Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
APPENDIX GFluid-let Cutting of Ordnance and High-Pressure Clean-Out of Energetic Materials Fluidjet cutting is a topic of interest to many groups. The fluid used is usually water, and high-pressure wa- ter jets have been used by industry to cut through many materials (e.g., metal and plastic) for more than 25 years (Summers, 1997~. As part of the ACWA pro- gram, Teledyne-Commodore and Parsons-AlliedSignal have proposed using fluidjet cutting to (1) shear fuzes; (2) precisely section munitions; and (3) gain access to energetic materials by washing out "demilitarized" chunks, slivers, or sections of energetic materials from warheads and rocket motors. Parsons-AlliedSignal pro- poses using water; Teledyne-Commodore proposes ammonia. The use of high-pressure water or ammonia to cut explosive-loaded ordnance and/or to wash out energetic materials from ordnance casings is a proven technol- ogy. When shearing fuzes or sectioning munitions, the fluid jet often contains an abrasive, such as garnet, and the fluid pressure is normally about 2,722 aim (40,000 psi) to cut through the metal casing. When removing explosives or propellants from inside warheads or rocket motors, the fluid usually does not contain abra- sives, and the pressure is normally much lower, about 680 atm (10,000 psi). Critical issues include (1) identi- fication of hazards associated with the specific task; (2) design of the fluidjet cutting system; (3) determi- nation of processing parameters; (4) containment and segregation of residual metal, downloaded energetic materials, and other refuse; and (5) the development of a preventive maintenance schedule. 235 DESIGN PARAMETERS AND HAZARDS IDENTIFICATION Some of the design parameters for fluidjet cutting of ordnance and some of the hazards associated with its operation are well known. Target responses to the im- pact of high-velocity, nonabrasive water jets have been analyzed (Kang et al., 1993~; the mechanisms and pa- rameters of abrasive waterjet (AWJ) cutting have been examined (P.L. Miller, 1992a); some AWJ explosive safety tests have been evaluated (P.L. Miller, 1992b); and the effects of ultra high-pressure water jets on high explosives have been determined (P.L. Miller, 1992c). Some design issues associated with fluidjet cutting systems have been reviewed by a team from Lawrence Livermore National Laboratory and the Pantex Plant in Amarillo, Texas (Kang et al., 1993), who were inter- ested in identifying the physics governing the most efficient mass-removal process when a material is sub- jected to waterjet impact. Theoretical and experimen- tal investigations were performed on the effects of a nonabrasive water jet impinging on a solid surface. At jet velocities below 1,500 m/s, the maximum impact pressure can be calculated from the pressure across a one-dimensional water-hammer compression wave (Cook et al., 1962~. The test data have been correlated to the following expression (Heymann, 1968~: AP = Pc - Pu = PUCuVj [1 + 2 (vi/cu)] where P denotes the pressure, r the liquid density, C the speed of sound, and Vj the jet velocity. The
236 ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS subscripts u and c signify conditions in the undisturbed liquid region and the compressed liquid region, respec- tively. Impact and machining experiments were con- ducted on various materials with waterjet reservoir pressures up to 2,720 aim (40,000 psi). Test results in- dicated that a maximum mass-removal rate takes place when the distance between the target piece and the nozzle exit (stand-off distance) is several hundred nozzle diameters. At this long stand-off, the jet disinte- grates into a series of ligaments and droplets impinging on the surface. Typical nozzle diameters are about 0.35 mm (0.014 in) to 1.5 mm (0.060 in), depending on the material to be cut and the cutting technique. The techniques can either be optimized for removing material or for cut- ting and pulverizing material simultaneously for recla- mation and reuse. If multiple port nozzles are used, the sum of the port diameters should not exceed a maxi- mum design criterion, such as 1.5 mm (0.060 in). The length-to-diameter ratio of nozzles used for nonabra- sive fluidjet cutting depends on the fluid pressure and cutting attributes but is usually about 50: 1. The parameters that affect safety and risk include water pressure, nozzle design, abrasive concentration and particle size, and cutting procedure. Several hun- dred thousand explosive-loaded projectiles have been safely cut using fluidjet technology. Metals ranging from aluminum 6061 to titanium Ti-6Al-4V have been cut using waterjet streams laced with garnet grit. The optimum particle size of garnet grit depends on the metal being cut. The softer the metal, the larger the grit size. A grit size of about 150 microns has been found to be very close to optimal for cutting through steel casings. Two cutting techniques have also been investigated, cutting laterally across the projectile (like a saw) and cutting rotationally (similar to a lathe). The rotational method is faster. An average time for AWJ cutting through 4.2 inch, Composition B-loaded mortars was 33 seconds using the rotational method and 57 seconds using the lateral method (P.L. Miller, 1992a). Ammo- niajet cutting appears to be even faster. Abrasive am- moniajet cutting has been reported to be about 25 per- cent faster than AWJ cutting (Teledyne-Commodore, 1998~. Both waterjet and AWJ cutting of booster and main- charge