DESENSITIZING EXPLOSIVE MATERIALS USING A VACUUM VESSEL
A system and method for desensitizing an explosive material using a vacuum vessel having an enclosed volume. The explosive material is placed in the enclosed volume of the vacuum vessel, and immersed in a desensitizing liquid also in the enclosed volume. The pressure in the enclosed volume is reduced with respect to atmospheric pressure conditions to at least partially saturate the explosive material with the desensitizing liquid.
1. Field
The present disclosure relates generally to a system and method for desensitizing explosive materials, and more specifically to using a vacuum vessel to saturate an explosive material with a desensitizing liquid.
2. Description of Related Art
Pyrotechnic devices can be used to produce brilliant aerial firework displays and also create vibrant special effects for musical performances or other theatric productions. A typical fireworks display may involve the installation and ignition of a large number of pyrotechnic devices. In some cases, the pyrotechnic devices are installed in an array of launch tubes or other fixtures. Each pyrotechnic device is typically wired or fused to a central ignition station, which may be located remotely from the firing location. A human operator or automated control device located at the ignition station may fire the pyrotechnic devices in an orchestrated sequence to produce the desired fireworks display or special effect.
For large fireworks displays including, for example, more than 100 pyrotechnic devices, it is not uncommon for one or more pyrotechnic devices to fail to ignite. The reason for the failure may be due to a defect in a pyrotechnic device, a failed fuse, or an error in the ignition control. Regardless of the cause, the undetonated pyrotechnic device is typically removed from the firing location and transported off-site for disposal.
Because pyrotechnic devices include explosive materials, safety precautions are typically exercised when handling or transporting potentially defective devices. In some cases, an undetonated pyrotechnic device is removed from the launch tube or fixture, placed in a container filled with water, and soaked for a period of time before being transported. In other cases, the undetonated pyrotechnic device is soaked for a period of time without removing it from the launch tube or fixture. The soaking time depends, in part, on the hygroscopic properties of the pyrotechnic device and is typically overestimated to ensure that the pyrotechnic device has been fully wetted. While this technique may improve the safety of the pyrotechnic device during transportation, the presence of large quantities of water may complicate the disposal of the pyrotechnic device. Specifically, after the device has been transported, it must be removed from the container of water and dried before it can be deactivated and/or destroyed. To ensure that the pyrotechnic device is dried safely, a drying operation is typically conducted in a quarantined or remote location over an extended period of time, which consumes significant time and resources.
It is generally desirable to obtain a system and method of deactivating pyrotechnics without the above-mentioned drawbacks of traditional techniques.
BRIEF SUMMARYOne exemplary embodiment is directed to a method for desensitizing an explosive material using a vacuum vessel having an enclosed volume. The explosive material is placed in the enclosed volume of the vacuum vessel, and immersed in a desensitizing liquid also in the enclosed volume. The pressure in the enclosed volume is reduced with respect to atmospheric pressure conditions to at least partially saturate the explosive material with the desensitizing liquid.
In some embodiments, reducing the pressure of the enclosed volume includes applying a vacuum of at least 10 inches of mercury (Hg) to the enclosed volume. In some embodiments, reducing the pressure of the enclosed volume includes applying a vacuum of at least 29 inches of mercury (Hg) with respect to atmospheric pressure conditions. In some embodiments, reducing the pressure of the enclosed volume includes applying a vacuum of at least 10 inches of mercury (Hg) to the enclosed volume for at least 1 minute. In some embodiments, reducing the pressure of the enclosed volume includes applying a vacuum of at least 29 inches of mercury (Hg) to the enclosed volume for at least 10 seconds.
In one exemplary embodiment, the enclosed volume of the vacuum vessel is vented to atmospheric pressure conditions. The pressure in the interior enclosed volume is then reduced with respect to atmospheric pressure conditions for a subsequent time.
In one exemplary embodiment, the explosive material is weighed to obtain a pre-treatment weight. The explosive material is weighed again after having reduced the pressure to obtain a post-treatment weight. If the difference between the pre-treatment weight and the post-treatment weight exceeds a threshold, the pressure of in the enclosed volume is reduced for a subsequent time. In some embodiments, the desensitizing liquid is a flammable or combustible liquid. In some embodiments, the explosive material is a pyrotechnic composition contained in a pyrotechnic device. In one exemplary embodiment, the explosive material is removed from the vacuum vessel and incinerated.
