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Fire Protection
The following technical information is from FireFly
and ICEweb sponsor PROdetec.
How
to Protect Industrial Processes from Fire and Dust Explosions -
Anything that has been transformed into fine particles can explode.
Unfortunately, all too often it does. - Every year, many serious fires and
explosions occur in industrial plants as a result of dust. Yes, dust. Fine
inflammable material is explosive! The statistics speak for themselves. Dust
explosions lead to considerable material damage and long production shutdowns.
Every year there are also accidents with fatal consequences
Extinguishing
is as Important as Detection
- This technical bulletin covers;
- Water Extinguishing - Different applications and problems of
fire require totally different types of water extinguishing methods. Large water
droplets with powerful full cone water spray is needed to penetrate material
flows in chutes or pneumatic conveying systems. For extinguishing of flames in
enclosed volumes or open areas, smaller droplet sizes are an advantage due to
their high evaporation rate, efficient heat absorption and its ability to
displace oxygen. Designing a superior extinguishing system is a well-defined
science.
- Isolation and Inerting - In some processes, gas may be
more suitable as an extinguishing agent. Carbon dioxide and nitrogen are
excellent extinguishing agents provided that the affected section of the process
can be isolated. This requires extremely fast acting valves.
- Diverting - Another extinguishing method used in the Firefly
system is mechanical diverting. When an ignition source has been detected, a
divert valve is opened which redirects the material flow out of the process
line. The process itself need not even be stopped.
- Steam Extinquishing - The choice of extinguishing agent is
generally determined by the products handled in the process. Another factor is
the availability of an extinguishing agent.
Fire
Protection adds Value to Offshore Project Planning - Larry Watrous
- The importance of fire protection in the design and construction of offshore
structures can be a critical factor in the success of today’s offshore oil and
gas projects. Integrating this component into the planning of a production
facility is taking on increasing importance. This article addresses the changing
needs and expectations, scope of equipment and services, and regulation in the
fire protection discipline, as well as the capabilities and roles of the fire
protection professional. The article further emphasizes the timing necessary for
implementing a formal fire protection program in the design and construction of
new offshore structures or the revamping of existing facilities, and the need
for the expertise of a trained fire protection engineer to be involved with the
development of all phases of these projects - from Mustang Engineering.
Design
Engineering Key to Adequate Fire Protection - Larry Watrous -
This article has useful tips on the skills required of a Fire Protection
Engineer - from Mustang Engineering.
11.11 The
Fire Industry Association (FIA) is a not-for-profit trade association with the
aim of promoting the professional status of the UK fire safety industry. The
FIA's main objective is to promote the professional standards of the fire
industry. They provide technical knowledge and advice to anyone who needs it
regarding fire safety in the UK. This site is an excellent Fire Detection and
Protection resource. It provides;
- Technical
Updates - General technical information of interest. This
includes consultation requests from UK Government on new or proposed
legislation, public comment drafts of Standards, and comment drafts of FIA
technical documents as well as the notification of publication of new standards
and legislation.
- Fact
Files - Fact Files are a collation of
technical, legislative or procedural facts on a single subject or closely
associated group.
- Guidance
Notes - These are recommendations and
interpretations by the FIA (written by Council, Committee, and Secretariat etc)
to give help and guidance to members and non-members on technical subjects,
legislative matters, FIA processes/procedures etc.
- Codes
of Practice - These are ‘how to’
documents that are drafted and formatted in a similar fashion to a national
standard by the FIA (written by Council, Committee, and Secretariat etc) to give
help and guidance to members and non-members, primarily on technical
subjects.
PLEASE SCROLL DOWN TO SEE THE VARIOUS FIRE
PROTECTION METHODS
Enclosures Protected by Gaseous Fire Fighting
Systems
11.11
Guidance
on the Pressure Relief and Post Discharge Venting of Enclosures Protected by
Gaseous Fire Fighting Systems - This document provides
guidance on fulfilling the requirements contained in BS EN15004-1 and BS 5306-4,
in respect to over and under pressurisation venting - clauses 7.4.1 and 10.3.3.
respectively and post discharge extract - clauses 5.3 h) and 15.9 respectively.
