Now the High Value High Risk industries, such as Oil and Gas, petrochemical, chemical, pharmaceutical, ammunition manufacturing facilities, reactor vessels, amongst many others, can drastically enhance their protection level from potential fires or explosions, and their means of combating these.
In many cases, for incidents in these industries, every fraction of a second counts and it is important to use high speed, effective means of detecting and combating fast growing fires or fuel explosions to prevent or minimize any damage to the body or lives of personnel and assets.
Such capabilities and technologies are readily available, having already been in use and proven in action for many years by providing mandatory, essential protection of troops manning military vehicles on the battlefield, many of which for the US Armed Forces where they are known as Automatic Fire Detection and Suppression (AFES) systems.
Within these industries, the flammable vapors and dust explosion hazards continue to represent a constant threat when manufacturing, using and/or handling combustible gases, liquids and powders. Existing fire detection and suppression means include confinement, in special cases when the explosive material is also very toxic, explosion area isolation, partial inerting, automatic suppression and the most widely used method, which is explosion venting. It is clear that there is a need for additional, greater capabilities to provide protection and mitigation means for explosions and fires within fractions of seconds.
This article addresses in particular the various AFES systems alongside their current uses, and how a wide range of industries could benefit from them.
AFES In Military Applications
AFES systems protect against combat-initiated fuel explosions by detecting penetration and initiation in less than 3 milliseconds and slow-growth fires within 200 milliseconds, extinguishing within 3 seconds . Explosion suppression systems need to be individually designed, tested and qualified to address the different required performance and configurations for the specific application, within a wide range of military vehicles, from combat, ammunition support to tactical vehicles and furthermore to battle tanks.
Although systems are different, they have common components which are key to any system. Modular components are designed to fit into any type of armored vehicle and incorporates explosion/fire detection and fast suppression technologies. Special systems are designed for the crew/troop compartments and different systems for the engine compartment. The explosion/fire scenarios of these compartments are different and as a result, so are the detection means. In the crew compartment, the system protects personnel by reducing pressure build-up resulting from fuel explosions, limiting skin damage and minimizing formation of toxic gaseous by-products. In the engine compartment, the system has the capability of detecting overheat and fire and has successfully extinguishing fuel fires.
Each system must feature at least one type of detector, controller and suppression agent.
Common detector types are IR3 or UV/IR, depending on the detection type and speed and accuracy required, with the controller and extinguisher type selected to suit the application and its location. With the AFES system constantly being updated, the modern AFES system is free of false alarms, with a response of less than 5 milliseconds, and the capability to efficiently detect all types of fuel fires.
The extinguishing sub-systems are either pressurized cylinders containing gaseous, liquid or powder extinguishing agent or non-pressurized gas generators (or hybrids) containing the suppressing agent and a minute propellant activator that propels the extinguishing agent. In either case the dispersion pattern of the extinguishing agent is of critical importance to the successful suppression of the fireball and prevention of flame deflagration to detonation process.
Vehicles that have large quantities of fuel, oil, grease, etc, include the Bradley vehicle family, including variants M2, IFV, M4 command and control, Bradley ESV Engineer and the M993 MLRS Launch Rocket System, as well as the new Scout SV vehicle family including its six variants: Scout Reconnaissance; Protected Mobility (PMRS); Command & Control; Engineering; Repair; Recovery. When the vehicle is being hit the fuel may spill or be sprayed in the volume to create an explosive cloud. The hit also results in a vast release of energy, spray of plasma and red hot fragments that readily ignite the fuel mixture to create a fireball or fuel explosion.
The FAASV, which is in fact mobile ammunition storage with a hydraulic feeding system, has a unique nature and construction, making fire hazards one of the most dangerous threats to the vehicle and its crew. The vehicle's volume is packed with munitions and propellants, hydraulic system and lubricants that if ignited will result in a slow or rapid growing fire that may ignite the propellant to form a violent fire that cannot be extinguished by a traditional AFES. Propellant fire may develop to detonation/explosion and cause the vehicle destruction. To rapidly detect and suppress any type of fuel fire the FAASV was selected as one of the first vehicles for AFES installation in the 1980's.
When AFES systems were introduced to the MRAP and MATV Tactical Vehicles, the AFES system was further improved, providing the renowned modern AFES system, with increased survivability against fires initiated by Incendiary Explosives Devices (IED) and penetrating munitions with detection by either high speed optical flame detectors for crew compartments or spot and linear rate-of-rise heat detectors for the engine compartments.
Using Military Technology In Industrial Applications
Several industrial applications, particularly high-value high risk ones, were considered for the integration of the detection and suppression systems described previously due to similar hazards and requirements to military standards. According to NFPA 69 Standard on Explosion Prevention Systems , the paragraph addressing “Deflagration Control by Suppression” describes enclosures that can be protected by a deflagration suppression system and can include reactor vessels, mixers, blenders, pulverizers, mills, dryers, ovens, filters, screens and dust collectors, storage equipment including pressure tanks and mobile facilities, pneumatic conveyors and bucket elevators and many other enclosures
Ammunition Manufacturing Facilities
The facility is located in a secluded closed area and includes a conveyor and a cutter machine that cuts long propellant rods to small pieces that are collected in a receptacle. The cutting process is performed under wet conditions, however hazards associated with static electricity along the conveyor or sparks from the cutting machine have led to the requirement of special fire protection means.
Propellant Mixer
Various sizes of propellant mixers are located in specially designed prefabricated storage enclosures. Mobile raw material containers (moving on rails) transport the ingredients to the mixers where the chemicals undergo polymerization. Static electricity or abnormal chemical reaction may cause a deflagration to detonation event.
Chemical Industry
The new emerging Renewable and Alternative Fuels industry features various chemical processes and production facilities that require unique fire detection and suppression means. This industry includes biodiesel (synthetic diesel) plants that produce diesel fuel from biomass, Ethanol fuels produced from grains, cellulose and sugar cane, renewable diesel produced from thermo-depolymerized oils and fats, various hydrocarbons/biomass-to liquid processes that produce alternative fuels.
Reactor Vessels
One of the most attractive and popular new alternative fuel is the Ethanol that is produced from corn in two different processes: wet milling or dry milling. Fermentation and distillation tanks pose a major explosion /fire hazard that can be mitigated by employing adequate fast fire protection means, similar to the ones implemented in the ammunition industry.
Mechanical Preprocessing Enclosures
Conversion of cellulosic biomass to ethanol is less productive and more expensive than the conversion of corn to ethanol. Cellulosic biomass, however, is a less expensive and more abundant feedstock than corn. The first step in this ethanol production process is mechanical process where dirt and debris are removed from incoming biomass (e.g., bales of corn stover, wheat straw, or grasses), which is shred into small particles. The dust explosion hazard in these mechanical preprocessing enclosures can be mitigated by proper fast methods of protection.
Conclusion
The well proven technology of the Automatic Fire Extinguishing (SAFE) systems that protect life and limit the body injuries and vehicle damage have demonstrated effectiveness and the ability to save lives.
This technology and hardware have been adopted and perfected by to address a variety of hazards and applications and provide new performance and means to address and reduce the potential damages that may be caused by fuel or gas rapidly growing fires or explosions as the protection that