In one exemplary embodiment, the explosive material is placed in a perforated basket and the perforated basket is placed in the interior enclosed volume of the vacuum vessel. In some cases, the desensitizing liquid is added to the enclosed volume after explosive material is placed in the enclosed volume. In other cases, the desensitizing liquid is added to the enclosed volume before explosive material is placed in the enclosed volume, and the explosive material is immersed in the desensitizing liquid as it is placed in the enclosed volume of the vacuum vessel.
One exemplary embodiment is directed to a system for desensitizing an explosive material. The system comprises a vacuum vessel having an enclosed volume. The system also comprises a desensitizing liquid at least partially filling the enclosed volume of the vacuum vessel. An explosive material is disposed within the enclosed volume and at least partially immersed in the desensitizing liquid; and
a vacuum source pneumatically connected to the enclosed volume of the vacuum vessel, the vacuum source configured to reduce the pressure in the enclosed volume with respect to atmospheric pressure conditions.
The following description sets forth exemplary methods, parameters and the like. It should be recognized, however, that the exemplary methods and parameters are not intended as a limitation on the scope of the present disclosure but are instead provided as a description of exemplary embodiments. Similarly, descriptions of specific devices, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the various embodiments. Thus, the various embodiments are not intended to be limited to the examples described herein and shown, but are to be accorded the scope consistent with the claims.
As described above, when a pyrotechnic device fails to detonate, it is typically transported to a remote location for deactivation and disposal. Because pyrotechnics typically contain a significant amount of explosive materials, it is generally desirable to desensitize the explosive material before the device is transported. The techniques and systems described herein can be used to desensitize a variety of pyrotechnic devices using a vacuum vessel in preparation for safe transport and disposal.
The following examples are described with respect to the desensitization of an explosive material that is contained in a pyrotechnic or other explosive device (e.g., gunpowder contained in a mortar shell firework). In general, the techniques and systems described below can be used to desensitize different types of materials that may produce an explosion on ignition or detonation, referred to herein as explosive materials. Explosive materials may be included as part of a chemical composition or mixture and integrated into a variety of devices or form factors. For example, the following techniques and systems can be used to desensitize materials, including black powder, pyrotechnic compositions, and other explosive materials capable of absorbing a liquid. The explosive materials may be integrated in a variety of devices or form factors, including artillery shells, rockets, flares, fountains, and any other explosive device capable of absorbing a liquid.
In general, an explosive material includes one or more fuel materials which can be oxidized to produce kinetic and thermal energy. In some cases, a powdered form of aluminum, magnesium, charcoal, or other material is used as a fuel in a pyrotechnic composition. The oxygen in the surrounding air can readily react with the powdered fuel which, on ignition, results in rapid oxidation of the fuel and releases an intense burst of energy typically characterized as an explosion.
The techniques and systems described herein can be used to desensitize an explosive material by controlling the overall rate of oxidation and thereby controlling the corresponding rate of energy release. In some cases, rapid oxidation of the fuel material can be prevented by soaking the explosive material in a non-flammable liquid, such as water. The presence of water reduces or eliminates exposure of the fuel material to oxygen in the air and helps to prevent an explosion. Thus, a non-flammable liquid may be suitable as a desensitizing liquid. However, as described above, the water must be removed and the explosive material completely dried before it can be destroyed.
Alternatively, the rate of oxidation of the fuel material can be significantly slowed by wetting or soaking the explosive material in a flammable or combustible liquid, thereby preventing an explosion. Typically, the oxidation rate of a flammable or combustible liquid is significantly lower than that of an explosive material. If the explosive material is wetted or soaked in a flammable or combustible liquid, the overall rate of oxidation of the soaked material may be significantly slowed, resulting in a release of energy that can be characterized as a controlled burn rather than an explosion. One reason for the slowed oxidation is due to the oxygen consumption of the burning flammable or combustible liquid, which reduces the amount of oxygen available for reaction with the explosive material.
Thus, a flammable or combustible liquid may also be suitable for use as a desensitizing liquid due, in part, to its ability to significantly slow the oxidation of the explosive material. Additionally, using a flammable or combustible liquid as a desensitizing liquid may facilitate destruction of the explosive material. For example, an explosive material that is saturated with a flammable or combustible material may be safely incinerated or burned in a burn pit or incineration oven. Exemplary flammable or combustible liquids that may be used include methyl soyate, propylene glycol, diesel, or any polar solvent. Other liquids may also be suitable for use as a desensitizing liquid.