It considers the design, selection and installation of vents to safeguard the
structural integrity of enclosures protected by fixed gaseous fire fighting
systems and the post discharge venting provisions where used - from the FIA.
CARBON DIOXIDE
Carbon Dioxide is a tried and trusted fire
Protection concept, which basically dumps C02 into an area limiting any
oxygen and suffocating any fire. The major disadvantage with this is the
risk to human life, hence considerable effort has to be ensured in
ensuring human evacuation before the dump occurs.
The following article "Carbon
Dioxide – CO2 provides effective
and reliable fire protection"
gives a useful overview.
Why are HALONS no longer used
as Fire suppression systems?
Halon fire-fighting systems were banned on new buildings
from July 1992 because of the
detrimental effects of CFC-based products on the ozone layer.
The principle of operation of the Hi-fog system is that the spray heads are all
activated simultaneously to propel the small water droplets which have a greater surface
area at very high momentum into the whole space which act to absorb the fire’s
energy. The droplets vaporise almost completely, cooling the flames and forming steam that
displaces the oxygen. The result is rapid and efficient and the extinguishing effect is
combined with the cooling of the surrounding air, flue gases and surfaces to prevent
re-ignition. Hi-fog’s sprinklers have a suction effect that draws in the gases, cools
them and washes particles to the floor. The suction in the small sprinkler is 10m3/min
and can be up to 25m3/min in the large.
Advantages of the
Hi-fog system are:
- Uses small amounts of fresh water, with
no additives, stored in high – integrity cylinders.
- It is highly effective against all types
of hydrocarbon fires.
- The small quantity of water used means
that water damage is negligible.
- It does not damage the environment.
- Superior fire suppression.
- Reduced smoke damage.
- Lightweight.
- Small pipe sizes.
- Fast and easy installation.
- Fast extinguishing.
- Effective cooling and cleaning of smoke.
- Electric power not required.
Disadvantages of the Hi-fog system are:
11.11
Code
of Practice for the Design and Installation of Commercial and Industrial
Watermist Systems - This Code of Practice gives recommendations for the design, installation, commissioning and
maintenance of watermist systems, and gives performance criteria for fixed watermist systems
for specific commercial and industrial hazards. Annex A of this Code provides a template for the
testing and validation of watermist system applications by qualified fire testing laboratories.
The Code of Practice does not cover watermist systems on ships, in aircraft, on vehicles and
mobile fire appliances or for below ground systems in the mining industry. It does not cover the
use of watermist for explosion protection.
11.11
Using
High Pressure Water Mist Fire Protection Systems for Offshore Oil Drilling and
Producing Facilities - Larry W Owen - Almost every portion of the platform requires some
form of fire protection. Many of the spaces found on offshore oil drilling and production facilities can be
protected with water mist systems. Water mist systems have tremendous fire suppression and extinguishing
capabilities whether the area protected contains flammable liquids or ordinary combustibles. System
testing protocols developed by the International Maritime Organization (IMO) have set the standard for
water mist design requirements. Coupled with the National Fire Protection Association (NFPA) 750
Standard on Water Mist Fire Protection, these global guidelines set the benchmark for fire protection
engineering companies to use when designing water mist systems. Water mist systems provide suppression and
extinguishment of fires through the use of three primary mechanisms, cooling, oxygen depletion
(inerting) and radiant heat blocking - from touch briefings
11.11Water
Mist for Fire Protection of Heritage - This is an excellent technical paper
which provides a vast amount of information on water mist systems.Water mist application is the most subtle way of water extinguishing. It provides safe and practical environment
for rescue work, it protects visitors and staff, it incur minimal secondary damage in valid or unintentional
activations and substantially remove harmful particles from smoke. Apart from the above and general extinguishing capabilities of water, mist applications add several advantages
over standard sprinkler systems, which often justifies a moderate extra cost. Mist systems discharge less water and
use small-diameter pipes. Water supply may not run empty, as does limited gas supplies or other extinguishing
media. Water mist may be turned off and on again. Water mist can be used where water was not previously
considered practical. Water mist is used in hand held extinguishers, fire hose nozzles, small standalone
units, object protection systems, room filling systems, hand held impact guns and large water mist
impact monitors. Applications include museum vaults, heritage buildings, hotels, churches and art
galleries - from heritagefire.net.
