Communications: electrical – Condition responsive indicating system – With particular coupling link
Reexamination Certificate
2003-03-10
2004-11-16
Goins, Davetta W. (Department: 2632)
Communications: electrical
Condition responsive indicating system
With particular coupling link
C340S588000, C340S589000, C089S036170, C089S041210, C378S057000, C169S046000, C252S002000, C342S450000, C702S153000
Reexamination Certificate
active
06819237
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
The invention described herein may be manufactured and used by or for the government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
FIELD OF THE INVENTION
The field of the present invention pertains to a fire protection apparatus and system for detecting and extinguishing sparks, flames, or fire. More particularly, the invention relates to a fire fighting system for detecting and extinguishing a spark, flame, or fire on a heat sensitive explosive object, which identifies, locates and relays vital information related to the particular endangered explosive object. The invention protects heat sensitive objects, regardless of how they are heated. Throughout the description of the present invention, explosive objects such as bombs and missiles are used to illustrate the use of the invention; however, the invention can be used to protect any heat sensitive object from detonation, thermal damage, explosion, or chemical release of hazardous materials.
BACKGROUND OF THE INVENTION
To prevent fires, and the resulting loss of life and property, the use of flame detectors or flame detection systems are not only voluntarily adopted in many situations, but are also required by the appropriate authority for implementing the National Fire Protection Association's (NFPA) codes, standards, and regulations. Facilities faced with a constant threat of fire, such as petrochemical facilities and refineries, semiconductor fabrication plants, paint facilities, co-generation plants, aircraft hangers, silane gas storage facilities, gas turbines and power plants, gas compressor stations, munitions plants, airbag manufacturing plants, and so on are examples of environments that typically require constant monitoring of potential fire hazard situations.
An environment in which shipboard ordnances were exposed to the threat of detonation occurred on Jul. 29, 1967 on the nation's first carrier, the USS Forrestal. The U.S. Navy was conducting combat operations off the coast of North Vietnam in the Tonkin Gulf on Yankee Station. A Zuni rocket accidentally fired from a F-4 Phantom on the starboard side of the ship into a parked and armed A-4 Skyhawk. The accidental launch and subsequent impact caused the 400 gallon belly fuel tank and a 1,000 pound bomb on the Skyhawk to fall off. The tank broke open spilling JP5 (jet fuel) onto the flight deck and ignited a fire. Within 90 seconds the bomb was the first to cook-off and explode, causing a massive chain reaction of explosions that engulfing half the airwing's aircraft, and blew huge holes in the 3″ thick steel flight deck. Fed by fuel and bombs from other aircraft armed and ready for the coming strike, the fire spread quickly and many pilots and support personnel were trapped and burned alive. Fuel and bombs spilled into the holes in the flight deck igniting fires on decks further into the bowels of the ship. The crew heroically fought the fire and carried armed bombs to the side of the ship to throw them overboard for 13 hours. Once the fires were under control, the extent of the devastation was apparent. Most tragic was the loss to the crew: 134 had lost their lives, while an additional 64 were injured.
A fire on the flight deck of an aircraft carrier can quickly become catastrophic due to various types of stored explosive items and heat sensitive objects aboard. The firefighting crew, although highly trained and motivated to control and extinguish the conflagration, can be quickly eliminated in such a scenario because of their proximity to the detonating weapons that cook-off in the fire. This leaves less experienced, and less trained, trying to fight an extremely dangerous fire. It should be noted that a fire is not necessary in order to create a severe fire hazard or explosion in an industrial or military environment. An example of this comes from another aircraft carrier tragedy aboard the USS Enterprise (CVN-65), Jan. 14, 1969. This time, no fire existed prior to the start of weapons cooking-off. Rather, a Zuni rocket, loaded for combat on an F-4 Phantom, was heated until it exploded when the turbine exhaust from an aircraft starter unit (called a “huffer”) was inadvertently positioned to blow directly on the weapons warhead. Subsequently, fire broke out when to damaged fuel tanks leaking fuel onto the deck ignited, causing the tragic death of 27 sailors.
Three primary contributing factors to a fire are: (1) fuel (such as JP5 aboard the USS Forrestal); (2) heat derived from jet exhaust or sympathetic detonation; and (3) oxygen. When the fuel is heated above its ignition temperature (or “flash point”) in the presence of oxygen, a fire will occur. A fire can self-extinguish if one of the three above mentioned factors is reduced or eliminated. Thus, when the fuel supply of the fire is cut off, the fire typically stops. When a fire fails to self-extinguish, current fire protection systems incorporate flame detectors which are expected to activate suppression agents to extinguish the fire and thereby prevent major damage. It must be noted that the extinguishment of a fire does not remove the explosion hazard when certain industrial and military chemical compounds (such as explosives and propellants) have been heated by the fire that was extinguished. Under such conditions a phenomena known as “thermal runaway” can occur and an explosion can happen even after the device (weapon) has been removed from the fire and cooled. Once a complex chemical compound (like explosives or propellants) reaches its point-of-no-return, no amount of cooling can prevent it from cooking-off. In such cases, it is imperative to know the heating history of the compound in order to gauge when it will explode.
Flame detectors must meet standards set by the NFPA, which are becoming increasingly stringent. Thus, increased sensitivity, faster reaction times, and fewer false alarms are not only desirable, but are now a requirement. Previous flame detectors have many drawbacks. The drawbacks of these previous devices have led to false alarms, which unnecessarily stop production or activate fire suppression systems when no fire is present.
One drawback of the most common types of flame detectors is that they can only sense radiant energy in one or more of either the ultraviolet, visible, near band infrared (IR), or carbon dioxide (CO
2
) 4.3 micron band spectra. Such flame detectors tend to be unreliable and can fail to distinguish false alarms, including those caused by non-fire radiant energy sources (such as industrial ovens), or controlled fire sources that are not dangerous (such as a lighter). Disrupting an automated process in response to a false alarm can, as noted, have tremendous financial setbacks.
Another drawback of previous fire detectors is their lack of reliability, which can be viewed as largely stemming from their approach to fire detection. The most advanced fire detectors available tend to involve simple microprocessor controls and processing software of roughly the same complexity as those used for controlling microwave ovens. The sensitivity levels of these previous devices are usually calibrated only once, during manufacture. However, the sensitivity levels often change as time passes, causing such conventional flame detectors to fail to detect real fires or to false alarm. In addition, previous fire detectors require a continual source of energy to maintain the fire detection capabilities.
Many of the conventional flame detectors are limited by their utilization of pyroelectric sensors, which only detect the change in radiant heat emitted from a fire. Such pyroelectric sensors depend upon temperature changes caused by radiant energy fluctuations, and are susceptible to premature aging, degraded sensitivity and instability with the passage of time. In addition, such pyroelectric sensors do not take into account natural temperature variations resulting from environmental temperature changes that typically occur during the
Boggs Matthew L.
Bowman Howard L.
Wilson John E.
Goins Davetta W.
Haley Charlene A.
The United States of America as represented by the Secretary of
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