The system and techniques described below can be used to desensitize an explosive material using a desensitizing liquid. In particular, the explosive material is immersed in a desensitizing liquid and a vacuum is applied to achieve saturation of the explosive material. By applying a vacuum to a submerged explosive material, air may be removed from the explosive material and the desensitizing liquid may more readily permeate the explosive material as compared to being submerged at atmospheric pressure conditions. In some cases, the use of vacuum reduces the time necessary to saturate the explosive material. In some cases, the use of vacuum allows saturation levels that may not have been possible under typical atmospheric conditions.
The system and techniques described below use a vacuum or reduced pressure conditions to desensitize an explosive material for transport and destruction. In particular, the system and techniques described below use a vacuum vessel to saturate an explosive material with a desensitizing liquid.
As shown in
In this example, the vessel lid 104 is configured to rest on the top of vessel base 102 to form a vacuum seal between the two components. In this particular implementation, the vessel lid 104 includes a lid flange 110, which includes an o-ring seal member 111 installed in a groove of the lid flange 110. When the vessel lid 104 is placed on the vessel base 102, the o-ring seal member 111 and lid flange 110 seat against the base flange 112. The weight of the vessel lid 104 presses the o-ring seal member 111 against the base flange 112 and forms a vacuum seal. The base flange 112 also includes an outer ring 113, which helps to align the vessel lid 104 with the vessel base 102. In this example, the vessel lid 104 is not mechanically attached or fixed to the vessel base 102. This feature allows the vessel lid 104 to lift off the vessel base 102 in case a positive pressure inside the vacuum vessel 100 is created due to an unintentional combustion or ignition of the contents. In some cases, the vessel lid 104 is fixed to the vessel base 102 for transportation or storage purposes.
As shown in
As shown in
In a typical implementation, the volume of the desensitizing liquid 120 is approximately half of the total liquid capacity of the vessel base 102. In this example, the total volume of the vessel base 102 is approximately 100 gallons and the volume of the desensitizing liquid 120 is approximately 50 gallons. If the volume of the explosive material being treated is less than half of the total volume of the vessel base 102, the explosive material in the basket 106 may be fully submerged without overflowing the vessel base 102. The volume of the desensitizing liquid 120 as compared to the total liquid capacity of the vessel base 102 may vary depending on the volume and shape of the explosive material being desensitized.
As shown in
As shown in
As discussed above, a vacuum seal is formed when the vessel lid 104 is placed on the vessel base 102. After the vessel lid 10 has been lowered (using the winch 202) onto the vessel base 102, the vacuum pump 210 may be used to reduce the pressure of the enclosed volume of the vacuum vessel 100 by applying a vacuum. The pressure of the enclosed volume may be returned to atmospheric pressure by operating the two-way valve 214 and/or powering off the vacuum pump 210. The operation of the system 200 is explained in more detail below with respect to
The system 200 of
In operation 402, the explosive material is placed in the vacuum vessel. With reference to
In operation 404, the explosive material is immersed in a desensitizing liquid. The explosive material may be partially or fully immersed in the desensitizing liquid. With reference to
In operation 406, the pressure is reduced in the enclosed volume of the vacuum vessel. Specifically, the pressure of the enclosed volume is reduced to a pressure that is lower than atmospheric pressure conditions. Generally, the reduced pressure facilitates the at least partial saturation of the explosive material with the desensitizing liquid. In many cases, the reduced pressure increases the saturation rate of the explosive material as compared to the explosive material being immersed in a desensitizing liquid under atmospheric pressure conditions. In some cases, the reduced pressure achieves a saturation level that may have not been possible if the explosive material had been immersed in the desensitizing liquid under atmospheric pressure conditions.
The reduction in pressure is typically performed using a vacuum pump or other vacuum source. With reference to
The vacuum may be maintained for a period of time of at least 10 seconds. In some cases, the vacuum is maintained for a period of time of at least 1 minute. The amount of vacuum that is applied and the duration of the vacuum cycle may depend, in part, on the hygroscopic properties of the explosive material and/or device packaging.
In some cases, multiple vacuum cycles are performed. For example, the enclosed volume of the vacuum vessel may be momentarily vented to atmospheric conditions after having applied a vacuum for a period of time. Then a vacuum may be reapplied to the enclosed volume of the vacuum vessel and the pressure reduced for a second, subsequent period of time. Each vacuum cycle that is performed may increase the saturation of the explosive material with the desensitizing liquid. In general, if lower vacuum levels are used, more cycles may be required to achieve saturation of the explosive material.
