1. Technical Field
This disclosure relates to packaging resistant to flame penetration, particularly packaging for shipping containers of oxidizing material.
2. Background
An example of packaging requiring resistance to flame penetration are the chemical oxygen generators used in the aviation industry, and commonly shipped in the cargo hold of an aircraft. The reader should note, however, that this disclosure is not limited to the protection of chemical oxygen generators, but is applicable to the enclosure of other types of gas containers, gas generators, explosives, or any container having chemical contents that may react under flames.
Various safety precautions are taken to prevent actuation of oxygen generators and similar devices during shipment. These precautions include enclosure of the chemical oxygen generator in a primary package that reduces the possibility of mechanical actuation. However, a fire in the cargo hold of an aircraft could raise the temperature of such a chemical oxygen generator enough to cause actuation of the generator, or cause actuation by flame penetration of the packaging to the generator. The present subject matter provides outer packaging, and a method making it, to mitigate the effect of such a fire on chemical oxygen generators contained in the packaging.
The National Transportation Safety Board (NTSB) determined that one of the probable causes of the May 11, 1996 crash of ValuJet Airlines flight No. 592 was a fire in the airplane's cargo compartment initiated and enhanced by the actuation of one or more chemical oxygen generators carried as cargo in violation of requirements in the Hazardous Materials Regulations (HMR 49 CFR Parts 171 through 180). Recommendations issued by the NTSB following this tragedy addressed both the initiation of the fire by the improperly packaged generators and the possible enhancement of an aircraft cargo-compartment fire by the oxygen produced by the generators or other cargo. A number of corrective measures were included in NTSB Docket HM-224A. The final rule pointed out the possibility of further reducing the risks by enclosure of boxes containing chemical oxygen generators in an overpack or outer packaging meeting certain flame penetration resistance, thermal protection and integrity standards.
Later rule-making procedures addressed the additional features of flame penetration resistance, thermal protection and integrity. In 2007, the Department of Transportation, Pipeline and Hazardous Materials Safety Administration, issued final rule HM224B, “Transportation of Compressed Oxygen, Other Oxidizing Gases and Chemical Oxygen Generators on Aircraft.” This regulation specifies that after Sep. 30, 2009, a chemical oxygen generator and a chemical oxygen generator installed in equipment, must be placed in a rigid outer packaging that, among other things, conforms to the requirements of The Flame Penetration Resistance Test in part III of Appendix F to 14 CFR part 25, applied to at least three specimens of the outer packaging of a specified dimension, and on all design features, within five minutes of application of the flame source; and the maximum allowable temperature at a point four inches above the test specimen, centered over the burner cone, must not exceed 205° C. (400° F.). Furthermore, a chemical oxygen generator in the rigid outer packaging, when placed in a 205° C. (400° F.) oven for three hours must not actuate.
Present packaging aimed at satisfying these requirements is bulky, complicated to assemble, and unduly expensive, or all three.
The drawings are not to scale.
An “overpack,” is the container for a sensitive chemical cargo that is usually enclosed in some sort of primary packaging. The disclosed overpack comprises a box (110), preferably double-walled cardboard, which is lined with layers of metal foil and ceramic fiber paper that form an inner liner (160). The size and shape of the box (110) is determined by the number and size of containers to be placed in it. In one embodiment, the contents may be one or a number of individually packaged devices, such as chemical oxygen generators. (The reader should understand that the term “oxygen generator” in this application refers generally to any heat or flame-sensitive component of product.)
Flame penetration resistance can be provided by ceramic papers, felts or fabrics such as those offered by Unifrax, of Niagara Falls, N.Y., under the trade name of FIBERFRAX. For this purpose, such sheets of ceramic fiber (interchangeably called “felt,” “paper” or “fabric” in this application), preferably 1/16 inch to ¼ inch thick, preferably about ⅛ inch thick, are attached to one side of a cardboard carton. Such cartons are preferably double wall, 275 lb test, for shipping integrity. Packaging material other than cardboard could be used. The overall size and shape of the cardboard carton will be determined by the size of the container or equipment it will receive, allowing space for the ceramic fiber sheets, metal foil, and assembly means.
Metal foil (130), preferably aluminum foil, having a thickness of about 1 mil to 4 mils, preferably about 2 mils, provides a serviceable surface and protects the included ceramic paper (140). The foil (130) also prevents penetration of the compartment (225) by hot gasses from flames. Parts of the foil (130) will also be the points of attachment of the foil (130) and the ceramic paper (140) to the box (110). All surfaces of the ceramic paper (140) that will, at one time or another, be visible looking into the compartment (225) are covered with foil (130), and, where needed, additional foil (130) is provided for bonding. Any of a number of adhesive means are adequate; hot melt adhesive has been found suitable. An example of a suitable hot melt glue is Technomelt from Henkel Adhesives, of Elgin, Illinois. The surface of the foil (130) that will contact the included contents provides additional advantages of low coefficient of friction, allowing the intended contents to be slid into the box, and low emissivity, which slows heat transfer from a flame to the contents.
The figures illustrate the construction of the box with the liner (160) of foil (130) and ceramic fiber (140), per the following table of reference numerals:
After a laid-flat box (110) has been thus equipped with a ceramic paper and aluminum foil liner (160) as shown in the figures, the edges (165) of the liner (160) are lapped and stapled to make a joint or seam (195).
The stapled seam (195) is covered with a patch (190) of ceramic paper (180) and metal foil (170), the various parts being bonded over the seam (195) using any of a variety of adhesives. We have found that neoprene glue is adequate. The foil side of the patch (190) should face the compartment (225).
Note that the box (110) may be any convenient size and shape, not necessarily the rectangular cross-section box (110) shown. In some embodiments, the staples (210) enter the wall of the box (110) and pass through the liner (160), thus attaching the liner (160) to the box (110).
A drawing of a schematic cross section of the wall of the flame resistant packaging system (100) is shown in
When the flame penetration-resistant system (100) is needed for shipment, it can be prepared for receiving and article to be transported according to the following steps, as generally illustrated in
The assembled and flattened packaging system (100) is retrieved from a storage location and placed on a workspace.
In
In
In
In
In
In
In
In
In
In
In
In
This application claims the priority of U.S. Provisional Application Ser. No. 61/411,194, filed Nov. 8, 2010, entitled “Flame And Heat Resistant Packaging System And Method Of Making Same,” which application is incorporated by reference into the present application.
Number | Date | Country | |
---|---|---|---|
61411194 | Nov 2010 | US |