The name INERGEN is derived from a combination of INERTgas and nitrogen.
The composition of the gas "Inergen" (IG-541 or 52.40.08) is Nitrogen
(52+/-4%), Argon (40+/-4%) and Carbon Dioxide (8+/1%) of which the concentration used is
35-50%.
The atmosphere consists of 21% Oxygen, 78% Nitrogen, 0.02% Carbon Dioxide and a variety
of other gases.
When INERGEN is introduced into the atmosphere the resulting compositions are as
follows:
66.5 to 70% Nitrogen
11.5 to 16.4% Oxygen
3.1 to 4.3% Carbon Dioxide
This resulting composition can extinguish fires caused by a wide range of flammable
liquids, gases and solids. It achieves its effect by reducing the oxygen level.
The volume calculations of the protected areas are critical and hence it is recommended
that they be double-checked to ensure accuracy.
INERGEN SYSTEMS are environmentally friendly and are very safe when sized correctly.
People are still able to breathe in the reduced levels of Oxygen and exit the area without
risk to their health. The reduced Oxygen level does not support combustion.
The disadvantages of INERGEN include that it should only be used for total flooding
applications and that the enclosure around the fire hazard should be tight enough to hold
the required concentration of Inergen for a period sufficient to extinguish a fire. In
addition if a Halon system is being replaced the volume required is larger, hence the
bottle storage area may become a problem.
See the article "Inergen
is the world's leading fire suppression agent".
FM-200 is chemically known as heptafluropropane and is sometimes referred to as
HFC-227ea. It is a colourless, liquefied compressed gas. It is stored as a liquid and
dispensed into the hazard as an electrically non-conductive vapour. FM200 extinguishes
fire by both its chemical effect (80%) and its physical effect (20%). It has been
classified as being suitable for use as a total flooding agent in occupied areas.
FM200 is effective as a fire extinguishing agent for use on Class A surface fires,
Class B flammable liquid fires and Class E electrical fires.
Although FM200 is considered non-toxic to humans in concentrations used for fighting
fires certain safety considerations should be considered when handling and applying the
agent.
| The major disadvantage of FM200 is that it decomposes to form halogen acids when
exposed to open flames. The discharge from FM200 may create a hazard to personnel from the
natural agent itself and from these products of decomposition that result when the agent
is exposed to fire or other hot surfaces. Exposure to the agent is generally of less
concern than the exposure to decomposition products, however both should be avoided. The
formation of these acids is minimised by using early warning detection systems and proper
system installation. |
PYROGEN
Pyrogen is described as being the world's first
commercially available Aerosol Fire Extinquishing System get more information
from: http://www.pyrogen.co.uk/downloads/PyroGen%20(2008)%20brochure.pdf
VERY EARLY SMOKE DETECTION
Very early smoke detection systems are used for the sensitive electronic detection of
smoke. They are used as an early warning system.
A typical very early smoke detection system consists of five major components:
- The air sample transport system (usually small diameter PVC pipes).
- A filtering arrangement to remove large dust particles.
- An optical detector that carries out the actual examination of the air sample.
- An air pump that keeps the air samples moving through the system.
- The controller electronics that interprets the detector's results.
The sampling pipe or pipes are connected directly to a dust filter designed to remove
particles greater than 25 microns in diameter. Dust particles greater than this size have
been proved to be potentially troublesome and eliminated by filtering. When the air sample
enters the detector chamber, it is exposed to an intense light flash from a Xenon lamp. An
extremely sensitive photoelectronic receiver detects light scattered off particles
suspended in the air stream. The resulting signal is amplified and processed to produce an
analog reading of the smoke intensity. The steam of air is continuously refreshed.
Systems that use broad-spectrum light sources such as Xenon are much more sensitive in
a much broader spectral bandwidth than those that rely on light emitting diodes. Xenon
closely emulates the spectrum, the intensity of sunlight and it covers the complete
spectrum. It extends well into the ultraviolet and deeply into the infrared. Therefore the
detector can respond to particles of all sizes and it performs well for a wide range of
possible fuels and throughout the stages of fire growth.