explosives have been demonstrated to be safe and practical. Even though the impact values from wa- terjet velocities exceed the threshold impact limits for explosives, the energetic initiation mechanism for wa- terjet impingement/cutting is different than for "con- ventional" solid-solid impacts and is well understood. When both projectile diameters and impedance mis- matches are taken into account, the results agree with published models for impact velocities (P.L. Miller, 1992b). A substantial safety margin for using nonabra- sive waterjet cutting of main-charge explosives has also been documented by the Naval Surface Warfare Center (NSWC) Crane Division (Liddard and Roslund, 1993; Worsey et al., 1990~. A graph of the impact ini- tiation probabilities for several high explosives is pro- vided in Figure G- 1 as a log-log plot of velocity versus fluidjet diameter. The lines represent the velocities at which initiation would be expected to occur 50 percent of the time (Verb. Jet impact is the most likely cause of initiation of energetic materials during fluidjet cutting. The maxi- mum pressure for continuous water flow, with existing equipment, is believed to be about 10,200 aim (150,000 psi). The water jet generated by this driving force has a sonic velocity of about 1,475 m/s (4,900 ft/s), which represents an upper bound for water because it is also the pressure at which water freezes at 25°C (77°F). In testing by Alliant Techsystems, pentaerythritol tetranitrate (PETN) and trinitrotoluene (TNT) were 2x1 o4 104 1 o 3 Fluid-jet regime 5 10~1 10° 1o1 2X101 Diameter (mm) TNT Exp D Picric acid Comp B HEX Tetryl RDX PETN FIGURE G-1 Waterjet velocity at which explosives will initiate 50 percent of the time as a function of the fluidjet diameter.
APPENDIX G selected to represent the sensitivity range of explosives of interest in demilitarization. PETN is an impact-sen- sitive booster explosive component; TNT is a relatively impact-insensitive explosive used as a main charge. Fifty waterjet impact tests were performed on pressed PETN samples and cast TNT samples. Neither PETN nor TNT was initiated by the impact of water jets at this pressure (P.L. Miller, 1992c). SURVEY OF PRACTICE AND PRODUCTION The use of fluidjet cutting to gain access to muni- tions for demilitarization and/or resource, reclamation, and reuse has been demonstrated and/or used by the Department of Defense (DOD) and many contractors. The user community can be separated into uses of non- abrasive jets and users of abrasive jets. A limited survey of nonabrasive waterjet cutting of energetic materials was recently published (Estabrook, 1994~. Nonabrasive water jets have been used to down- load explosives from warheads by the NSWC Indian Head Division at Yorktown, Virginia (Lowell, 1986), and the NSWC Crane Division in Crane, Indiana (Sum- mers et al., 1988; Burch, 1998), as well as at the West- ern Area Demilitarization Facility in Hawthorne, Ne- vada (Day and Zimmermann, 1994~. Nonabrasive water jets have also been routinely used in the propel- lant industry to download composite rocket motors to reclaim cases. This technology has been demonstrated by Thiokol, Aerojet GenCorp, and many others. Non- abrasive ammonia jets have been used by the Army in Huntsville, Alabama, to download rocket motors from cases as a first step in a novel recovery process (Melvin, 1992; Morgan, 1994~. Carbon dioxide pellets have been entrained in a pressurized pneumatic jet at velocities of 20 m/s to 300 m/s to demonstrate an "environmentally friendly" means of downloading (or "blasting out") explosives from projectiles by the Army at Picatinny Arsenal in New Jersey (Hwang, 1995~. The Air Force has even investigated using high-pressure liquid nitro- gen as a cryogenic jet to remove propellant from large rocket motors (Coppola,1995~. AWJ has been recently reviewed in the literature (Summers, 1997~. In the United States, the AWJ technique combines abrasive with the high-velocity jet stream after it leaves the ini- tial acceleration nozzle. The resulting mixture is then refocused through a second nozzle. AWJ has been used 237 / / L/ / \ Entrainment abrasive water-jet cutting DIAJET abrasive water-jet cutting FIGURE G-2 Comparison of the AWJ and ASJ (DIAJET) abrasivejet cutting techniques. by Alliant Techsystems to section thousands of projec- tiles without incident. In the United Kingdom, an alter- native method of abrasive slurry jetting (ASJ), mar- keted under the name "DIAJET," is being developed (D. Miller, 1995~. In the ASJ method, the abrasive is fed into the waterjet stream before it is accelerated through a nozzle. These two techniques are compared in Figure G-2. The ASJ technique is potentially more efficient than AWJ because of higher cutting rates at reduced pressures and reduced operating costs. For ex- ample, the AWJ operating pressure is typically in the range of 2,382 to 3,743 atm (35,000 to 55,000 psi) for sectioning ordnance; the ASJ operating pressure is be- tween 238 and 680 aim (3,500 and 10,000 psi). ASJ is being implemented by the Defense Evaluation and Re- search Agency (DERA) in the United Kingdom to de- militarize obsolete ordnance and "render safe" un- exploded ordnance, such as abandoned mines. ASJ is also being considered for implementation in the United States as a more efficient method for demilitarizing ordnance (Fossey, 1998). INCIDENTS ASSOCIATED WITH DEMILITARIZATION OF ORDNANCE A few incidents have been associated with the de- militarization of ordnance using jet-cutting techniques.
