|
FIRE
SUPPRESSION SYSTEMS (Extinguishant
Systems)
When
areas may be unattended for periods and where it is vital
that an outbreak of fire be dealt with speedily an
automatic extinguishing system provides the only solution.
A standard sprinkler system will put a fire out but only
after it has developed sufficient heat to activate the
sprinkler head. Apart from fire damage the resultant water
damage can be very costly.
A
gaseous total-flooding extinguishing system activated by
smoke detection provides a rapid response to a developing
fire with a clean agent leaving no residue or equipment
damage. For that reason such systems are widely used to
protect high-value storage areas or electronic equipment
rooms. They
ensure a fire is dealt with rapidly no matter when it
occurs and before it can cause serious damage itself or activate
the sprinkler system.
Points
to consider:
1.
Extinguishant
gases need to be retained in the protected enclosure for
some time to ensure the fire is out. It is important that
the protected space be sufficiently well sealed to meet
the required retention time. An enclosure integrity test
is therefore vital to guarantee the effectiveness of the
system.
2.
Void
spaces must be protected or sealed. Ceiling tiles must be
fixed securely so they do not lift or else the ceiling
void must be protected.
3.
Extinguishant
cylinders must be securely fixed to solid walls or frames
because the instantaneous release of the agent may be
violent.
4.
Air
handling ducts entering or leaving the protected area must
be fitted with dampers that are powered-open/spring-shut.
5.
Doors
should be fitted with door-release units so that they are
never wedged or propped open.
6.
Personnel
who will be working in the protected area should be
adequately trained.
7.
The
status of the system should be easily seen by personnel
entering the room.
8.
Following
a release of gas it may be some time before replacement
cylinders are fitted. Consideration should be given to an
unconnected reserve that can be quickly connected to
re-instate the system.
9.
A
connected reserve allows a ‘second-shot’ of gas if
needed.
FM200:
Developed
as a direct replacement for Halon following it’s
planned withdrawal from general use, FM200 is a man-made
gas manufactured by the Great Lakes Corporation and is
UL and FM approved.
Principle
of Operation:
FM200 operates on two levels, the physical and the
chemical.The physical effect of FM200 is achieved by the
gas absorbing heat from the flames and this is the
principal way in which it extinguishes fire, but in
addition there is a chemical effect where the gas curtails
the complex chain reactions occurring in flames.
Advantages:
FM200 is clean, leaving no residue and does not damage
equipment. The amount of agent required is small by
comparison with the inert gases and so there is no
requirement for a large bottle store.
Limitations:
Being
a man-made gas FM200 is not cheap to produce, and so the
cost of refilling after a discharge will be costly
compared to the inert gases.
Design
considerations: The
quantity of gas required must be determined from the
volume of the protected space.
The amount of nozzles will be determined by the
throw from each nozzle and the maximum amount of gas that
can flow through a nozzle. The pipework design is critical
and must ensure the gas is released in 10 seconds.
Systems
are designed in accordance with NFPA 2001 and the BFPSA
Code of Practice for Gaseous Fire Fighting Systems.
Our
FM200 systems are manufactured by HYGOOD now part of
Macron.
For
more details on FM200 and other systems available from
Hygood visit the Hygood website using the link below:
ARGONITE
is
an inert gas, similar to Inergen, and as such has several
advantages over FM200, although there are corresponding
disadvantages.Both
are a blend of gases that exist naturally in the
atmosphere. Argonite is a mixture of 50% argon and 50%
nitrogen, and Inergen is similar with a small amount of CO2
added (8%).
Principle
of operation:
Argonite operates at a concentration of 40%, effectively
diluting the air in the protected space, reducing the
oxygen concentration to 12.6%, a level that will not
support combustion but will still support life. It takes
60 seconds to discharge the gas. The 50/50 mix of the two
inert gases has a molecular weight similar to air, which
gives increased retention times. The CO2 additive
in Inergen is intended to assist respiration in conditions
of reduced oxygen, but if there are toxic products of
combustion present increased respiration can accelerate
their effects.
Advantages:
Being composed of naturally occurring gases the refill
costs are low and test discharges are affordable.
Limitations:
The
large amounts of gas needed require a large
‘footprint’ for bottle storage, in many cases a
separate room and in extreme cases a separate building.
Design
Considerations: The quantity of extinguishing gas
agent must be determined from the volume of the protected
space. The amount of nozzles must be determined by the
throw from each nozzle and the maximum amount of agent
will determine the number of cylinders required. The
cylinders will require a footprint of 880mm by 670mm (6
bottles in a double row) for every 200m3 of
protected space.Where several spaces need to be protected
a multi-way system provides a very cost-effective
solution, with one set of bottles being used to protect
all the spaces and the gas being directed by solenoids to
the correct nozzles.
Argonite
systems are manufactured by Ginge Kerr and for more
information on the systems Ginge Kerr supply visit their
website http://www.ginge-kerr.com/
or for their Argonite website use the link below:
Firetrace
is
a system for protection of small enclosures with vital
equipment. Ideal applications are protection of MCC panels
or security video equipment. A Firetrace System consists
of a bottle of exinguishant gas and a thin-walled flexible
tube which is passed through or around the equipment to
protected. When a fire
occurs and touches the tubing the Firetrace Tube wall
softens and bursts at the hottest point allowing swift
accurate delivery of the extinguishing medium to the
source of the fire. Ideal applications: switchgear, skips,
bins, post boxes, agricultural machinery, store cupboards,
electrical control panels, unmanned closed machinery rooms
(yachts and engine compartments), unmanned pumping
stations, fume cabinets in laboratories, robotic
welding/machining processes, storage for chemicals, and
many more.
Firetrace Bottle and Tubing
Firetrace installed in Electrical Cabinet
Principle
of Operation: When
a fire occurs this tubing, which is pressurised, melts
creating a small hole pointing towards the ignition
source, thereby releasing the gas. Pressures
switches are used to activate a fire alarm system and to
shut off the power.
Advantages:
The
great advantage is the simlicity of installation. The
tubing can be ran through several cabinets and the gas
will only be released where the fire starts. It's
operation is totally mechanical and fail-safe, i.e. it
relies on failure to operate it.
Limitations:
The
system is really only suitable for cabinets and other
enclosures, as the quantity of gas is relatively small,
however Firetrace also have indirect systems where the
tubing is used to activate a larger system with
distribution pipework and nozzles.
Design
considerations: The
system should be designed so that the quantity of gas to
be released will be sufficient to overcome any leakage
from an protected space. Where electrical equipment is
being proteced it is vital that power be automatically
shut off by the system.
Firetrace
equipment is manufactured by Firetrace Ltd. and more
details can be found at their website by clicking on the
logo below:
|
