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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.

Other Links
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.

Fire and Explosion Guidance Part 2: Avoidance and Mitigation of Fires - The primary objective of this document is to offer guidance on practices and methodologies which can lead to a reduction in risk to life, the environment and the integrity of offshore facilities exposed to fire hazards - from Logical Software.

Fire Systems Integrity Assurance - Experience has shown that fire detection and protection systems are not always designed or specified in sufficient detail to ensure that they meet the performance criteria necessary to reliably achieve their intended role; this can result in fire systems not providing the performance required when called upon to do so. The OGP has produced a Fire System Integrity Assurance report, which provides guidance on issues involved in the assurance of fire system integrity from development of appropriate performance criteria through to routine system testing and inspection, in order to assess ongoing performance against the original criteria. The objective of the report is to provide a high level model of the steps to be addressed in assuring fire system integrity and to give guidance on technical points to be considered at each stage, drawing on practical experience from oil and gas installations - from OGP.  

Fire Prevention Requirements for Information and Communication Technology (ICT) rooms - Best Practice Document - This document provides specification of the Norwegian HE sector’s recommended fire protection requirements for ICT rooms. The aim of this document is to raise personnel awareness concerning the fire protection issue, and to enhance the quality of fire protection measures within the sector. Furthermore, it is intended that the recommendations in this document will form the basis of expansion, renovation and new building projects, and that they will be applied in everyday work contexts - from Terena.  

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. 

Protection of Piping Systems Subject To Fires and Explosions - This document aims to fill this gap by providing guidance on the protection and response of piping systems and piping supports subject to fires and explosions. The guidance covers the methods used to carry out both simplified design checks and advanced non linear analysis - from HSE (UK).

PLEASE SCROLL DOWN TO SEE THE VARIOUS FIRE PROTECTION METHODS


Enclosure Fire Protection

Enclosure Passive Fire Protection

Innovative Passive Fire Protection Cabinets Extend Margin of Safety for Critical Plant Shutdown Equipment - The cabinets ensure that equipment such as emergency shutdown valves remain operational by keeping them below 60 degrees Centigrade for periods of up to 64 minutes in the event of a hydrocarbon-based fire, to allow time for controlled shutdown - from Intertek

Enclosures Protected by Gaseous Fire Fighting Systems

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.


 hifog.1.jpg (7477 bytes)

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:

 Disadvantages of the Hi-fog system are:

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.

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.

Water 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:

  1. The air sample transport system (usually small diameter PVC pipes).
  2. A filtering arrangement to remove large dust particles.
  3. An optical detector that carries out the actual examination of the air sample.
  4. An air pump that keeps the air samples moving through the system.
  5. 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.