238 ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS Five recent, diverse incidents are discussed here. The first incident, which occurred in 1996 at the Alliant Techsystems Proving Grounds (Blixrud, 1996), hap- pened during the mechanical defuzing of obsolete 8- inch Navy projectiles immediately prior to demilitari- zation by jet cutting. The cause of the incident was pinching picrates in the threads while unscrewing a corroded fuze. The lesson learned was that all ordnance must be carefully inspected before processing to iden- tify and remove ordnance that require special treatment from routine operations. This incident might not have occurred if jet cutting had been used to remove the fuze (rather than unscrewing it mechanically). A second incident involved the fluidiet nozzle be- coming detached from the lance during the high-pres- sure water wash-out of explosive from a munition war- head. When the nozzle impacted the explosive, it initiated and deflagrated. The lesson learned was that metal parts must be routinely inspected for signs of fatigue. The third and fourth incidents occurred at Aii~ant Techsystems during system trials and safety demon- strations. Both incidents involved abrasive water-Jet cutting of 20 mm ammunition that contained lead azide, which was press-loaded at high density and deliber- ately chosen to determine whether initiation would oc- cur. During abrasive waterjet cutting, the lead azide initiated and detonated. After this happened the first time, some design parameters were altered and the tests were repeated. The results were the same the second time. A fifth incident, which occurred at DERA West Freugh in Scotland in 1995 (Moore, 1999), involved handling ordnance that had been demilitarized by abrasive jet cutting. About three days after explo- sive-loaded ordnance had been sectioned, workers performing normal procedures were injured when the ordnance unexpectedly initiated. Evidently, the cause of the initiation was embedded particles from the abrasive jet cutting operation that had sensitized the explosive to impact, especially when the explo- sive surface was dehydrated. The lessons learned are that sectioned ordnance should be kept wet while applying impact, shear, or other forces to it and that spent abrasive should not be allowed to "dry out" while it may still be contaminated. PREVENTATIVE MAINTENANCE The high-pressure pumps used for jet cutting require extensive preventative maintenance and are, thus, re- sponsible for most of the down time for jet-cutting sys- tems. Wear of the nozzle is a primary concern for safety and performance. Nozzle wear is worst with the AWJ method, followed by the ASJ method, and least with nonabrasive techniques. For AWJ, the nozzle usually clogs at least once during start-up. The more often the system is shut down and restarted, the worse the wear. However, for AWJ, the average service life of a nozzle is about 1,000 hours of operation. Any closed-loop fluidjet cutting system has "dead spots" in which sediment, energetic material, metallic particles, and spent abrasive can accumulate. The num- ber of dead spots should be minimized when the sys- tem is designed and built. Filter housings, traps, and other solids-capture features in closed-loop systems should have a preventative maintenance plan based on actual processing data or experience to ensure that un- desired combinations of trace .se~iment. ener~et.ic mn · . . ... .. . _ ~ _ A-- - - - ---I --- --D- terlals, metallic particles, and spent abrasives do not dry out sufficiently to undergo exothermic reduction- oxidation reactions. If ammonia jets are used, precau- tions must be taken to minimize the residence time of materials awaiting further processing to prevent exothermic ammonolysis. REFERENCES Blixrud, C. 1996. Investigation Report, 8" Demilitalization. Memo- randum from Craig Blixrud, Alliant Techsystems, to M. Dolby and B. Ford, Alliant Techsystems, May 21, 1996. Burch, D. 1998. Recovery of RDX and HMX from Military Muni- tions. Presented at the JANAF PDCS/S&EPS Joint Meeting, NASA Johnson Space Center, Houston, Texas, April 21-24, 1998. Cook, M.A., R.T. Keyes, and W.O. Ursenbach. 1962. Measure- ments of detonation pressure. Journal of Applied Physics 33: 3413-3421. Coppola, E.N. 1995. Cryogenic Propellant Removal System (PRS). Pp.324-332 in Proceedings of the 3rd Global Demilitarization Symposium. Arlington, Va.: Joint Ordnance Commanders Group Demilitarization and Disposal Subgroup. Day and Zimmerman. 1994. Western Area Demilitarization Facil- ity. Pp. 300-332 in Proceedings of the 2nd Demilitarization Sym- posium. Arlington, Va.: Joint Ordnance Commanders Group Demilitarization and Disposal Subgroup. Estabrook, L.C. 1994. Water-Jet Cutting of Energetic Materials. Pp. 200-209 in Proceedings of the Life Cycles of Energetic
