Flameless Ration Heater (FRH)
Since 1992 a Flameless Ration Heater (FRH) has beeb added to each Meal, Ready to Eat (MRE) field ration menu. Zestotherm was the originator and manufacturer of the water activated heater designed for the U.S. Army, although several companies now supply the market. Approximately 30 million FRHs were purchased every year.
The main course of an MRE is something like chicken stew or spaghetti and meatballs in a plastic and aluminum foil pouch. Soldiers heat the food by dropping the pouch into a pot of boiling water or leaning it against the exhaust manifold or radiator of a vehicle engine. When there’s not enough time to boil water or wait for dinner to heat on an engine, they use the FRH that comes with each MRE.
Its really easy to use. Simply drop the food pouch into the FRH, which is enclosed in a thin, plastic sleeve. You then add a small amount of water to the sleeve and shove it into the food-pouch box. It may help to tip the package up at an angle, by leaning it against a brick, shoe, or whatever is handy.
Flameless Ration Heater.
See also: Heating Individual Field Rations.
Chemistry of the Flameless Ration Heater (FRH)
The FRH contains magnesium metal that combines with water to form magnesium hydroxide. That combination causes an “exothermic oxidation-reduction reaction." The reaction throws off enough energy to heat the meal without flame or smoke, and without getting too hot or dangerous. Besides the magnesium, the FRH contains some iron powder and salt which promote the reaction. If the magnesium in an FRH has been exposed to moist air at any time, its surface will be coated with a thin layer of insoluble magnesium hydroxide; the FRH probably will work but less well.
Hazards Associated with the Flameless Ration Heater (FRH)
In March of 2001, a freight container packed with FRH cases burst into flames, a spectacular chemical blaze that destroyed the container and dockside equipment. This and other incidents have resulted in much more care being associated with shipping and storing of the FRH. Hydrogen gas has been detected, in small amounts, leaking from FRH packages and some cases are at elevated temperatures even without a water source. In general, FRH packages are now treated like a hazardous material such as gasoline and not like rations.
Nonflammable Ration Heater (NRH)
Although the FRH was considered extremely successful since its development in 1990, its heat is produced by a metal alloy chemical reacting with water. This reaction produces hydrogen gas, which is potentially flammable if confined. As a result, the FRH was classified as a "Dangerous When Wet Material," necessitating transportation and storage restrictions. The Army wanted somthing better.
To solve this problem, the Nonflammable Ration Heater (NRH) was developed as an alternative heater for the Meal, Ready-to-Eat (MRE). The new NRH consists of anhydride powders that provide two sources of heat when activated with water, the first from hydration and the second from neutralization. Therefore, the heater is both self-neutralizing and fail-safe. To use the NRH requires only one ounce of water and it weighs less than two ounces. No toxic gasses are produced by the NRH and therefore unrestricted operation, transportation and storage is permitted. It also costs about 10 cents less per unit.
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