If saturation of the explosive material has been achieved by, for example, fully wetting the explosive material with the desensitizing liquid, the explosive material may be considered desensitized. The degree of saturation that is sufficient to desensitize the explosive material may depend on the hygroscopic properties of the explosive material and/or the device packaging. In general, as discussed above, an explosive material that has been saturated with a flammable or combustible liquid may be safer to transport than an explosive material that has not been saturated.
After the explosive material has been desensitized using process 400, the explosive material may be transported to another location for disposal. An additional benefit of using a flammable or combustible liquid to desensitize the explosive material is that the desensitized explosive material may be destroyed by incineration without having to perform an intermediate drying operation.
In operation 451, the explosive material is weighed to obtain a pre-treatment weight. In some cases, the pre-treatment weight represents the dry weight of the explosive material. In other cases, the pre-treatment weight represents the weight of the explosive material after having been subjected to a previous vacuum cycle resulting in the explosive material becoming at least partially saturated with a desensitizing liquid. It is not necessary that the precise weight of the explosive material be determined since the pre-treatment weight is used as a relative measure for the purposes of process 450. For example, if the explosive material is integrated in a pyrotechnic device or other package, the entire device or package is weighed. In such a case, the weight of the entire device or package may be considered the pre-treatment weight.
Operations 452, 454, and 456 are substantially similar to operations 402, 404, and 406, described above with respect to
In one example, 5 vacuum cycles are performed. Each vacuum cycle applies a vacuum of at least 29 inches of Hg to the enclosed volume of the vacuum vessel. The vacuum may be applied and maintained for at least 1 minute before venting the enclosed vacuum to atmospheric pressure conditions. In some cases, 5 to 10 vacuum cycles are applied as part of a vacuum treatment. In some case, more than 10 vacuum cycles are performed as part of a vacuum treatment. In some cases, between 2 and 5 vacuum cycles are performed as part of a vacuum treatment. The amount of reduced pressure and duration of the vacuum cycle may also vary depending on the number of cycles performed and the properties of the explosive material being treated. In some cases, the amount of vacuum and/or the duration of the vacuum cycle may be reduced if the number of cycles is increased. For example, a vacuum least 10 inches of Hg may be applied. In other cases, a vacuum of at least 25 inches of Hg may be applied. In other cases, the duration of the vacuum cycle may be at least 30 seconds. In some cases, the duration of the vacuum cycle may be at least 10 seconds.
In operation 458, the explosive material is weighed to obtain a post-treatment weight. The post-treatment weight represents the wetted weight of the explosive material. As described above, because the post-treatment weight is used as a relative measure, it is not necessary to determine the precise weight of the explosive material.
In operation 460, if the difference in weight is greater than a threshold, an additional vacuum treatment is performed. The difference in the weight of the explosive material before and after treatment indicates the amount of additional saturation that was achieved by the vacuum treatment. If there is a small change in the weight of the explosive material, the saturation of the explosive material may be complete. A large change in weight may indicate that further saturation of the explosive material is possible. The threshold that is used for operation 460 may depend on multiple factors, including the composition of the explosive, the type of desensitization liquid used, and the parameters of the vacuum cycle.
In one example, a threshold of 10% is used to determine if additional vacuum treatments are to be performed. More specifically, if the difference between the pre-treatment weight and the post-treatment weight divided by the pre-treatment weight is greater than 10%, then an additional vacuum treatment is performed. In another example, a threshold of 5% is used to determine if additional vacuum treatments are to be performed. Alternative threshold values, including 1%, 2%, 3%, 4%, 15%, and 20%, may be used.
Although a feature may appear to be described in connection with a particular embodiment, one skilled in the art would recognize that various features of the described embodiments may be combined. Moreover, aspects described in connection with an embodiment may stand alone.
Claims
1. A method for desensitizing an explosive material using a vacuum vessel having an enclosed volume, the method comprising:
- placing the explosive material in the enclosed volume of the vacuum vessel, immersing the explosive material in a desensitizing liquid in the enclosed volume; and
- reducing the pressure in the enclosed volume with respect to atmospheric pressure conditions to at least partially saturate the explosive material with the desensitizing liquid.
2. The method of claim 1, wherein reducing the pressure of the enclosed volume includes applying a vacuum of at least 10 inches of mercury (Hg) to the enclosed volume.