APPENDIX G Materials 1994 Conference. Paper LA-UR-95-1090. Los Alamos, N.M.: Los Alamos National Laboratory. Fossey, R.D. 1998. The use of an Abrasive Waterjet System at 700 bar for the Cutting of Military Munitions as Part of a Demilita- rization Program. Pp. 453-466 in Proceedings of the 14th Inter- national Conference on Jetting Technology. Brugge, Belgium: British Hydrodynamics Research Group. Heymann, F.J. 1968. On the shock wave velocity and impact pres- sure in high-speed liquid-solid impact. Journal of Basic Engi- neering 90: 400-402 Hwang, M. 1995. Carbon Dioxide Blast Demilitarization of Explo- sive-Loaded Projectiles. Pp. 471-484 in Proceedings of the 3 Global Demiliterization Symposium. Arlington, Va.: Joint Ord- nance Commanders Group Demilitarization and Disposal Sub- group. Kang, S-W., T. Reitter, G. Carlson, J. Crutchmer, D. Garrett, P. Kramer, and B. Do. 1993. Target Responses to the Impact of High-Velocity, Nonabrasive Water Jets. Pp. 71-86 in Proceed- ings of the 7th American Water Jet Conference, Vol.1. Seattle, Wash.: Water Jet Technology Association. Liddard, T.P., and L.S. Roslund.1993. Projectile/Fragment Impact Sensitivity of Explosives. NSWC T89-184. Crane, Ind.: Naval Surface Warfare Center Crane Division. Lowell, M.D. 1986. PBX Downloading by High Pressure Water Jet. Presented at the Load, Assemble, and Packaging Section Meeting of the American Defense Preparedness Association (ADPA), Long Beach, California, March 12-13, 1986. Melvin, W.S. 1992. Critical Fluid Demilitarization and Ingredient Reclamation Technology: Critical Technology Report. Red- stone Arsenal, Ala.: U.S. Army Missile Command. Miller, D. 1995. Abrasive Water Jet Technology for Demilitariza- tion in Europe. Pp. 445-455 in Proceedings of the 3rd Global Demilitarization Symposium. Arlington, Va.: Joint Ordnance Commanders Group Demilitarization and Disposal Subgroup. 239 Miller, P.L. 1992a. The Mechanisms and Parameters of Abrasive Waterjet (AWJ) Cutting of High-Explosive Projectiles. Pre- sented at the 25th Department of Defense Explosive Safety Board Seminar, Anaheim, California, August 18-21, 1992. Miller, P.L. 1992b. Abrasive Waterjets (AWJ) Explosive Safety Tests. Presented at the 25th Department of Defense Explosive Safety Board Seminar, Anaheim, California, August 18-21, 1992. Miller, P.L. 1992c. The Effects of Ultrahigh-Pressure Waterjet Impact on High-Explosives. Presented at the 25th Department of Defense Explosive Safety Board Seminar, Anaheim, Califor- nia, August 18-21, 1992. Moore, I. 1999. Telephone conversation between Ian Moore, DERA Shoeburyness, United Kingdom, and Kirk Newman, Naval Sur- face Warfare Center, Indian Head Division, Yorktown, Virginia, March 3, 1999. Morgan, M.E. 1994. Critical Fluid Demilitarization and Ingredient Reclamation Technology. Pp. 365-376 in Proceedings of the 3rd Global Demilitarization Symposium. Arlington, Va.: Joint Ordnance Commanders Group Demilitarization and Disposal Subgroup. Summers, D.A. 1997. Literature Review on the State-of-the-Art in Abrasive Waterjet Cutting. Crane, Ind.: Naval Surface Warfare Center Crane Division. Summers, D.A., W.Z. Wu, P.N. Worsey, and L.E. Craig. 1988. PBX Demilitarization. NWSC/CR/RDTR-427. Crane, Ind.: Naval Surface Warfare Center Crane Division. Teledyne-Commodore. 1998. Demonstration of Simulated Chemi- cal Agent Rocket Demilitarization Using Solvated Electron Technology and Ammonia Fluid Jet Technology. Huntsville, Ala.: Teledyne-Commodore. Worsey, P.N., D.A. Summers, and L.E. Craig. 1990. Waterjet Im- pact Sensitivity Test Manual. NWSC/CR/RDTR-541. Crane, Ind.: Naval Surface Warfare Center Crane Division.
