbon carrier gas concentrations above the Lowest Observed Adverse Effect
Level (LOAEL) nor the Approximate Lethal Concentration (ALC) nor should a
dispersed aerosol system be used with an inert gas carrier at gas
concentrations above 52% calculated on the net volume of the protected space at
the maximum expected ambient temperature.
13.
The system and its components should be suitably designed to withstand ambient
temperature changes, vibration, humidity, shock, impact, clogging,
electromagnetic compatibility and corrosion normally encountered in machinery
spaces. Generators in condensed aerosol systems should be designed to prevent
self-activation at a temperature below 250C.
14.
The system and its components should be designed, manufactured and installed in
accordance with standards acceptable to the Organization. As a minimum, the
design and installation standards should cover the following elements:
.1 safety:
.1 toxicity;
.2 noise,
generator/nozzle discharge;
.3 decomposition
products;
.4 obscuration;
and
.5 minimum safe
distance required between generators and escape routes and combustible
materials;
.2 storage
container design and arrangement:
.1 strength
requirements;
.2
maximum/minimum fill density, operating temperature range;
.3 pressure and
weight indication;
.4 pressure
relief; and
.5 agent
identification, production date, installation date and hazard classification;
.3 agent supply,
quantity, quality standards, shelf life and service life of agent and igniter;
.4 handling and
disposal of generator after service life;
.5 pipes and
fittings:
.1 strength,
material properties, fire resistance; and
.2 cleaning
requirements;
.6 valves:
.1 testing
requirements; and
.2 elastomer
compatibility;
.7
generators/nozzles:
.1 height and
area testing requirements;
.2 elevated
temperature resistance; and
.3 mounting
location requirements considering safe distances to escape routes and
combustible materials;
.8 actuation and
control systems:
.1 testing
requirements; and
.2 backup power
requirements;
.9 alarms and
indicators:
.1 predischarge
alarm, agent discharge alarms and time delays;
.2 supervisory
circuit requirements;
.3 warning
signs, audible and visual alarms; and
.4 annunciation
of faults;
.10 enclosure
integrity and leakage requirements:
.1 enclosure
leakage;
.2 openings; and
.3 mechanical
ventilation interlocks;
.11 electrical
circuits for pyrotechnic generators:
.1 requirements
for mounting and protection of cables;
.12 design
density requirements, total flooding quantity;
.13 agent flow
calculation:
.1 verification
and approval of design calculation method;
.2 fitting
losses and/or equivalent length; and
.3 discharge
time;
.14 inspection,
maintenance, service and testing requirements; and
.15 handling and
storage requirements for pyrotechnical components.
15. The generator/nozzle type, maximum generator/nozzle spacing,
maximum generator/nozzle installation height and minimum generator/nozzle
pressure should be within limits tested.
16. Installations should be limited to the maximum volume tested.
17. Where agent containers are stored within a protected space,
the containers should be evenly distributed throughout the space and meet the
following provisions:
.1 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;
.2 electric
power circuits connecting the generators should be monitored for fault
conditions and loss of power. Visual and audible alarms should be provided to
indicate this;
.3 pneumatic,
electric or hydraulic power circuits connecting the generators 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;
.4 within the
protected space, electrical circuits essential for the release of the system
should be fire resistant according to standard IEC 60331 or 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;
.5 each
dispersed aerosol 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;
.6 the
arrangement of generators 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 generator 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 test density can still be discharged having regard to the
requirement for uniform distribution of medium throughout the space; and
.7 dispersed
aerosol 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, in the onboard safety centre or in the space where the fire
control equipment is centralized should be provided to indicate this condition.
18. The release of an extinguishing agent may produce significant
over and under pressurization in the protected space. Constructive measures to
limit the induced pressures to acceptable limits may have to be provided.
19. For all ships, the fire-extinguishing system design manual
should address recommended procedures for the control and disposal of products
of agent decomposition. The performance of fire-extinguishing arrangements on
passenger ships should not present health hazards from decomposed extinguishing
agents, (e.g., on passenger ships, the decomposition products should not be
discharged in the vicinity of assembly stations).
20. Spare parts and operating and maintenance instructions,
including operational tests for the system should be provided as recommended by
the manufacturer.
21. The temperature profile of the discharge stream from condensed
aerosol generators should be measured in
accordance with appendix 1. This data should be used to establish the minimum
safe distances away from the generator where the discharge temperatures do not
exceed 75ºC and 200ºC.
22. The casing temperature of condensed aerosol generators should be measured in accordance with appendix 1. This
data should be used to establish the minimum safe distances away from the
generator where the discharge temperatures do not exceed 75ºC and
200ºC.
23. Generators should be separated from escape routes and other areas where personnel may be present by at
least the minimum safe distances determined in paragraphs 21 and 22 above for
exposure to 75ºC.
24. Generators should be separated from combustible materials by
at least the minimum safe distances determined in paragraphs 21 and 22 above for exposure to 200ºC.
25. The useful life of condensed aerosol generators should be
determined by the manufacturer for the temperature range and conditions likely
to be encountered on board ships. Generators should be replaced before the end
of their useful life. Each generator should be permanently marked with the date
of manufacture and the date of mandatory replacement.
APPENDIX 1.
TEST METHOD FOR FIRE TESTING OF FIXED AEROSOL FIRE-EXTINGUISHING SYSTEMS
1.1
This test method is intended for evaluating the extinguishing effectiveness of
fixed aerosol fire-extinguishing systems for the protection of machinery spaces
of category A.
1.2
The test method is applicable to aerosols and covers the minimum requirements
for fire-extinguishing.
1.3
The test programme has two objectives:
.1 establishing
the extinguishing effectiveness of a given agent at its tested concentration;
and
.2 establishing
that the particular agent distribution system puts the agent into the enclosure
in such a way as to fully flood the volume to achieve an extinguishing
concentration at all points.
The
components to be tested should be supplied by the manufacturer together with
design and installation criteria, operational instructions, drawings and
technical data sufficient for the identification of the components.
This
test procedure is intended for the determination of the effectiveness of
different aerosol agent extinguishing systems against spray fires, pool fires
and class A fires. It also establishes the minimum safe distances from
condensed aerosol generators to personnel and combustible materials.
3.2.1
Test room
The
tests should be performed in 100 m2 room, with no horizontal
dimension less than 8 m, with a ceiling height of 5 m. The test