3. The method of claim 1, wherein reducing the pressure of the enclosed volume includes applying a vacuum of at least 29 inches of mercury (Hg) with respect to atmospheric pressure conditions.
4. The method of claim 1, wherein reducing the pressure of the enclosed volume includes applying a vacuum of at least 10 inches of mercury (Hg) to the enclosed volume for at least 1 minute.
5. The method of claim 1, wherein reducing the pressure of the enclosed volume includes applying a vacuum of at least 29 inches of mercury (Hg) to the enclosed volume for at least 10 seconds.
6. The method of claim 1, further comprising:
- venting the enclosed volume of the vacuum vessel to atmospheric pressure conditions; and
- reducing the pressure in the interior enclosed volume with respect to atmospheric pressure conditions for a subsequent time.
7. The method of claim 1, further comprising:
- removing the explosive material from the vacuum vessel; and
- incinerating the explosive material.
8. The method of claim 1, further comprising:
- weighing the explosive material to obtain a pre-treatment weight;
- weighing the explosive material after having reduced the pressure to obtain a post-treatment weight; and
- if the difference between the pre-treatment weight and the post-treatment weight exceeds a threshold, reducing the pressure of in the enclosed volume for a subsequent time.
9. The method of claim 1, wherein the desensitizing liquid is a flammable or combustible liquid.
10. The method of claim 1, wherein the explosive material is a pyrotechnic composition contained in a pyrotechnic device.
11. The method of claim 1, wherein the explosive material is placed in a perforated basket and the perforated basket is placed in the interior enclosed volume of the vacuum vessel.
12. The method of claim 1, wherein the desensitizing liquid is added to the enclosed volume after explosive material is placed in the enclosed volume.
13. The method of claim 1, wherein the desensitizing liquid is added to the enclosed volume before explosive material is placed in the enclosed volume, and wherein the explosive material is immersed in the desensitizing liquid as it is placed in the enclosed volume of the vacuum vessel.
14. A method for desensitizing an explosive material using a vacuum vessel having an enclosed volume, the method comprising:
- weighing the explosive material to obtain a pre-treatment weight;
- placing the explosive material in the vacuum vessel;
- immersing the explosive material in a desensitizing liquid in the enclosed volume;
- reducing the pressure in the interior enclosed volume with respect to atmospheric pressure conditions to at least partially saturate the explosive material with the desensitizing liquid;
- weighing the partially saturated explosive material to obtain a post-treatment weight; and
- if the difference between the pre-treatment weight and the post-treatment weight exceeds a threshold, reducing the pressure in the enclosed volume for a subsequent period of time.
15. A system for desensitizing an explosive material, the system comprising:
- a vacuum vessel having an enclosed volume;
- a desensitizing liquid at least partially filling the enclosed volume of the vacuum vessel;
- an explosive material disposed within the enclosed volume and at least partially immersed in the desensitizing liquid; and
- a vacuum source pneumatically connected to the enclosed volume of the vacuum vessel, the vacuum source configured to reduce the pressure in the enclosed volume with respect to atmospheric pressure conditions.
16. The system of claim 15, wherein the enclosed volume of the vacuum vessel is at a reduced pressure of at least 10 inches of mercury (Hg) with respect to atmospheric pressure conditions.
17. The system of claim 15, wherein the enclosed volume of the vacuum vessel is at a reduced pressure of at least 29 inches of mercury (Hg) with respect to atmospheric pressure conditions.
18. The system of claim 15, wherein the vacuum vessel comprises:
- a vessel base;
- a vessel lid resting on the vessel base forming a vacuum seal between the vessel base and the vessel lid, wherein the vessel lid is not mechanically attached or fixed to the vessel base.
19. The system of claim 18, wherein the vessel lid is configured to lift in response to the enclosed volume having a positive pressure with respect to atmospheric pressure conditions, wherein the positive pressure is sufficient to counteract the weight of the vessel lid.
20. The system of claim 19, wherein the vessel lid includes an o-ring for creating a vacuum seal between the vessel lid and the vessel base.
Type: Application
Filed: Apr 25, 2013
Publication Date: Oct 30, 2014
Applicant: MP ASSOCIATES, INC. (Ione, CA)
Inventors: Thaine R. MORRIS (Los Angeles, CA), David J. PIER (Zephyr Cove, NV)
Application Number: 13/870,855
International Classification: F42B 4/00 (20060101);